BOK Financial (BOKF) 10-K 1 Mar 19 2018 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Jan. 31, 2019	Jun. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	BOK FINANCIAL CORP ET AL
Entity Central Index Key	875,357
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Current Reporting Status	No
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Public Float			$ 2,441,480,672
Entity Common Stock, Shares Outstanding		72,251,266
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018

Consolidated Statements of Earn

Consolidated Statements of Earnings - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest and dividend revenue [Abstract]
Loans	$ 891,587	$ 696,479	$ 581,030
Residential mortgage loans held for sale	8,123	8,706	12,658
Trading securities	57,531	17,002	8,527
Investment securities	14,775	16,121	16,894
Available for sale securities	197,317	177,070	175,321
Fair value option securities	15,205	16,755	6,723
Restricted equity securities	21,555	18,490	17,238
Interest-bearing cash and cash equivalents	22,333	22,128	10,726
Total interest revenue	1,228,426	972,751	829,117
Interest Expense [Abstract]
Deposits	95,517	53,803	40,494
Borrowed funds	138,215	69,124	35,099
Subordinated debentures	9,827	8,123	6,296
Total interest expense	243,559	131,050	81,889
Net interest and dividend revenue	984,867	841,701	747,228
Provision for credit losses	8,000	(7,000)	65,000
Net interest and dividend revenue after provision for credit losses	976,867	848,701	682,228
Total fees and commissions	643,642	681,235	685,831
Other gains (losses), net	(2,731)	11,213	4,947
Gain (loss) on derivatives, net	(422)	779	(15,685)
Loss on fair value option securities, net	(25,572)	(2,733)	(10,555)
Change in fair value of mortgage servicing rights	4,668	172	(2,193)
Gain (loss) on available for sale securities, net	(2,801)	4,428	11,675
Total other operating revenue	616,784	695,094	674,020
Other operating expense [Abstract]
Personnel	583,131	573,408	553,119
Business promotion	30,523	28,877	26,582
Charitable contributions to BOKF Foundation	2,846	2,000	2,000
Professional fees and services	59,099	51,067	56,783
Net occupancy and equipment	97,981	86,477	80,024
Insurance	23,318	19,653	32,489
Data processing and communications	114,796	146,970	131,841
Printing, postage and supplies	17,169	15,689	15,584
Net losses and operating expenses of repossessed assets	17,052	9,687	3,359
Amortization of intangible assets	9,620	6,779	6,862
Mortgage banking costs	46,298	52,856	61,387
Other expense	26,333	32,054	47,560
Total other operating expense	1,028,166	1,025,517	1,017,590
Net income before taxes	565,485	518,278	338,658
Federal and state income taxes	119,061	182,593	106,377
Net income	446,424	335,685	232,281
Net income (loss) attributable to Non-controlling interests	778	1,041	(387)
Net income attributable to BOK Financial Corporation shareholders	$ 445,646	$ 334,644	$ 232,668
Earnings per share: [Abstract]
Basic (in dollars per share)	$ 6.63	$ 5.11	$ 3.53
Diluted (in dollars per share)	$ 6.63	$ 5.11	$ 3.53
Average shares used in computation: [Abstract]
Basic (in shares)	66,628,640	64,745,364	65,085,627
Diluted (in shares)	66,662,273	64,806,284	65,143,898
Dividends declared per share (in dollars per share)	$ 1.90	$ 1.77	$ 1.73
Brokerage and trading revenue [Member]
Total fees and commissions	$ 108,323	$ 131,601	$ 138,377
Transaction card revenue [Member]
Total fees and commissions	84,025	119,988	116,452
Fiduciary and asset management revenue [Member]
Total fees and commissions	184,703	162,889	135,387
Deposit service charges and fees [Member]
Total fees and commissions	112,153	112,079	111,589
Mortgage banking revenue [Member]
Total fees and commissions	97,787	104,719	133,914
Other revenue [Member]
Total fees and commissions	$ 56,651	$ 49,959	$ 50,112

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 446,424		$ 335,685		$ 232,281
Other comprehensive income (loss), before income taxes: [Abstract]
Net change in unrealized gain (loss)	(48,010)		(26,152)		(41,521)
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities, Taxable securities	0		0		(112)
Loss (gain) on available for sale securities, net	2,801		(4,428)		(11,675)
Other comprehensive loss, before income taxes	(45,209)		(30,580)		(53,308)
Federal and state income taxes	(11,507)	[1]	(11,923)	[2]	(20,754)	[2]
Other comprehensive loss, net of income taxes	(33,702)		(18,657)		(32,554)
Comprehensive income	412,722		317,028		199,727
Comprehensive income (loss) attributable to non-controlling interests	778		1,041		(387)
Comprehensive income attributable to BOK Financial Corp. shareholders	$ 411,944		$ 315,987		$ 200,114
[1]	Calculated using a 25 percent blended federal and state statutory tax rate.
[2]	Calculated using a 39 percent blended federal and state statutory tax rate.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets [Abstract]
Cash and due from banks	$ 741,749	$ 602,510
Interest-bearing cash and cash equivalents	401,675	1,714,544
Trading securities	1,956,923	462,676
Investment securities	355,187	461,793
Available for sale securities	8,857,120	8,321,578
Fair value option securities	283,235	755,054
Restricted equity securities	344,447	320,189
Residential mortgage loans held for sale	149,221	221,378
Loans	21,656,730	17,153,424
Allowance for loan losses	(207,457)	(230,682)
Loans, net of allowance	21,449,273	16,922,742
Premises and equipment, net	330,033	317,335
Receivables	204,960	178,800
Goodwill	1,049,263	447,430
Intangible assets, net	134,849	28,658
Mortgage servicing rights	259,254	252,867
Real estate and other repossessed assets, net of allowance	17,487	28,437
Derivative contracts	320,929	220,502
Cash surrender value of bank-owned life insurance	381,608	316,498
Receivable on unsettled securities sales	336,400	340,077
Other assets	446,891	359,092
Total assets	38,020,504	32,272,160
Deposits [Abstract]
Noninterest-bearing demand deposits	10,414,592	9,243,338
Interest-bearing Deposit Liabilities [Abstract]
Transaction	12,206,576	10,250,393
Savings	529,215	469,158
Time	2,113,380	2,098,416
Total deposits	25,263,763	22,061,305
Funds purchased and repurchase agreements	1,018,411	574,963
Other borrowings	6,124,390	5,134,897
Subordinated debentures	275,913	144,677
Accrued interest, taxes and expense	192,826	164,895
Derivative contracts	362,306	171,963
Due on unsettled securities purchases	156,370	338,745
Other liabilities	183,480	162,381
Total liabilities	33,577,459	28,753,826
Shareholders' equity: [Abstract]
Common stock	5	4
Capital surplus	1,334,030	1,035,895
Retained earnings	3,369,654	3,048,487
Treasury stock	(198,995)	(552,845)
Accumulated other comprehensive loss	(72,585)	(36,174)
Total shareholders’ equity	4,432,109	3,495,367
Non-controlling interests	10,936	22,967
Total equity	4,443,045	3,518,334
Total liabilities and equity	$ 38,020,504	$ 32,272,160

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Investment securities [Abstract]
Investment securities, fair value	$ 367,298	$ 480,035
Real estate and other repossessed assets, allowance	$ 13,665	$ 12,648
Shareholders' equity: [Abstract]
Common stock, par value (in dollars per share)	$ 0.00006	$ 0.00006
Common stock, shares authorized (in shares)	2,500,000,000	2,500,000,000
Common stock, shares issued (in shares)	75,711,492	75,147,686
Common stock, shares outstanding (in shares)	75,711,492	75,147,686
Treasury stock, shares at cost (in shares)	3,588,560	9,752,749

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total Shareholders' Equity [Member]	Non-Controlling Interests [Member]
Balance, beginning of period (in shares) at Dec. 31, 2015		74,530			8,636
Balance, beginning of period at Dec. 31, 2015	$ 3,267,639	$ 4	$ 982,009	$ 2,704,121	$ (477,165)	$ 21,587	$ 3,230,556	$ 37,083
Net income	232,281			232,668			232,668	(387)
Other comprehensive loss	(32,554)					(32,554)	(32,554)
Repurchase of common stock (in shares)					1,005
Repurchase of common stock	(66,792)				$ (66,792)		(66,792)
Stock options exercised (in shares)		214
Stock options exercised	12,465		12,465				12,465
Non-vested shares awarded, net (in shares)		249
Non-vested shares awarded,net	1,590		1,590				1,590
Vesting of non-vested shares (in shares)					15
Vesting of non-vested shares	(95)				$ (95)		(95)
Share-based compensation	10,471		10,471				10,471
Cash dividends on common stock	(113,455)			(113,455)			(113,455)
Capital calls and distributions, net	(5,193)							(5,193)
Balance, end of period (in shares) at Dec. 31, 2016		74,993			9,656
Balance, end of period at Dec. 31, 2016	3,306,357	$ 4	1,006,535	2,823,334	$ (544,052)	(10,967)	3,274,854	31,503
Net income	335,685			334,644			334,644	1,041
Other comprehensive loss	(18,657)					(18,657)	(18,657)
Repurchase of common stock (in shares)					80
Repurchase of common stock	(7,403)				$ (7,403)		(7,403)
Stock options exercised (in shares)		100
Stock options exercised	5,758		5,758				5,758
Non-vested shares awarded, net (in shares)		55
Non-vested shares awarded,net	0		0				0
Vesting of non-vested shares (in shares)					17
Vesting of non-vested shares	(1,390)				$ (1,390)		(1,390)
Share-based compensation	23,602		23,602				23,602
Cash dividends on common stock	(116,041)			(116,041)			(116,041)
Capital calls and distributions, net	(9,577)							(9,577)
Reclassification of stranded accumulated other comprehensive loss to retained earnings related to tax reform	(6,550)			6,550		(6,550)
Balance, end of period (in shares) at Dec. 31, 2017		75,148			9,753
Balance, end of period at Dec. 31, 2017	3,518,334	$ 4	1,035,895	3,048,487	$ (552,845)	(36,174)	3,495,367	22,967
Transition adjustment of net unrealized gains on equity securities	(2,709)			2,709		(2,709)
Balance, beginning of period, Adjusted	3,518,334	$ 4	1,035,895	3,051,196	$ (552,845)	(38,883)	3,495,367	22,967
Net income	446,424			445,646			445,646	778
Other comprehensive loss	(33,702)					(33,702)	(33,702)
Repurchase of common stock (in shares)					616
Repurchase of common stock	(53,465)				$ (53,465)		(53,465)
Stock options exercised (in shares)		54
Stock options exercised	2,781		2,781				2,781
Non-vested shares awarded, net (in shares)		109
Non-vested shares awarded,net			0
Vesting of non-vested shares (in shares)					31
Vesting of non-vested shares	(2,870)				$ (2,870)		(2,870)
Share-based compensation	4,229		4,229				4,229
Cash dividends on common stock	(127,188)			(127,188)			(127,188)
Issuance of shares for CoBiz acquisition (in shares)		400			(6,811)
Issuance of shares fro CoBiz acquisition	701,311	$ 1	291,125		$ 410,185		701,311
Capital calls and distributions, net	(12,809)							(12,809)
Balance, end of period (in shares) at Dec. 31, 2018		75,711			3,589
Balance, end of period at Dec. 31, 2018	4,443,045	$ 5	$ 1,334,030	$ 3,369,654	$ (198,995)	$ (72,585)	$ 4,432,109	$ 10,936
Transition adjustment of net unrealized gains on equity securities	$ 2,700

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows From Operating Activities: [Abstract]
Net income	$ 446,424	$ 335,685	$ 232,281
Adjustments to reconcile net income to net cash provided by (used in) operating activities: [Abstract]
Provision for credit losses	8,000	(7,000)	65,000
Change in fair value of mortgage servicing rights due to market changes	(4,668)	(172)	2,193
Change in fair value of mortgage servicing rights due to principal payments	33,528	33,527	40,744
Net unrealized losses from derivative contracts	4,686	3,704	11,234
Share-based compensation	4,229	23,602	10,471
Depreciation and amortization	60,843	54,466	47,016
Net amortization of securities discounts and premiums	30,945	28,693	41,643
Net losses (gains) on financial instruments and other losses(gains), net	9,585	(2,828)	(13,011)
Net gain on mortgage loans held for sale	(35,705)	(47,159)	(63,636)
Mortgage loans originated for sale	(2,587,297)	(3,286,873)	(6,117,417)
Proceeds from sale of mortgage loans held for sale	2,691,144	3,405,890	6,193,587
Capitalized mortgage servicing rights	(35,247)	(39,149)	(71,405)
Change in trading and fair value option securities	(1,023,097)	(804,204)	149,921
Change in receivables	(38,346)	321,880	(603,861)
Change in other assets	27,507	(5,506)	(49,565)
Change in accrued interest, taxes and expense	(5,191)	18,191	44,269
Change in other liabilities	(139,346)	182,184	(11,413)
Net cash provided by (used in) operating activities	(552,006)	214,931	(91,949)
Cash Flows From Investing Activities: [Abstract]
Proceeds from maturities or redemptions of investment securities	124,864	112,022	86,847
Proceeds from maturities or redemptions of available for sale securities	1,122,680	1,841,217	1,740,226
Purchases of investment securities	(4,468)	(32,972)	(41,590)
Purchases of available for sale securities	(1,955,172)	(2,845,557)	(2,333,740)
Proceeds from sales of available for sale securities	745,643	1,309,215	899,381
Change in amount receivable on unsettled available for sale securities transactions	38,347	(68,792)	33,005
Loans originated, net of principal collected	(1,553,033)	(78,232)	(621,605)
Net payments on derivative asset contracts	(114,417)	479,409	(103,668)
Acquisitions, net of cash acquired	(175,755)	0	56,017
Proceeds from disposition of assets	308,762	274,029	198,922
Purchases of assets	(345,082)	(250,783)	(199,802)
Net cash provided by (used in) investing activities	(1,807,631)	739,556	(286,007)
Cash Flows From Financing Activities: [Abstract]
Net change in demand deposits, transaction deposits and savings accounts	(13,870)	(563,406)	1,277,285
Net change in time deposits	(73,089)	(123,384)	(216,084)
Net change in other borrowed funds	1,295,484	(10,909)	(606,476)
Repayment of subordinated debentures	0	0	(226,550)
Issuance of subordinated debentures, net of issuance costs	0	0	144,615
Change in amount due on unsettled security purchases	(41,319)	144,690	(10,389)
Issuance of common and treasury stock, net	(88)	4,368	12,455
Net change in derivative margin accounts	85,466	(17,726)	(28,806)
Net payments or proceeds on derivative liability contracts	114,076	(485,119)	106,051
Repurchase of common stock	(53,465)	(7,403)	(66,792)
Dividends paid	(127,188)	(116,041)	(113,455)
Net cash provided by (used in) financing activities	1,186,007	(1,174,930)	271,854
Net increase (decrease) in cash and cash equivalents	(1,173,630)	(220,443)	(106,102)
Cash and cash equivalents at beginning of period	2,317,054	2,537,497	2,643,599
Cash and cash equivalents at end of period	1,143,424	2,317,054	2,537,497
Supplemental Cash Flow Information: [Abstract]
Cash paid for interest	243,121	127,513	82,876
Cash paid for taxes	92,291	121,697	79,883
Net loans and bank premises transferred to repossessed real estate and other assets	9,880	7,367	36,391
Increase in U.S. government guaranteed loans eligible for repurchase	100,238	148,107	120,406
Increase in receivables from conveyance of GNMA OREO	$ 38,216	$ 40,528	$ 68,873

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies [Text Block]	Significant Accounting Policies Basis of Presentation The Consolidated Financial Statements of BOK Financial Corporation (“BOK Financial” or “the Company”) have been prepared in conformity with accounting principles generally accepted in the United States ("U.S. GAAP"), including interpretations of U.S. GAAP issued by federal banking regulators and general practices of the banking industry. The Consolidated Financial Statements include the accounts of BOK Financial and its subsidiaries, principally BOKF, NA, CoBiz Bank, BOK Financial Securities, Inc., The Milestone Group, Inc. and Cavanal Hill Distributors, Inc. All significant intercompany transactions are eliminated in consolidation. The Consolidated Financial Statements include the assets, liabilities, non-controlling interests and results of operations of variable interest entities (“VIEs”) when BOK Financial is determined to be the primary beneficiary. Variable interest entities are generally defined as entities that either do not have sufficient equity to finance their activities without support from other parties or whose equity investors lack a controlling financial interest. Determination that the Company is the primary beneficiary considers the power to direct the activities that most significantly impact the variable interest's economic performance and the obligation to absorb losses of the variable interest or the right to receive benefits of the variable interest that could be significant to the variable interest. Certain prior year amounts have been reclassified to conform to current year presentation. Nature of Operations BOK Financial, through its subsidiaries, provides a wide range of financial services to commercial and industrial customers, other financial institutions, municipalities, and consumers. These services include depository and cash management; lending and lease financing; mortgage banking; securities brokerage, trading and underwriting; and personal and corporate trust. BOKF, NA operates as Bank of Oklahoma primarily in the Tulsa and Oklahoma City metropolitan areas of the state of Oklahoma and Bank of Texas primarily in the Dallas, Fort Worth and Houston metropolitan areas of the state of Texas. In addition, BOKF, NA does business as Bank of Albuquerque in Albuquerque, New Mexico; Colorado State Bank and Trust in Denver, Colorado; Bank of Arizona in Phoenix, Arizona; Mobank in Kansas City, Missouri/Kansas and Bank of Arkansas in Northwest Arkansas. BOKF, NA also operates the TransFund electronic funds network, Cavanal Hill Investment Management, and BOK Financial Asset Management, Inc. On October 1, 2018, BOK Financial acquired CoBiz Financial, Inc. and CoBiz Bank, its wholly owned subsidiary. CoBiz Financial has been merged into BOK Financial. CoBiz Bank will be merged into BOKF, NA in the first quarter of 2019. Use of Estimates Preparation of BOK Financial's Consolidated Financial Statements requires management to make estimates of future economic activities, including loan collectability, prepayments and cash flows from customer accounts. These estimates are based upon current conditions and information available to management. Actual results may differ significantly from these estimates. Acquisitions Assets and liabilities acquired, including identifiable intangible assets, are recorded at fair value on the acquisition date. The purchase price includes consideration paid at closing and the estimated fair value of contingent consideration that will be paid in the future, subject to achieving defined performance criteria. Premiums and discounts assigned to interest-earning assets and interest-bearing liabilities are amortized over the lives of the acquired assets and liabilities on either an individual instrument or pool basis. Provision for credit losses is recognized for changes in credit quality after the acquisition date. Goodwill is recognized as the excess of the purchase price over the net fair value of assets acquired and liabilities assumed. The Consolidated Statements of Earnings include the results of operations from the acquisition date. Goodwill and Intangible Assets Goodwill and intangible assets generally result from business combinations and are evaluated for each of BOK Financial's reporting units for impairment annually or more frequently if conditions indicate impairment. The evaluation of possible impairment of goodwill and intangible assets involves significant judgment based upon short-term and long-term projections of future performance. Reporting units are defined by the Company as significant lines of business within each operating segment. This definition is consistent with the manner in which the chief operating decision maker assesses the performance of the Company and makes decisions concerning the allocation of resources. The Company qualitatively assesses whether it is more likely than not that the fair value of the reporting units are less than their carrying value, including goodwill. Reporting unit carrying value includes sufficient capital to exceed regulatory requirements. This assessment includes consideration of relevant events and circumstances including but not limited to macroeconomic conditions, industry and market conditions, the financial and stock performance of the Company and other relevant factors. If the Company concludes based on the qualitative assessment that goodwill may be impaired, a quantitative one-step impairment test will be applied to goodwill at all reporting units. The quantitative analysis compares the fair value of the reporting unit with its carrying value, including goodwill. The fair value of each reporting unit is estimated by the discounted future earnings method. Goodwill is considered impaired if the fair value of the reporting unit is less than the carrying value of the reporting unit, including goodwill. Intangible assets are generally composed of customer relationships, naming rights, non-compete agreements and core deposit premiums. They are amortized using accelerated or straight-line methods, as appropriate, over the estimated benefit periods. These periods range from 3 years to 20 years . The net book values of identifiable intangible assets are evaluated for impairment when economic conditions indicate impairment may exist. Cash Equivalents Due from banks, funds sold (generally federal funds sold for one day ), resell agreements (which generally mature within one day to 30 days ) and investments in money market funds are considered cash equivalents. Securities Securities are identified as trading, investment (held to maturity) or available for sale at the time of purchase based upon the intent of management, liquidity and capital requirements, regulatory limitations and other relevant factors. Trading securities, which are acquired for profit through resale, are carried at fair value with unrealized gains and losses included in current period earnings. Investment securities are carried at amortized cost. Amortization is computed by methods that approximate level yield and is adjusted for changes in prepayment estimates. Securities identified as available for sale are carried at fair value. Unrealized gains and losses are recorded, net of deferred income taxes, as accumulated other comprehensive income in shareholders' equity. Available for sale securities are separately identified as pledged to creditors if the creditor has the right to sell or re-pledge the collateral. The purchase or sale of securities is recognized on a trade date basis. Realized gains and losses on sales of securities are based upon specific identification of the security sold. A receivable or payable is recognized for subsequent transaction settlement. Securities meeting certain criteria may also be transferred from the available for sale classification to the investment securities portfolio at fair value on the date of transfer. The unrealized gain or loss at the date of transfer is retained in accumulated other comprehensive income and in the carrying value of the investment securities portfolio. Such amounts are amortized over the estimated remaining life of the security as an adjustment to yield, offsetting the related amortization of the premium or accretion of the discount on the transferred securities. On a quarterly basis, the Company performs separate evaluations of impaired debt investment and available for sale securities to determine if the decline in fair value below the amortized cost is other-than-temporary. Management determines whether it intends to sell or if it is more likely than not that it will be required to sell impaired securities. This determination considers current and forecasted liquidity requirements and securities portfolio management. If the Company intends to sell or it is more likely than not that it will be required to sell the impaired debt security, a charge is recognized against earnings for the entire unrealized loss. For all impaired debt securities for which there is no intent or expected requirement to sell, the evaluation considers all available evidence to assess whether it is more likely than not that all amounts due would not be collected according to the security's contractual terms. Impairment of debt securities rated investment grade by nationally-recognized rating agencies is considered temporary unless specific contrary information is identified. Impairment of debt securities rated below investment grade by at least one of the nationally recognized rating agencies is evaluated based on projections of estimated cash flows. Any expected credit loss due to the inability to collect all amounts due according to the security's contractual terms is recognized as a charge against earnings. Any remaining unrealized loss related to other factors would be recognized in other comprehensive income, net of taxes. BOK Financial may elect to carry certain securities at fair value with changes in fair value recognized in current period income. These securities are held with the intent that gains or losses will offset changes in the fair value of mortgage servicing rights or certain derivative instruments. Restricted equity securities represent equity interests the Company is required to hold in the Federal Reserve Banks and Federal Home Loan Banks. Restricted equity securities are carried at cost as these securities do not have a readily determined fair value because ownership of these shares is restricted and they lack a market. The fair value of our securities portfolio is generally based on a single price for each financial instrument provided to us by a third-party pricing service determined by one or more of the following: • Quoted prices for similar, but not identical, assets or liabilities in active markets; • Quoted prices for identical or similar assets or liabilities in inactive markets; • Inputs other than quoted prices that are observable, such as interest rate and yield curves, volatilities, prepayment speeds, loss severities, credit risks and default rates; and • Other inputs derived from or corroborated by observable market inputs. The underlying methods used by the third-party pricing services are considered in determining the primary inputs used to determine fair values. We evaluate the methodologies employed by the third-party pricing services by comparing the price provided by the pricing service with other sources, including brokers' quotes, sales or purchases of similar instruments and discounted cash flows to establish a basis for reliance on the pricing service values. Significant differences between the pricing service provided value and other sources are discussed with the pricing service to understand the basis for their values. Based on all observable inputs, management may adjust prices obtained from third-party pricing services to more appropriately reflect the prices that would be received to sell assets or paid to transfer liabilities in orderly transactions in the current market. Derivative Instruments Derivative instruments may be used by the Company as part of its internal risk management programs or may be offered to customers. All derivative instruments are carried at fair value and changes in fair value are generally reported in income as they occur. The determination of fair value of derivative instruments considers changes in interest rates, commodity prices and foreign exchange rates. Fair values for exchange-traded contracts are based on quoted prices in an active market for identical instruments. Fair values for over-the-counter contracts are generated internally using third-party valuation models. Inputs used in third-party valuation models to determine fair values are considered significant other observable inputs. Credit risk is also considered in determining fair value. Deterioration in the credit rating of customers or other counterparties reduces the fair value of asset contracts. Deterioration of our credit rating could decrease the fair value of our derivative liabilities. When bilateral netting agreements or similar agreements exist between the Company and its counterparties that create a single legal claim or obligation to pay or receive the net amount in settlement of the individual derivative contracts, the Company reports derivative assets and liabilities on a net by derivative contract by counterparty basis. Derivative contracts may also require the Company to provide or receive cash margin as collateral for derivative assets and liabilities. Derivative assets and liabilities are reported net of cash margin when certain conditions are met. In addition, derivative contracts executed with customers under Customer Risk Management Programs may be secured by non-cash collateral in conjunction with a credit agreement with that customer. Access to collateral in the event of default is reasonably assured. Derivative instruments may be designated as cash flow hedges of variable rate assets or liabilities, or of anticipated transactions. Changes in the fair value of derivative instruments designated as cash flow hedges are recorded in accumulated other comprehensive income to the extent they are effective. The amount recorded in other comprehensive income is reclassified to earnings in the same periods as the hedged cash flows impact earnings. The ineffective portion of changes in fair value is reported in current earnings. BOK Financial may use derivative instruments in managing its interest rate sensitivity, as part of its economic hedge of the changes in the fair value of mortgage servicing rights and to mitigate the market risk of holding trading securities. Changes in the fair value of derivative instruments used in managing interest rate sensitivity and as part of its economic hedge of changes in the fair value of mortgage servicing rights are included in Other Operating Revenue - Gain (loss) on derivatives, net in the Consolidated Statements of Earnings. Changes in the fair value of derivative instruments used to mitigate the market risk of holding trading securities are included in Operating Revenue - Brokerage and trading revenue. BOK Financial also enters into mortgage loan commitments that are considered derivative contracts. Forward sales contracts that have not been designated as hedging instruments are used to economically hedge these mortgage loan commitments as well as mortgage loans held for sale. Mortgage loan commitments are carried at fair value based upon quoted prices. Changes in the fair value of mortgage loan commitments, mortgage loans held for sale and forward sales contracts are reported in Other Operating Revenue - Mortgage banking revenue. BOK Financial offers programs that permit its customers to manage various risks, including fluctuations in energy, cattle and other agricultural products, interest rates and foreign exchange rates with derivative contracts. Customers may also manage interest rate risk through interest rate swaps used by the borrower to modify interest rate terms of their loans or to-be-announced securities used by our mortgage banking customers to hedge their loan production. Derivative contracts are executed between the customers and BOK Financial. Offsetting contracts are executed between BOK Financial and other selected counterparties to minimize market risk from changes in commodity prices, interest rates or foreign exchange rates. The counterparty contracts are identical to customer contracts, except for a fixed pricing spread or fee paid to BOK Financial as profit and compensation for administrative costs and credit risk which is recognized over the life of the contracts and included in other Operating Revenue - Brokerage and trading revenue in the Consolidated Statements of Earnings. Loans Loans are either secured or unsecured based on the type of loan and the financial condition of the borrower. Repayment is generally expected from cash flow or proceeds from the sale of selected assets of the borrower. BOK Financial is exposed to risk of loss on loans due to the borrower's financial difficulties, which may arise from any number of factors, including problems within the respective industry or local economic conditions. Access to collateral, in the event of borrower default, is reasonably assured through adherence to applicable lending laws and through sound lending standards and credit review procedures. Accounting policies for all loans, excluding residential loans guaranteed by U.S. government agencies, are as follows. Interest is accrued at the applicable interest rate on the outstanding principal amount. Loans are placed on nonaccruing status when, in the opinion of management, full collection of principal or interest is uncertain. Internally risk graded loans are individually evaluated for nonaccruing status quarterly. Non-risk graded loans are generally placed on nonaccruing status when 90 days or more past due or within 60 days of being notified of the borrower's bankruptcy filing. Interest previously accrued but not collected is charged against interest income when the loan is placed on nonaccruing status. Payments received on nonaccruing loans are applied to principal or recognized as interest income, according to management's judgment as to the collectability of principal. Loans may be returned to accruing status when, in the opinion of management, full collection of principal and interest, including principal previously charged off, is probable based on improvements in the borrower's financial condition or a sustained period of performance. For loans acquired with no evidence of credit deterioration, discounts are accreted on either an individual basis for loans with unique characteristics or on a pool basis for groups of homogeneous loans. Accretion is discontinued when a loan with an individually attributed discount is placed on nonaccruing status. Loans to borrowers experiencing financial difficulties may be modified in troubled debt restructurings ("TDRs"). All TDRs are generally classified as nonaccruing, excluding loans guaranteed by U.S. government agencies. Modifications generally consist of extension of payment terms or interest rate concessions and may result either voluntarily through negotiations with the borrower or involuntarily through court order. Generally, principal and accrued but unpaid interest is not voluntarily forgiven. Performing loans may be renewed under the current collateral, debt service ratio and other underwriting standards. Nonaccruing loans may also be renewed and will remain classified as nonaccruing. Occasionally, loans, other than residential mortgage loans, may be held for sale in order to manage credit concentration. These loans are carried at the lower of cost or fair value with gains or losses recognized in gain (loss) on assets. All loans are charged-off when the loan balance or a portion of the loan balance is no longer supported by the paying capacity of the borrower or when the required cash flow is reduced in a TDR. The charge-off amount is determined through an evaluation of available cash resources and collateral value. Internally risk graded loans are evaluated quarterly and charge-offs are taken in the quarter in which the loss is identified. Non-risk graded loans that are past due between 60 days and 180 days , based on the loan product type, are charged off. Loans to borrowers whose personal obligation has been discharged through Chapter 7 bankruptcy proceedings are charged off within 60 days of notice of the bankruptcy filing, regardless of payment status. Loan origination and commitment fees and direct loan acquisition and origination costs are deferred and amortized as an adjustment to yield over the life of the loan or over the commitment period, as applicable. Amortization does not anticipate loan prepayments. Net unamortized fees are recognized in full at time of payoff. Qualifying residential mortgage loans guaranteed by U.S. government agencies have been sold into GNMA pools. Under certain performance conditions specified in government programs, the Company has the right, but not the obligation to repurchase loans from GNMA pools. These loans no longer qualify for sale accounting and are recognized in the Consolidated Balance Sheets. Guaranteed loans are considered to be impaired because we do not expect to receive all principal and interest based on the loan's contractual terms. The principal balance continues to be guaranteed, however, interest accrues at a curtailed rate as specified in the programs. The carrying value of these loans is reduced based on an estimate of expected cash flows discounted at the original note rate plus a liquidity spread. Guaranteed loans may be modified in TDRs in accordance with U.S. government agency guidelines. Interest continues to accrue at the modified rate. Guaranteed loans may either be resold into GNMA pools after a performance period specified by the programs or foreclosed and conveyed to the guarantors. Loans are disaggregated into portfolio segments and further disaggregated into classes. The portfolio segment is the level at which the Company develops and documents a systematic method for determining its Allowance for Credit Losses. Classes are based on the risk characteristics of the loans and the Company's method for monitoring and assessing credit risk. Allowance for Loan Losses and Accrual for Off-Balance Sheet Credit Risk The appropriateness of the allowance for loan losses and accrual for off-balance sheet credit risk (collectively "Allowance for Credit Losses") is assessed by management based on an ongoing quarterly evaluation of the probable estimated losses inherent in the portfolio, including probable losses on both outstanding loans and unused commitments to provide financing. A consistent well-documented methodology has been developed and is applied by an independent Credit Administration department to assure consistency across the Company. The allowance for loan losses consists of specific allowances attributed to impaired loans that have not yet been charged down to amounts we expect to recover, general allowances based on estimated loss rates by loan class and nonspecific allowances based on factors that affect more than one portfolio segment. There were no changes to the methodology for estimating general allowances during 2018 or 2017 . Loans are considered to be impaired when it becomes probable that BOK Financial will be unable to collect all amounts due according to the contractual terms of the loan agreements. Internally risk graded loans are evaluated individually for impairment. Substantially all commercial and commercial real estate loans and certain residential mortgage and personal loans are risk graded based on a quarterly evaluation of the borrowers' ability to repay. Certain commercial loans and most residential mortgage and personal loans are small balance, homogeneous pools of loans that are not risk graded. Non-risk graded loans are identified as impaired based on performance status. Generally, non-risk graded loans 90 days or more past due, modified in a troubled debt restructuring or in bankruptcy are considered to be impaired. Specific allowances for impaired loans are measured by an evaluation of estimated future cash flows discounted at the loan's initial effective interest rate or the fair value of collateral for certain collateral dependent loans. The fair value of real property held as collateral is generally based on third party appraisals that conform to Uniform Standards of Professional Appraisal Practice, less estimated selling costs. Appraised values are on an “as-is” basis and generally are not adjusted by the Company. Updated appraisals are obtained at least annually or more frequently if market conditions indicate collateral values may have declined. Collateral value of mineral rights is generally determined by our internal staff of engineers based on projected cash flows from proven oil and gas reserves under existing economic and operating conditions. The value of other collateral is generally determined by our special assets staff based on projected liquidation cash flows under current market conditions. Collateral values and available cash resources that support impaired loans are evaluated quarterly. Historical statistics may be used as a practical way to estimate impairment in limited situations, such as when a collateral dependent loan is identified as impaired at the end of a reporting period until an appraisal of collateral value is received or a full assessment of future cash flows is completed. Estimates of future cash flows and collateral values require significant judgments and may be volatile. General allowances for unimpaired loans are based on an estimated loss rate by loan class. The appropriate historical gross loss rate for each loan class is determined by the greater of the current loss rate based on the most recent twelve months or a ten-year average gross loss rate. Recoveries are not directly considered in the estimation of historical loss rates. Recoveries generally do not follow predictable patterns and are not received until well-after the charge-off date as a result of protracted legal actions. For risk graded loans, historical gross loss rates are adjusted for changes in risk grading. For each loan class, the current weighted average risk grade is compared to the long-term weighted average risk grade. This comparison determines whether credit risk in each loan class is increasing or decreasing. Historical loss rates are adjusted upward or downward in proportion to changes in average risk grading. General allowances for unimpaired loans also consider inherent risks identified for each loan class. Inherent risks consider loss rates that most appropriately represent the current credit cycle and other factors attributable to a specific loan class which have not yet been represented in the historical gross loss rates or risk grading. These factors include changes in commodity prices or engineering imprecision which may affect the value of reserves that secure our energy loan portfolio, construction risk that may affect commercial real estate loans, changes in regulations and public policy that may disproportionately impact health care loans and changes in loan products. Nonspecific allowances are maintained for risks beyond factors specific to a particular portfolio segment or loan class. These factors include trends in the economy in our primary lending areas, concentration in large-balance loans and other relevant factors. An accrual for off-balance sheet credit risk is included in Other liabilities in the Consolidated Balance Sheets. The appropriateness of the accrual is determined in the same manner as the allowance for loan losses. A provision for credit losses is charged against or credited to earnings in amounts necessary to maintain an appropriate Allowance for Credit Losses. Recoveries of loans previously charged off are added to the allowance when received. Real Estate and Other Repossessed Assets Real estate and other repossessed assets are acquired in partial or total forgiveness of loans. These assets are initially recognized at cost, which is determined by fair value at date of foreclosure less estimated disposal costs. They are subsequently carried at the lower of cost or current fair value less estimated disposal costs. Decreases in fair value below cost are recognized as asset-specific valuation allowances which may be reversed when supported by future increases in fair value. Subsequent increases in fair value may be used to reduce the allowance but not below zero. Fair values of real estate are based on “as is” appraisals which are updated at least annually or more frequently for certain asset types or assets located in certain distressed markets. Fair values based on appraisals are generally considered to be based on significant other observable inputs. The Company also considers decreases in listing price and other relevant information in quarterly evaluations and reduces the carrying value of real estate and other repossessed assets when necessary. Fair values based on list prices and other relevant information are generally considered to be based on significant unobservable inputs. Additional costs incurred to complete real estate and other repossessed assets may increase the carrying value, up to current fair value based on “as completed” appraisals. The fair value of mineral rights included in repossessed assets are generally determined by our internal staff of engineers based on projected cash flows from proven oil and gas reserves under existing economic and operating conditions. The value of other repossessed assets is generally determined by our special assets staff based on projected liquidation cash flows under current market conditions. Income generated by these assets is recognized as received. Operating expenses are recognized as incurred. Gains or losses on sales of real estate and other repossessed assets are based on the cash proceeds received less the cost basis of the asset, net of any valuation allowances. The estimated disposal costs of real estate and other repossessed assets are evaluated by the Company on an annual basis based on actual results. Transfers of Financial Assets BOK Financial regularly transfers financial assets as part of its mortgage banking activities and periodically may transfer other financial assets. Transfers are recorded as sales when the criteria for surrender of control are met. The Company has elected to carry certain residential mortgage loans held for sale at fair value under the fair value option. Changes in fair value are recognized in net income as they occur. These loans are reported separately in the Consolidated Balance Sheets and changes in fair value are recorded in Other Operating Revenue - Mortgage banking revenue in the Consolidated Statements of Earnings. Fair value of conforming residential mortgage loans that will be sold to U.S. government agencies is based on sales commitments or market quotes considered Level 2 inputs. Fair value of mortgage loans that are unable to be sold to U.S. government agencies is based on Level 3 inputs using quoted prices of loans that are sold in securitization transactions with a liquidity discount applied. The fair value is corroborated with an independent third party on at least an annual basis. BOK Financial retains a repurchase obligation under underwriting representations and warranties related to residential mortgage loans transferred and generally retains the right to service the loans. The Company may incur a recourse obligation in limited circumstances. Separate accruals are recognized in Other liabilities in the Consolidated Balance Sheets for repurchase and recourse obligations. These reserves reflect the estimated amount of probable loss the Company will incur as a result of repurchasing a loan, indemnifications, and other settlement resolutions. Repurchases of loans with an origination defect that are also credit impaired are considered collateral dependent and are initially recognized at net realizable value (appraised value less the cost to sell). The difference between unpaid principal balance and net realizable value is not accreted. Repurchases of loans with an origination defect that are not credit impaired are carried at fair value as of the repurchase date. Interest income continues to accrue on these loans and the discount is accreted over the estimated life of the loan. The Company may also choose to purchase GNMA loans once certain mandated delinquency criteria are met. The loans that are eligible and are chosen to be repurchased are initially re

Securities

Securities	12 Months Ended
	Dec. 31, 2018
Marketable Securities [Abstract]
Securities [Text Block]	Securities Trading Securities The fair value and net unrealized gain (loss) included in trading securities is as follows (in thousands): December 31, 2018 December 31, 2017 Fair Value Net Unrealized Gain (Loss) Fair Value Net Unrealized Gain (Loss) U.S. government agency debentures $ 63,765 $ 254 $ 21,196 $ 8 U.S. government agency residential mortgage-backed securities 1,791,584 9,966 392,673 (517 ) Municipal and other tax-exempt securities 34,507 (1 ) 13,559 83 Asset-backed securities 42,656 685 23,885 (26 ) Other trading securities 24,411 65 11,363 4 Total trading securities $ 1,956,923 $ 10,969 $ 462,676 $ (448 ) Investment Securities The amortized cost and fair values of investment securities are as follows (in thousands): December 31, 2018 Amortized Fair Gross Unrealized Cost Value Gain Loss Municipal and other tax-exempt securities $ 137,296 $ 138,562 $ 1,858 $ (592 ) U.S. government agency residential mortgage-backed securities 12,612 12,770 293 (135 ) Other debt securities 205,279 215,966 12,257 (1,570 ) Total investment securities $ 355,187 $ 367,298 $ 14,408 $ (2,297 ) December 31, 2017 Amortized Fair Gross Unrealized Cost Value Gain Loss Municipal and other tax-exempt securities $ 228,186 $ 230,349 $ 2,967 $ (804 ) U.S. government agency residential mortgage-backed securities 15,891 16,242 446 (95 ) Other debt securities 217,716 233,444 17,095 (1,367 ) Total investment securities $ 461,793 $ 480,035 $ 20,508 $ (2,266 ) The amortized cost and fair values of investment securities at December 31, 2018 , by contractual maturity, are as shown in the following table (dollars in thousands): Less than One Year One to Five Years Six to Ten Years Over Ten Years Total Weighted Average Maturity² Municipal and other tax-exempt securities: Carrying value $ 41,475 $ 46,363 $ 35,077 $ 14,381 $ 137,296 4.73 Fair value 41,371 46,123 36,471 14,597 138,562 Nominal yield¹ 2.25 % 3.94 % 6.00 % 4.32 % 4.00 % Other debt securities: Carrying value $ 16,282 $ 61,830 $ 115,606 $ 11,561 $ 205,279 5.50 Fair value 16,327 63,923 125,050 10,666 215,966 Nominal yield 3.88 % 4.69 % 5.76 % 4.33 % 5.21 % Total fixed maturity securities: Carrying value $ 57,757 $ 108,193 $ 150,683 $ 25,942 $ 342,575 5.19 Fair value 57,698 110,046 161,521 25,263 354,528 Nominal yield 2.71 % 4.37 % 5.82 % 4.32 % 4.73 % Residential mortgage-backed securities: Carrying value $ 12,612 ³ Fair value 12,770 Nominal yield 4 2.77 % Total investment securities: Carrying value $ 355,187 Fair value 367,298 Nominal yield 4.65 % 1 Calculated on a taxable equivalent basis using a 25 percent effective tax rate. 2 Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without penalty. 3 The average expected lives of residential mortgage-backed securities were 4.7 years based upon current prepayment assumptions. 4 The nominal yield on residential mortgage-backed securities is based upon prepayment assumptions at the purchase date. Actual yields earned may differ significantly based upon actual prepayments. See Quarterly Financial Summary - Unaudited for current yields on the investment securities portfolio. Available for Sale Securities The amortized cost and fair value of available for sale securities are as follows (in thousands): December 31, 2018 Amortized Fair Gross Unrealized Cost Value Gain Loss OTTI U.S. Treasury securities $ 496 $ 493 $ — $ (3 ) $ — Municipal and other tax-exempt securities 2,782 2,864 82 — — Residential mortgage-backed securities: U.S. government agencies: FNMA 3,414,573 3,367,124 10,559 (58,008 ) — FHLMC 1,723,399 1,699,779 5,189 (28,809 ) — GNMA 748,351 737,805 401 (10,947 ) — Total U.S. government agencies 5,886,323 5,804,708 16,149 (97,764 ) — Private issue 40,948 59,736 18,788 — — Total residential mortgage-backed securities 5,927,271 5,864,444 34,937 (97,764 ) — Commercial mortgage-backed securities guaranteed by U.S. government agencies 2,986,297 2,953,889 7,955 (40,363 ) — Other debt securities 35,545 35,430 12 (127 ) — Total available for sale securities $ 8,952,391 $ 8,857,120 $ 42,986 $ (138,257 ) $ — December 31, 2017 Amortized Fair Gross Unrealized Cost Value Gain Loss OTTI U.S. Treasury securities $ 1,000 $ 1,000 $ — $ — $ — Municipal and other tax-exempt securities 27,182 27,080 181 (283 ) — Residential mortgage-backed securities: U.S. government agencies: FNMA 3,021,551 2,997,563 11,549 (35,537 ) — FHLMC 1,545,971 1,531,009 3,148 (18,110 ) — GNMA 787,626 780,580 1,607 (8,653 ) — Total U.S. government agencies 5,355,148 5,309,152 16,304 (62,300 ) — Private issue 74,311 93,221 19,301 — (391 ) Total residential mortgage-backed securities 5,429,459 5,402,373 35,605 (62,300 ) (391 ) Commercial mortgage-backed securities guaranteed by U.S. government agencies 2,858,885 2,834,961 1,963 (25,887 ) — Other debt securities 25,500 25,481 50 (69 ) — Perpetual preferred stock 12,562 15,767 3,205 — — Equity securities and mutual funds 14,487 14,916 515 (86 ) — Total available for sale securities $ 8,369,075 $ 8,321,578 $ 41,519 $ (88,625 ) $ (391 ) The amortized cost and fair values of available for sale securities at December 31, 2018 , by contractual maturity, are as shown in the following table (dollars in thousands): Less than One Year One to Five Years Six to Ten Years Over Ten Years Total Weighted Average Maturity 4 U.S. Treasury securities: Amortized cost $ — $ 496 $ — $ — $ 496 1.08 Fair value — 493 — — 493 Nominal yield — % 1.99 % — % — % 1.99 % Municipal and other tax-exempt securities: Amortized cost $ 1,057 $ 1,725 $ — $ — 2,782 1.67 Fair value 1,063 1,801 — — 2,864 Nominal yield¹ 6.69 % 6.45 % — % — % 6.54 % Commercial mortgage-backed securities: Amortized cost $ 77,558 $ 1,107,567 $ 1,497,468 $ 303,704 2,986,297 6.90 Fair value 76,902 1,088,991 1,486,939 301,057 2,953,889 Nominal yield 1.66 % 2.06 % 2.44 % 2.54 % 2.29 % Other debt securities: Amortized cost $ — $ — $ — $ 35,545 35,545 13.61 Fair value — — — 35,430 35,430 Nominal yield — % — % — % 1.94 % 5 1.94 % Total fixed maturity securities: Amortized cost $ 78,615 $ 1,109,788 $ 1,497,468 $ 339,249 $ 3,025,120 6.98 Fair value 77,965 1,091,285 1,486,939 336,487 2,992,676 Nominal yield 1.73 % 2.07 % 2.44 % 2.48 % 2.29 % Residential mortgage-backed securities: Amortized cost $ 5,927,271 2 Fair value 5,864,444 Nominal yield 3 2.41 % Total available-for-sale securities: Amortized cost $ 8,952,391 Fair value 8,857,120 Nominal yield 2.37 % 1 Calculated on a taxable equivalent basis using a 25 percent effective tax rate. 2 The average expected lives of mortgage-backed securities were 4.1 years based upon current prepayment assumptions. 3 The nominal yield on mortgage-backed securities is based upon prepayment assumptions at the purchase date. Actual yields earned may differ significantly based upon actual prepayments. See Quarterly Financial Summary –– Unaudited following for current yields on available for sale securities portfolio. 4 Expected maturities may differ from contractual maturities, because borrowers may have the right to call or prepay obligations with or without penalty. 5 Nominal yield on other debt securities with contractual maturity dates over ten years are based on variable rates which generally are reset within 35 days . Sales of available for sale securities resulted in gains and losses as follows (in thousands): Year Ended December 31, 2018 2017 2016 Proceeds $ 745,643 $ 1,309,215 $ 899,381 Gross realized gains 7,117 10,223 11,696 Gross realized losses (9,918 ) (5,795 ) (21 ) Related federal and state income tax expense (713 ) 1,722 4,542 The fair value of debt securities pledged as collateral for repurchase agreements, public trust funds on deposit and for other purposes, as required by law was $9.1 billion at December 31, 2018 and $7.3 billion at December 31, 2017 . The secured parties do not have the right to sell or re-pledge these securities. Temporarily Impaired Securities as of December 31, 2018 (In thousands) Number of Securities Less Than 12 Months 12 Months or Longer Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Investment: Municipal and other tax-exempt securities 72 $ 18,255 $ 69 $ 66,141 $ 523 $ 84,396 $ 592 U.S. government agency residential mortgage-backed securities – Other 2 — — 5,633 135 5,633 135 Other debt securities 72 13,372 64 23,028 1,506 36,400 1,570 Total investment securities 146 $ 31,627 $ 133 $ 94,802 $ 2,164 $ 126,429 $ 2,297 Number of Securities Less Than 12 Months 12 Months or Longer Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Available for sale: U.S. Treasury securities 1 $ — $ — $ 493 $ 3 $ 493 $ 3 Municipal and other tax-exempt securities — — — — — — — Residential mortgage-backed securities: U.S. government agencies: FNMA 162 161,089 542 2,135,377 57,466 2,296,466 58,008 FHLMC 85 71,205 328 1,129,730 28,481 1,200,935 28,809 GNMA 42 278,530 288 376,263 10,659 654,793 10,947 Total U.S. agencies 289 510,824 1,158 3,641,370 96,606 4,152,194 97,764 Private issue 1 — — — — — — — Total residential mortgage-backed securities 289 510,824 1,158 3,641,370 96,606 4,152,194 97,764 Commercial mortgage-backed securities guaranteed by U.S. government agencies 197 179,258 394 1,969,504 39,969 2,148,762 40,363 Other debt securities 3 9,982 63 20,436 64 30,418 127 Total available for sale securities 490 $ 700,064 $ 1,615 $ 5,631,803 $ 136,642 $ 6,331,867 $ 138,257 1 Includes securities for which an unrealized loss remains in AOCI after an other-than-temporary credit loss has been recognized in income. Temporarily Impaired Securities as of December 31, 2017 (In thousands) Number of Securities Less Than 12 Months 12 Months or Longer Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Investment: Municipal and other tax- exempt securities 100 $ 145,960 $ 643 $ 5,833 $ 161 $ 151,793 $ 804 U.S. government agency residential mortgage-backed securities – Other 1 — — 3,356 95 3,356 95 Other debt securities 49 20,091 1,238 3,076 129 23,167 1,367 Total investment securities 150 $ 166,051 $ 1,881 $ 12,265 $ 385 $ 178,316 $ 2,266 Number of Securities Less Than 12 Months 12 Months or Longer Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Available for sale: U.S. Treasury securities — $ — $ — $ — $ — $ — $ — Municipal and other tax-exempt securities 19 12,765 18 4,802 265 17,567 283 Residential mortgage-backed securities: U. S. government agencies: FNMA 113 1,203,041 9,618 824,029 25,919 2,027,070 35,537 FHLMC 69 863,778 7,297 385,816 10,813 1,249,594 18,110 GNMA 27 201,887 1,452 248,742 7,201 450,629 8,653 Total U.S. agencies 209 2,268,706 18,367 1,458,587 43,933 3,727,293 62,300 Private issue 1 8 5,898 391 — — 5,898 391 Total residential mortgage-backed securities 217 2,274,604 18,758 1,458,587 43,933 3,733,191 62,691 Commercial mortgage-backed securities guaranteed by U.S. government agencies 185 1,465,703 11,824 652,296 14,063 2,117,999 25,887 Other debt securities 2 19,959 41 472 28 20,431 69 Perpetual preferred stock — — — — — — — Equity securities and mutual funds 111 911 7 2,203 79 3,114 86 Total available for sale securities 534 $ 3,773,942 $ 30,648 $ 2,118,360 $ 58,368 $ 5,892,302 $ 89,016 1 Includes securities for which an unrealized loss remains in AOCI after an other-than-temporary credit loss has been recognized in income. Based on evaluations of impaired securities as of December 31, 2018 , the Company does not intend to sell any impaired available for sale securities before fair value recovers to the current amortized cost and it is more-likely-than-not that the Company will not be required to sell impaired securities before fair value recovers, which may be maturity. No other-than-temporary impairment losses were recorded in earnings during 2018 and none were recorded in 2017 . Cumulative other-than-temporary impairment on available for sale securities was $45 million at December 31, 2018 and $55 million at December 31, 2017 . The decrease compared to the prior year was due to sales during 2018. Fair Value Option Securities Fair value option securities represent securities which the Company has elected to carry at fair value and are separately identified on the Consolidated Balance Sheets with changes in the fair value recognized in earnings as they occur. Certain residential mortgage-backed securities issued by U.S. government agencies and derivative contracts are held as an economic hedge of the mortgage servicing rights. The fair value and net unrealized gain (loss) included in Fair value option securities is as follows (in thousands): December 31, 2018 December 31, 2017 Fair Value Net Unrealized Gain (Loss) Fair Value Net Unrealized Gain (Loss) U.S. government agency residential mortgage-backed securities $ 283,235 $ 2,766 $ 755,054 $ (1,877 )

Derivatives

Derivatives	12 Months Ended
	Dec. 31, 2018
Derivative Instrument Detail [Abstract]
Derivatives [Text Block]	Derivatives The following table summarizes the fair values of derivative contracts recorded as “derivative contracts” assets and liabilities in the balance sheet at December 31, 2018 (in thousands): Assets Notional 1 Gross Fair Value Netting Adjustments Net Fair Value Before Cash Collateral Cash Collateral Fair Value Net of Cash Collateral Customer risk management programs: Interest rate contracts To-be-announced residential mortgage-backed securities $ 10,671,151 $ 92,231 $ (26,787 ) $ 65,444 $ — $ 65,444 Interest rate swaps 1,924,131 36,112 (6,688 ) 29,424 (7,934 ) 21,490 Energy contracts 1,472,209 206,418 (60,983 ) 145,435 (106,752 ) 38,683 Agricultural contracts 21,210 842 (201 ) 641 — 641 Foreign exchange contracts 184,990 183,759 — 183,759 — 183,759 Equity option contracts 89,085 2,021 — 2,021 (648 ) 1,373 Total customer risk management programs 14,362,776 521,383 (94,659 ) 426,724 (115,334 ) 311,390 Internal risk management programs 15,909,988 50,410 (40,871 ) 9,539 — 9,539 Total derivative contracts $ 30,272,764 $ 571,793 $ (135,530 ) $ 436,263 $ (115,334 ) $ 320,929 Liabilities Notional¹ Gross Fair Value Netting Adjustments Net Fair Value Before Cash Collateral Cash Collateral Fair Value Net of Cash Collateral Customer risk management programs: Interest rate contracts To-be-announced residential mortgage-backed securities $ 10,558,151 $ 90,388 $ (26,787 ) $ 63,601 $ (63,596 ) $ 5 Interest rate swaps 1,924,131 36,288 (6,688 ) 29,600 (4,110 ) 25,490 Energy contracts 1,434,247 202,494 (60,983 ) 141,511 (1,490 ) 140,021 Agricultural contracts 21,214 812 (201 ) 611 — 611 Foreign exchange contracts 177,423 175,922 — 175,922 — 175,922 Equity option contracts 89,085 2,021 — 2,021 — 2,021 Total customer risk management programs 14,204,251 507,925 (94,659 ) 413,266 (69,196 ) 344,070 Internal risk management programs 19,634,642 66,422 (40,871 ) 25,551 (7,315 ) 18,236 Total derivative contracts $ 33,838,893 $ 574,347 $ (135,530 ) $ 438,817 $ (76,511 ) $ 362,306 1 Notional amounts for commodity contracts are converted into dollar-equivalent amounts based on dollar prices at the inception of the contract. The following table summarizes the fair values of derivative contracts recorded as “derivative contracts” assets and liabilities in the balance sheet at December 31, 2017 (in thousands): Assets Notional 1 Gross Fair Value Netting Adjustments Net Fair Value Before Cash Collateral Cash Collateral Fair Value Net of Cash Collateral Customer risk management programs: Interest rate contracts To-be-announced residential mortgage-backed securities $ 12,347,542 $ 23,606 $ (18,096 ) $ 5,510 $ — $ 5,510 Interest rate swaps 1,478,944 28,278 — 28,278 (4,964 ) 23,314 Energy contracts 1,190,067 103,044 (47,873 ) 55,171 (196 ) 54,975 Agricultural contracts 53,238 1,576 (960 ) 616 — 616 Foreign exchange contracts 132,397 129,551 — 129,551 (448 ) 129,103 Equity option contracts 99,633 5,503 — 5,503 (920 ) 4,583 Total customer risk management programs 15,301,821 291,558 (66,929 ) 224,629 (6,528 ) 218,101 Internal risk management programs 4,736,701 9,494 (7,093 ) 2,401 — 2,401 Total derivative contracts $ 20,038,522 $ 301,052 $ (74,022 ) $ 227,030 $ (6,528 ) $ 220,502 Liabilities Notional¹ Gross Fair Value Netting Adjustments Net Fair Value Before Cash Collateral Cash Collateral Fair Value Net of Cash Collateral Customer risk management programs: Interest rate contracts To-be-announced residential mortgage-backed securities $ 11,537,742 $ 20,367 $ (18,096 ) $ 2,271 $ (704 ) $ 1,567 Interest rate swaps 1,478,944 28,298 — 28,298 (12,896 ) 15,402 Energy contracts 1,166,924 101,603 (47,873 ) 53,730 (42,767 ) 10,963 Agricultural contracts 48,552 1,551 (960 ) 591 — 591 Foreign exchange contracts 126,251 123,321 — 123,321 (53 ) 123,268 Equity option contracts 99,633 5,503 — 5,503 — 5,503 Total customer risk management programs 14,458,046 280,643 (66,929 ) 213,714 (56,420 ) 157,294 Internal risk management programs 5,728,421 21,762 (7,093 ) 14,669 — 14,669 Total derivative contracts $ 20,186,467 $ 302,405 $ (74,022 ) $ 228,383 $ (56,420 ) $ 171,963 1 Notional amounts for commodity contracts are converted into dollar-equivalent amounts based on dollar prices at the inception of the contract. The following summarizes the pre-tax net gains (losses) on derivative instruments and where they are recorded in the Consolidated Statements of Earnings (in thousands): Year Ended December 31, 2018 2017 2016 Brokerage and Trading Revenue Gain (Loss) on Derivatives, Net Brokerage and Trading Revenue Gain (Loss) on Derivatives, Net Brokerage and Trading Revenue Gain (Loss) on Derivatives, Net Customer risk management programs: Interest rate contracts To-be-announced residential mortgage-backed securities $ 27,190 $ — $ 34,532 $ — $ 38,523 $ — Interest rate swaps 2,614 — 2,647 — 2,589 — Energy contracts 8,443 — 5,536 — 5,027 — Agricultural contracts 53 — 79 — 111 — Foreign exchange contracts 535 — 1,352 — 945 — Equity option contracts — — — — — — Total customer risk management programs 38,835 — 44,146 — 47,195 — Internal risk management programs (13,643 ) (422 ) 4,615 779 (4,592 ) (15,685 ) Total derivative contracts $ 25,192 $ (422 ) $ 48,761 $ 779 $ 42,603 $ (15,685 ) As discussed in Note 7 , certain derivative contracts not designated as hedging instruments related to mortgage loan commitments and forward sales contracts are included in Residential mortgage loans held for sale on the Consolidated Balance Sheets. See Note 7 for additional discussion of notional, fair value and impact on earnings of these contracts.

Loans and Allowances for Credit

Loans and Allowances for Credit Losses	12 Months Ended
	Dec. 31, 2018
Loans Receivable, Net [Abstract]
Loans and Allowances for Credit Losses [Text Block]	Loans and Allowances for Credit Losses The portfolio segments of the loan portfolio are as follows (in thousands): December 31, 2018 December 31, 2017 Fixed Rate Variable Rate Non-accrual Total Fixed Rate Variable Rate Non-accrual Total Commercial $ 2,251,188 $ 11,285,049 $ 99,841 $ 13,636,078 $ 2,217,432 $ 8,379,240 $ 137,303 $ 10,733,975 Commercial real estate 1,477,274 3,265,918 21,621 4,764,813 548,692 2,928,440 2,855 3,479,987 Residential mortgage 1,830,224 358,254 41,555 2,230,033 1,608,655 317,584 47,447 1,973,686 Personal 190,687 834,889 230 1,025,806 154,517 810,990 269 965,776 Total $ 5,749,373 $ 15,744,110 $ 163,247 $ 21,656,730 $ 4,529,296 $ 12,436,254 $ 187,874 $ 17,153,424 Accruing loans past due (90 days) 1 $ 1,338 $ 633 Foregone interest on nonaccrual loans $ 15,502 $ 16,496 1 Excludes residential mortgage loans guaranteed by agencies of the U.S. government. At December 31, 2018 , loans to businesses and individuals with collateral primarily located in Texas totaled $6.4 billion or 30% of the total loan portfolio. Loans to businesses and individuals with collateral primarily located in Oklahoma totaled $3.5 billion or 16% of our total loan portfolio. Loans to businesses and individuals with collateral primarily located in Colorado totaled $3.3 billion or 15% of our total loan portfolio. Loans for which the collateral location is not relevant, such as unsecured loans and reserve-based energy loans, are distributed by the borrower’s primary operating location. These geographic concentrations subject the loan portfolio to the general economic conditions within these areas. At December 31, 2017 , loans to businesses and individuals with collateral primarily located in Texas totaled $5.8 billion or 34% of the loan portfolio and loans to businesses and individuals with collateral primarily located in Oklahoma totaled $3.3 billion or 19% of the loan portfolio. Commercial Commercial loans represent loans for working capital, facilities acquisition or expansion, purchases of equipment and other needs of commercial customers primarily located within our geographical footprint. Commercial loans are underwritten individually and represent on-going relationships based on a thorough knowledge of the customer, the customer’s industry and market. While commercial loans are generally secured by the customer’s assets including real property, inventory, accounts receivable, operating equipment, interest in mineral rights and other property and may also include personal guarantees of the owners and related parties, the primary source of repayment of the loans is the on-going cash flow from operations of the customer’s business. Inherent lending risk is centrally monitored on a continuous basis from underwriting throughout the life of the loan for compliance with commercial lending policies. At December 31, 2018 , commercial loans with collateral primarily located in Texas totaled $4.1 billion or 30% of the commercial loan portfolio segment. Commercial loans with collateral primarily located in Oklahoma totaled $2.2 billion or 16% of the commercial loan portfolio segment. Commercial loans with collateral primarily located in Colorado totaled $2.0 billion or 15% of the commercial loan portfolio segment. The commercial loan portfolio segment is further divided into loan classes. The services loan class totaled $3.3 billion or 15% of total loans. Approximately $2.3 billion of loans in the services class consisted of loans with individual balances of less than $10 million . Businesses included in the services class include commercial services, Native American tribal governments, financial services, entertainment and recreation and education. The energy loan class totaled $3.6 billion or 17% of total loans, including $2.9 billion of outstanding loans to energy producers. Approximately 57% of committed production loans were secured by properties primarily producing oil and 43% are secured by properties producing natural gas. The healthcare loan class totaled $2.7 billion or 13% of total loans. The healthcare loan class consists primarily of loans for the development and operation of senior housing and care facilities, including independent living, assisted living and skilled nursing. Healthcare also includes loans to hospitals and other medical service providers. At December 31, 2017 , commercial loans with collateral primarily located in Texas totaled $3.6 billion or 34% of the commercial loan portfolio segment and commercial loans with collateral primarily located in Oklahoma totaled $2.0 billion or 18% of the commercial loan portfolio segment. The energy loan class totaled $2.9 billion or 17% of total loans, including $2.5 billion of outstanding loans to energy producers. At December 31, 2017 , approximately 57% of committed production loans were secured by properties primarily producing oil and 43% were secured by properties producing natural gas. The services loan class totaled $2.5 billion or 15% of total loans. Approximately $1.5 billion of loans in the services category consisted of loans with individual balances of less than $10 million . The healthcare loan class totaled $2.2 billion or 13% of total loans. Commercial Real Estate Commercial real estate loans are for the construction of buildings or other improvements to real estate and property held by borrowers for investment purposes primarily within our geographical footprint. We require collateral values in excess of the loan amounts, demonstrated cash flows in excess of expected debt service requirements, equity investment in the project and a portion of the project already sold, leased or permanent financing already secured. The expected cash flows from all significant new or renewed income producing property commitments are stress tested to reflect the risks in varying interest rates, vacancy rates and rental rates. As with commercial loans, inherent lending risks are centrally monitored on a continuous basis from underwriting throughout the life of the loan for compliance with applicable lending policies. At December 31, 2018 , 26% of commercial real estate loans are secured by properties primarily located in the Dallas and Houston areas of Texas. An additional 16% of commercial real estate loans are secured by properties located primarily in the Denver, Colorado metropolitan area. At December 31, 2017 , 35% of commercial real estate loans were secured by properties in Texas, 12% of commercial real estate loans were secured by properties in Oklahoma. Residential Mortgage and Personal Residential mortgage loans provide funds for our customers to purchase or refinance their primary residence or to borrow against the equity in their home. Residential mortgage loans are secured by a first or second mortgage on the customer’s primary residence. Personal loans consist primarily of loans secured by the cash surrender value of insurance policies and marketable securities. It also includes direct loans secured by and for the purchase of automobiles, recreational and marine equipment as well as other unsecured loans. Residential mortgage and personal loans are made in accordance with underwriting policies. Credit scoring is assessed based on significant credit characteristics including credit history, residential and employment stability. Residential mortgage loans retained in the Company’s portfolio are primarily composed of various mortgage programs to support customer relationships including jumbo mortgage loans, non-builder construction loans and special loan programs for high net worth individuals and certain professionals. Jumbo loans may be fixed or variable rate and are fully amortizing. Jumbo loans generally conform to government sponsored entity standards, except that the loan size exceeds maximums required under these standards. These loans generally require a minimum FICO score of 720 and a maximum debt-to-income ratio (“DTI”) of 38% . Loan-to-value (“LTV”) ratios are tiered from 60% to 100% , depending on the market. Special mortgage programs include fixed and variable fully amortizing loans tailored to the needs of certain healthcare professionals. Variable rate loans are fully indexed at origination and may have fixed rates for 3 years to 10 years , then adjust annually thereafter. At December 31, 2018 and 2017 , residential mortgage loans included $191 million and $198 million , respectively, of loans guaranteed by U.S. government agencies previously sold into GNMA mortgage pools. These loans either have been repurchased or are eligible to be repurchased by the Company when certain defined delinquency criteria are met. Although payments on these loans generally are past due more than 90 days, interest continues to accrue based on the government guarantee. Home equity loans totaled $719 million at December 31, 2018 and $733 million at December 31, 2017 . At December 31, 2018 , 59% of the home equity loan portfolio was comprised of first lien loans and 41% of the home equity portfolio was comprised of junior lien loans. Junior lien loans were distributed 40% to amortizing term loans and 60% to revolving lines of credit. At December 31, 2017 , 64% of the home equity portfolio was comprised of first lien loans and 36% of the home equity loan portfolio was comprised of junior lien loans. Junior lien loans were distributed 46% to amortizing term loans and 54% to revolving lines of credit. Home equity loans generally require a minimum FICO score of 700 and a maximum DTI of 40%. The maximum loan amount available for our home equity loan products is generally $400 thousand . Revolving loans have a 5 year revolving period followed by 15 year term of amortizing repayments. Interest-only home equity loans may not be extended for any additional revolving time. All other home equity loans may be extended at management's discretion for an additional 5 year revolving term subject to an update of certain credit information. At December 31, 2018 , 26% of residential mortgage loans are secured by properties located in Oklahoma, 28% of residential mortgage loans are secured by properties located in Texas and 19% of residential mortgage are secured by properties located in Colorado. At December 31, 2017 , 31% of residential mortgage loans were secured by properties in Oklahoma, 30% of residential mortgage were secured by properties in Texas, 11% of residential mortgage loans are secured by properties in Colorado and 9% of residential mortgage loans are secured by properties in New Mexico. Purchase Credit Impaired Loans In conjunction with the acquisition of CoBiz Financial on October, 1, 2018, the Company acquired certain loans for which there was evidence of deterioration of credit quality since origination and for which it was probable that all contractually required payments would not be collected ("PCI loans"). At December 31, 2018, the carrying amount of PCI loans was $31 million and the unpaid balance was $47 million . The accretable yield related to these PCI loans was $843 thousand . Credit Commitments Commitments to extend credit are agreements to lend to a customer as long as there is no violation of conditions established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. At December 31, 2018 , outstanding commitments totaled $12 billion . Because some commitments are expected to expire before being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. BOK Financial uses the same credit policies in making commitments as it does loans. The amount of collateral obtained, if deemed necessary, is based upon management’s credit evaluation of the borrower. Standby letters of credit are conditional commitments issued to guarantee the performance of a customer to a third party. Because the credit risk involved in issuing standby letters of credit is essentially the same as that involved in extending loan commitments, BOK Financial uses the same credit policies in evaluating the creditworthiness of the customer. Additionally, BOK Financial uses the same evaluation process in obtaining collateral on standby letters of credit as it does for loan commitments. The term of these standby letters of credit is defined in each commitment and typically corresponds with the underlying loan commitment. At December 31, 2018 , outstanding standby letters of credit totaled $582 million . Commercial letters of credit are used to facilitate customer trade transactions with the drafts being drawn when the underlying transaction is consummated. At December 31, 2018 , outstanding commercial letters of credit totaled $1.9 million . Allowances for Credit Losses BOK Financial maintains an allowance for loan losses and an accrual for off-balance sheet credit risk. The accrual for off-balance sheet credit risk is maintained at a level that is appropriate to cover estimated losses associated with credit instruments that are not currently recognized as assets such as loan commitments, standby letters of credit or guarantees. As discussed in greater detail in Note 7 , the Company also has separate accruals related to off-balance sheet credit risk related to residential mortgage loans previously sold with full or partial recourse and for residential mortgage loans sold to government sponsored agencies under standard representations and warranties. The allowance for loan losses consists of specific allowances attributed to impaired loans that have not yet been charged down to amounts we expect to recover, general allowances for unimpaired loans based on estimated loss rates by loan class and nonspecific allowances based on general economic conditions, concentration in loans with large balances and other relevant factors. The activity in the allowance for loan losses and the accrual for off-balance sheet credit risk related to loan commitments and standby letters of credit for the year ended December 31, 2018 is summarized as follows (in thousands): Commercial Commercial Real Estate Residential Mortgage Personal Nonspecific Allowance Total Allowance for loan losses: Beginning balance $ 124,269 $ 56,621 $ 18,451 $ 9,124 $ 22,217 $ 230,682 Provision for loan losses 12,521 (147 ) (1,156 ) 3,175 (4,449 ) 9,944 Loans charged off (37,880 ) — (378 ) (5,325 ) — (43,583 ) Recoveries 3,316 3,552 1,047 2,499 — 10,414 Ending balance $ 102,226 $ 60,026 $ 17,964 $ 9,473 $ 17,768 $ 207,457 Accrual for off-balance sheet credit risk: Beginning balance $ 3,644 $ 45 $ 43 $ 2 $ — $ 3,734 Provision for off-balance sheet credit risk (1,989 ) 7 9 29 — (1,944 ) Ending balance $ 1,655 $ 52 $ 52 $ 31 $ — $ 1,790 Total provision for credit losses $ 10,532 $ (140 ) $ (1,147 ) $ 3,204 $ (4,449 ) $ 8,000 The activity in the allowance for loan losses and the accrual for off-balance sheet credit risk related to loan commitments and standby letters of credit for the year ended December 31, 2017 is summarized as follows (in thousands): Commercial Commercial Real Estate Residential Mortgage Personal Nonspecific Allowance Total Allowance for loan losses: Beginning balance $ 140,213 $ 50,749 $ 18,224 $ 8,773 $ 28,200 $ 246,159 Provision for loan losses (595 ) 4,008 116 2,964 (5,983 ) 510 Loans charged off (19,810 ) (76 ) (649 ) (5,064 ) — (25,599 ) Recoveries 4,461 1,940 760 2,451 — 9,612 Ending balance $ 124,269 $ 56,621 $ 18,451 $ 9,124 $ 22,217 $ 230,682 Accrual for off-balance sheet credit risk: Beginning balance $ 11,063 $ 123 $ 50 $ 8 $ — $ 11,244 Provision for off-balance sheet credit risk (7,419 ) (78 ) (7 ) (6 ) — (7,510 ) Ending balance $ 3,644 $ 45 $ 43 $ 2 $ — $ 3,734 Total provision for credit losses $ (8,014 ) $ 3,930 $ 109 $ 2,958 $ (5,983 ) $ (7,000 ) The activity in the allowance for loan losses and the accrual for off-balance sheet credit risk related to loan commitments and standby letters of credit for the year ended December 31, 2016 is summarized as follows (in thousands): Commercial Commercial Real Estate Residential Mortgage Personal Nonspecific Allowance Total Allowance for loan losses: Beginning balance $ 130,334 $ 41,391 $ 19,509 $ 4,164 $ 30,126 $ 225,524 Provision for loan losses 43,980 8,075 (1,972 ) 7,310 (1,926 ) 55,467 Loans charged off (35,828 ) — (1,312 ) (5,448 ) — (42,588 ) Recoveries 1,727 1,283 1,999 2,747 — 7,756 Ending balance $ 140,213 $ 50,749 $ 18,224 $ 8,773 $ 28,200 $ 246,159 Accrual for off-balance sheet credit risk: Beginning balance $ 1,506 $ 153 $ 30 $ 22 $ — $ 1,711 Provision for off-balance sheet credit risk 9,557 (30 ) 20 (14 ) — 9,533 Ending balance $ 11,063 $ 123 $ 50 $ 8 $ — $ 11,244 Total provision for credit losses $ 53,537 $ 8,045 $ (1,952 ) $ 7,296 $ (1,926 ) $ 65,000 The allowance for loan losses and recorded investment of the related loans by portfolio segment for each impairment measurement method at December 31, 2018 is as follows (in thousands): Collectively Measured for Impairment Individually Measured for Impairment Total Recorded Investment Related Allowance Recorded Investment Related Allowance Recorded Investment Related Allowance Commercial $ 13,536,237 $ 93,494 $ 99,841 $ 8,732 $ 13,636,078 $ 102,226 Commercial real estate 4,743,192 60,026 21,621 — 4,764,813 60,026 Residential mortgage 2,188,478 17,964 41,555 — 2,230,033 17,964 Personal 1,025,576 9,473 230 — 1,025,806 9,473 Total 21,493,483 180,957 163,247 8,732 21,656,730 189,689 Nonspecific allowance — — — — — 17,768 Total $ 21,493,483 $ 180,957 $ 163,247 $ 8,732 $ 21,656,730 $ 207,457 The allowance for loan losses and recorded investment of the related loans by portfolio segment for each impairment measurement method at December 31, 2017 is as follows (in thousands): Collectively Measured for Impairment Individually Measured for Impairment Total Recorded Investment Related Allowance Recorded Investment Related Allowance Recorded Investment Related Allowance Commercial $ 10,596,672 $ 115,438 $ 137,303 $ 8,831 $ 10,733,975 $ 124,269 Commercial real estate 3,477,132 56,621 2,855 — 3,479,987 56,621 Residential mortgage 1,926,239 18,451 47,447 — 1,973,686 18,451 Personal 965,507 9,124 269 — 965,776 9,124 Total 16,965,550 199,634 187,874 8,831 17,153,424 208,465 Nonspecific allowance — — — — — 22,217 Total $ 16,965,550 $ 199,634 $ 187,874 $ 8,831 $ 17,153,424 $ 230,682 Credit Quality Indicators The Company utilizes loan class and risk grading as primary credit quality indicators. Substantially all commercial and commercial real estate loans and certain residential mortgage and personal loans are risk graded based on a quarterly evaluation of the borrowers’ ability to repay the loans. Certain commercial loans and most residential mortgage and personal loans are small, homogeneous pools that are not risk graded. The allowance for loan losses and recorded investment of the related loans by portfolio segment for risk graded and non-risk graded loans at December 31, 2018 is as follows (in thousands): Internally Risk Graded Non-Graded Total Recorded Investment Related Allowance Recorded Investment Related Allowance Recorded Investment Related Allowance Commercial $ 13,586,654 $ 101,303 $ 49,424 $ 923 $ 13,636,078 $ 102,226 Commercial real estate 4,764,813 60,026 — — 4,764,813 60,026 Residential mortgage 505,046 3,310 1,724,987 14,654 2,230,033 17,964 Personal 948,890 6,633 76,916 2,840 1,025,806 9,473 Total 19,805,403 171,272 1,851,327 18,417 21,656,730 189,689 Nonspecific allowance — — — — — 17,768 Total $ 19,805,403 $ 171,272 $ 1,851,327 $ 18,417 $ 21,656,730 $ 207,457 The allowance for loan losses and recorded investment of the related loans by portfolio segment for risk graded and non-risk graded loans at December 31, 2017 is as follows (in thousands): Internally Risk Graded Non-Graded Total Recorded Investment Related Allowance Recorded Investment Related Allowance Recorded Investment Related Allowance Commercial $ 10,706,035 $ 123,383 $ 27,940 $ 886 $ 10,733,975 $ 124,269 Commercial real estate 3,479,987 56,621 — — 3,479,987 56,621 Residential mortgage 234,477 2,947 1,739,209 15,504 1,973,686 18,451 Personal 877,390 6,461 88,386 2,663 965,776 9,124 Total 15,297,889 189,412 1,855,535 19,053 17,153,424 208,465 Nonspecific allowance — — — — — 22,217 Total $ 15,297,889 $ 189,412 $ 1,855,535 $ 19,053 $ 17,153,424 $ 230,682 Loans are considered to be performing if they are in compliance with the original terms of the agreement which is consistent with the regulatory guideline of “pass.” Performing also includes loans considered to be “other loans especially mentioned” by regulatory guidelines and all residential mortgage loans guaranteed by agencies of the U.S. government that continue to accrue interest based on criteria of the guarantor's programs. Other loans especially mentioned are currently performing in compliance with the original terms of the agreement but may have a potential weakness that deserves management's close attention, consistent with regulatory guidelines. The risk grading process identified certain loans that have a well-defined weakness (e.g. inadequate debt service coverage or liquidity or marginal capitalization; repayment may depend on collateral or other risk mitigation) that may jeopardize liquidation of the debt and represent a greater risk due to deterioration in the financial condition of the borrower. This is consistent with the regulatory guideline for “substandard.” Because the borrowers are still performing in accordance with the original terms of the loan agreements, these loans were not placed in nonaccruing status. Nonaccruing loans represent loans for which full collection of principal and interest in accordance with the original terms of the loan agreements is uncertain. This is substantially the same criteria used to determine whether a loan is impaired and includes certain loans considered “substandard” and all loans considered “doubtful” by regulatory guidelines. The following table summarizes the Company’s loan portfolio at December 31, 2018 by the risk grade categories (in thousands): Internally Risk Graded Non-Graded Performing Pass Other Loans Especially Mentioned Accruing Substandard Nonaccrual Performing Nonaccrual Total Commercial: Energy $ 3,414,039 $ 42,176 $ 86,624 $ 47,494 $ — $ — $ 3,590,333 Services 3,161,157 49,761 32,661 8,567 — — 3,252,146 Wholesale/retail 1,593,902 18,809 7,131 1,316 — — 1,621,158 Manufacturing 668,438 30,934 22,230 8,919 — — 730,521 Healthcare 2,664,381 14,920 37,698 16,538 — — 2,733,537 Public finance 876,336 — — — — — 876,336 Other commercial and industrial 756,815 1,266 7,588 16,954 49,371 53 832,047 Total commercial 13,135,068 157,866 193,932 99,788 49,371 53 13,636,078 Commercial real estate: Residential construction and land development 148,234 — — 350 — — 148,584 Retail 885,588 11,926 1,289 20,279 — — 919,082 Office 1,059,334 10,532 3,054 — — — 1,072,920 Multifamily 1,287,471 281 12 301 — — 1,288,065 Industrial 776,898 — 1,208 — — — 778,106 Other commercial real estate 555,301 1,188 876 691 — — 558,056 Total commercial real estate 4,712,826 23,927 6,439 21,621 — — 4,764,813 Residential mortgage: Permanent mortgage 467,233 52 9,730 1,991 819,199 21,960 1,320,165 Permanent mortgages guaranteed by U.S. government agencies — — — — 183,734 7,132 190,866 Home equity 25,743 — 296 — 682,491 10,472 719,002 Total residential mortgage 492,976 52 10,026 1,991 1,685,424 39,564 2,230,033 Personal 944,256 115 4,443 76 76,762 154 1,025,806 Total $ 19,285,126 $ 181,960 $ 214,840 $ 123,476 $ 1,811,557 $ 39,771 $ 21,656,730 The following table summarizes the Company’s loan portfolio at December 31, 2017 by the risk grade categories (in thousands): Internally Risk Graded Non-Graded Performing Pass Other Loans Especially Mentioned Accruing Substandard Nonaccrual Performing Nonaccrual Total Commercial: Energy $ 2,632,986 $ 60,288 $ 144,598 92,284 $ — $ — $ 2,930,156 Services 2,478,945 13,927 26,533 2,620 — — 2,522,025 Wholesale/retail 1,443,917 19,263 5,502 2,574 — — 1,471,256 Manufacturing 472,869 6,653 11,290 5,962 — — 496,774 Healthcare 2,182,231 3,186 43,305 14,765 — — 2,243,487 Public finance 541,775 — — — — — 541,775 Other commercial and industrial 473,366 7 8,161 19,028 27,870 70 528,502 Total commercial 10,226,089 103,324 239,389 137,233 27,870 70 10,733,975 Commercial real estate: Residential construction and land development 113,190 1,828 395 1,832 — — 117,245 Retail 686,915 4,243 98 276 — — 691,532 Office 824,408 7,087 — 275 — — 831,770 Multifamily 979,969 — 48 — — — 980,017 Industrial 573,014 — — — — — 573,014 Other commercial real estate 285,506 145 286 472 — — 286,409 Total commercial real estate 3,463,002 13,303 827 2,855 — — 3,479,987 Residential mortgage: Permanent mortgage 232,492 — 822 1,163 784,928 24,030 1,043,435 Permanent mortgages guaranteed by U.S. government agencies — — — — 188,327 9,179 197,506 Home equity — — — — 719,670 13,075 732,745 Total residential mortgage 232,492 — 822 1,163 1,692,925 46,284 1,973,686 Personal 875,696 1,548 63 83 88,200 186 965,776 Total $ 14,797,279 $ 118,175 $ 241,101 141,334 $ 1,808,995 $ 46,540 $ 17,153,424 Impaired Loans Loans are considered to be impaired when it is probable that the Company will not be able to collect all amounts due according to the contractual terms of the loan agreement. This includes all nonaccruing loans, all loans modified in a troubled debt restructuring and all loans repurchased from GNMA pools. A summary of impaired loans follows (in thousands): As of December 31, 2018 Year Ended Recorded Investment December 31, 2018 Unpaid Principal Balance Total With No With Allowance Related Allowance Average Recorded Interest Income Recognized Commercial: Energy $ 79,675 $ 47,494 $ 18,639 $ 28,855 $ 5,362 $ 69,645 $ — Services 13,437 8,567 8,489 78 74 4,509 — Wholesale/retail 1,722 1,316 1,015 301 101 1,784 — Manufacturing 10,055 8,919 8,673 246 246 7,249 — Healthcare 24,319 16,538 10,563 5,975 2,949 14,297 — Public finance — — — — — — — Other commercial and industrial 26,955 17,007 17,007 — — 17,976 — Total commercial 156,163 99,841 64,386 35,455 8,732 115,460 — Commercial real estate: Residential construction and land development 1,306 350 350 — — 1,091 — Retail 27,680 20,279 20,279 — — 10,278 — Office — — — — — 137 — Multifamily 301 301 301 — — 151 — Industrial — — — — — — — Other commercial real estate 851 691 691 — — 581 — Total commercial real estate 30,138 21,621 21,621 — — 12,238 — Residential mortgage: Permanent mortgage 28,716 23,951 23,951 — — 24,572 1,233 Permanent mortgage guaranteed by U.S. government agencies 1 196,296 190,866 190,866 — — 180,813 7,172 Home equity 12,196 10,472 10,472 — — 11,774 — Total residential mortgage 237,208 225,289 225,289 — — 217,159 8,405 Personal 278 230 230 — — 250 — Total $ 423,787 $ 346,981 $ 311,526 $ 35,455 $ 8,732 $ 345,107 $ 8,405 1 All permanent mortgage loans guaranteed by U.S. government agencies are considered impaired as we do not expect full collection of contractual principal and interest. At December 31, 2018 , $7.1 million of these loans are nonaccruing and $184 million are accruing based on the guarantee by U.S. government agencies. Generally, no interest income is recognized on impaired loans until all principal balances, including amounts charged-off, have been recovered. As of December 31, 2017 Year Ended Recorded Investment December 31, 2017 Unpaid Principal Balance Total With No Allowance With Allowance Related Allowance Average Recorded Investment Interest Income Recognized Commercial: Energy $ 111,011 $ 92,284 $ 40,968 $ 51,316 $ 8,814 $ 112,392 $ — Services 5,324 2,620 2,620 — — 5,396 — Wholesale/retail 9,099 2,574 2,574 — — 6,990 — Manufacturing 6,073 5,962 5,962 — — 5,446 — Healthcare 25,140 14,765 14,765 — — 7,795 — Public finance — — — — — — — Other commercial and industrial 27,957 19,098 19,080 18 17 20,108 — Total commercial 184,604 137,303 85,969 51,334 8,831 158,127 — Commercial real estate: Residential construction and land development 3,285 1,832 1,832 — — 2,633 — Retail 509 276 276 — — 301 — Office 287 275 275 — — 351 — Multifamily — — — — — 19 — Industrial — — — — — 38 — Other commercial real estate 670 472 472 — — 847 — Total commercial real estate 4,751 2,855 2,855 — — 4,189 — Residential mortgage: Permanent mortgage 30,435 25,193 25,193 — — 24,024 1,229 Permanent mortgage guaranteed by U.S. government agencies 1 203,814 197,506 197,506 — — 199,244 7,632 Home equity 14,548 13,075 13,075 — — 12,297 — Total residential mortgage 248,797 235,774 235,774 — — 235,565 8,861 Personal 307 269 269 — — 280 — Total $ 438,459 $ 376,201 $ 324,867 $ 51,334 $ 8,831 $ 398,161 $ 8,861 1 All permanent mortgage loans guaranteed by U.S. government agencies are considered impaired as we do not expect full collection of contractual principal and interest. At December 31, 2017 , $9.2 million of these loans are nonaccruing and $188 million are accruing based on the guarantee by U.S. government agencies. Troubled Debt Restructurings At December 31, 2018 the Company has $166 million in troubled debt restructurings (TDRs), of which $86 million are accruing residential mortgage loans guaranteed by U.S. government agencies. Approximately $71 million of TDRs are performing in accordance with the modified terms. The loans designated as TDRs had $16.1 million in charge offs during the year ended December 31, 2018 . At December 31, 2017 , TDRs totaled $126 million , of which $74 million were accruing residential mortgage loans guaranteed by U.S. government agencies. Approximately $48 million of TDRs were performing. The loans designated as TDRs had $117 thousand in charge offs during the year ended December 31, 2017 . TDRs generally consist of interest rate concessions, payment stream concessions or a combination of concessions to distressed borrowers. During the year ended December 31, 2018 , $75 million of loans were restructured. During the year ended December 31, 2017 , $57 million of loans were restructured. Nonaccrual & Past Due Loans Past due status for all loan classes is based on the actual number of days since the last payment was due according to the contractual terms of the loans. A summary of loans currently performing, loans past due and accruing and nonaccrual loans as of December 31, 2018 is as follows (in thousands): Past Due Current 30 to 59 Days 60 to 89 Days 90 Days or More Nonaccrual Total Commercial: Energy $ 3,542,839 $ — — $ — $ 47,494 $ 3,590,333 Services 3,231,532 6,009 6,038 — 8,567 3,252,146 Wholesale/retail 1,619,290 515 37 — 1,316 1,621,158 Manufacturing 721,204 392 6 — 8,919 730,521 Healthcare 2,716,204 241 — 554 16,538 2,733,537 Public finance 876,336 — — — — 876,336 Other commercial and industrial 814,489 518 25 8 17,007 832,047 Total commercial 13,521,894 7,675 6,106 562 99,841 13,636,078 Commercial real estate: Residential construction and land development 147,705 249 280 — 350 148,584 Retail 884,424 14,379 — — 20,279 919,082 Office 1,072,920 — — — — 1,072,920 Multifamily 1,287,483 281 — — 301 1,288,065 Industrial 776,898 1,208 — — — 778,106 Other commercial real estate 556,239 412 — 714 691 558,056 Total commercial real estate 4,725,669 16,529 280 714 21,621 4,764,813 Residential mortgage: Permanent mortgage 1,292,652 3,196 366 — 23,951 1,320,165 Permanent mortgages guaranteed by U.S. government agencies 37,459 24,369 16,345 105,561 7,132 190,866 Home equity 707,017 1,102 352 59 10,472 719,002 Total residential mortgage 2,037,128 28,667 17,063 105,620 41,555 2,230,033 Personal 1,024,298 479 796 3 230 1,025,806 Total $ 21,308,989 $ 53,350 24,245 $ 106,899 $ 163,247 $ 21,656,730 A summary of loans currently performing, loans past due and accruing and nonaccrual loans as of December 31, 2017 is as follows (in thousands): Past Due Current 30 to 59 Days 60 to 89 Days 90 Days or More Nonaccrual Total Commercial: Energy $ 2,833,668 $ — 4,204 $ — $ 92,284 $ 2,930,156 Services 2,518,298 514 486 107 2,620 2,522,025 Wholesale/retail 1,468,284 398 — — 2,574 1,471,256 Manufacturing 490,739 — 73 — 5,962 496,774 Healthcare 2,213,504 15,218 — — 14,765 2,243,487 Public finance 541,775 — — — — 541,775 Other commercial and industrial 509,116 85 78 125 19,098 528,502 Total commercial 10,575,384 16,215 4,841 232 137,303 10,733,975 Commercial real estate: Residential construction and land development 115,213 200 — — 1,832 117,245 Retail 691,256 — — — 276 691,532 Office 831,118 254 — 123 275 831,770 Multifamily 979,625 22 370 — — 980,017 Industrial 573,014 — — — — 573,014 Other commercial real estate 285,937 — — — 472 286,409 Total commercial real estate 3,476,163 476 370 123 2,855 3,479,987 Residential mortgage: Permanent mortgage 1,014,588 3,435 219 — 25,193 1,043,435 Permanent mortgages guaranteed by U.S. government agencies 22

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Premises and Equipment Disclosure [Text Block]	Premises and Equipment Premises and equipment at December 31 are summarized as follows (in thousands): December 31, 2018 2017 Land $ 70,575 $ 71,348 Buildings and improvements 266,733 249,139 Software 150,207 188,826 Furniture and equipment 129,988 223,163 Construction in progress 27,514 23,348 Premises and equipment 645,017 755,824 Less accumulated depreciation 314,984 438,489 Premises and equipment, net of accumulated depreciation $ 330,033 $ 317,335 Depreciation expense of premises and equipment was $51 million , $48 million and $40 million for the years ended December 31, 2018 , 2017 and 2016

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets [Text Block]	Goodwill and Intangible Assets On October 1, 2018 , the Company acquired CoBiz Financial, Inc. ("CoBiz") , parent company of CoBiz Bank. CoBiz is headquartered in Denver, Colorado serving the Colorado and Arizona markets. The Company paid total consideration of $944 million , which included $243 million in cash along with the issuance of 7.2 million shares of BOK Financial common stock valued at $701 million in exchange for all the outstanding shares of CoBiz. Goodwill acquired is attributed to synergies expected to be gained through consolidation of administrative functions resulting in cost savings. A summary of the preliminary purchase price allocation and resulting goodwill at October 1, 2018 follows (in thousands): Cash and due from banks $ 80,827 Investment securities 17,287 Available for sale securities 546,776 Restricted equity securities 5,261 Loans (Unpaid principal balance - $3,066,521) 2,937,499 Premises and equipment 5,515 Receivables 24,893 Intangible assets 106,733 Real estate and other repossessed assets 5,155 Derivative contracts asset, net 8,197 Cash surrender value of bank-owned life insurance 55,740 Other assets 56,642 Total assets acquired 3,850,525 Deposits 3,289,071 Funds purchased and repurchase agreements 37,218 Subordinated debentures 131,197 Accrued interest, taxes and expense 33,122 Derivative contracts liability, net 12,303 Other liabilities 5,254 Total liabilities assumed 3,508,165 Net assets acquired 342,360 Less: Purchase price 944,193 Goodwill $ 601,833 The preliminary purchase price allocation represents acquired assets and liabilities at estimated fair value. Fair value for loans and intangibles assets was determined by applying discounted cash flow measurement techniques using significant unobservable (Level 3) inputs. These inputs include estimates of loss rates and prepayment speeds, customer attrition rates, operating costs, alternative funding costs and discount rates. The fair value of other acquired assets and liabilities was determined primarily through the use of significant other observable (Level 2) inputs. On May 1, 2018 , the Company acquired a majority voting interest in Switchgrass Holdings, LLC , a restaurant franchise owner and operator, pursuant to merchant banking regulations and restrictions. The purchase price for the acquisition was $14 million and included $6.7 million of intangible assets. On December 1, 2016 , the Company acquired MBT Bancshares (“MBT”) , parent company of Missouri Bank and Trust of Kansas City (“Mobank”) following regulatory approval of the transaction. Mobank operated four banking branches in the Kansas City, Mo. area. BOK Financial paid $103 million in an all-cash deal for all outstanding shares of MBT stock. The purchase price allocation resulted in $15 million of identifiable intangibles and $66 million of goodwill. The pro-forma impact of all acquisition transactions on earnings for periods prior to the acquisition dates were not material to the Company's financial statements. The following table presents the original cost and accumulated amortization of intangible assets (in thousands): Dec. 31, 2018 2017 Core deposit premiums $ 103,200 $ 6,510 Less accumulated amortization 5,032 808 Net core deposit premiums 98,168 5,702 Other identifiable intangible assets 63,497 44,468 Less accumulated amortization 26,816 21,512 Net other identifiable intangible assets 36,681 22,956 Total intangible assets, net $ 134,849 $ 28,658 Expected amortization expense for intangible assets that will continue to be amortized (in thousands): Core Deposit Premiums Other Identifiable Intangible Assets Total 2019 $ 14,332 $ 6,149 $ 20,481 2020 12,892 6,304 19,196 2021 11,893 5,606 17,499 2022 10,981 4,238 15,219 2023 10,145 3,199 13,344 Thereafter 37,925 11,185 49,110 $ 98,168 $ 36,681 $ 134,849 The changes in the carrying value of goodwill by operating segment are as follows (in thousands): Commercial Banking Consumer Banking Wealth Management Funds Management and Other Total Balance, December 31, 2016 272,196 39,023 71,520 66,160 448,899 Goodwill recognized during 2017 4,301 — — — 4,301 Sales of consolidated merchant banking investments during 2017 (5,219 ) — (25 ) — (5,244 ) Adjustment 1 41,992 4,435 19,207 (66,160 ) (526 ) Balance, December 31, 2017 313,270 43,458 90,702 — 447,430 Goodwill recognized during 2018 2 — — — 601,833 601,833 Balance, December 31, 2018 $ 313,270 $ 43,458 $ 90,702 $ 601,833 $ 1,049,263 1 Goodwill from Mobank acquisition was not yet allocated to the segments as of December 31, 2016. Adjustment was made in 2017 for final purchase price adjustments and to allocate to the segments. 2 Goodwill related to the CoBiz acquisition was not yet allocated to the operating segments as of December 31, 2018 and is included in Funds Management and Other above. The annual goodwill evaluations for 2018 and 2017

Mortgage Banking Activities Mor

Mortgage Banking Activities Mortgage Banking Activities (Notes)	12 Months Ended
	Dec. 31, 2018
Mortgage Banking [Abstract]
Mortgage Banking Activities [Text Block]	Mortgage Banking Activities Residential Mortgage Loan Production The Company originates, markets and services conventional and government-sponsored residential mortgage loans. Generally, conforming fixed rate residential mortgage loans are held for sale in the secondary market and non-conforming and adjustable-rate residential mortgage loans are held for investment. The volume of mortgage loans originated for sale and secondary market prices are the primary drivers of originating and marketing revenue. Residential mortgage loan commitments are generally outstanding for 60 to 90 days, which represents the typical period from commitment to originate a residential mortgage loan to when the closed loan is sold to an investor. Residential mortgage loan commitments are subject to both credit and interest rate risk. Credit risk is managed through underwriting policies and procedures, including collateral requirements, which are generally accepted by the secondary loan markets. Exposure to interest rate fluctuations is partially managed through forward sales of residential mortgage-backed securities and forward sales contracts. These latter contracts set the price for loans that will be delivered in the next 60 to 90 days. The unpaid principal balance of residential mortgage loans held for sale, notional amounts of derivative contracts related to residential mortgage loan commitments and forward contract sales and their related fair values included in Mortgage loans held for sale on the Consolidated Balance Sheets were (in thousands): December 31, 2018 December 31, 2017 Unpaid Principal Balance/ Notional Fair Value Unpaid Principal Balance/ Notional Fair Value Residential mortgage loans held for sale $ 145,057 $ 146,971 $ 212,525 $ 215,113 Residential mortgage loan commitments 160,848 5,378 222,919 6,523 Forward sales contracts 274,000 (3,128 ) 380,159 (258 ) $ 149,221 $ 221,378 No residential mortgage loans held for sale were 90 days or more past due or considered impaired as of December 31, 2018 or December 31, 2017 . No credit losses were recognized on residential mortgage loans held for sale for the years ended December 31, 2018 , 2017 and 2016 . Mortgage banking revenue was as follows (in thousands): Year Ended 2018 2017 2016 Production revenue: Net realized gains on sales of mortgage loans $ 36,379 $ 45,128 $ 68,947 Net change in unrealized gain on mortgage loans held for sale (674 ) 2,031 (5,311 ) Net change in the fair value of mortgage loan commitments (1,145 ) (3,210 ) 1,599 Net change in the fair value of forward sales contracts (2,870 ) (5,451 ) 4,393 Total mortgage production revenue 31,690 38,498 69,628 Servicing revenue 66,097 66,221 64,286 Total mortgage banking revenue $ 97,787 $ 104,719 $ 133,914 Mortgage production revenue includes gain (loss) on residential mortgage loans held for sale and changes in the fair value of derivative contracts not designated as hedging instruments related to residential mortgage loan commitments and forward sales contracts. Servicing revenue includes servicing fee income and late charges on loans serviced for others. Residential Mortgage Servicing The Company generally retains the right to service residential mortgage loans sold and may purchase mortgage servicing rights. The unpaid principal balance of loans serviced for others is the primary driver of servicing revenue. The following represents a summary of mortgage servicing rights (Dollars in thousands): December 31, 2018 2017 2016 Number of residential mortgage loans serviced for others 132,463,000 136,528,000 139,340,000 Outstanding principal balance of residential mortgage loans serviced for others $ 21,658,335 $ 22,046,632 $ 21,997,568 Weighted average interest rate 3.99 % 3.94 % 3.97 % Remaining contractual term (in months) 293 297 301 Activity in capitalized mortgage servicing rights during the three years ended December 31, 2018 is as follows (in thousands): Balance, December 31, 2015 $ 218,605 Additions, net 71,405 Change in fair value due to loan runoff (40,744 ) Change in fair value due to market changes (2,193 ) Balance, December 31, 2016 247,073 Additions, net 39,149 Change in fair value due to loan runoff (33,527 ) Change in fair value due to market changes 172 Balance, December 31, 2017 252,867 Additions, net 35,247 Change in fair value due to loan runoff (33,528 ) Change in fair value due to market changes 4,668 Balance, December 31, 2018 $ 259,254 Changes in the fair value of mortgage servicing rights due to market changes are included in Other operating revenue in the Consolidated Statements of Earnings. Changes in fair value due to loan runoff are included in Mortgage banking costs. Mortgage servicing rights are not traded in active markets. Fair value is determined by discounting the projected net cash flows. Significant assumptions used to determine fair value considered to be significant unobservable inputs were as follows: December 31, 2018 2017 Discount rate – risk-free rate plus a market premium 9.90% 9.84% Prepayment rate - based upon loan interest rate, original term and loan type 8.05% - 15.74% 8.72%-15.16% Loan servicing costs – annually per loan based upon loan type: Performing loans $67 - $93 $65 - $88 Delinquent loans $150 - $500 $150 - $500 Loans in foreclosure $1,000 - $4,000 $1,000 - $4,000 Primary/secondary mortgage rate spread 105 bps 105 bps Escrow earnings rate – indexed to rates paid on deposit accounts with comparable average life 2.57% 2.24% Changes in primary residential mortgage interest rates directly affect the prepayment speeds used in valuing our mortgage servicing rights. A separate third party model is used to estimate prepayment speeds based on interest rates, housing turnover rates, estimated loan curtailment, anticipated defaults and other relevant factors. The prepayment model is updated periodically for changes in market conditions and adjusted to better correlate with actual performance of BOK Financial’s servicing portfolio. The aging status of our mortgage loans serviced for others by investor at December 31, 2018 follows (in thousands): Past Due Current 30 to 59 Days 60 to 89 Days 90 Days or More Total FHLMC $ 7,798,790 $ 58,271 $ 11,139 $ 25,239 $ 7,893,439 FNMA 6,458,561 63,321 12,413 20,858 6,555,153 GNMA 6,568,459 200,747 56,024 15,996 6,841,226 Other 362,268 4,297 81 1,871 368,517 Total $ 21,188,078 $ 326,636 $ 79,657 $ 63,964 $ 21,658,335

Deposits

Deposits	12 Months Ended
	Dec. 31, 2018
Deposits [Abstract]
Deposits [Text Block]	Interest expense on deposits is summarized as follows (in thousands): Year Ended December 31, 2018 2017 2016 Transaction deposits $ 65,859 $ 28,627 $ 13,906 Savings 439 359 386 Time: Certificates of deposits under $100,000 5,751 7,702 8,776 Certificates of deposits $100,000 and over 19,739 12,393 10,123 Other time deposits 3,729 4,722 7,303 Total time 29,219 24,817 26,202 Total $ 95,517 $ 53,803 $ 40,494 The aggregate amounts of time deposits in denominations of $250,000 or more at December 31, 2018 and 2017 were $ 756 million and $ 797 million , respectively. Time deposit maturities are as follows: 2019 – $ 1.3 billion , 2020 – $ 262 million , 2021 – $ 98 million , 2022 – $ 115 million , 2023 – $ 130 million and $ 211 million thereafter. The aggregate amount of overdrawn customer transaction deposits that have been reclassified as loan balances was $ 27 million at December 31, 2018 and $ 5.9 million at December 31, 2017

Other Borrowings

Other Borrowings	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Other borrowings [Text Block]	Other Borrowings Information relating to other borrowings is summarized as follows (dollars in thousands): As of Year Ended December 31, 2018 December 31, 2018 Balance Rate Average Balance Rate Maximum Parent company and other non-bank subsidiaries: Other borrowings $ 5,207 1.57 % $ 2,660 1.35 % $ 5,335 Subordinated debentures 275,913 5.34 % 177,884 5.52 % 275,913 Total parent company and other non-bank subsidiaries 281,120 180,544 5.46 % Subsidiary banks: Funds purchased 402,450 2.34 % 419,322 1.89 % 949,531 Repurchase agreements 615,961 0.36 % 464,582 0.28 % 615,961 Other borrowings: Federal Home Loan Bank advances 6,100,000 2.65 % 6,207,142 2.06 % 6,500,000 GNMA repurchase liability 15,552 4.43 % 14,783 4.47 % 16,529 Other 3,631 4.80 % 11,856 4.45 % 15,096 Total other borrowings 6,119,183 6,233,781 2.07 % Subordinated debentures — — % — — % — Total Subsidiary banks 7,137,594 7,117,685 1.94 % Total other borrowed funds $ 7,418,714 $ 7,298,229 2.03 % As of Year Ended December 31, 2017 December 31, 2017 Balance Rate Average Balance Rate Maximum Parent company and other non-bank subsidiaries: Other borrowings $ — — % $ 935 11.11 % $ 3,104 Subordinated debentures 144,677 5.60 % 147,954 5.57 % 151,875 Total parent company and other non-bank subsidiaries 144,677 148,889 5.65 % Subsidiary banks: Funds purchased 58,628 1.00 % 58,064 0.73 % 80,967 Repurchase agreements 516,335 0.17 % 433,791 0.10 % 536,094 Other borrowings: Federal Home Loan Bank advances 5,100,000 1.47 % 5,882,466 1.13 % 6,200,000 GNMA repurchase liability 19,947 4.22 % 20,509 4.59 % 24,139 Other 14,950 2.61 % 15,382 2.38 % 15,506 Total other borrowings 5,134,897 5,918,357 1.14 % Subordinated debentures — — % — — % — Total Subsidiary banks 5,709,860 6,410,212 1.07 % Total other borrowed funds $ 5,854,537 $ 6,559,101 1.18 % As of Year Ended December 31, 2016 December 31, 2016 Balance Rate Average Balance Rate Maximum Parent company and other non-bank subsidiaries: Other borrowings $ 1,092 8.27 % $ 2,073 16.11 % $ 3,157 Subordinated debentures 151,857 5.49 % 75,039 5.57 % 151,857 Total parent company and other non-bank subsidiaries 152,949 77,112 5.86 % Subsidiary banks: Funds purchased 57,929 0.38 % 78,222 0.24 % 567,103 Repurchase agreements 668,661 0.02 % 589,145 0.04 % 668,661 Other borrowings: Federal Home Loan Bank advances 4,800,000 0.72 % 5,985,656 0.55 % 6,500,000 GNMA repurchase liability 22,471 4.26 % 15,637 4.74 % 22,471 Other 15,292 2.66 % 15,670 2.41 % 15,797 Total other borrowings 4,837,763 6,016,963 0.57 % Subordinated debentures — — % 140,414 1.35 % 226,434 Total Subsidiary banks 5,564,353 6,824,744 0.54 % Total other borrowed funds $ 5,717,302 $ 6,901,856 0.60 % Aggregate annual principal repayments at December 31, 2018 are as follows (in thousands): Parent Company and Other Non-bank Subsidiaries Subsidiary Banks 2019 $ — $ 7,134,538 2020 — 575 2021 — 575 2022 — 575 2023 — 625 Thereafter 281,120 706 Total $ 281,120 $ 7,137,594 Funds purchased are unsecured and generally mature within one day to ninety days from the transaction date. Securities repurchase agreements are recorded as secured borrowings that generally mature within ninety days and are secured by certain available for sale securities. Additional information relating to securities sold under agreements to repurchase and related liabilities at December 31, 2018 and 2017 is as follows (dollars in thousands): December 31, 2018 Amortized Fair Repurchase Average Security Sold/Maturity Cost Value Liability 1 Rate U.S. government agency mortgage-backed securities: Overnight 1 $ 636,864 $ 628,229 $ 615,961 0.36 % Long-term — — — — % Total Agency Securities $ 636,864 $ 628,229 $ 615,961 0.36 % December 31, 2017 Amortized Fair Repurchase Average Security Sold/Maturity Cost Value Liability 1 Rate U.S. government agency mortgage-backed securities: Overnight 1 $ 525,452 $ 523,914 $ 516,335 0.17 % Long-term — — — — % Total Agency Securities $ 525,452 $ 523,914 $ 516,335 0.17 % 1 BOK Financial maintains control over the securities underlying overnight repurchase agreements and generally transfers control over securities underlying longer-term dealer repurchase agreements to the respective counterparty. Borrowings from the Federal Home Loan Banks are used for funding purposes. In accordance with policies of the Federal Home Loan Banks, BOK Financial has granted a blanket pledge of eligible assets (generally unencumbered U.S. Treasury and residential mortgage-backed securities, 1-4 family loans and multifamily loans) as collateral for these advances. The Federal Home Loan Banks have issued letters of credit totaling $266 million to secure BOK Financial’s obligations to depositors of public funds. The unused credit available to BOK Financial at December 31, 2018 pursuant to the Federal Home Loan Bank’s collateral policies is $1.9 billion . In 2016, BOK Financial issued $150 million of subordinated debt that will mature on June 30, 2056 . Interest on this debt bears an interest rate of 5.375% , payable quarterly. On June 30, 2021 , BOK Financial will have the option to redeem the debt at the principal amount plus accrued interest, subject to regulatory approval. As a result of the acquisition of CoBiz Financial, we obtained $60 million of subordinated debt issued in June 2015 that will mature on June 25, 2030 . This debt bears interest at the rate of 5.625% through June 2025 and thereafter, the notes will bear interest at an annual floating rate equal to three-month LIBOR plus 3.17% . The debt contains a call option that allows for repayment prior to contractual maturity. The call option is available on June 25, 2025 and quarterly thereafter at 100% of the principal amount. Also through CoBiz Financial, we acquired junior subordinated debentures split across three issuance tranches. Junior subordinated debentures of $21 million will mature September 17, 2033 and bear an interest rate of three-month LIBOR plus 2.95% that resets quarterly. Junior subordinated debentures of $31 million will mature on July 23, 2034 and bear an interest rate of three-month LIBOR plus 2.60% that resets quarterly. Junior subordinated debentures of $20 million will mature on September 30, 2035 and bear an interest rate of three-month LIBOR plus 1.45% that resets quarterly. The junior subordinated debentures are subject to early redemption prior to maturity. In conjunction with the acquisition of MBT, BOK Financial assumed $7.2 million of variable rate subordinated trust preferred debt. Interest was payable quarterly at three-month LIBOR plus 2.95% on $3.1 million and three-month LIBOR plus 1.82% on $4.1 million . This trust preferred debt was redeemed during 2017. BOK Financial Securities, Inc. may borrow funds from Pershing, LLC ("Pershing"), a clearing broker/dealer and a wholly owned subsidiary of Bank of New York Mellon, for the purposes of financing securities purchases or to facilitate funding of investment banking activities, on terms to be negotiated at the time of the borrowing. BOK Financial Securities, Inc. had no borrowings from Pershing outstanding at December 31, 2018 or December 31, 2017 . In 2007, BOKF, NA issued $250 million of subordinated debt due May 15, 2017 . Interest on this debt was based upon a fixed rate of 5.75% through May 14, 2012 and is based on a floating rate of three-month LIBOR plus 0.69% thereafter . The outstanding balance was called during 2016.

Federal and State Income Taxes

Federal and State Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal and State Income Taxes [Text Block]	Federal and State Income Taxes The Tax Cuts and Jobs Act (the "Tax Reform Act"), which was enacted on December 22, 2017, reduced the federal corporate tax rate from 35% to 21% for periods beginning January 1, 2018. We completed our accounting during 2018 for uncertainties that resulted from the Tax Reform Act. Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of deferred tax assets and liabilities are as follows (in thousands): December 31, 2018 2017 Deferred tax assets: Available for sale securities mark to market $ 24,441 $ 12,083 Share-based compensation 4,434 7,598 Credit loss allowances 49,804 58,666 Valuation adjustments 9,619 8,102 Deferred compensation 25,608 12,215 Unearned fees 9,814 9,265 Purchased loan discount 27,283 — Other 31,812 30,859 Total deferred tax assets 182,815 138,788 Deferred tax liabilities: Depreciation 13,901 15,817 Mortgage servicing rights 61,844 63,112 Lease financing 10,040 9,973 Acquired identifiable intangible 28,620 — Other 32,954 34,880 Total deferred tax liabilities 147,359 123,782 Net deferred tax assets $ 35,456 $ 15,006 No valuation allowance was necessary on deferred tax assets as of December 31, 2018 and 2017 . The significant components of the provision for income taxes attributable to continuing operations for BOK Financial are shown below (in thousands): Year Ended December 31, 2018 2017 2016 Current income tax expense: Federal $ 103,748 $ 141,607 $ 107,379 State 15,253 14,592 11,028 Total current income tax expense 119,001 156,199 118,407 Deferred income tax expense: Federal (190 ) 25,525 (11,340 ) State 250 869 (690 ) Total deferred income tax expense 60 26,394 (12,030 ) Total income tax expense $ 119,061 $ 182,593 $ 106,377 The reconciliations of income attributable to continuing operations at the U.S. federal statutory tax rate to income tax expense are as follows (in thousands): Year Ended December 31, 2018 2017 2016 Amount: Federal statutory tax $ 118,752 $ 181,397 $ 118,530 Tax exempt revenue (8,311 ) (12,402 ) (10,544 ) Effect of state income taxes, net of federal benefit 12,430 10,701 6,478 Utilization of tax credits, net of proportional amortization of low-income housing limited partnership investments (4,559 ) (6,811 ) (6,256 ) Share-based compensation (2,105 ) (2,817 ) — Implementation of Tax Reform Act (1,728 ) 11,672 — Deposit insurance 3,099 — — Other, net 1,483 853 (1,831 ) Total income tax expense $ 119,061 $ 182,593 $ 106,377 Year Ended December 31, 2018 2017 2016 Percent of pretax income: Federal statutory tax 21.0 % 35.0 % 35.0 % Tax exempt revenue (1.5 ) (2.4 ) (3.1 ) Effect of state income taxes, net of federal benefit 2.2 2.0 1.9 Utilization of tax credits, net of proportional amortization of low-income housing limited partnership investments (0.8 ) (1.3 ) (1.8 ) Share-based compensation (0.4 ) (0.5 ) — Implementation of Tax Reform Act (0.3 ) 2.3 — Deposit insurance 0.5 — — Other, net 0.4 0.1 (0.6 ) Total 21.1 % 35.2 % 31.4 % A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): 2018 2017 2016 Balance as of January 1 $ 18,110 $ 15,841 $ 13,232 Additions for tax for current year positions 2,649 4,645 5,640 Settlements during the period — — — Lapses of applicable statute of limitations (1,890 ) (2,376 ) (3,031 ) Balance as of December 31 $ 18,869 $ 18,110 $ 15,841 Of the above unrecognized tax benefits, $12.9 million , if recognized, would have affected the effective tax rate. BOK Financial recognizes interest and penalties accrued related to unrecognized tax benefits in income tax expense. The Company recognized $1.7 million for 2018 , $1.2 million for 2017 and $1.0 million for 2016 in interest and penalties. The Company had approximately $5.0 million and $4.0 million accrued for the payment of interest and penalties at December 31, 2018 and 2017 , respectively. Federal statutes remain open for federal tax returns filed in the previous three reporting periods. Various state income tax statutes remain open for the previous three to six

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Employee Benefits [Text Block]	Employee Benefits BOK Financial sponsors a defined benefit cash balance Pension Plan for all employees who satisfy certain age and service requirements. Pension Plan benefits were curtailed as of April 1, 2006. No participants may be added to the plan and no additional service benefits will be accrued. During 2018 and 2017 , interest accrued on employees' account balances at a variable rate tied to the five-year trailing average of five-year U.S. Treasury securities plus 1.5% . The rate has a floor of 3.0% and a ceiling of 5.0% . The 2018 quarterly variable rates ranged from 3.00% to 3.24% . The following table presents information regarding this plan (in thousands): December 31, 2018 2017 Change in projected benefit obligation: Projected benefit obligation at beginning of year $ 30,897 $ 34,964 Interest cost 973 1,153 Actuarial loss (gain) (1,417 ) 223 Benefits paid (6,033 ) (5,443 ) Projected benefit obligation at end of year 1,2 $ 24,547 $ 30,897 Change in plan assets: Plan assets at fair value at beginning of year $ 40,419 $ 41,769 Actual return on plan assets (804 ) 4,093 Benefits paid (6,033 ) (5,443 ) Plan assets at fair value at end of year $ 33,582 $ 40,419 Funded status of the plan $ 9,035 $ 9,522 Components of net periodic benefit: Interest cost $ 973 $ 1,153 Expected return on plan assets (2,065 ) (2,041 ) Other 509 184 Net periodic benefit cost (credit) $ (583 ) $ (704 ) 1 Projected benefit obligation equals accumulated benefit obligation. 2 Projected benefit obligation is based on January 1 measurement date. Weighted-average assumptions as of December 31: 2018 2017 Discount rate 4.10 % 3.30 % Expected return on plan assets 5.50 % 5.50 % As of December 31, 2018 , expected future benefit payments related to the Pension Plan were as follows (in thousands): 2019 $ 3,562 2020 2,257 2021 2,194 2022 2,299 2023 2,495 Thereafter 19,175 Total estimated future benefit payments $ 31,982 Assets of the Pension Plan consist primarily of shares in the Cavanal Hill Active Core Fund. The stated objective of this fund is to provide an attractive total return with a well-balanced mix of equities and bonds. The typical portfolio mix is approximately 60% equities and 40% bonds. The net asset value of shares in the Cavanal Hill Funds is reported daily based on market quotations for the Fund’s securities. Management considers the Fund's recent and long-term performance as indicators when setting the expected return on plan assets. The maximum tax deductible Pension Plan contribution for 2018 was $6.6 million . No minimum contribution was required for 2018 , 2017 or 2016 . Employee contributions to the Thrift Plan are eligible for Company matching equal to 6% of base compensation, as defined in the plan. The Company-provided matching contribution rates range from 50% for employees with less than 4 years of service to 200% for employees with 15 or more years of service. Additionally, a maximum Company-provided, non-elective annual contribution of up to $750 per participant is provided for employees whose annual base compensation is less than $40,000 . Participants may direct investments in their accounts to a variety of options, including a BOK Financial common stock fund and Cavanal Hill funds. Employer contributions, which are invested in accordance with the participant’s investment options, vest over five years . Thrift Plan expenses were $25.1 million for 2018 , $22.8 million for 2017 and $22.4 million for 2016

Share-Based Compensation Plans

Share-Based Compensation Plans	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation Plans [Text Block]	Share-Based Compensation Plans The shareholders and Board of Directors of BOK Financial have approved various share-based compensation plans. An independent compensation committee of the Board of Directors determines the number of awards granted to the Chief Executive Officer and other senior executives. Share-based compensation is granted to other officers and employees as determined by the Chief Executive Officer. The following table presents stock options outstanding under these plans (in thousands, except for per share data): Number Weighted- Average Exercise Price Aggregate Intrinsic Value Options outstanding at: December 31, 2016 218,524 51.95 6,793 December 31, 2017 117,551 53.26 4,592 December 31, 2018 63,058 $ 54.89 $ 1,163 Options vested at: December 31, 2016 93,117 $ 46.22 $ 3,429 December 31, 2017 51,286 48.62 2,241 December 31, 2018 33,573 53.09 679 No options have been awarded since 2013. At December 31, 2018 , the weighted average remaining contractual life of options outstanding was 2.12 years and the weighted average remaining contractual life of vested options was 1.04 years . The aggregate intrinsic value of options exercised was $ 2.3 million for 2018 , $ 3.5 million for 2017 and $ 6.2 million for 2016 . The Company also awards non-vested shares to certain officers and employees. Vesting of all non-vested shares is subject to service requirements. Additionally, vesting of certain non-vested shares is subject to performance criteria based on changes in the Company's earnings per share relative to defined peers. The following represents a summary of the non-vested stock awards for the three years ended December 31, 2018 (in thousands): Shares Weighted Average Grant Date Fair Value Non-vested at January 1, 2016 791,109 Granted 256,670 $55.35 Vested (213,941 ) $55.87 Forfeited (47,132 ) $57.86 Non-vested at December 31, 2016 786,706 Granted 177,807 $86.95 Vested (194,419 ) $63.07 Forfeited (102,991 ) $78.70 Non-vested at December 31, 2017 667,103 Granted 150,419 $85.58 Vested (242,215 ) $74.85 Forfeited (47,700 ) $75.68 Non-vested at December 31, 2018 527,607 Compensation expense recognized on non-vested shares totaled $3.6 million for 2018 , $23.2 million for 2017 and $10.2 million for 2016 . Unrecognized compensation cost of non-vested shares totaled $ 14.2 million at December 31, 2018 . We expect to recognize compensation expense of $ 9.7 million in 2019 , $ 4.3 million in 2020 , and $ 138 thousand in 2021 . Compensation cost for 189,179 non-vested shares is variable based on the current fair value of BOK Financial common shares. Vesting of 188,827

Related Parties

Related Parties	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Parties [Text Block]	Related Parties In compliance with applicable banking regulations, the Company may extend credit to certain executive officers, directors, principal shareholders and their affiliates (collectively referred to as “related parties”) in the ordinary course of business. The Company’s loans to related parties do not involve more than the normal credit risk. Activity in loans to related parties is summarized as follows (in thousands): Year Ended December 31, 2018 2017 Beginning balance $ 110,246 $ 136,945 Advances 1,479,735 1,559,291 Payments (1,514,841 ) (1,585,865 ) Adjustments 1 125 (125 ) Ending balance $ 75,265 $ 110,246 1 Adjustments generally consist of changes in status as a related party. As defined by banking regulations, loan commitments and equity investments from the subsidiary banks to a single affiliate may not exceed 10% of unimpaired capital and surplus while loan commitments and equity investments to all affiliates may not exceed 20% of unimpaired capital and surplus. All loans to affiliates must be fully secured by eligible collateral. At December 31, 2018 , loan commitments and equity investments were limited to $310 million to a single affiliate and $621 million to all affiliates. The largest loan commitment and equity investment to a single affiliate was $253 million and the aggregate loan commitments and equity investments to all affiliates were $313 million . The largest outstanding amount to a single affiliate at December 31, 2018 was $883 thousand and the total outstanding amounts to all affiliates were $883 thousand . At December 31, 2017 , total loan commitments and equity investments to all affiliates were $323 million and the total outstanding amounts to all affiliates were $16 million . We have $4.7 million of impaired loans from a related party with no allowance as the fair value of the collateral exceeds the outstanding principal balance at December 31, 2018. There were no nonaccruing or impaired related party loans outstanding at December 31, 2017. Certain related parties are customers of the Company for services other than loans, including consumer banking, corporate banking, risk management, wealth management, brokerage and trading, or fiduciary/trust services. The Company engages in transactions with related parties in the ordinary course of business in compliance with applicable regulations. The Company rents office space in facilities owned by affiliates of Mr. Kaiser, its Chairman and principal shareholder. Lease payments totaled $683 thousand for 2018, $1.0 million for 2017 and $1.1 million for 2016. The Company also invested $3.1 million and $580 thousand during the years ended 2018 and 2017, respectively, in QRC Valve Distributors, which is indirectly owned by Mr. Kaiser. QuikTrip Corporation has entered into a fee sharing agreement with TransFund, BOKF’s electronic funds transfer network (“TransFund”), respecting transactions completed at TransFund automated teller machines placed in QuikTrip locations. In 2018, BOKF paid QuikTrip approximately $9.2 million pursuant to this agreement. A BOK Financial director, is Chief Executive Officer, Chairman, and a significant shareholder of QuikTrip Corporation. Cavanal Hill Investment Management, Inc., a wholly-owned subsidiary of BOKF, NA, is the administrator to and investment advisor for the Cavanal Hill Funds (the "Funds"), a diversified, open-ended investment company established as a business trust under the Investment Company Act of 1940 (the "1940 Act"). BOKF, NA is custodian and Cavanal Hill Distributors, Inc. is distributor for the Funds. The Funds’ products are offered to customers, employee benefit plans, trusts and the general public in the ordinary course of business. Approximately 89% of the Funds’ assets of $ 3.4

Commitments and Contingent Liab

Commitments and Contingent Liabilities	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities [Text Block]	Commitments and Contingent Liabilities Litigation Contingencies As a member of Visa, BOK Financial is obligated for a proportionate share of certain covered litigation losses incurred by Visa under a retrospective responsibility plan. A contingent liability was recognized for the Company’s share of Visa’s covered litigation liabilities. Visa funded an escrow account to cover litigation claims, including covered litigation losses under the retrospective responsibility plan, with proceeds from its initial public offering in 2008 and from available cash. BOK Financial currently owns 252,233 Visa Class B shares which are convertible into 411,089 shares of Visa Class A shares after the final settlement of all covered litigation. Class B shares may be diluted in the future if the escrow fund is not adequate to cover future covered litigation costs. Therefore, no value has been currently assigned to the Class B shares and no value may be assigned until the Class B shares are converted into a known number of Class A shares. On June 24, 2015, BOKF, NA received a complaint alleging that an employee had colluded with a bond issuer and an individual in misusing revenues pledged to municipal bonds for which BOKF, NA served as trustee under the bond indenture. The Company conducted an investigation and concluded that employees in one of its Corporate Trust offices had, with respect to a single group of affiliated bond issuances, violated Company policies and procedures by waiving financial covenants, granting forbearances and accepting without disclosure to the bondholders, debt service payments from sources other than pledged revenues. The relationship manager was terminated. The Company reported the circumstances to, and cooperated with an investigation by, the Securities and Exchange Commission ("SEC"). On December 28, 2015, in an action brought by the SEC, the United States District Court for the District of New Jersey entered a judgment against the principals involved in issuing the bonds, precluding the principals from denying the alleged violations of the federal securities laws and requiring the principals to pay all outstanding principal, accrued interest, and other amounts required under the bond documents (now estimated to be approximately $40 million , less the value of the facilities securing repayment of the bonds), subject to oversight by a court appointed monitor. The obligation of the principal to pay all principal and interest on the bonds is non-dischargeable in bankruptcy. On September 7, 2016, BOKF, NA agreed, and the SEC entered, a consent order finding that the BOKF, NA had violated Section 17(a) of the Securities Act of 1933 and Section 10(b) of the Securities Exchange Act and requiring the BOKF, NA to disgorge $1,067,721 of fees and pay a civil penalty of $600,000 . The BOKF, NA has disgorged the fees and paid the penalty. On August 26, 2016, the BOKF, NA was sued in the United States District Court for New Jersey by two bondholders in a putative class action on behalf of all holders of the bonds alleging the BOKF, NA participated in the fraudulent sale of securities by the principals. On September 14, 2016, the BOKF, NA was sued in the District Court of Tulsa County, Oklahoma by 19 bondholders alleging the BOKF, NA participated in the fraudulent sale of securities by the principals. Two separate small groups of bondholders have filed arbitration complaints with the Financial Institutions Regulatory Association respecting the bonds and other bonds for which the BOKF, NA served as indenture trustee. Management has been advised by counsel that the BOKF, NA has valid defenses to the claims. The time by which the principal must perform the Court ordered payment plan currently expires on March 31, 2019. BOKF, NA expects the Court ordered payment plan to be continued from time to time until the principals complete the payment of the bonds, though there is no assurance that it will be. Accordingly, no loss is probable at this time and no provision for loss has been made. If the payment plan does not result in payment of the bonds, a loss could become probable. A reasonable estimate cannot be made at this time though the amount could be material to the Company. On March 5, 2018, BOKF, NA was sued in the Fulton, Georgia County District Court by the administratrix of a deceased resident who had sued for and obtained a judgment for wrongful death against one of the operators of a nursing home financed by one of the bonds which are the subject of the litigation discussed above. The judgment is alleged to total approximately $8 million in principal and interest at this time. Plaintiff alleges that BOKF, in its capacity as indenture trustee for the bonds, colluded with the borrower and others to defraud creditors of the nursing home by misleading the public about the solvency of the nursing home. Plaintiff alleges that this conduct has prevented her from collecting on her judgment. BOKF, NA is advised by counsel that the BOKF, NA has valid defenses to the plaintiffs’ claims and no loss is probable. On March 14, 2017, BOKF, NA was sued in the United States District Court for the Northern District of Oklahoma by bondholders in a second putative class action representing a different set of municipal securities. The bondholders in this second action allege two individuals purchased facilities from the principals who are the subject of the SEC New Jersey proceedings by means of the fraudulent sale of $60 million of municipal securities for which BOKF, NA also served as indenture trustee. The bondholders allege BOKF, NA failed to disclose that the seller of the purchased facilities had engaged in the conduct complained of in the New Jersey action. BOKF, NA properly performed all duties as indenture trustee of this second set of municipal securities, timely commenced proceedings against the issuer of the securities when default occurred, is cooperating with the SEC in actions against the two principals, is not a target of the SEC proceedings, and has been advised by counsel that BOKF, NA has valid defenses to the claims of these bondholders. Management is advised by counsel that a loss is not probable and that the loss, if any, cannot be reasonably estimated. On March 7, 2017, a plaintiff filed a putative class action in the United States District Court for the Northern District of Texas alleging an extended overdraft fee charged by BOKF, NA is interest and exceeds permitted rates. This action makes the same allegations as a putative class action that was dismissed by the United States District Court for the Northern District of Oklahoma on October 19, 2015. On August 22, 2018, a plaintiff filed a second putative class action in the United States District Court for New Mexico making the same allegations as the Texas action. On September 18, 2018, the District Court dismissed the Texas action. Management is advised by counsel that a loss is not probable in the New Mexico action or the Texas action and that the loss, if any, cannot be reasonably estimated. On July 6, 2018, a plaintiff served a petition in a putative class action in the Oklahoma District Court for Tulsa County Oklahoma alleging BOKF NA breached its Demand Deposit Agreements by charging overdraft and not sufficient funds fees to deposit accounts on the day of the transaction triggering the fee and by the bank's debit hold process causing overdraft fees. Management is advised by counsel that a loss is not probable and that the loss, if any, cannot be reasonably estimated. In the ordinary course of business, BOK Financial and its subsidiaries are subject to legal actions and complaints. Management believes, based upon the opinion of counsel, that the actions and liability or loss, if any, resulting from the final outcomes of the proceedings, will not have a material effect on the Company’s financial condition, results of operations or cash flows. Alternative Investment Commitments The Company sponsors two private equity funds and invests in several tax credit entities and other funds as permitted by banking regulations. Consolidation of these investments is based on the variable interest model. BOKF Equity, LLC, an indirect wholly-owned subsidiary, is the general partner of two consolidated private equity funds (“the Funds”). The Funds provide alternative investment opportunities to certain customers, some of which are related parties, through unaffiliated limited partnerships. Substantially all committed capital invested by these Funds has been returned to the partners. Consolidated tax credit entities represented the Company's interest in entities earning federal new market tax credits related to qualifying loans. These entities were liquidated in 2018. The Company also has interests in various alternative investments generally consisting of unconsolidated limited partnership interests in entities for which investment return is in the form of low income housing tax credits or other investments in merchant banking activities. The Company is prohibited by banking regulations from controlling or actively managing the activities of these investments and the Company's maximum exposure to loss is restricted to its investment balance. The Company's obligation to fund alternative investments is included in Other liabilities in the Consolidated Balance Sheets. A summary of consolidated and unconsolidated alternative investments as of December 31, 2018 and December 31, 2017 is as follows (in thousands): December 31, 2018 Loans Other Assets Other Liabilities Other Borrowings Non-controlling Interests Consolidated: Private equity funds $ — $ 9,516 $ — $ — $ 8,644 Tax credit entities — — — — — Other — 17,602 1,448 5,207 2,292 Total consolidated $ — $ 27,118 $ 1,448 $ 5,207 $ 10,936 Unconsolidated: Tax credit entities $ 58,981 $ 165,567 $ 53,198 $ — $ — Other — 62,406 20,687 — — Total unconsolidated $ 58,981 $ 227,973 $ 73,885 $ — $ — December 31, 2017 Loans Other Other Other Non-controlling Consolidated: Private equity funds $ — $ 14,783 $ — $ — $ 11,927 Tax credit entities 10,000 10,964 — 10,964 10,000 Other — 1,040 — — 1,040 Total consolidated $ 10,000 $ 26,787 $ — $ 10,964 $ 22,967 Unconsolidated: Tax credit entities $ 52,852 $ 153,506 $ 47,859 $ — $ — Other — 38,397 22,968 — — Total unconsolidated $ 52,852 $ 191,903 $ 70,827 $ — $ — Other Commitments and Contingencies Cavanal Hill Funds’ assets include U.S. Treasury and government securities money market funds. Assets of these funds consist of highly-rated, short-term obligations of the U.S. Treasury and Agencies. The net asset value of units in these funds was $1.00 at December 31, 2018 . An investment in these funds is not insured by the Federal Deposit Insurance Corporation or guaranteed by BOK Financial or any of its subsidiaries. BOK Financial may, but is not obligated to purchase assets from these funds to maintain the net asset value at $1.00 . No assets were purchased from the funds in 2018 or 2017 . Total rent expense for BOK Financial was $ 28.5 million in 2018 , $27.5 million in 2017 and $25.8 million in 2016 . At December 31, 2018 , future minimum lease payments for premises under operating leases were as follows: $25.8 million in 2019 , $24.8 million in 2020 , $21.3 million in 2021 , $15.2 million in 2022 , $13.0 million in 2023 and $78.6 million thereafter. BOKF, NA is obligated under a long-term lease for its bank premises in downtown Tulsa. The lease term, which began November 1, 1976, is for fifty-seven years with an option to terminate in 2024 with a two-year prior written notice. Premises leases may include options to renew at then current market rates and may include escalation provisions based upon changes in consumer price index or similar benchmarks. The Federal Reserve Bank requires member banks to maintain certain minimum average cash balances. Member banks may satisfy reserve balance requirements through holdings of vault cash and balances maintained directly with a Federal Reserve Bank. The combined average balance of vault cash and balances held at the Federal Reserve Bank was $1.2 billion for the year ended December 31, 2018 and $1.9 billion for the year ended December 31, 2017

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	Earnings Per Share The following table presents the computation of basic and diluted earnings per share (dollars in thousands, except per share data): Year Ended 2018 2017 2016 Numerator: Net income attributable to BOK Financial Corp. shareholders $ 445,646 $ 334,644 $ 232,668 Less: Earnings allocated to participating securities 3,737 3,561 2,883 Numerator for basic earnings per share – income available to common shareholders 441,909 331,083 229,785 Effect of reallocating undistributed earnings of participating securities 1 2 1 Numerator for diluted earnings per share – income available to common shareholders $ 441,910 $ 331,085 $ 229,786 Denominator: Weighted average shares outstanding 67,190,257 65,440,832 65,901,110 Less: Participating securities included in weighted average shares outstanding 561,617 695,468 815,483 Denominator for basic earnings per common share 66,628,640 64,745,364 65,085,627 Dilutive effect of employee stock compensation plans 1 33,633 60,920 58,271 Denominator for diluted earnings per common share 66,662,273 64,806,284 65,143,898 Basic earnings per share $ 6.63 $ 5.11 $ 3.53 Diluted earnings per share $ 6.63 $ 5.11 $ 3.53 1 Excludes employee stock options with exercise prices greater than current market price. — — —

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2018
Stockholders' Equity Note [Abstract]
Shareholders' Equity [Text Block]	Shareholders Equity Preferred Stock One billion shares of preferred stock with a par value of $0.00005 per share are authorized. The Series A Preferred Stock has no voting rights except as otherwise provided by Oklahoma corporate law and may be converted into one share of Common Stock for each 36 shares of Series A Preferred Stock at the option of the holder . Dividends are cumulative at an annual rate of ten percent of the $0.06 per share liquidation preference value when declared and are payable in cash. Aggregate liquidation preference is $15 million . No Series A Preferred Stock was outstanding in 2018 , 2017 or 2016 . Common Stock Common stock consists of 2.5 billion authorized shares with a $0.00006 par value. Holders of common shares are entitled to one vote per share at the election of the Board of Directors and on any question arising at any shareholders’ meeting and to receive dividends when and as declared. Additionally, regulations restrict the ability of national banks and bank holding companies to pay dividends. Subsidiary Banks The amounts of dividends that BOK Financial’s subsidiary banks can declare and the amounts of loans the subsidiary banks can extend to affiliates are limited by various federal banking regulations and state corporate law. Generally, dividends declared during a calendar year are limited to net profits, as defined, for the year plus retained profits for the preceding two years. The amounts of dividends are further restricted by minimum capital requirements. Regulatory Capital BOK Financial and the subsidiary banks are subject to various capital requirements administered by the federal banking agencies. Failure to meet minimum capital requirements can initiate certain mandatory and additional discretionary actions by regulators that could have a material effect on BOK Financial's operations. These capital requirements include quantitative measures of assets, liabilities and certain off-balance sheet items. The capital standards are also subject to qualitative judgments by the regulators. New capital rules were effective for BOK Financial on January 1, 2015. Components of these rules will phase in through January 1, 2019. A bank falling below the minimum capital requirements, including the capital conservation buffer, would be subject to regulatory restrictions on capital distributions (including but not limited to dividends and share repurchases) and executive bonus payments. For a banking institution to qualify as well capitalized, Common Equity Tier 1, Tier I, Total and Leverage capital ratios must be at least 6.5% , 8% , 10% and 5% , respectively. Tier I capital consists primarily of common stockholders' equity, excluding unrealized gains or losses on available for sale securities, less goodwill, core deposit premiums and certain other intangible assets. Total capital consists primarily of Tier I capital plus preferred stock, subordinated debt and allowances for credit losses, subject to certain limitations. The subsidiary banks exceeded the regulatory definition of well capitalized as of December 31, 2018 and December 31, 2017 . A summary of regulatory capital minimum requirements and levels follows (dollars in thousands): Minimum Capital Requirement Capital Conservation Buffer 1 Minimum Capital Requirement Including Capital Conservation Buffer Well Capitalized Bank Requirement December 31, 2018 December 31, 2017 Common Equity Tier 1 Capital (to Risk Weighted Assets): Consolidated 4.50% 2.50% 7.00% N/A $ 3,356,524 10.92 % $ 3,074,981 12.05 % BOKF, NA 4.50% N/A 4.50% 6.50% 2,894,119 10.50 % 2,870,694 11.34 % CoBiz Bank 2 4.50% N/A 4.50% 6.50% 317,944 10.65 % 399,768 12.19 % Tier I Capital (to Risk Weighted Assets): Consolidated 6.00% 2.50% 8.50% N/A $ 3,356,524 10.92 % $ 3,074,981 12.05 % BOKF, NA 6.00% N/A 6.00% 8.00% 2,894,119 10.50 % 2,870,694 11.34 % CoBiz Bank 2 6.00% N/A 6.00% 8.00% 317,944 10.65 % 399,768 12.19 % Total Capital (to Risk Weighted Assets): Consolidated 8.00% 2.50% 10.50% N/A $ 3,841,684 12.50 % $ 3,455,709 13.54 % BOKF, NA 8.00% N/A 8.00% 10.00% 3,103,366 11.26 % 3,105,117 12.27 % CoBiz Bank 2 8.00% N/A 8.00% 10.00% 382,944 12.83 % 434,012 13.23 % Leverage (Tier I Capital to Average Assets): Consolidated 4.00% N/A 4.00% N/A $ 3,356,524 8.96 % $ 3,074,981 9.31 % BOKF, NA 4.00% N/A 4.00% 5.00% 2,894,119 8.56 % 2,870,694 8.73 % CoBiz Bank 2 4.00% N/A 4.00% 5.00% 317,944 8.25 % 399,768 10.47 % 1 Capital conservation buffer is effective January 1, 2016 and is phased in through 2019. The phased in capital conservation buffer was 1.875% at December 31, 2018 and 1.25% at December 31, 2017 . The fully phased in requirement of 2.50% is included in the table above. 2 CoBiz Bank was acquired by BOK Financial effective October 1, 2018. Accumulated Other Comprehensive Income (Loss) AOCI includes unrealized gains and losses on available for sale ("AFS") securities and non-credit related unrealized losses on AFS securities for which an other-than-temporary impairment has been recorded in earnings. AOCI also includes unrealized gains on AFS securities that were transferred from AFS to investment securities in 2011. Such amounts were amortized over the estimated remaining life of the security as an adjustment to yield, offsetting the related amortization of premium on the transferred securities. Unrealized losses on employee benefit plans will be reclassified into income as pension plan costs are recognized over the remaining service period of plan participants. Gains and losses in AOCI are net of deferred income taxes. A rollforward of the components of accumulated other comprehensive income (loss) is included as follows (in thousands): Unrealized Gain (Loss) on Available for Sale Securities Investment Securities Transferred from AFS Employee Benefit Plans Total Balance, December 31, 2015 $ 23,284 $ 68 $ (1,765 ) $ 21,587 Net change in unrealized gain (loss) (41,333 ) — (188 ) (41,521 ) Reclassification adjustments included in earnings: Interest revenue, Investment securities, Taxable securities — (112 ) — (112 ) Gain on available for sale securities, net (11,675 ) — — (11,675 ) Other comprehensive income (loss), before income taxes (53,008 ) (112 ) (188 ) (53,308 ) Federal and state income tax 1 (20,637 ) (44 ) (73 ) (20,754 ) Other comprehensive income (loss), net of income taxes (32,371 ) (68 ) (115 ) (32,554 ) Balance, December 31, 2016 (9,087 ) — (1,880 ) (10,967 ) Net change in unrealized gain (loss) (28,170 ) — 2,018 (26,152 ) Reclassification adjustments included in earnings: Interest revenue, Investment securities, Taxable securities — — — — Gain on available for sale securities, net (4,428 ) — — (4,428 ) Other comprehensive income (loss), before income taxes (32,598 ) — 2,018 (30,580 ) Federal and state income tax 1 (12,708 ) — 785 (11,923 ) Other comprehensive income (loss), net of income taxes (19,890 ) — 1,233 (18,657 ) Reclassification of stranded accumulated other comprehensive loss related to tax reform (6,408 ) — (142 ) (6,550 ) Balance, December 31, 2017 (35,385 ) — (789 ) (36,174 ) Transition adjustment for net unrealized gains on equity securities (2,709 ) — — (2,709 ) Net change in unrealized gain (loss) (46,941 ) — (1,069 ) (48,010 ) Reclassification adjustments included in earnings: Interest revenue, Investment securities, Taxable securities — — — — Loss on available for sale securities, net 2,801 — — 2,801 Other comprehensive income (loss), before income taxes (44,140 ) — (1,069 ) (45,209 ) Federal and state income tax 2 (11,235 ) — (272 ) (11,507 ) Other comprehensive income (loss), net of income taxes (32,905 ) — (797 ) (33,702 ) Balance, December 31, 2018 $ (70,999 ) $ — $ (1,586 ) $ (72,585 ) 1 Calculated using a 39 percent blended federal and state statutory tax rate. 2

Reportable Segments

Reportable Segments	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Reportable Segments [Text Block]	Reportable Segments BOK Financial operates three principal lines of business: Commercial Banking, Consumer Banking and Wealth Management. Commercial Banking includes lending, treasury and cash management services and customer risk management products to small businesses, middle market and larger commercial customers. Commercial Banking also includes the TransFund EFT network. Consumer Banking includes retail lending and deposit services, lending and deposit services to small business customers served through the consumer branch network and all mortgage banking activities. Wealth Management provides fiduciary services, private bank services and investment advisory services in all markets. Wealth Management also underwrites state and municipal securities and engages in brokerage and trading activities. In addition to its lines of business, BOK Financial has a Funds Management unit. The primary purpose of this unit is to manage overall liquidity needs and interest rate risk. Each line of business borrows funds from and provides funds to the Funds Management unit as needed to support their operations. Operating results for Funds Management and Other include the effect of interest rate risk positions and risk management activities, securities gains and losses including impairment charges, the provision for credit losses in excess of net loans charged off, tax planning strategies and certain executive compensation costs that are not attributed to the lines of business. BOK Financial allocates resources and evaluates performance of its lines of business after allocation of funds, actual net credit losses and capital costs. In addition, we measure the performance of our business lines after allocation of certain indirect expenses and taxes on statutory rates. The allocation for the prior comparable periods have been revised on a comparable basis. The cost of funds borrowed from the Funds Management unit by the operating lines of business is transfer priced at rates that approximate market rates for funds with similar duration. Market rates are generally based on the applicable LIBOR or interest rate swap rates, adjusted for prepayment risk. This method of transfer-pricing funds that support assets of the operating lines of business tends to insulate them from interest rate risk. The value of funds provided by the operating lines of business to the Funds Management unit is based on rates which approximate the wholesale market rates for funds with similar duration and re-pricing characteristics. Market rates are generally based on LIBOR or interest rate swap rates. The funds credit formula applied to deposit products with indeterminate maturities is established based on their re-pricing characteristics reflected in a combination of the short-term LIBOR rates and a moving average of an intermediate term swap rate, with an appropriate spread applied to both. Shorter duration products are weighted towards the short-term LIBOR rate and longer duration products are weighted towards intermediate swap rates. The expected duration ranges from 30 days for certain rate-sensitive deposits to five years. Substantially all revenue is from domestic customers. No single external customer accounts for more than 10% of total revenue. Net loans charged off and provision for credit losses represents net loans charged off as attributed to the lines of business and the provision for credit losses in excess of net charge-offs attributed to Funds Management and Other. The operations of CoBiz, acquired on October 1, 2018 were not yet allocated to the operating segments at December 31, 2018. Accordingly, the operations, assets and liabilities of CoBiz were included in Funds Management and Other for 2018. The acquisition of Mobank on December 1, 2016 was allocated to the operating segments in 2017. Reportable segments reconciliation to the Consolidated Financial Statements for the year ended December 31, 2018 is as follows (in thousands): Commercial Consumer Wealth Management Funds Management and Other BOK Financial Consolidated Net interest and dividend revenue from external sources $ 726,856 $ 83,231 $ 81,527 $ 93,253 $ 984,867 Net interest revenue (expense) from internal sources (156,254 ) 73,448 31,505 51,301 — Net interest and dividend revenue 570,602 156,679 113,032 144,554 984,867 Provision for credit losses 30,358 5,143 (288 ) (27,213 ) 8,000 Net interest and dividend revenue after provision for credit losses 540,244 151,536 113,320 171,767 976,867 Other operating revenue 162,701 178,123 296,369 (20,409 ) 616,784 Other operating expense 192,811 210,187 248,959 376,209 1,028,166 Net direct contribution 510,134 119,472 160,730 (224,851 ) 565,485 Gain (loss) on financial instruments, net 26 (25,021 ) 7 24,988 — Change in fair value of mortgage servicing rights — 4,668 — (4,668 ) — Gain (loss) on repossessed assets, net (6,532 ) 247 — 6,285 — Corporate expense allocations 45,818 63,700 44,190 (153,708 ) — Net income before taxes 457,810 35,666 116,547 (44,538 ) 565,485 Federal and state income taxes 121,434 9,085 30,003 (41,461 ) 119,061 Net income 336,376 26,581 86,544 (3,077 ) 446,424 Net income attributable to non-controlling interests — — — 778 778 Net income attributable to BOK Financial Corp. shareholders $ 336,376 $ 26,581 $ 86,544 $ (3,855 ) $ 445,646 Average assets $ 18,431,411 $ 8,303,262 $ 8,446,006 $ (243,149 ) $ 34,937,530 Reportable segments reconciliation to the Consolidated Financial Statements for the year ended December 31, 2017 is as follows (in thousands): Commercial Consumer Wealth Management Funds Management and Other BOK Financial Consolidated Net interest and dividend revenue from external sources $ 618,325 $ 84,286 $ 45,024 $ 94,066 $ 841,701 Net interest revenue (expense) from internal sources (89,106 ) 53,916 38,344 (3,154 ) — Net interest and dividend revenue 529,219 138,202 83,368 90,912 841,701 Provision for credit losses 13,877 4,786 (696 ) (24,967 ) (7,000 ) Net interest and dividend revenue after provision for credit losses 515,342 133,416 84,064 115,879 848,701 Other operating revenue 208,404 184,878 301,434 378 695,094 Other operating expense 228,119 221,679 246,626 329,093 1,025,517 Net direct contribution 495,627 96,615 138,872 (212,836 ) 518,278 Gain (loss) on financial instruments, net 52 (2,054 ) — 2,002 — Change in fair value of mortgage servicing rights — 172 — (172 ) — Gain (loss) on repossessed assets, net (2,681 ) 223 387 2,071 — Corporate expense allocations 34,253 67,320 40,562 (142,135 ) — Net income before taxes 458,745 27,636 98,697 (66,800 ) 518,278 Federal and state income taxes 188,241 10,750 38,848 (55,246 ) 182,593 Net income 270,504 16,886 59,849 (11,554 ) 335,685 Net income attributable to non-controlling interests — — — 1,041 1,041 Net income attributable to BOK Financial Corp. shareholders $ 270,504 $ 16,886 $ 59,849 $ (12,595 ) $ 334,644 Average assets $ 17,730,654 $ 8,544,117 $ 7,072,622 $ (399,899 ) $ 32,947,494 Reportable segments reconciliation to the Consolidated Financial Statements for the year ended December 31, 2016 is as follows (in thousands): Commercial Consumer Wealth Management Funds Management and Other BOK Financial Consolidated Net interest and dividend revenue from external sources $ 501,042 $ 77,283 $ 33,006 $ 135,897 $ 747,228 Net interest revenue (expense) from internal sources (62,655 ) 43,156 29,043 (9,544 ) — Net interest and dividend revenue 438,387 120,439 62,049 126,353 747,228 Provision for credit losses 32,961 4,925 (801 ) 27,915 65,000 Net interest and dividend revenue after provision for credit losses 405,426 115,514 62,850 98,438 682,228 Other operating revenue 198,902 216,285 283,222 (24,389 ) 674,020 Other operating expense 217,993 247,478 250,995 301,124 1,017,590 Net direct contribution 386,335 84,321 95,077 (227,075 ) 338,658 Gain (loss) on financial instruments, net 10 (26,252 ) (42 ) 26,284 — Change in fair value of mortgage servicing rights — (2,193 ) — 2,193 — Gain on repossessed assets, net 669 979 — (1,648 ) — Corporate expense allocations 36,134 65,567 42,378 (144,079 ) — Net income before taxes 350,880 (8,712 ) 52,657 (56,167 ) 338,658 Federal and state income taxes 146,740 (3,389 ) 20,976 (57,950 ) 106,377 Net income 204,140 (5,323 ) 31,681 1,783 232,281 Net loss attributable to non-controlling interests — — — (387 ) (387 ) Net income attributable to BOK Financial Corp. shareholders $ 204,140 $ (5,323 ) $ 31,681 $ 2,170 $ 232,668 Average assets $ 17,175,325 $ 8,254,666 $ 7,373,080 $ (524,669 ) $ 32,278,402

Fees and Commission Revenue (No

Fees and Commission Revenue (Notes)	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Fees and Commissions Revenue [Text Block]	Fees and Commissions Revenue Fees and commissions revenue by reportable segment and primary service line is as follows for the year ended December 31, 2018 . Commercial Consumer Wealth Management Funds Management and Other Consolidated Out of Scope 1 In Scope 2 Trading revenue $ — $ — $ 28,077 $ — $ 28,077 $ 28,077 $ — Customer hedging revenue 7,748 — 27,512 3,574 38,834 38,834 — Retail brokerage revenue — — 19,030 3,120 22,150 — 22,150 Investment banking revenue 7,628 — 11,634 — 19,262 6,380 12,882 Brokerage and trading revenue 15,376 — 86,253 6,694 108,323 73,291 35,032 TransFund EFT network revenue 72,280 4,017 (82 ) 6 76,221 — 76,221 Merchant services revenue 7,666 59 — 79 7,804 — 7,804 Transaction card revenue 79,946 4,076 (82 ) 85 84,025 — 84,025 Personal trust revenue — — 96,839 — 96,839 — 96,839 Corporate trust revenue — — 22,292 — 22,292 — 22,292 Institutional trust & retirement plan services revenue — — 44,400 — 44,400 — 44,400 Investment management services and other — — 19,729 1,443 21,172 — 21,172 Fiduciary and asset management revenue — — 183,260 1,443 184,703 — 184,703 Commercial account service charge revenue 41,931 1,445 2,331 1,565 47,272 — 47,272 Overdraft fee revenue 370 36,177 134 (145 ) 36,536 — 36,536 Check card revenue — 20,967 — 339 21,306 — 21,306 Automated service charge and other deposit fee revenue 282 6,621 62 74 7,039 — 7,039 Deposit service charges and fees 42,583 65,210 2,527 1,833 112,153 — 112,153 Mortgage production revenue — 31,690 — — 31,690 31,690 — Mortgage servicing revenue — 67,980 — (1,883 ) 66,097 66,097 — Mortgage banking revenue — 99,670 — (1,883 ) 97,787 97,787 — Other revenue 24,044 9,218 24,507 (1,118 ) 56,651 38,306 18,345 Total fees and commissions revenue $ 161,949 $ 178,174 $ 296,465 $ 7,054 $ 643,642 $ 209,384 $ 434,258 1 Out of scope revenue generally relates to financial instruments or contractual rights and obligations within the scope of other applicable accounting guidance. 2 In scope revenue represents revenue subject to FASB ASC Topic 606,

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements [Text Block]	Fair Value Measurements Fair value is defined by applicable accounting guidance as the price to sell an asset or transfer a liability in an orderly transaction between market participants in the principal market for the given asset or liability at the measurement date based on market conditions at that date. An orderly transaction assumes exposure to the market for a customary period for marketing activities prior to the measurement date and not a forced liquidation or distressed sale. Certain assets and liabilities are recorded in the Company’s financial statements at fair value. Some are recorded on a recurring basis and some on a non-recurring basis. For some assets and liabilities, observable market transactions and market information might be available. For other assets and liabilities, observable market transactions and market information might not be available. A hierarchy for fair value has been established which categorizes into three levels the inputs to valuation techniques used to measure fair value. The three levels are as follows: Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) - fair value is based on unadjusted quoted prices in active markets for identical assets or liabilities. Significant Other Observable Inputs (Level 2) - fair value is based on significant other observable inputs which are generally determined based on a single price for each financial instrument provided to us by an applicable third-party pricing service and is based on one or more of the following: • Quoted prices for similar, but not identical, assets or liabilities in active markets; • Quoted prices for identical or similar assets or liabilities in inactive markets; • Inputs other than quoted prices that are observable, such as interest rate and yield curves, volatilities, prepayment speeds, loss severities, credit risks and default rates; • Other inputs derived from or corroborated by observable market inputs. Significant Unobservable Inputs (Level 3) - fair value is based upon model-based valuation techniques for which at least one significant assumption is not observable in the market. Transfers between levels are recognized as of the end of the reporting period. There were no transfers in or out of quoted prices in active markets for identical instruments to significant other observable inputs or significant unobservable inputs during the year ended December 31, 2018 and 2017 , respectively. Transfers between significant other observable inputs and significant unobservable inputs during the year ended December 31, 2018 and 2017 are included in the summary of changes in recurring fair values measured using unobservable inputs. Additionally, $208 million of held-to-maturity other debt securities were transferred from significant other observable inputs to significant unobservable inputs at December 31, 2018 due to a lack of currently available observable inputs. The underlying methods used by the third-party pricing services are considered in determining the primary inputs used to determine fair values. Management has evaluated the methodologies employed by the third-party pricing services by comparing the price provided by the pricing service with other sources, including brokers' quotes, sales or purchases of similar instruments and discounted cash flows to establish a basis for reliance on the pricing service values. Significant differences between the pricing service provided value and other sources are discussed with the pricing service to understand the basis for their values. Based on all observable inputs, management may adjust prices obtained from third-party pricing services to more appropriately reflect the prices that would be received to sell assets or paid to transfer liabilities in orderly transactions in the current market. No significant adjustments were made to prices provided by third-party pricing services at December 31, 2018 and 2017 . Assets and Liabilities Measured at Fair Value on a Recurring Basis The fair value of financial assets and liabilities that are measured on a recurring basis is as follows as of December 31, 2018 (in thousands): Total Quoted Prices in Active Markets for Identical Instruments Significant Other Observable Inputs Significant Unobservable Inputs Assets: Trading securities: U.S. government agency debentures $ 63,765 $ — $ 63,765 $ — U.S. government agency residential mortgage-backed securities 1,791,584 — 1,791,584 — Municipal and other tax-exempt securities 34,507 — 34,507 — Asset-backed securities 42,656 — 42,656 — Other trading securities 24,411 — 24,411 — Total trading securities 1,956,923 — 1,956,923 — Available for sale securities: U.S. Treasury securities 493 493 — — Municipal and other tax-exempt securities 2,864 — 2,864 — U.S. government agency residential mortgage-backed securities 5,804,708 — 5,804,708 — Privately issued residential mortgage-backed securities 59,736 — 59,736 — Commercial mortgage-backed securities guaranteed by U.S. government agencies 2,953,889 — 2,953,889 — Other debt securities 35,430 — 34,958 472 Total available for sale securities 8,857,120 493 8,856,155 472 Fair value option securities – U.S. government agency residential mortgage-backed securities 283,235 — 283,235 — Residential mortgage loans held for sale 149,221 — 134,014 15,207 Mortgage servicing rights, net 1 259,254 — — 259,254 Derivative contracts, net of cash margin 2 320,929 44,074 276,855 — Liabilities: Derivative contracts, net of cash margin 2 362,306 — 362,306 — 1 A reconciliation of the beginning and ending fair value of mortgage servicing rights and disclosures of significant assumptions used to determine fair value are presented in Note 7 , Mortgage Banking Activities . 2 See Note 3 for detail of fair value of derivative contracts by contract type. Derivative contracts in a net asset position that were valued based on quoted prices in active markets or identical instruments (Level 1) are exchange-traded interest rate, energy and agricultural derivative contracts, net of cash margin. Derivative contracts in a net liability position that were valued using quoted prices in active markets for identical instruments (Level 1) are exchange-traded interest rate derivative contracts, fully offset by cash margin. The fair value of financial assets and liabilities that are measured on a recurring basis is as follows as of December 31, 2017 (in thousands): Total Quoted Prices in Active Markets for Identical Instruments Significant Other Observable Inputs Significant Unobservable Inputs Assets: Trading securities: U.S. government agency debentures $ 21,196 $ — $ 21,196 $ — U.S. government agency residential mortgage-backed securities 392,673 — 392,673 — Municipal and other tax-exempt securities 13,559 — 13,559 — Asset-backed securities 23,885 — 23,885 — Other trading securities 11,363 — 11,363 — Total trading securities 462,676 — 462,676 — Available for sale securities: U.S. Treasury securities 1,000 1,000 — — Municipal and other tax-exempt securities 27,080 — 22,278 4,802 U.S. government agency residential mortgage-backed securities 5,309,152 — 5,309,152 — Privately issued residential mortgage-backed securities 93,221 — 93,221 — Commercial mortgage-backed securities guaranteed by U.S. government agencies 2,834,961 — 2,834,961 — Other debt securities 25,481 — 25,009 472 Perpetual preferred stock 15,767 — 15,767 — Equity securities and mutual funds 14,916 — 14,916 — Total available for sale securities 8,321,578 1,000 8,315,304 5,274 Fair value option securities – U.S. government agency residential mortgage-backed securities 755,054 — 755,054 — Residential mortgage loans held for sale 221,378 — 209,079 12,299 Mortgage servicing rights, net 1 252,867 — — 252,867 Derivative contracts, net of cash margin 2 220,502 8,179 212,323 — Liabilities: Derivative contracts, net of cash margin 2 171,963 — 171,963 — 1 A reconciliation of the beginning and ending fair value of mortgage servicing rights and disclosures of significant assumptions used to determine fair value are presented in Note 7 , Mortgage Banking Activities. 2 See Note 3 for detail of fair value of derivative contracts by contract type. Derivative contracts in a net asset position that were valued based on quoted prices in active markets for identical instruments (Level 1) are exchange-traded interest rate, energy and agricultural derivative contracts, net of cash margin. Derivative contracts in a net liability position that were valued using quoted prices in active markets for identical instruments based on quoted prices in active markets for identical instruments (Level 1) are exchange-traded interest rate and energy derivative contracts, fully offset by cash margin. Following is a description of the Company's valuation methodologies used for assets and liabilities measured on a recurring basis: Securities The fair values of trading, available for sale and fair value option securities are based on quoted prices for identical instruments in active markets, when available. If quoted prices for identical instruments are not available, fair values are based on significant other observable inputs such as quoted prices of comparable instruments or interest rates and credit spreads, yield curves, volatilities, prepayment speeds and loss severities. The fair value of certain available for sale and held-to-maturity municipal and other debt securities may be based on significant unobservable inputs. These significant unobservable inputs include limited observed trades, projected cash flows, current credit rating of the issuers and, when applicable, the insurers of the debt and observed trades of similar debt. Discount rates are primarily based on reference to interest rate spreads on comparable securities of similar duration and credit rating as determined by the nationally-recognized rating agencies adjusted for a lack of trading volume. Significant unobservable inputs are developed by investment securities professionals involved in the active trading of similar securities. A summary of significant inputs used to value these securities follows. A management committee composed of senior members from the Company's Capital Markets, Risk Management and Finance departments assess the appropriateness of these inputs quarterly. Derivatives All derivative instruments are carried on the balance sheet at fair value. Fair values for exchange-traded contracts are based on quoted prices. Fair values for over-the-counter interest rate, commodity and foreign exchange contracts are based on valuations provided either by third-party dealers in the contracts, quotes provided by independent pricing services, or a third-party provided pricing model that uses significant other observable market inputs. Credit risk is considered in determining the fair value of derivative instruments. Management determines fair value adjustments based on various risk factors including but not limited to counterparty credit rating or equivalent loan grading, derivative contract notional size, price volatility of the underlying commodity, duration of the derivative contracts and expected loss severity. Expected loss severity is based on historical losses for similarly risk graded commercial loan customers. Decreases in counterparty credit rating or grading and increases in price volatility and expected loss severity all tend to increase the credit quality adjustment which reduces the fair value of asset contracts. We also consider our own credit risk in determining the fair value of derivative contracts. Changes in our credit rating would affect the fair value of our derivative liabilities. In the event of a credit downgrade, the fair value of our derivative liabilities would increase. Residential Mortgage Loans Held for Sale Residential mortgage loans held for sale are carried on the balance sheet at fair value. The fair values of conforming residential mortgage loans held for sale are based upon quoted market prices of such loans sold in securitization transactions, including related unfunded loan commitments. The fair value of mortgage loans that are unable to be sold to U.S. government agencies is determined using quoted prices of loans that are sold in securitization transactions with a liquidity discount applied. The following represents the changes related to assets measured at fair value on a recurring basis using significant unobservable inputs (in thousands): Available for Sale Securities Residential mortgage loans held for sale Municipal and other tax-exempt securities Other debt securities Balance, December 31, 2016 $ 5,789 $ 4,152 $ 11,617 Transfer to Level 3 from Level 2 1 — — 3,507 Purchases and capital calls — — — Redemptions and distributions (1,100 ) — — Proceeds from sales — (3,900 ) (2,944 ) Gain (loss) recognized in earnings: Mortgage banking revenue — — 119 Other comprehensive income (loss): Net change in unrealized gain (loss) 113 220 — Balance, December 31, 2017 4,802 472 12,299 Transfer to Level 3 from Level 2 1 — — 6,183 Purchases and capital calls — — — Redemptions and distributions (5,095 ) — — Proceeds from sales — — (2,706 ) Gain (loss) recognized in earnings: Mortgage banking revenue — — (569 ) Other comprehensive income (loss): Net change in unrealized gain (loss) 293 — — Balance, December 31, 2018 $ — $ 472 $ 15,207 1 Recurring transfers to Level 3 from Level 2 consist of residential mortgage loans intended for sale to U.S. government agencies that fail to meet conforming standards. A summary of quantitative information about assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3) as of December 31, 2018 follows (in thousands): Quantitative Information about Level 3 Recurring Fair Value Measurements Fair Value Valuation Technique(s) Significant Unobservable Input Range (Weighted Average) Available for sale securities: Other debt securities 472 Discounted cash flows 1 Interest rate spread 7.88%-7.88% (7.88%) 3 94.44%-94.44% (94.44%) 2 Residential mortgage loans held for sale 15,207 Quoted prices of loans sold in securitization transactions, with a liquidity discount applied Liquidity discount applied to the market value of mortgage loans qualifying for sale to U.S. government agencies 92.38% 1 Discounted cash flows developed using discount rates primarily based on reference to interest rate spreads for comparable securities of similar duration and credit rating as determined by the nationally-recognized rating agencies, adjusted for lack of trading volume. 2 Represents fair value as a percentage of par value. 3 Interest rate yields used to value investment grade taxable securities based on comparable short-term taxable securities which are generally yielding approximately 3% . A summary of quantitative information about Recurring Fair Value Measurements based on Significant Unobservable Inputs (Level 3) as of December 31, 2017 follows (in thousands): Quantitative Information about Level 3 Recurring Fair Value Measurements Fair Value Valuation Technique(s) Significant Unobservable Input Range (Weighted Average) Available for sale securities: Municipal and other tax-exempt securities $ 4,802 Discounted cash flows 1 Interest rate spread 6.60%-6.60% (6.60%) 2 92.25%-94.76% (93.75%) 3 Other debt securities 472 Discounted cash flows 1 Interest rate spread 6.85%-6.85% (6.85%) 4 94.39%-94.39% (94.39%) 3 Residential mortgage loans held for sale 12,299 Quoted prices of loans sold in securitization transactions, with a liquidity discount applied Liquidity discount applied to the market value of mortgage loans qualifying for sale to U.S. government agencies 94.75% 1 Discounted cash flows developed using discount rates primarily based on reference to interest rate spreads for comparable securities of similar duration and credit rating as determined by the nationally-recognized rating agencies, adjusted for lack of trading volume. 2 Interest rate yields used to value investment grade tax-exempt securities represent a spread of 372 to 466 basis points over average yields for comparable tax-exempt securities. 3 Represents fair value as a percentage of par value. 4 Interest rate yields used to value investment grade taxable securities based on comparable short-term taxable securities which are generally yielding less than 3% . Fair Value of Assets and Liabilities Measured on a Non-Recurring Basis Assets measured at fair value on a non-recurring basis include pension plan assets, which are based on quoted prices in active markets for identical instruments, collateral for certain impaired loans and real property and other assets acquired to satisfy loans, which are based primarily on comparisons to completed sales of similar assets. See Note 6 for information related to the non-recurring fair value measurement of CoBiz Financial. The following represents the carrying value of assets measured at fair value on a non-recurring basis and related losses recorded during the year. The carrying value represents only those assets with the balance sheet date for which the fair value was adjusted during the year: Carrying Value at December 31, 2018 Fair Value Adjustments for the Quoted Prices in Active Markets for Identical Instruments Significant Other Observable Inputs Significant Unobservable Inputs Gross charge-offs against allowance for loan losses Net losses and expenses of repossessed assets, net Impaired loans $ — $ 1,074 $ 17,401 $ 17,434 $ — Real estate and other repossessed assets — 4,795 6,366 — 7,269 Carrying Value at December 31, 2017 Fair Value Adjustments for the Quoted Prices in Active Markets for Identical Instruments Significant Other Observable Inputs Significant Unobservable Inputs Gross charge-offs against allowance for loan losses Net losses and expenses of repossessed assets, net Impaired loans $ — $ 7,436 $ 7,626 $ 12,145 $ — Real estate and other repossessed assets — 3,483 5,481 — 6,372 The fair value of collateral-dependent impaired loans and real estate and other repossessed assets and the related fair value adjustments are generally based on unadjusted third-party appraisals. Our appraisal review policies require appraised values to be supported by observed inputs derived principally from or corroborated by observable market data. Appraisals that are not based on observable inputs or that require significant adjustments or fair value measurements that are not based on third-party appraisals are considered to be based on significant unobservable inputs. Non-recurring fair value measurements of collateral-dependent impaired loans and real estate and other repossessed assets based on significant unobservable inputs are generally due to estimates of current fair values between appraisal dates. Significant unobservable inputs include listing prices for comparable assets, uncorroborated expert opinions or management's knowledge of the collateral or industry. Non-recurring fair value measurements of collateral dependent loans secured by mineral rights are generally determined by our internal staff of engineers on projected cash flows under current market conditions and are based on significant unobservable inputs. Projected cash flows are discounted according to risk characteristics of the underlying oil and gas properties. Assets are evaluated to demonstrate with reasonable certainty that crude oil, natural gas and natural gas liquids can be recovered from known oil and gas reservoirs under existing economic and operating conditions at current prices with existing conventional equipment, operating methods and costs. Significant unobservable inputs are developed by asset management and workout professionals and approved by senior Credit Administration executives. A summary of quantitative information about Non-recurring Fair Value Measurements based on Significant Unobservable Inputs (Level 3) as of December 31, 2018 follows (in thousands): Quantitative Information about Level 3 Non-recurring Fair Value Measurements Fair Value Valuation Technique(s) Significant Unobservable Input Range (Weighted Average) Impaired loans $ 17,401 Discounted cash flows Management knowledge of industry and non-real estate collateral including but not limited to recoverable oil & gas reserves, forward looking commodity prices, and estimated operating costs 35% - 80% (50%) 1 Real estate and other repossessed assets 6,366 Discounted cash flows Recoverable oil and gas reserves, forward-looking commodity prices, estimated operating costs N/A 1 Represents fair value as a percentage of the unpaid principal balance. The table above excludes the initial measurement of assets and liabilities that were acquired as part of the CoBiz acquisition in October 1, 2018. These assets and liabilities were recorded at their fair value upon acquisition in accordance with U.S. GAAP and were not re-measured during the periods presented unless specifically required by U.S. GAAP. Acquisition date fair values represent either Level 2 fair value measurements (investment securities, deposits, property, equipment, and debt) or Level 3 fair value measurements (loans and core deposit intangible assets). Refer to Note 6, Goodwill and Intangible Assets, for further detail regarding the CoBiz acquisition. A summary of quantitative information about Non-recurring Fair Value Measurements based on Significant Unobservable Inputs (Level 3) as of December 31, 2017 follows (in thousands): Quantitative Information about Level 3 Non-recurring Fair Value Measurements Fair Value Valuation Technique(s) Significant Unobservable Input Range (Weighted Average) Impaired loans $ 7,626 Discounted cash flows Recoverable oil and gas reserves, forward-looking commodity prices and estimated operating costs 40% - 86% (59%) 1 Real estate and other repossessed assets 5,481 Discounted cash flows Recoverable oil and gas reserves, forward-looking commodity prices and estimated operating costs N/A 1 Represents fair value as a percentage of the unpaid principal balance. The fair value of pension plan assets was approximately $34 million at December 31, 2018 and $40 million at December 31, 2017 , determined by significant other observable inputs. Fair value adjustments of pension plan assets along with changes in the projected benefit obligation are recognized in other comprehensive income. Fair Value of Financial Instruments The following table presents the carrying values and estimated fair values of all financial instruments, including those financial assets and liabilities that are not measured and reported at fair value on a recurring basis or non-recurring (dollars in thousands): December 31, 2018 Carrying Value Estimated Fair Value Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash and due from banks $ 741,749 $ 741,749 $ 741,749 $ — $ — Interest-bearing cash and cash equivalents 401,675 401,675 401,675 — — Trading securities: U.S. government agency debentures 63,765 63,765 — 63,765 — U.S. government agency residential mortgage-backed securities 1,791,584 1,791,584 — 1,791,584 — Municipal and other tax-exempt securities 34,507 34,507 — 34,507 — Asset-backed securities 42,656 42,656 — 42,656 — Other trading securities 24,411 24,411 — 24,411 — Total trading securities 1,956,923 1,956,923 — 1,956,923 — Investment securities: Municipal and other tax-exempt securities 137,296 138,562 — 138,562 — U.S. government agency residential mortgage-backed securities 12,612 12,770 — 12,770 — Other debt securities 205,279 215,966 — 7,905 208,061 Total investment securities 355,187 367,298 — 159,237 208,061 Available for sale securities: U.S. Treasury securities 493 493 493 — — Municipal and other tax-exempt securities 2,864 2,864 — 2,864 — U.S. government agency residential mortgage-backed securities 5,804,708 5,804,708 — 5,804,708 — Privately issued residential mortgage-backed securities 59,736 59,736 — 59,736 — Commercial mortgage-backed securities guaranteed by U.S. government agencies 2,953,889 2,953,889 — 2,953,889 — Other debt securities 35,430 35,430 — 34,958 472 Total available for sale securities 8,857,120 8,857,120 493 8,856,155 472 Fair value option securities – U.S. government agency residential mortgage-backed securities 283,235 283,235 — 283,235 — Residential mortgage loans held for sale 149,221 149,221 — 134,014 15,207 Loans: Commercial 13,636,078 13,526,162 — — 13,526,162 Commercial real estate 4,764,813 4,713,747 — — 4,713,747 Residential mortgage 2,230,033 2,213,951 — — 2,213,951 Personal 1,025,806 1,024,368 — — 1,024,368 Total loans 21,656,730 21,478,228 — — 21,478,228 Allowance for loan losses (207,457 ) — — — — Loans, net of allowance 21,449,273 21,478,228 — — 21,478,228 Mortgage servicing rights 259,254 259,254 — — 259,254 Derivative instruments with positive fair value, net of cash margin 320,929 320,929 44,074 276,855 — Deposits with no stated maturity 23,150,383 23,150,383 — — 23,150,383 Time deposits 2,113,380 2,073,538 — — 2,073,538 Other borrowed funds 7,142,801 6,771,953 — — 6,771,953 Subordinated debentures 275,913 261,977 — 261,977 — Derivative instruments with negative fair value, net of cash margin 362,306 362,306 — 362,306 — December 31, 2017 Carrying Value Estimated Fair Value Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash and due from banks $ 602,510 $ 602,510 $ 602,510 $ — $ — Interest-bearing cash and cash equivalents 1,714,544 1,714,544 1,714,544 — — Trading securities: U.S. government agency debentures 21,196 21,196 — 21,196 — U.S. government agency residential mortgage-backed securities 392,673 392,673 — 392,673 — Municipal and other tax-exempt securities 13,559 13,559 — 13,559 — Asset-backed securities 23,885 23,885 — 23,885 — Other trading securities 11,363 11,363 — 11,363 — Total trading securities 462,676 438,791 — 438,791 — Investment securities: Municipal and other tax-exempt securities 228,186 230,349 — 230,349 — U.S. government agency residential mortgage-backed securities 15,891 16,242 — 16,242 — Other debt securities 217,716 233,444 — 233,444 — Total investment securities 461,793 480,035 — 480,035 — Available for sale securities: U.S. Treasury securities 1,000 1,000 1,000 — — Municipal and other tax-exempt securities 27,080 27,080 — 22,278 4,802 U.S. government agency residential mortgage-backed securities 5,309,152 5,309,152 — 5,309,152 — Privately issued residential mortgage-backed securities 93,221 93,221 — 93,221 — Commercial mortgage-backed securities guaranteed by U.S. government agencies 2,834,961 2,834,961 — 2,834,961 — Other debt securities 25,481 25,481 — 25,009 472 Perpetual preferred stock 15,767 15,767 — 15,767 — Equity securities and mutual funds 14,916 14,916 — 14,916 — Total available for sale securities 8,321,578 8,321,578 1,000 8,315,304 5,274 Fair value option securities – U.S. government agency residential mortgage-backed securities 755,054 755,054 — 755,054 — Residential mortgage loans held for sale 221,378 221,378 — 208,946 12,432 Loans: Commercial 10,733,975 10,524,627 — — 10,524,627 Commercial real estate 3,479,987 3,428,733 — — 3,428,733 Residential mortgage 1,973,686 1,977,721 — — 1,977,721 Personal 965,776 956,706 — — 956,706 Total loans 17,153,424 16,887,787 — — 16,887,787 Allowance for loan losses (230,682 ) — — — — Loans, net of allowance 16,922,742 16,887,787 — — 16,887,787 Mortgage servicing rights 252,867 252,867 — — 252,867 Derivative instruments with positive fair value, net of cash margin 220,502 220,502 8,179 212,323 — Deposits with no stated maturity 19,962,889 19,962,889 — — 19,962,889 Time deposits 2,098,416 2,064,558 — — 2,064,558 Other borrowed funds 5,709,860 5,703,121 — — 5,703,121 Subordinated debentures 144,677 148,207 — 148,207 — Derivative instruments with negative fair value, net of cash margin 171,963 171,963 — 171,963 — Because no market exists for certain of these financial instruments and management does not intend to sell these financial instruments, the fair values shown in the tables above may not represent values at which the respective financial instruments could be sold individually or in the aggregate at the given reporting date. Fair Value Election As more fully disclosed in Note 2 and Note 7

Parent Company Only Financial S

Parent Company Only Financial Statements Parent Company Only Financial Statements	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Disclosure [Abstract]
Condensed Financial Information of Parent Company Only Disclosure [Text Block]	Parent Company Only Financial Statements Summarized financial information for BOK Financial – Parent Company Only follows: Balance Sheets (In thousands) December 31, 2018 2017 Assets Cash and cash equivalents $ 167,093 $ 205,876 Available for sale securities — 16,185 Loan to bank subsidiary 65,228 — Investment in bank subsidiaries 4,236,654 3,255,912 Investment in non-bank subsidiaries 218,007 170,966 Other assets 32,999 4,065 Total assets $ 4,719,981 $ 3,653,004 Liabilities and Shareholders’ Equity Liabilities: Other liabilities $ 11,959 $ 12,960 Subordinated debentures 275,913 144,677 Total liabilities 287,872 157,637 Shareholders’ equity: Common stock 5 4 Capital surplus 1,334,030 1,035,895 Retained earnings 3,369,654 3,048,487 Treasury stock (72,585 ) (36,174 ) Accumulated other comprehensive loss (198,995 ) (552,845 ) Total shareholders’ equity 4,432,109 3,495,367 Total liabilities and shareholders’ equity $ 4,719,981 $ 3,653,004 Statements of Earnings (In thousands) Year Ended December 31, 2018 2017 2016 Dividends, interest and fees received from bank subsidiaries $ 426,071 $ 150,149 $ 15,237 Dividends, interest and fees received from non-bank subsidiaries 12,800 17,500 25,923 Other revenue 954 936 1,612 Total revenue 439,825 168,585 42,772 Interest expense 9,827 8,239 4,182 Other operating expense 12,110 2,014 1,978 Total expense 21,937 10,253 6,160 Net income before taxes, other losses, net, and equity in undistributed income of subsidiaries 417,888 158,332 36,612 Other losses, net (3,921 ) — — Net income before taxes and equity in undistributed income of subsidiaries 413,967 158,332 36,612 Federal and state income taxes (7,078 ) (4,305 ) (1,920 ) Net income before equity in undistributed income of subsidiaries 421,045 162,637 38,532 Equity in undistributed income of bank subsidiaries 37,515 181,552 216,120 Equity in undistributed income of non-bank subsidiaries (12,914 ) (9,545 ) (21,984 ) Net income attributable to BOK Financial Corp. shareholders $ 445,646 $ 334,644 $ 232,668 Statements of Cash Flows (In thousands) Year Ended December 31, 2018 2017 2016 Cash Flows From Operating Activities: Net income $ 445,646 $ 334,644 $ 232,668 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed income of bank subsidiaries (37,515 ) (181,552 ) (216,120 ) Equity in undistributed income of non-bank subsidiaries 12,914 9,545 21,984 Change in other assets (1,072 ) 12 (2,933 ) Change in other liabilities (13,434 ) 7,457 (1,285 ) Net cash provided by operating activities 406,539 170,106 34,314 Cash Flows From Investing Activities: Proceeds from sales of available for sale securities — 3,000 1,632 Investment in subsidiaries (31,901 ) (4,355 ) (26,000 ) Acquisitions, net of cash acquired (232,680 ) — (105,520 ) Net cash used in investing activities (264,581 ) (1,355 ) (129,888 ) Cash Flows From Financing Activities: Net change in other borrowed funds — (7,217 ) — Issuance of subordinated debentures, net of issuance costs — — 144,615 Issuance of common and treasury stock, net (88 ) 4,368 12,455 Dividends paid (127,188 ) (116,041 ) (113,455 ) Repurchase of common stock (53,465 ) (7,403 ) (66,792 ) Net cash used in financing activities (180,741 ) (126,293 ) (23,177 ) Net increase (decrease) in cash and cash equivalents (38,783 ) 42,458 (118,751 ) Cash and cash equivalents at beginning of period 205,876 163,418 282,169 Cash and cash equivalents at end of period $ 167,093 $ 205,876 $ 163,418 Cash paid for interest $ 11,457 $ 6,211 $ 4,127

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Events The Company evaluated events from the date of the Consolidated Financial Statements on December 31, 2018

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation [Policy Text Block]	The Consolidated Financial Statements of BOK Financial Corporation (“BOK Financial” or “the Company”) have been prepared in conformity with accounting principles generally accepted in the United States ("U.S. GAAP"), including interpretations of U.S. GAAP issued by federal banking regulators and general practices of the banking industry.
Consolidation [Policy Text Block]	The Consolidated Financial Statements include the accounts of BOK Financial and its subsidiaries, principally BOKF, NA, CoBiz Bank, BOK Financial Securities, Inc., The Milestone Group, Inc. and Cavanal Hill Distributors, Inc. All significant intercompany transactions are eliminated in consolidation.
Reclassifications [Text Block]	Certain prior year amounts have been reclassified to conform to current year presentation.
Nature of Operations [Text Block]	Nature of Operations BOK Financial, through its subsidiaries, provides a wide range of financial services to commercial and industrial customers, other financial institutions, municipalities, and consumers. These services include depository and cash management; lending and lease financing; mortgage banking; securities brokerage, trading and underwriting; and personal and corporate trust. BOKF, NA operates as Bank of Oklahoma primarily in the Tulsa and Oklahoma City metropolitan areas of the state of Oklahoma and Bank of Texas primarily in the Dallas, Fort Worth and Houston metropolitan areas of the state of Texas. In addition, BOKF, NA does business as Bank of Albuquerque in Albuquerque, New Mexico; Colorado State Bank and Trust in Denver, Colorado; Bank of Arizona in Phoenix, Arizona; Mobank in Kansas City, Missouri/Kansas and Bank of Arkansas in Northwest Arkansas. BOKF, NA also operates the TransFund electronic funds network, Cavanal Hill Investment Management, and BOK Financial Asset Management, Inc. On October 1, 2018, BOK Financial acquired CoBiz Financial, Inc. and CoBiz Bank, its wholly owned subsidiary. CoBiz Financial has been merged into BOK Financial. CoBiz Bank will be merged into BOKF, NA in the first quarter of 2019.
Use of Estimates [Policy Text Block]	Use of Estimates
Acquisitions [Policy Text Block]	Acquisitions
Goodwill and Intangible Assets [Policy Text Block]	Goodwill and Intangible Assets Goodwill and intangible assets generally result from business combinations and are evaluated for each of BOK Financial's reporting units for impairment annually or more frequently if conditions indicate impairment. The evaluation of possible impairment of goodwill and intangible assets involves significant judgment based upon short-term and long-term projections of future performance. Reporting units are defined by the Company as significant lines of business within each operating segment. This definition is consistent with the manner in which the chief operating decision maker assesses the performance of the Company and makes decisions concerning the allocation of resources. The Company qualitatively assesses whether it is more likely than not that the fair value of the reporting units are less than their carrying value, including goodwill. Reporting unit carrying value includes sufficient capital to exceed regulatory requirements. This assessment includes consideration of relevant events and circumstances including but not limited to macroeconomic conditions, industry and market conditions, the financial and stock performance of the Company and other relevant factors. If the Company concludes based on the qualitative assessment that goodwill may be impaired, a quantitative one-step impairment test will be applied to goodwill at all reporting units. The quantitative analysis compares the fair value of the reporting unit with its carrying value, including goodwill. The fair value of each reporting unit is estimated by the discounted future earnings method. Goodwill is considered impaired if the fair value of the reporting unit is less than the carrying value of the reporting unit, including goodwill. Intangible assets are generally composed of customer relationships, naming rights, non-compete agreements and core deposit premiums. They are amortized using accelerated or straight-line methods, as appropriate, over the estimated benefit periods. These periods range from 3 years to 20 years
Cash Equivalents [Policy Text Block]	Cash Equivalents Due from banks, funds sold (generally federal funds sold for one day ), resell agreements (which generally mature within one day to 30 days
Securities [Policy Text Block]	Securities Securities are identified as trading, investment (held to maturity) or available for sale at the time of purchase based upon the intent of management, liquidity and capital requirements, regulatory limitations and other relevant factors. Trading securities, which are acquired for profit through resale, are carried at fair value with unrealized gains and losses included in current period earnings. Investment securities are carried at amortized cost. Amortization is computed by methods that approximate level yield and is adjusted for changes in prepayment estimates. Securities identified as available for sale are carried at fair value. Unrealized gains and losses are recorded, net of deferred income taxes, as accumulated other comprehensive income in shareholders' equity. Available for sale securities are separately identified as pledged to creditors if the creditor has the right to sell or re-pledge the collateral. The purchase or sale of securities is recognized on a trade date basis. Realized gains and losses on sales of securities are based upon specific identification of the security sold. A receivable or payable is recognized for subsequent transaction settlement. Securities meeting certain criteria may also be transferred from the available for sale classification to the investment securities portfolio at fair value on the date of transfer. The unrealized gain or loss at the date of transfer is retained in accumulated other comprehensive income and in the carrying value of the investment securities portfolio. Such amounts are amortized over the estimated remaining life of the security as an adjustment to yield, offsetting the related amortization of the premium or accretion of the discount on the transferred securities. On a quarterly basis, the Company performs separate evaluations of impaired debt investment and available for sale securities to determine if the decline in fair value below the amortized cost is other-than-temporary. Management determines whether it intends to sell or if it is more likely than not that it will be required to sell impaired securities. This determination considers current and forecasted liquidity requirements and securities portfolio management. If the Company intends to sell or it is more likely than not that it will be required to sell the impaired debt security, a charge is recognized against earnings for the entire unrealized loss. For all impaired debt securities for which there is no intent or expected requirement to sell, the evaluation considers all available evidence to assess whether it is more likely than not that all amounts due would not be collected according to the security's contractual terms. Impairment of debt securities rated investment grade by nationally-recognized rating agencies is considered temporary unless specific contrary information is identified. Impairment of debt securities rated below investment grade by at least one of the nationally recognized rating agencies is evaluated based on projections of estimated cash flows. Any expected credit loss due to the inability to collect all amounts due according to the security's contractual terms is recognized as a charge against earnings. Any remaining unrealized loss related to other factors would be recognized in other comprehensive income, net of taxes. BOK Financial may elect to carry certain securities at fair value with changes in fair value recognized in current period income. These securities are held with the intent that gains or losses will offset changes in the fair value of mortgage servicing rights or certain derivative instruments. Restricted equity securities represent equity interests the Company is required to hold in the Federal Reserve Banks and Federal Home Loan Banks. Restricted equity securities are carried at cost as these securities do not have a readily determined fair value because ownership of these shares is restricted and they lack a market. The fair value of our securities portfolio is generally based on a single price for each financial instrument provided to us by a third-party pricing service determined by one or more of the following: • Quoted prices for similar, but not identical, assets or liabilities in active markets; • Quoted prices for identical or similar assets or liabilities in inactive markets; • Inputs other than quoted prices that are observable, such as interest rate and yield curves, volatilities, prepayment speeds, loss severities, credit risks and default rates; and • Other inputs derived from or corroborated by observable market inputs. The underlying methods used by the third-party pricing services are considered in determining the primary inputs used to determine fair values. We evaluate the methodologies employed by the third-party pricing services by comparing the price provided by the pricing service with other sources, including brokers' quotes, sales or purchases of similar instruments and discounted cash flows to establish a basis for reliance on the pricing service values. Significant differences between the pricing service provided value and other sources are discussed with the pricing service to understand the basis for their values. Based on all observable inputs, management may adjust prices obtained from third-party pricing services to more appropriately reflect the prices that would be received to sell assets or paid to transfer liabilities in orderly transactions in the current market.
Derivatives Instruments [Policy Text Block]	Derivative Instruments Derivative instruments may be used by the Company as part of its internal risk management programs or may be offered to customers. All derivative instruments are carried at fair value and changes in fair value are generally reported in income as they occur. The determination of fair value of derivative instruments considers changes in interest rates, commodity prices and foreign exchange rates. Fair values for exchange-traded contracts are based on quoted prices in an active market for identical instruments. Fair values for over-the-counter contracts are generated internally using third-party valuation models. Inputs used in third-party valuation models to determine fair values are considered significant other observable inputs. Credit risk is also considered in determining fair value. Deterioration in the credit rating of customers or other counterparties reduces the fair value of asset contracts. Deterioration of our credit rating could decrease the fair value of our derivative liabilities. When bilateral netting agreements or similar agreements exist between the Company and its counterparties that create a single legal claim or obligation to pay or receive the net amount in settlement of the individual derivative contracts, the Company reports derivative assets and liabilities on a net by derivative contract by counterparty basis. Derivative contracts may also require the Company to provide or receive cash margin as collateral for derivative assets and liabilities. Derivative assets and liabilities are reported net of cash margin when certain conditions are met. In addition, derivative contracts executed with customers under Customer Risk Management Programs may be secured by non-cash collateral in conjunction with a credit agreement with that customer. Access to collateral in the event of default is reasonably assured. Derivative instruments may be designated as cash flow hedges of variable rate assets or liabilities, or of anticipated transactions. Changes in the fair value of derivative instruments designated as cash flow hedges are recorded in accumulated other comprehensive income to the extent they are effective. The amount recorded in other comprehensive income is reclassified to earnings in the same periods as the hedged cash flows impact earnings. The ineffective portion of changes in fair value is reported in current earnings. BOK Financial may use derivative instruments in managing its interest rate sensitivity, as part of its economic hedge of the changes in the fair value of mortgage servicing rights and to mitigate the market risk of holding trading securities. Changes in the fair value of derivative instruments used in managing interest rate sensitivity and as part of its economic hedge of changes in the fair value of mortgage servicing rights are included in Other Operating Revenue - Gain (loss) on derivatives, net in the Consolidated Statements of Earnings. Changes in the fair value of derivative instruments used to mitigate the market risk of holding trading securities are included in Operating Revenue - Brokerage and trading revenue. BOK Financial also enters into mortgage loan commitments that are considered derivative contracts. Forward sales contracts that have not been designated as hedging instruments are used to economically hedge these mortgage loan commitments as well as mortgage loans held for sale. Mortgage loan commitments are carried at fair value based upon quoted prices. Changes in the fair value of mortgage loan commitments, mortgage loans held for sale and forward sales contracts are reported in Other Operating Revenue - Mortgage banking revenue. BOK Financial offers programs that permit its customers to manage various risks, including fluctuations in energy, cattle and other agricultural products, interest rates and foreign exchange rates with derivative contracts. Customers may also manage interest rate risk through interest rate swaps used by the borrower to modify interest rate terms of their loans or to-be-announced securities used by our mortgage banking customers to hedge their loan production. Derivative contracts are executed between the customers and BOK Financial. Offsetting contracts are executed between BOK Financial and other selected counterparties to minimize market risk from changes in commodity prices, interest rates or foreign exchange rates. The counterparty contracts are identical to customer contracts, except for a fixed pricing spread or fee paid to BOK Financial as profit and compensation for administrative costs and credit risk which is recognized over the life of the contracts and included in other Operating Revenue - Brokerage and trading revenue in the Consolidated Statements of Earnings.
Loans [Policy Text Block]	Loans Loans are either secured or unsecured based on the type of loan and the financial condition of the borrower. Repayment is generally expected from cash flow or proceeds from the sale of selected assets of the borrower. BOK Financial is exposed to risk of loss on loans due to the borrower's financial difficulties, which may arise from any number of factors, including problems within the respective industry or local economic conditions. Access to collateral, in the event of borrower default, is reasonably assured through adherence to applicable lending laws and through sound lending standards and credit review procedures. Accounting policies for all loans, excluding residential loans guaranteed by U.S. government agencies, are as follows. Interest is accrued at the applicable interest rate on the outstanding principal amount. Loans are placed on nonaccruing status when, in the opinion of management, full collection of principal or interest is uncertain. Internally risk graded loans are individually evaluated for nonaccruing status quarterly. Non-risk graded loans are generally placed on nonaccruing status when 90 days or more past due or within 60 days of being notified of the borrower's bankruptcy filing. Interest previously accrued but not collected is charged against interest income when the loan is placed on nonaccruing status. Payments received on nonaccruing loans are applied to principal or recognized as interest income, according to management's judgment as to the collectability of principal. Loans may be returned to accruing status when, in the opinion of management, full collection of principal and interest, including principal previously charged off, is probable based on improvements in the borrower's financial condition or a sustained period of performance. For loans acquired with no evidence of credit deterioration, discounts are accreted on either an individual basis for loans with unique characteristics or on a pool basis for groups of homogeneous loans. Accretion is discontinued when a loan with an individually attributed discount is placed on nonaccruing status. Loans to borrowers experiencing financial difficulties may be modified in troubled debt restructurings ("TDRs"). All TDRs are generally classified as nonaccruing, excluding loans guaranteed by U.S. government agencies. Modifications generally consist of extension of payment terms or interest rate concessions and may result either voluntarily through negotiations with the borrower or involuntarily through court order. Generally, principal and accrued but unpaid interest is not voluntarily forgiven. Performing loans may be renewed under the current collateral, debt service ratio and other underwriting standards. Nonaccruing loans may also be renewed and will remain classified as nonaccruing. Occasionally, loans, other than residential mortgage loans, may be held for sale in order to manage credit concentration. These loans are carried at the lower of cost or fair value with gains or losses recognized in gain (loss) on assets. All loans are charged-off when the loan balance or a portion of the loan balance is no longer supported by the paying capacity of the borrower or when the required cash flow is reduced in a TDR. The charge-off amount is determined through an evaluation of available cash resources and collateral value. Internally risk graded loans are evaluated quarterly and charge-offs are taken in the quarter in which the loss is identified. Non-risk graded loans that are past due between 60 days and 180 days , based on the loan product type, are charged off. Loans to borrowers whose personal obligation has been discharged through Chapter 7 bankruptcy proceedings are charged off within 60 days of notice of the bankruptcy filing, regardless of payment status. Loan origination and commitment fees and direct loan acquisition and origination costs are deferred and amortized as an adjustment to yield over the life of the loan or over the commitment period, as applicable. Amortization does not anticipate loan prepayments. Net unamortized fees are recognized in full at time of payoff. Qualifying residential mortgage loans guaranteed by U.S. government agencies have been sold into GNMA pools. Under certain performance conditions specified in government programs, the Company has the right, but not the obligation to repurchase loans from GNMA pools. These loans no longer qualify for sale accounting and are recognized in the Consolidated Balance Sheets. Guaranteed loans are considered to be impaired because we do not expect to receive all principal and interest based on the loan's contractual terms. The principal balance continues to be guaranteed, however, interest accrues at a curtailed rate as specified in the programs. The carrying value of these loans is reduced based on an estimate of expected cash flows discounted at the original note rate plus a liquidity spread. Guaranteed loans may be modified in TDRs in accordance with U.S. government agency guidelines. Interest continues to accrue at the modified rate. Guaranteed loans may either be resold into GNMA pools after a performance period specified by the programs or foreclosed and conveyed to the guarantors.
Allowance for Loan Losses and Accrual for Off-Balance Sheet Credit Losses [Policy Text Block]	Allowance for Loan Losses and Accrual for Off-Balance Sheet Credit Risk The appropriateness of the allowance for loan losses and accrual for off-balance sheet credit risk (collectively "Allowance for Credit Losses") is assessed by management based on an ongoing quarterly evaluation of the probable estimated losses inherent in the portfolio, including probable losses on both outstanding loans and unused commitments to provide financing. A consistent well-documented methodology has been developed and is applied by an independent Credit Administration department to assure consistency across the Company. The allowance for loan losses consists of specific allowances attributed to impaired loans that have not yet been charged down to amounts we expect to recover, general allowances based on estimated loss rates by loan class and nonspecific allowances based on factors that affect more than one portfolio segment. There were no changes to the methodology for estimating general allowances during 2018 or 2017 . Loans are considered to be impaired when it becomes probable that BOK Financial will be unable to collect all amounts due according to the contractual terms of the loan agreements. Internally risk graded loans are evaluated individually for impairment. Substantially all commercial and commercial real estate loans and certain residential mortgage and personal loans are risk graded based on a quarterly evaluation of the borrowers' ability to repay. Certain commercial loans and most residential mortgage and personal loans are small balance, homogeneous pools of loans that are not risk graded. Non-risk graded loans are identified as impaired based on performance status. Generally, non-risk graded loans 90 days or more past due, modified in a troubled debt restructuring or in bankruptcy are considered to be impaired. Specific allowances for impaired loans are measured by an evaluation of estimated future cash flows discounted at the loan's initial effective interest rate or the fair value of collateral for certain collateral dependent loans. The fair value of real property held as collateral is generally based on third party appraisals that conform to Uniform Standards of Professional Appraisal Practice, less estimated selling costs. Appraised values are on an “as-is” basis and generally are not adjusted by the Company. Updated appraisals are obtained at least annually or more frequently if market conditions indicate collateral values may have declined. Collateral value of mineral rights is generally determined by our internal staff of engineers based on projected cash flows from proven oil and gas reserves under existing economic and operating conditions. The value of other collateral is generally determined by our special assets staff based on projected liquidation cash flows under current market conditions. Collateral values and available cash resources that support impaired loans are evaluated quarterly. Historical statistics may be used as a practical way to estimate impairment in limited situations, such as when a collateral dependent loan is identified as impaired at the end of a reporting period until an appraisal of collateral value is received or a full assessment of future cash flows is completed. Estimates of future cash flows and collateral values require significant judgments and may be volatile. General allowances for unimpaired loans are based on an estimated loss rate by loan class. The appropriate historical gross loss rate for each loan class is determined by the greater of the current loss rate based on the most recent twelve months or a ten-year average gross loss rate. Recoveries are not directly considered in the estimation of historical loss rates. Recoveries generally do not follow predictable patterns and are not received until well-after the charge-off date as a result of protracted legal actions. For risk graded loans, historical gross loss rates are adjusted for changes in risk grading. For each loan class, the current weighted average risk grade is compared to the long-term weighted average risk grade. This comparison determines whether credit risk in each loan class is increasing or decreasing. Historical loss rates are adjusted upward or downward in proportion to changes in average risk grading. General allowances for unimpaired loans also consider inherent risks identified for each loan class. Inherent risks consider loss rates that most appropriately represent the current credit cycle and other factors attributable to a specific loan class which have not yet been represented in the historical gross loss rates or risk grading. These factors include changes in commodity prices or engineering imprecision which may affect the value of reserves that secure our energy loan portfolio, construction risk that may affect commercial real estate loans, changes in regulations and public policy that may disproportionately impact health care loans and changes in loan products. Nonspecific allowances are maintained for risks beyond factors specific to a particular portfolio segment or loan class. These factors include trends in the economy in our primary lending areas, concentration in large-balance loans and other relevant factors. An accrual for off-balance sheet credit risk is included in Other liabilities in the Consolidated Balance Sheets. The appropriateness of the accrual is determined in the same manner as the allowance for loan losses.
Real Estate and Other Repossessed Assets [Policy Text Block]	Real Estate and Other Repossessed Assets Real estate and other repossessed assets are acquired in partial or total forgiveness of loans. These assets are initially recognized at cost, which is determined by fair value at date of foreclosure less estimated disposal costs. They are subsequently carried at the lower of cost or current fair value less estimated disposal costs. Decreases in fair value below cost are recognized as asset-specific valuation allowances which may be reversed when supported by future increases in fair value. Subsequent increases in fair value may be used to reduce the allowance but not below zero. Fair values of real estate are based on “as is” appraisals which are updated at least annually or more frequently for certain asset types or assets located in certain distressed markets. Fair values based on appraisals are generally considered to be based on significant other observable inputs. The Company also considers decreases in listing price and other relevant information in quarterly evaluations and reduces the carrying value of real estate and other repossessed assets when necessary. Fair values based on list prices and other relevant information are generally considered to be based on significant unobservable inputs. Additional costs incurred to complete real estate and other repossessed assets may increase the carrying value, up to current fair value based on “as completed” appraisals. The fair value of mineral rights included in repossessed assets are generally determined by our internal staff of engineers based on projected cash flows from proven oil and gas reserves under existing economic and operating conditions. The value of other repossessed assets is generally determined by our special assets staff based on projected liquidation cash flows under current market conditions. Income generated by these assets is recognized as received. Operating expenses are recognized as incurred. Gains or losses on sales of real estate and other repossessed assets are based on the cash proceeds received less the cost basis of the asset, net of any valuation allowances.
Transfers of Financial Assets [Policy Text Block]	Transfers of Financial Assets BOK Financial regularly transfers financial assets as part of its mortgage banking activities and periodically may transfer other financial assets. Transfers are recorded as sales when the criteria for surrender of control are met. The Company has elected to carry certain residential mortgage loans held for sale at fair value under the fair value option. Changes in fair value are recognized in net income as they occur. These loans are reported separately in the Consolidated Balance Sheets and changes in fair value are recorded in Other Operating Revenue - Mortgage banking revenue in the Consolidated Statements of Earnings. Fair value of conforming residential mortgage loans that will be sold to U.S. government agencies is based on sales commitments or market quotes considered Level 2 inputs. Fair value of mortgage loans that are unable to be sold to U.S. government agencies is based on Level 3 inputs using quoted prices of loans that are sold in securitization transactions with a liquidity discount applied. The fair value is corroborated with an independent third party on at least an annual basis. BOK Financial retains a repurchase obligation under underwriting representations and warranties related to residential mortgage loans transferred and generally retains the right to service the loans. The Company may incur a recourse obligation in limited circumstances. Separate accruals are recognized in Other liabilities in the Consolidated Balance Sheets for repurchase and recourse obligations. These reserves reflect the estimated amount of probable loss the Company will incur as a result of repurchasing a loan, indemnifications, and other settlement resolutions. Repurchases of loans with an origination defect that are also credit impaired are considered collateral dependent and are initially recognized at net realizable value (appraised value less the cost to sell). The difference between unpaid principal balance and net realizable value is not accreted. Repurchases of loans with an origination defect that are not credit impaired are carried at fair value as of the repurchase date. Interest income continues to accrue on these loans and the discount is accreted over the estimated life of the loan.
Mortgage Servicing Rights [Policy Text Block]	Mortgage Servicing Rights Mortgage servicing rights may be purchased or may be recognized when mortgage loans are originated and sold with servicing rights retained. All mortgage servicing rights are carried at fair value. Changes in the fair value are recognized in earnings as they occur. Mortgage servicing rights are not traded in active markets. A cash flow model is used to determine fair value. Key assumptions and estimates, including projected prepayment speeds and assumed servicing costs, earnings on escrow deposits, ancillary income and discount rates, used by this model are based on current market sources. Assumptions used to value mortgage servicing rights are considered significant unobservable inputs. A separate third-party model is used to estimate prepayment speeds based on interest rates, housing turnover rates, estimated loan curtailment, anticipated defaults and other relevant factors. The prepayment model is updated daily for changes in market conditions and adjusted to better correlate with actual performance of BOK Financial's servicing portfolio. Fair value estimates from outside sources are received at least annually to corroborate the results of the valuation model.
Premises and Equipment [Policy Text Block]	Premises and Equipment Premises and equipment are carried at cost, including capitalized interest when appropriate, less accumulated depreciation and amortization. Depreciation and amortization are computed on a straight-line basis over the estimated useful lives of the assets or, for leasehold improvements, over the shorter of the estimated useful lives or remaining lease terms. Useful lives range from 5 years to 40 years for buildings and improvements, 3 years to 10 years for software and related implementation costs, and 3 years to 10 years for furniture and equipment. Construction in progress represents facilities construction and data processing systems projects underway that have not yet been placed into service. Depreciation and amortization begin once the assets are placed into service. Repair and maintenance costs, including software maintenance and enhancement costs, are charged to expense as incurred. Software licensing costs are generally charged to expense as incurred. Software licensing costs are capitalized if the contractual right to take possession of the software exists and it is feasible to take possession without significant penalty. Capitalized costs are amortized over the shorter of the estimated useful life of the software or remaining contractual life of the license. Premises no longer used by the Company are transferred to real estate and other repossessed assets. The transferred amount is the lower of cost less accumulated depreciation or fair value less estimated disposal costs as of the transfer date. Rent expense for leased premises is recognized as incurred over the lease term. The effects of rent holidays, significant rent escalations and other adjustments to rent payments are recognized on a straight-line basis over the lease term.
Federal and State Income Taxes [Policy Text Block]	Federal and State Income Taxes BOK Financial and its subsidiaries file consolidated tax returns. The subsidiaries provide for income taxes on a separate return basis and remit to BOK Financial amounts determined to be currently payable. BOK Financial is agent for its subsidiaries under the Company's tax sharing agreements and has no ownership rights to any refunds received for the benefit of its subsidiaries. Current income tax expense or benefit is based on an evaluation that considers estimated taxable income, tax credits, and statutory federal and state income tax rates. The amount of current income tax expense or benefit recognized in any period may differ from amounts reported to taxing authorities. Annually, tax returns are filed with each jurisdiction where the Company conducts business and recognized current income tax expense or benefit is adjusted to the filed tax returns. Deferred tax assets and liabilities are based upon the temporary differences between the values of assets and liabilities as recognized in the financial statements and their related tax basis using enacted tax rates in effect for the year in which the differences are expected to be recovered or settled. The effect of changes in statutory tax rates on the measurement of deferred tax assets and liabilities is recognized through income tax expense in the period the change is enacted. A valuation allowance is provided when it is more likely than not that some portion of the entire deferred tax asset may not be realized.
Employee Benefit Plans [Policy Text Block]	Employee Benefit Plans
Shared-Based Compensation Plans [Policy Text Block]	Share-Based Compensation Plans BOK Financial awards stock options and non-vested common shares as compensation to certain officers. Compensation cost is generally fixed based on the grant date fair value of the award. The grant date fair value of stock options is based on the Black-Scholes option pricing model. Stock options generally have graded vesting over 7 years . Each tranche is considered a separate award for valuation and compensation cost recognition. Grant date fair value of non-vested shares is based on the then-current market value of BOK Financial common stock. Non-vested shares generally cliff vest in 3 years and are subject to a holding period after vesting of 2 years . Compensation cost of non-vested shares granted under the Executive Incentive Plan varies based on changes in the fair value of BOKF common shares. Compensation cost is recognized as expense over the service period, which is generally the vesting period. Expense is reduced for estimated forfeitures over the vesting period and adjusted for actual forfeitures as they occur. Stock-based compensation awarded to certain officers has performance conditions that affect the number of awards granted. Compensation cost is adjusted based on the probable outcome of the performance conditions. Tax effects of share-based payments are recognized through tax expense. Dividends on non-vested shares that are not subject to forfeiture are charged to retained earnings.
Other Operating Revenue [Policy Text Block]	Other Operating Revenue Fees and commissions revenue is generated through the sales of products, consisting primarily of financial instruments, and the performance of services for customers under contractual obligations. Revenue from providing services for customers is recognized at the time services are provided in an amount that reflects the consideration we expect to be entitled to for those services. Revenue is recognized based on the application of five steps: • Identify the contract with a customer • Identify the performance obligations in the contract • Determine the transaction price • Allocate the transaction price to the performance obligations in the contract • Recognize revenue when (or as) the Company satisfies a performance obligation For contracts with multiple performance obligations, individual performance obligations are accounted for separately if the customer can benefit from the good or service on its own or with other resources readily available to the customer and the promise to transfer goods and services to the customer is separately identifiable in the contract. The transaction price is allocated to the performance obligations based on relative standalone selling prices. Revenue is recognized on a gross basis whenever we have primary responsibility and risk in providing the services or products to our customers and have discretion in establishing the price for the services or products. Revenue is recognized on a net basis whenever we act as an agent for products or services of others. Brokerage and trading revenue includes revenues from trading, customer hedging, retail brokerage and investment banking. Trading revenue includes net realized and unrealized gains primarily related to sales of securities to institutional customers and related derivative contracts. Customer hedging revenue includes realized and unrealized changes in the fair value of derivative contracts held for customer risk management programs including credit valuation adjustments, as necessary. We offer commodity, interest rate, foreign exchange and equity derivatives to our customers. These customer contracts are offset with contracts with selected counterparties and exchanges to minimize changes in market risk from changes in commodity prices, interest rates or foreign exchange rates. Retail brokerage revenue represents fees and commissions earned on sales of fixed income securities, annuities, mutual funds and other financial instruments to retail customers. Investment banking revenue includes fees earned upon completion of underwriting and financial advisory services. Investment banking revenue also includes fees earned in conjunction with loan syndications. Transaction card revenue includes merchant discount fees and electronic funds transfer network fees, net of interchange fees paid to card issuers and assessments paid to card networks. Merchant discount fees represent fees paid by customers for account management and electronic processing of card transactions. Merchant discount fees are recognized at the time the customer’s transactions are processed or other services are performed. The Company also maintains the TransFund electronic funds transfer network for the benefit of its members, which includes the BOKF, NA. Electronic funds transfer fees are recognized as electronic transactions processed on behalf of its members. Fiduciary and asset management revenue includes fees from asset management, custody, recordkeeping, investment advisory and administration services. Revenue is recognized on an accrual basis at the time the services are performed and may be based on either the fair value of the account or the service provided. Deposit service charges and fees include commercial account service charges, overdraft fees, check card fee revenue and automated service charge and other deposit service fees. Fees are recognized at least quarterly in accordance with published deposit account agreements and disclosure statements for retail accounts or contractual agreements for commercial accounts. Item charges for overdraft or non-sufficient funds items are recognized as items are presented for payment. Account balance charges and activity fees are accrued monthly and collected in arrears. Commercial account activity fees may be offset by an earnings credit based on account balances. Check card fees represent interchange fees paid by a merchant bank for transactions processed from cards issued by the Company. Check card fees are recognized when transactions are processed.
Newly Adopted and Pending Accounting Pronouncements [Policy Text Block]	Newly Adopted and Pending Accounting Pronouncements The following is a summary of newly adopted and pending accounting pronouncements that may have a more than insignificant effect on the Company's financial statements. Financial Accounting Standards Board ("FASB") FASB Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers ("ASU 2014-09") On May 28, 2014, the FASB issued ASU 2014-09 to clarify the principles for recognizing revenue by providing a more robust framework that will give greater consistency and comparability in revenue recognition practices. In the new framework, an entity recognizes revenue in an amount that reflects the consideration to which the entity expects to be entitled in exchange for goods or services. The new model requires the identification of performance obligations included in contracts with customers, a determination of the transaction price and an allocation of the price to those performance obligations. The entity recognizes revenue when performance obligations are satisfied. Revenue from financial assets and liabilities is explicitly excluded from the scope of ASU 2014-09. Management adopted the standard in the first quarter of 2018 using the modified retrospective transition method. There were no significant cumulative effect adjustments as a result of implementation as of January 1, 2018 as our current revenue recognition policies generally conformed with the principals in ASU 2014-09. FASB Accounting Standards Update No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) ("ASU 2016-08") On March 17, 2016, the FASB Issued ASU 2016-08 to amend the principal versus agent implementation guidance in ASU 2014-09. The ASU clarifies that an entity should evaluate whether it is the principal or the agent for each specified good or service promised in a contract with a customer. Management adopted the standard in the first quarter of 2018. Interchange fees paid to issuing banks for card transactions processed related to its merchant processing services previously included in data processing and communication expense are now netted against the amounts charged to the merchant in transaction card processing revenue. FASB Accounting Standards Update No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-01") On January 5, 2016, the FASB issued ASU 2016-01 over the recognition and measurement of financial assets and liabilities. The update requires equity investments, in general, to be measured at fair value with changes in fair value recognized in earnings. It also eliminates the requirement to disclose the methods and significant assumptions used to estimate the fair value for financial instruments measured at amortized cost, requires entities to use the exit price notion when measuring fair value, requires an entity to present separately in other comprehensive income the portion of the total change in fair value of a liability resulting from a change in the instrument-specific credit risk when the fair value option has been elected, requires separate presentation of financial assets and liabilities by measurement category and form on the balance sheet or accompanying notes, clarifies that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity's other deferred tax assets, and simplifies the impairment assessment of equity investments without readily determinable fair values. Management adopted the standard in the first quarter of 2018. Upon adoption, net unrealized gains of $2.7 million from equity securities were reclassified from other comprehensive income to retained earnings. FASB Accounting Standards Update No. 2016-02, Leases (Topic 842) ("ASU 2016-02") On February 25, 2016, the FASB issued ASU 2016-02 to increase transparency and comparability by recognizing lease assets and liabilities on the balance sheet and disclosing key information about leasing arrangements. Lessees will be required to recognize an obligation for future lease payments measured on a discounted basis and a right-of-use asset. The ASU is effective for the Company for interim and annual periods beginning after December 15, 2018. As originally issued, ASU 2016-02 required implementation through the modified transition method applied as of the earliest period presented in the financial statements. In 2018 an additional and optional transition method that allows entities to apply the standard as of the adoption date was approved. BOKF elected this optional transition method. BOKF elected all practical expedients other than the lessee's practical expedient to combine lease and non-lease components which would further gross up the lease liability and related right of use asset. The implementation of ASU 2016-02 increased the reported right of use assets and liabilities by approximately $137 million . The effect on retained earnings was immaterial. FASB Accounting Standards Update No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Assets Measured at Amortized Cost ("ASU 2016-13") On June 16, 2016, the FASB issued ASU 2016-13 in order to provide more timely recording of credit losses on loans and other financial instruments. The ASU adds an impairment model (known as the current expected credit loss ("CECL") model) that is based on expected credit losses rather than incurred credit losses. It requires measurement of all expected credit losses for financial assets carried at amortized cost, including loans and related off-balance sheet credit exposure and investment securities, based on historical experience, current conditions, and reasonable and supportable forecasts. ASU 2016-13 also changes the recognition of other-than-temporary impairment of available for sale securities to an allowance methodology from a direct write-down methodology. ASU 2016-13 will be effective for the Company for annual reporting periods beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted for annual reporting periods beginning after December 15, 2018. ASU 2016-13 will be applied through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. The Company has established a CECL implementation team in order to evaluate the impact the adoption of ASU 2016-13 will have on the Company's financial statements. The CECL implementation team, overseen by the Chief Credit Officer, Chief Financial Officer, and Chief Risk Officer, has developed a project plan that incorporates input from various departments within the bank including Credit, Financial Reporting, Risk, and Information Technology among others. Key implementation activities for 2018 included portfolio segmentation, credit risk driver identification, model development, as well as process and information systems enhancements. Key implementation initiatives for 2019 include model validation and development of governance and control and disclosure frameworks. The Company will adopt the standard on January 1, 2020. FASB Accounting Standards Update No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments ("ASU 2016-15") On August 26, 2016, the FASB issued ASU 2016-15, which amends guidance in ASC 230 on the classification of certain cash receipts and payments in the statement of cash flows. The amendments address eight cash flow issues. Management adopted the standard in first quarter of 2018. Adoption of ASU 2016-15 did not have a material impact on the Company's financial statements. FASB Accounting Standards Update No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities ("ASU 2017-12") On August 28, 2017, the FASB issued ASU 2017-12, which amends the hedge accounting recognition and presentation requirements in ASC 815 in order to improve transparency and understandability of information and reduce the complexity. The update expands the types of transactions eligible for hedge accounting, eliminates the requirement to separately measure and present hedge ineffectiveness, simplifies hedge effectiveness assessments and updates documentation and presentation requirements. The update allows the reclassification of certain debt securities from held to maturity to available for sale if the debt security is eligible to be hedged under the last-of-layer method. ASU 2017-12 is effective for the Company for fiscal years beginning after December 15, 2018, and interim periods therein; however, early adoption was permitted. Adoption of ASU 2017-12 had no material impact on the Company's financial statements. FASB Accounting Standards Update No. 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118 (SAB 118). On March 13, 2018, the FASB issued ASU 2018-05, which adds SEC guidance related to SAB 118 - Income Tax Accounting Implications of the Tax Cuts and Jobs Act . ASU 2018-05 was effective upon issuance. The adoption of ASU 2018-05 has not had a significant impact in 2018. FASB Accounting Standards Update No. 2018-15, Intangibles - Goodwill and Other Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract ("ASU 2018-15")

Reclassifications (Policies)

Reclassifications (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Reclassifications [Text Block]	Certain prior year amounts have been reclassified to conform to current year presentation.

Securities (Tables)

Securities (Tables)	12 Months Ended
	Dec. 31, 2018
Marketable Securities [Abstract]
Trading Securities [Table Text Block]	The fair value and net unrealized gain (loss) included in trading securities is as follows (in thousands): December 31, 2018 December 31, 2017 Fair Value Net Unrealized Gain (Loss) Fair Value Net Unrealized Gain (Loss) U.S. government agency debentures $ 63,765 $ 254 $ 21,196 $ 8 U.S. government agency residential mortgage-backed securities 1,791,584 9,966 392,673 (517 ) Municipal and other tax-exempt securities 34,507 (1 ) 13,559 83 Asset-backed securities 42,656 685 23,885 (26 ) Other trading securities 24,411 65 11,363 4 Total trading securities $ 1,956,923 $ 10,969 $ 462,676 $ (448 )
Investment Securities (Held-to-Maturity) [Table Text Block]	The amortized cost and fair values of investment securities are as follows (in thousands): December 31, 2018 Amortized Fair Gross Unrealized Cost Value Gain Loss Municipal and other tax-exempt securities $ 137,296 $ 138,562 $ 1,858 $ (592 ) U.S. government agency residential mortgage-backed securities 12,612 12,770 293 (135 ) Other debt securities 205,279 215,966 12,257 (1,570 ) Total investment securities $ 355,187 $ 367,298 $ 14,408 $ (2,297 ) December 31, 2017 Amortized Fair Gross Unrealized Cost Value Gain Loss Municipal and other tax-exempt securities $ 228,186 $ 230,349 $ 2,967 $ (804 ) U.S. government agency residential mortgage-backed securities 15,891 16,242 446 (95 ) Other debt securities 217,716 233,444 17,095 (1,367 ) Total investment securities $ 461,793 $ 480,035 $ 20,508 $ (2,266 ) The amortized cost and fair values of investment securities at December 31, 2018 , by contractual maturity, are as shown in the following table (dollars in thousands): Less than One Year One to Five Years Six to Ten Years Over Ten Years Total Weighted Average Maturity² Municipal and other tax-exempt securities: Carrying value $ 41,475 $ 46,363 $ 35,077 $ 14,381 $ 137,296 4.73 Fair value 41,371 46,123 36,471 14,597 138,562 Nominal yield¹ 2.25 % 3.94 % 6.00 % 4.32 % 4.00 % Other debt securities: Carrying value $ 16,282 $ 61,830 $ 115,606 $ 11,561 $ 205,279 5.50 Fair value 16,327 63,923 125,050 10,666 215,966 Nominal yield 3.88 % 4.69 % 5.76 % 4.33 % 5.21 % Total fixed maturity securities: Carrying value $ 57,757 $ 108,193 $ 150,683 $ 25,942 $ 342,575 5.19 Fair value 57,698 110,046 161,521 25,263 354,528 Nominal yield 2.71 % 4.37 % 5.82 % 4.32 % 4.73 % Residential mortgage-backed securities: Carrying value $ 12,612 ³ Fair value 12,770 Nominal yield 4 2.77 % Total investment securities: Carrying value $ 355,187 Fair value 367,298 Nominal yield 4.65 % 1 Calculated on a taxable equivalent basis using a 25 percent effective tax rate. 2 Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without penalty. 3 The average expected lives of residential mortgage-backed securities were 4.7 years based upon current prepayment assumptions. 4 The nominal yield on residential mortgage-backed securities is based upon prepayment assumptions at the purchase date. Actual yields earned may differ significantly based upon actual prepayments. See Quarterly Financial Summary - Unaudited for current yields on the investment securities portfolio.
Available for Sale Securities [Table Text Block]	The amortized cost and fair value of available for sale securities are as follows (in thousands): December 31, 2018 Amortized Fair Gross Unrealized Cost Value Gain Loss OTTI U.S. Treasury securities $ 496 $ 493 $ — $ (3 ) $ — Municipal and other tax-exempt securities 2,782 2,864 82 — — Residential mortgage-backed securities: U.S. government agencies: FNMA 3,414,573 3,367,124 10,559 (58,008 ) — FHLMC 1,723,399 1,699,779 5,189 (28,809 ) — GNMA 748,351 737,805 401 (10,947 ) — Total U.S. government agencies 5,886,323 5,804,708 16,149 (97,764 ) — Private issue 40,948 59,736 18,788 — — Total residential mortgage-backed securities 5,927,271 5,864,444 34,937 (97,764 ) — Commercial mortgage-backed securities guaranteed by U.S. government agencies 2,986,297 2,953,889 7,955 (40,363 ) — Other debt securities 35,545 35,430 12 (127 ) — Total available for sale securities $ 8,952,391 $ 8,857,120 $ 42,986 $ (138,257 ) $ — December 31, 2017 Amortized Fair Gross Unrealized Cost Value Gain Loss OTTI U.S. Treasury securities $ 1,000 $ 1,000 $ — $ — $ — Municipal and other tax-exempt securities 27,182 27,080 181 (283 ) — Residential mortgage-backed securities: U.S. government agencies: FNMA 3,021,551 2,997,563 11,549 (35,537 ) — FHLMC 1,545,971 1,531,009 3,148 (18,110 ) — GNMA 787,626 780,580 1,607 (8,653 ) — Total U.S. government agencies 5,355,148 5,309,152 16,304 (62,300 ) — Private issue 74,311 93,221 19,301 — (391 ) Total residential mortgage-backed securities 5,429,459 5,402,373 35,605 (62,300 ) (391 ) Commercial mortgage-backed securities guaranteed by U.S. government agencies 2,858,885 2,834,961 1,963 (25,887 ) — Other debt securities 25,500 25,481 50 (69 ) — Perpetual preferred stock 12,562 15,767 3,205 — — Equity securities and mutual funds 14,487 14,916 515 (86 ) — Total available for sale securities $ 8,369,075 $ 8,321,578 $ 41,519 $ (88,625 ) $ (391 ) The amortized cost and fair values of available for sale securities at December 31, 2018 , by contractual maturity, are as shown in the following table (dollars in thousands): Less than One Year One to Five Years Six to Ten Years Over Ten Years Total Weighted Average Maturity 4 U.S. Treasury securities: Amortized cost $ — $ 496 $ — $ — $ 496 1.08 Fair value — 493 — — 493 Nominal yield — % 1.99 % — % — % 1.99 % Municipal and other tax-exempt securities: Amortized cost $ 1,057 $ 1,725 $ — $ — 2,782 1.67 Fair value 1,063 1,801 — — 2,864 Nominal yield¹ 6.69 % 6.45 % — % — % 6.54 % Commercial mortgage-backed securities: Amortized cost $ 77,558 $ 1,107,567 $ 1,497,468 $ 303,704 2,986,297 6.90 Fair value 76,902 1,088,991 1,486,939 301,057 2,953,889 Nominal yield 1.66 % 2.06 % 2.44 % 2.54 % 2.29 % Other debt securities: Amortized cost $ — $ — $ — $ 35,545 35,545 13.61 Fair value — — — 35,430 35,430 Nominal yield — % — % — % 1.94 % 5 1.94 % Total fixed maturity securities: Amortized cost $ 78,615 $ 1,109,788 $ 1,497,468 $ 339,249 $ 3,025,120 6.98 Fair value 77,965 1,091,285 1,486,939 336,487 2,992,676 Nominal yield 1.73 % 2.07 % 2.44 % 2.48 % 2.29 % Residential mortgage-backed securities: Amortized cost $ 5,927,271 2 Fair value 5,864,444 Nominal yield 3 2.41 % Total available-for-sale securities: Amortized cost $ 8,952,391 Fair value 8,857,120 Nominal yield 2.37 % 1 Calculated on a taxable equivalent basis using a 25 percent effective tax rate. 2 The average expected lives of mortgage-backed securities were 4.1 years based upon current prepayment assumptions. 3 The nominal yield on mortgage-backed securities is based upon prepayment assumptions at the purchase date. Actual yields earned may differ significantly based upon actual prepayments. See Quarterly Financial Summary –– Unaudited following for current yields on available for sale securities portfolio. 4 Expected maturities may differ from contractual maturities, because borrowers may have the right to call or prepay obligations with or without penalty. 5 Nominal yield on other debt securities with contractual maturity dates over ten years are based on variable rates which generally are reset within 35 days . Sales of available for sale securities resulted in gains and losses as follows (in thousands): Year Ended December 31, 2018 2017 2016 Proceeds $ 745,643 $ 1,309,215 $ 899,381 Gross realized gains 7,117 10,223 11,696 Gross realized losses (9,918 ) (5,795 ) (21 ) Related federal and state income tax expense (713 ) 1,722 4,542
Schedule of Unrealized Loss on Investments [Table Text Block]	Temporarily Impaired Securities as of December 31, 2018 (In thousands) Number of Securities Less Than 12 Months 12 Months or Longer Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Investment: Municipal and other tax-exempt securities 72 $ 18,255 $ 69 $ 66,141 $ 523 $ 84,396 $ 592 U.S. government agency residential mortgage-backed securities – Other 2 — — 5,633 135 5,633 135 Other debt securities 72 13,372 64 23,028 1,506 36,400 1,570 Total investment securities 146 $ 31,627 $ 133 $ 94,802 $ 2,164 $ 126,429 $ 2,297 Number of Securities Less Than 12 Months 12 Months or Longer Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Available for sale: U.S. Treasury securities 1 $ — $ — $ 493 $ 3 $ 493 $ 3 Municipal and other tax-exempt securities — — — — — — — Residential mortgage-backed securities: U.S. government agencies: FNMA 162 161,089 542 2,135,377 57,466 2,296,466 58,008 FHLMC 85 71,205 328 1,129,730 28,481 1,200,935 28,809 GNMA 42 278,530 288 376,263 10,659 654,793 10,947 Total U.S. agencies 289 510,824 1,158 3,641,370 96,606 4,152,194 97,764 Private issue 1 — — — — — — — Total residential mortgage-backed securities 289 510,824 1,158 3,641,370 96,606 4,152,194 97,764 Commercial mortgage-backed securities guaranteed by U.S. government agencies 197 179,258 394 1,969,504 39,969 2,148,762 40,363 Other debt securities 3 9,982 63 20,436 64 30,418 127 Total available for sale securities 490 $ 700,064 $ 1,615 $ 5,631,803 $ 136,642 $ 6,331,867 $ 138,257 1 Includes securities for which an unrealized loss remains in AOCI after an other-than-temporary credit loss has been recognized in income. Temporarily Impaired Securities as of December 31, 2017 (In thousands) Number of Securities Less Than 12 Months 12 Months or Longer Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Investment: Municipal and other tax- exempt securities 100 $ 145,960 $ 643 $ 5,833 $ 161 $ 151,793 $ 804 U.S. government agency residential mortgage-backed securities – Other 1 — — 3,356 95 3,356 95 Other debt securities 49 20,091 1,238 3,076 129 23,167 1,367 Total investment securities 150 $ 166,051 $ 1,881 $ 12,265 $ 385 $ 178,316 $ 2,266 Number of Securities Less Than 12 Months 12 Months or Longer Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Available for sale: U.S. Treasury securities — $ — $ — $ — $ — $ — $ — Municipal and other tax-exempt securities 19 12,765 18 4,802 265 17,567 283 Residential mortgage-backed securities: U. S. government agencies: FNMA 113 1,203,041 9,618 824,029 25,919 2,027,070 35,537 FHLMC 69 863,778 7,297 385,816 10,813 1,249,594 18,110 GNMA 27 201,887 1,452 248,742 7,201 450,629 8,653 Total U.S. agencies 209 2,268,706 18,367 1,458,587 43,933 3,727,293 62,300 Private issue 1 8 5,898 391 — — 5,898 391 Total residential mortgage-backed securities 217 2,274,604 18,758 1,458,587 43,933 3,733,191 62,691 Commercial mortgage-backed securities guaranteed by U.S. government agencies 185 1,465,703 11,824 652,296 14,063 2,117,999 25,887 Other debt securities 2 19,959 41 472 28 20,431 69 Perpetual preferred stock — — — — — — — Equity securities and mutual funds 111 911 7 2,203 79 3,114 86 Total available for sale securities 534 $ 3,773,942 $ 30,648 $ 2,118,360 $ 58,368 $ 5,892,302 $ 89,016 1
Schedule of Fair Value Option Securities [Table Text Block]	The fair value and net unrealized gain (loss) included in Fair value option securities is as follows (in thousands): December 31, 2018 December 31, 2017 Fair Value Net Unrealized Gain (Loss) Fair Value Net Unrealized Gain (Loss) U.S. government agency residential mortgage-backed securities $ 283,235 $ 2,766 $ 755,054 $ (1,877 )

Derivatives (Tables)

Derivatives (Tables)	12 Months Ended
	Dec. 31, 2018
Derivative Instrument Detail [Abstract]
Derivative Contracts [Table Text Block]	The following table summarizes the fair values of derivative contracts recorded as “derivative contracts” assets and liabilities in the balance sheet at December 31, 2018 (in thousands): Assets Notional 1 Gross Fair Value Netting Adjustments Net Fair Value Before Cash Collateral Cash Collateral Fair Value Net of Cash Collateral Customer risk management programs: Interest rate contracts To-be-announced residential mortgage-backed securities $ 10,671,151 $ 92,231 $ (26,787 ) $ 65,444 $ — $ 65,444 Interest rate swaps 1,924,131 36,112 (6,688 ) 29,424 (7,934 ) 21,490 Energy contracts 1,472,209 206,418 (60,983 ) 145,435 (106,752 ) 38,683 Agricultural contracts 21,210 842 (201 ) 641 — 641 Foreign exchange contracts 184,990 183,759 — 183,759 — 183,759 Equity option contracts 89,085 2,021 — 2,021 (648 ) 1,373 Total customer risk management programs 14,362,776 521,383 (94,659 ) 426,724 (115,334 ) 311,390 Internal risk management programs 15,909,988 50,410 (40,871 ) 9,539 — 9,539 Total derivative contracts $ 30,272,764 $ 571,793 $ (135,530 ) $ 436,263 $ (115,334 ) $ 320,929 Liabilities Notional¹ Gross Fair Value Netting Adjustments Net Fair Value Before Cash Collateral Cash Collateral Fair Value Net of Cash Collateral Customer risk management programs: Interest rate contracts To-be-announced residential mortgage-backed securities $ 10,558,151 $ 90,388 $ (26,787 ) $ 63,601 $ (63,596 ) $ 5 Interest rate swaps 1,924,131 36,288 (6,688 ) 29,600 (4,110 ) 25,490 Energy contracts 1,434,247 202,494 (60,983 ) 141,511 (1,490 ) 140,021 Agricultural contracts 21,214 812 (201 ) 611 — 611 Foreign exchange contracts 177,423 175,922 — 175,922 — 175,922 Equity option contracts 89,085 2,021 — 2,021 — 2,021 Total customer risk management programs 14,204,251 507,925 (94,659 ) 413,266 (69,196 ) 344,070 Internal risk management programs 19,634,642 66,422 (40,871 ) 25,551 (7,315 ) 18,236 Total derivative contracts $ 33,838,893 $ 574,347 $ (135,530 ) $ 438,817 $ (76,511 ) $ 362,306 1 Notional amounts for commodity contracts are converted into dollar-equivalent amounts based on dollar prices at the inception of the contract. The following table summarizes the fair values of derivative contracts recorded as “derivative contracts” assets and liabilities in the balance sheet at December 31, 2017 (in thousands): Assets Notional 1 Gross Fair Value Netting Adjustments Net Fair Value Before Cash Collateral Cash Collateral Fair Value Net of Cash Collateral Customer risk management programs: Interest rate contracts To-be-announced residential mortgage-backed securities $ 12,347,542 $ 23,606 $ (18,096 ) $ 5,510 $ — $ 5,510 Interest rate swaps 1,478,944 28,278 — 28,278 (4,964 ) 23,314 Energy contracts 1,190,067 103,044 (47,873 ) 55,171 (196 ) 54,975 Agricultural contracts 53,238 1,576 (960 ) 616 — 616 Foreign exchange contracts 132,397 129,551 — 129,551 (448 ) 129,103 Equity option contracts 99,633 5,503 — 5,503 (920 ) 4,583 Total customer risk management programs 15,301,821 291,558 (66,929 ) 224,629 (6,528 ) 218,101 Internal risk management programs 4,736,701 9,494 (7,093 ) 2,401 — 2,401 Total derivative contracts $ 20,038,522 $ 301,052 $ (74,022 ) $ 227,030 $ (6,528 ) $ 220,502 Liabilities Notional¹ Gross Fair Value Netting Adjustments Net Fair Value Before Cash Collateral Cash Collateral Fair Value Net of Cash Collateral Customer risk management programs: Interest rate contracts To-be-announced residential mortgage-backed securities $ 11,537,742 $ 20,367 $ (18,096 ) $ 2,271 $ (704 ) $ 1,567 Interest rate swaps 1,478,944 28,298 — 28,298 (12,896 ) 15,402 Energy contracts 1,166,924 101,603 (47,873 ) 53,730 (42,767 ) 10,963 Agricultural contracts 48,552 1,551 (960 ) 591 — 591 Foreign exchange contracts 126,251 123,321 — 123,321 (53 ) 123,268 Equity option contracts 99,633 5,503 — 5,503 — 5,503 Total customer risk management programs 14,458,046 280,643 (66,929 ) 213,714 (56,420 ) 157,294 Internal risk management programs 5,728,421 21,762 (7,093 ) 14,669 — 14,669 Total derivative contracts $ 20,186,467 $ 302,405 $ (74,022 ) $ 228,383 $ (56,420 ) $ 171,963 1
Derivative Instruments, Gain (Loss) in Statement of Earnings [Table Text Block]	The following summarizes the pre-tax net gains (losses) on derivative instruments and where they are recorded in the Consolidated Statements of Earnings (in thousands): Year Ended December 31, 2018 2017 2016 Brokerage and Trading Revenue Gain (Loss) on Derivatives, Net Brokerage and Trading Revenue Gain (Loss) on Derivatives, Net Brokerage and Trading Revenue Gain (Loss) on Derivatives, Net Customer risk management programs: Interest rate contracts To-be-announced residential mortgage-backed securities $ 27,190 $ — $ 34,532 $ — $ 38,523 $ — Interest rate swaps 2,614 — 2,647 — 2,589 — Energy contracts 8,443 — 5,536 — 5,027 — Agricultural contracts 53 — 79 — 111 — Foreign exchange contracts 535 — 1,352 — 945 — Equity option contracts — — — — — — Total customer risk management programs 38,835 — 44,146 — 47,195 — Internal risk management programs (13,643 ) (422 ) 4,615 779 (4,592 ) (15,685 ) Total derivative contracts $ 25,192 $ (422 ) $ 48,761 $ 779 $ 42,603 $ (15,685 )

Loans and Allowances for Cred_2

Loans and Allowances for Credit Losses (Tables)	12 Months Ended
	Dec. 31, 2018
Loans Receivable, Net [Abstract]
Schedule of the Loans by Portfolio Segment [Table Text Block]	The portfolio segments of the loan portfolio are as follows (in thousands): December 31, 2018 December 31, 2017 Fixed Rate Variable Rate Non-accrual Total Fixed Rate Variable Rate Non-accrual Total Commercial $ 2,251,188 $ 11,285,049 $ 99,841 $ 13,636,078 $ 2,217,432 $ 8,379,240 $ 137,303 $ 10,733,975 Commercial real estate 1,477,274 3,265,918 21,621 4,764,813 548,692 2,928,440 2,855 3,479,987 Residential mortgage 1,830,224 358,254 41,555 2,230,033 1,608,655 317,584 47,447 1,973,686 Personal 190,687 834,889 230 1,025,806 154,517 810,990 269 965,776 Total $ 5,749,373 $ 15,744,110 $ 163,247 $ 21,656,730 $ 4,529,296 $ 12,436,254 $ 187,874 $ 17,153,424 Accruing loans past due (90 days) 1 $ 1,338 $ 633 Foregone interest on nonaccrual loans $ 15,502 $ 16,496 1
Rollforward of Allowance For Loan Losses And Accrual for Off-Balnace Sheet Credit Losses [Table Text Block]	The activity in the allowance for loan losses and the accrual for off-balance sheet credit risk related to loan commitments and standby letters of credit for the year ended December 31, 2018 is summarized as follows (in thousands): Commercial Commercial Real Estate Residential Mortgage Personal Nonspecific Allowance Total Allowance for loan losses: Beginning balance $ 124,269 $ 56,621 $ 18,451 $ 9,124 $ 22,217 $ 230,682 Provision for loan losses 12,521 (147 ) (1,156 ) 3,175 (4,449 ) 9,944 Loans charged off (37,880 ) — (378 ) (5,325 ) — (43,583 ) Recoveries 3,316 3,552 1,047 2,499 — 10,414 Ending balance $ 102,226 $ 60,026 $ 17,964 $ 9,473 $ 17,768 $ 207,457 Accrual for off-balance sheet credit risk: Beginning balance $ 3,644 $ 45 $ 43 $ 2 $ — $ 3,734 Provision for off-balance sheet credit risk (1,989 ) 7 9 29 — (1,944 ) Ending balance $ 1,655 $ 52 $ 52 $ 31 $ — $ 1,790 Total provision for credit losses $ 10,532 $ (140 ) $ (1,147 ) $ 3,204 $ (4,449 ) $ 8,000 The activity in the allowance for loan losses and the accrual for off-balance sheet credit risk related to loan commitments and standby letters of credit for the year ended December 31, 2017 is summarized as follows (in thousands): Commercial Commercial Real Estate Residential Mortgage Personal Nonspecific Allowance Total Allowance for loan losses: Beginning balance $ 140,213 $ 50,749 $ 18,224 $ 8,773 $ 28,200 $ 246,159 Provision for loan losses (595 ) 4,008 116 2,964 (5,983 ) 510 Loans charged off (19,810 ) (76 ) (649 ) (5,064 ) — (25,599 ) Recoveries 4,461 1,940 760 2,451 — 9,612 Ending balance $ 124,269 $ 56,621 $ 18,451 $ 9,124 $ 22,217 $ 230,682 Accrual for off-balance sheet credit risk: Beginning balance $ 11,063 $ 123 $ 50 $ 8 $ — $ 11,244 Provision for off-balance sheet credit risk (7,419 ) (78 ) (7 ) (6 ) — (7,510 ) Ending balance $ 3,644 $ 45 $ 43 $ 2 $ — $ 3,734 Total provision for credit losses $ (8,014 ) $ 3,930 $ 109 $ 2,958 $ (5,983 ) $ (7,000 ) The activity in the allowance for loan losses and the accrual for off-balance sheet credit risk related to loan commitments and standby letters of credit for the year ended December 31, 2016 is summarized as follows (in thousands): Commercial Commercial Real Estate Residential Mortgage Personal Nonspecific Allowance Total Allowance for loan losses: Beginning balance $ 130,334 $ 41,391 $ 19,509 $ 4,164 $ 30,126 $ 225,524 Provision for loan losses 43,980 8,075 (1,972 ) 7,310 (1,926 ) 55,467 Loans charged off (35,828 ) — (1,312 ) (5,448 ) — (42,588 ) Recoveries 1,727 1,283 1,999 2,747 — 7,756 Ending balance $ 140,213 $ 50,749 $ 18,224 $ 8,773 $ 28,200 $ 246,159 Accrual for off-balance sheet credit risk: Beginning balance $ 1,506 $ 153 $ 30 $ 22 $ — $ 1,711 Provision for off-balance sheet credit risk 9,557 (30 ) 20 (14 ) — 9,533 Ending balance $ 11,063 $ 123 $ 50 $ 8 $ — $ 11,244 Total provision for credit losses $ 53,537 $ 8,045 $ (1,952 ) $ 7,296 $ (1,926 ) $ 65,000 The allowance for loan losses and recorded investment of the related loans by portfolio segment for each impairment measurement method at December 31, 2018 is as follows (in thousands): Collectively Measured for Impairment Individually Measured for Impairment Total Recorded Investment Related Allowance Recorded Investment Related Allowance Recorded Investment Related Allowance Commercial $ 13,536,237 $ 93,494 $ 99,841 $ 8,732 $ 13,636,078 $ 102,226 Commercial real estate 4,743,192 60,026 21,621 — 4,764,813 60,026 Residential mortgage 2,188,478 17,964 41,555 — 2,230,033 17,964 Personal 1,025,576 9,473 230 — 1,025,806 9,473 Total 21,493,483 180,957 163,247 8,732 21,656,730 189,689 Nonspecific allowance — — — — — 17,768 Total $ 21,493,483 $ 180,957 $ 163,247 $ 8,732 $ 21,656,730 $ 207,457 The allowance for loan losses and recorded investment of the related loans by portfolio segment for each impairment measurement method at December 31, 2017 is as follows (in thousands): Collectively Measured for Impairment Individually Measured for Impairment Total Recorded Investment Related Allowance Recorded Investment Related Allowance Recorded Investment Related Allowance Commercial $ 10,596,672 $ 115,438 $ 137,303 $ 8,831 $ 10,733,975 $ 124,269 Commercial real estate 3,477,132 56,621 2,855 — 3,479,987 56,621 Residential mortgage 1,926,239 18,451 47,447 — 1,973,686 18,451 Personal 965,507 9,124 269 — 965,776 9,124 Total 16,965,550 199,634 187,874 8,831 17,153,424 208,465 Nonspecific allowance — — — — — 22,217 Total $ 16,965,550 $ 199,634 $ 187,874 $ 8,831 $ 17,153,424 $ 230,682
Schedule of Credit Quality Indicators [Table Text Block]	The allowance for loan losses and recorded investment of the related loans by portfolio segment for risk graded and non-risk graded loans at December 31, 2018 is as follows (in thousands): Internally Risk Graded Non-Graded Total Recorded Investment Related Allowance Recorded Investment Related Allowance Recorded Investment Related Allowance Commercial $ 13,586,654 $ 101,303 $ 49,424 $ 923 $ 13,636,078 $ 102,226 Commercial real estate 4,764,813 60,026 — — 4,764,813 60,026 Residential mortgage 505,046 3,310 1,724,987 14,654 2,230,033 17,964 Personal 948,890 6,633 76,916 2,840 1,025,806 9,473 Total 19,805,403 171,272 1,851,327 18,417 21,656,730 189,689 Nonspecific allowance — — — — — 17,768 Total $ 19,805,403 $ 171,272 $ 1,851,327 $ 18,417 $ 21,656,730 $ 207,457 The allowance for loan losses and recorded investment of the related loans by portfolio segment for risk graded and non-risk graded loans at December 31, 2017 is as follows (in thousands): Internally Risk Graded Non-Graded Total Recorded Investment Related Allowance Recorded Investment Related Allowance Recorded Investment Related Allowance Commercial $ 10,706,035 $ 123,383 $ 27,940 $ 886 $ 10,733,975 $ 124,269 Commercial real estate 3,479,987 56,621 — — 3,479,987 56,621 Residential mortgage 234,477 2,947 1,739,209 15,504 1,973,686 18,451 Personal 877,390 6,461 88,386 2,663 965,776 9,124 Total 15,297,889 189,412 1,855,535 19,053 17,153,424 208,465 Nonspecific allowance — — — — — 22,217 Total $ 15,297,889 $ 189,412 $ 1,855,535 $ 19,053 $ 17,153,424 $ 230,682 Loans are considered to be performing if they are in compliance with the original terms of the agreement which is consistent with the regulatory guideline of “pass.” Performing also includes loans considered to be “other loans especially mentioned” by regulatory guidelines and all residential mortgage loans guaranteed by agencies of the U.S. government that continue to accrue interest based on criteria of the guarantor's programs. Other loans especially mentioned are currently performing in compliance with the original terms of the agreement but may have a potential weakness that deserves management's close attention, consistent with regulatory guidelines. The risk grading process identified certain loans that have a well-defined weakness (e.g. inadequate debt service coverage or liquidity or marginal capitalization; repayment may depend on collateral or other risk mitigation) that may jeopardize liquidation of the debt and represent a greater risk due to deterioration in the financial condition of the borrower. This is consistent with the regulatory guideline for “substandard.” Because the borrowers are still performing in accordance with the original terms of the loan agreements, these loans were not placed in nonaccruing status. Nonaccruing loans represent loans for which full collection of principal and interest in accordance with the original terms of the loan agreements is uncertain. This is substantially the same criteria used to determine whether a loan is impaired and includes certain loans considered “substandard” and all loans considered “doubtful” by regulatory guidelines. The following table summarizes the Company’s loan portfolio at December 31, 2018 by the risk grade categories (in thousands): Internally Risk Graded Non-Graded Performing Pass Other Loans Especially Mentioned Accruing Substandard Nonaccrual Performing Nonaccrual Total Commercial: Energy $ 3,414,039 $ 42,176 $ 86,624 $ 47,494 $ — $ — $ 3,590,333 Services 3,161,157 49,761 32,661 8,567 — — 3,252,146 Wholesale/retail 1,593,902 18,809 7,131 1,316 — — 1,621,158 Manufacturing 668,438 30,934 22,230 8,919 — — 730,521 Healthcare 2,664,381 14,920 37,698 16,538 — — 2,733,537 Public finance 876,336 — — — — — 876,336 Other commercial and industrial 756,815 1,266 7,588 16,954 49,371 53 832,047 Total commercial 13,135,068 157,866 193,932 99,788 49,371 53 13,636,078 Commercial real estate: Residential construction and land development 148,234 — — 350 — — 148,584 Retail 885,588 11,926 1,289 20,279 — — 919,082 Office 1,059,334 10,532 3,054 — — — 1,072,920 Multifamily 1,287,471 281 12 301 — — 1,288,065 Industrial 776,898 — 1,208 — — — 778,106 Other commercial real estate 555,301 1,188 876 691 — — 558,056 Total commercial real estate 4,712,826 23,927 6,439 21,621 — — 4,764,813 Residential mortgage: Permanent mortgage 467,233 52 9,730 1,991 819,199 21,960 1,320,165 Permanent mortgages guaranteed by U.S. government agencies — — — — 183,734 7,132 190,866 Home equity 25,743 — 296 — 682,491 10,472 719,002 Total residential mortgage 492,976 52 10,026 1,991 1,685,424 39,564 2,230,033 Personal 944,256 115 4,443 76 76,762 154 1,025,806 Total $ 19,285,126 $ 181,960 $ 214,840 $ 123,476 $ 1,811,557 $ 39,771 $ 21,656,730 The following table summarizes the Company’s loan portfolio at December 31, 2017 by the risk grade categories (in thousands): Internally Risk Graded Non-Graded Performing Pass Other Loans Especially Mentioned Accruing Substandard Nonaccrual Performing Nonaccrual Total Commercial: Energy $ 2,632,986 $ 60,288 $ 144,598 92,284 $ — $ — $ 2,930,156 Services 2,478,945 13,927 26,533 2,620 — — 2,522,025 Wholesale/retail 1,443,917 19,263 5,502 2,574 — — 1,471,256 Manufacturing 472,869 6,653 11,290 5,962 — — 496,774 Healthcare 2,182,231 3,186 43,305 14,765 — — 2,243,487 Public finance 541,775 — — — — — 541,775 Other commercial and industrial 473,366 7 8,161 19,028 27,870 70 528,502 Total commercial 10,226,089 103,324 239,389 137,233 27,870 70 10,733,975 Commercial real estate: Residential construction and land development 113,190 1,828 395 1,832 — — 117,245 Retail 686,915 4,243 98 276 — — 691,532 Office 824,408 7,087 — 275 — — 831,770 Multifamily 979,969 — 48 — — — 980,017 Industrial 573,014 — — — — — 573,014 Other commercial real estate 285,506 145 286 472 — — 286,409 Total commercial real estate 3,463,002 13,303 827 2,855 — — 3,479,987 Residential mortgage: Permanent mortgage 232,492 — 822 1,163 784,928 24,030 1,043,435 Permanent mortgages guaranteed by U.S. government agencies — — — — 188,327 9,179 197,506 Home equity — — — — 719,670 13,075 732,745 Total residential mortgage 232,492 — 822 1,163 1,692,925 46,284 1,973,686 Personal 875,696 1,548 63 83 88,200 186 965,776 Total $ 14,797,279 $ 118,175 $ 241,101 141,334 $ 1,808,995 $ 46,540 $ 17,153,424
Summary of Impaired Loans [Table Text Block]	As of December 31, 2018 Year Ended Recorded Investment December 31, 2018 Unpaid Principal Balance Total With No With Allowance Related Allowance Average Recorded Interest Income Recognized Commercial: Energy $ 79,675 $ 47,494 $ 18,639 $ 28,855 $ 5,362 $ 69,645 $ — Services 13,437 8,567 8,489 78 74 4,509 — Wholesale/retail 1,722 1,316 1,015 301 101 1,784 — Manufacturing 10,055 8,919 8,673 246 246 7,249 — Healthcare 24,319 16,538 10,563 5,975 2,949 14,297 — Public finance — — — — — — — Other commercial and industrial 26,955 17,007 17,007 — — 17,976 — Total commercial 156,163 99,841 64,386 35,455 8,732 115,460 — Commercial real estate: Residential construction and land development 1,306 350 350 — — 1,091 — Retail 27,680 20,279 20,279 — — 10,278 — Office — — — — — 137 — Multifamily 301 301 301 — — 151 — Industrial — — — — — — — Other commercial real estate 851 691 691 — — 581 — Total commercial real estate 30,138 21,621 21,621 — — 12,238 — Residential mortgage: Permanent mortgage 28,716 23,951 23,951 — — 24,572 1,233 Permanent mortgage guaranteed by U.S. government agencies 1 196,296 190,866 190,866 — — 180,813 7,172 Home equity 12,196 10,472 10,472 — — 11,774 — Total residential mortgage 237,208 225,289 225,289 — — 217,159 8,405 Personal 278 230 230 — — 250 — Total $ 423,787 $ 346,981 $ 311,526 $ 35,455 $ 8,732 $ 345,107 $ 8,405 1 All permanent mortgage loans guaranteed by U.S. government agencies are considered impaired as we do not expect full collection of contractual principal and interest. At December 31, 2018 , $7.1 million of these loans are nonaccruing and $184 million are accruing based on the guarantee by U.S. government agencies. Generally, no interest income is recognized on impaired loans until all principal balances, including amounts charged-off, have been recovered. As of December 31, 2017 Year Ended Recorded Investment December 31, 2017 Unpaid Principal Balance Total With No Allowance With Allowance Related Allowance Average Recorded Investment Interest Income Recognized Commercial: Energy $ 111,011 $ 92,284 $ 40,968 $ 51,316 $ 8,814 $ 112,392 $ — Services 5,324 2,620 2,620 — — 5,396 — Wholesale/retail 9,099 2,574 2,574 — — 6,990 — Manufacturing 6,073 5,962 5,962 — — 5,446 — Healthcare 25,140 14,765 14,765 — — 7,795 — Public finance — — — — — — — Other commercial and industrial 27,957 19,098 19,080 18 17 20,108 — Total commercial 184,604 137,303 85,969 51,334 8,831 158,127 — Commercial real estate: Residential construction and land development 3,285 1,832 1,832 — — 2,633 — Retail 509 276 276 — — 301 — Office 287 275 275 — — 351 — Multifamily — — — — — 19 — Industrial — — — — — 38 — Other commercial real estate 670 472 472 — — 847 — Total commercial real estate 4,751 2,855 2,855 — — 4,189 — Residential mortgage: Permanent mortgage 30,435 25,193 25,193 — — 24,024 1,229 Permanent mortgage guaranteed by U.S. government agencies 1 203,814 197,506 197,506 — — 199,244 7,632 Home equity 14,548 13,075 13,075 — — 12,297 — Total residential mortgage 248,797 235,774 235,774 — — 235,565 8,861 Personal 307 269 269 — — 280 — Total $ 438,459 $ 376,201 $ 324,867 $ 51,334 $ 8,831 $ 398,161 $ 8,861 1 All permanent mortgage loans guaranteed by U.S. government agencies are considered impaired as we do not expect full collection of contractual principal and interest. At December 31, 2017 , $9.2 million of these loans are nonaccruing and $188 million are accruing based on the guarantee by U.S. government agencies.
Summary of Loans by Aging Status [Table Text Block]	A summary of loans currently performing, loans past due and accruing and nonaccrual loans as of December 31, 2018 is as follows (in thousands): Past Due Current 30 to 59 Days 60 to 89 Days 90 Days or More Nonaccrual Total Commercial: Energy $ 3,542,839 $ — — $ — $ 47,494 $ 3,590,333 Services 3,231,532 6,009 6,038 — 8,567 3,252,146 Wholesale/retail 1,619,290 515 37 — 1,316 1,621,158 Manufacturing 721,204 392 6 — 8,919 730,521 Healthcare 2,716,204 241 — 554 16,538 2,733,537 Public finance 876,336 — — — — 876,336 Other commercial and industrial 814,489 518 25 8 17,007 832,047 Total commercial 13,521,894 7,675 6,106 562 99,841 13,636,078 Commercial real estate: Residential construction and land development 147,705 249 280 — 350 148,584 Retail 884,424 14,379 — — 20,279 919,082 Office 1,072,920 — — — — 1,072,920 Multifamily 1,287,483 281 — — 301 1,288,065 Industrial 776,898 1,208 — — — 778,106 Other commercial real estate 556,239 412 — 714 691 558,056 Total commercial real estate 4,725,669 16,529 280 714 21,621 4,764,813 Residential mortgage: Permanent mortgage 1,292,652 3,196 366 — 23,951 1,320,165 Permanent mortgages guaranteed by U.S. government agencies 37,459 24,369 16,345 105,561 7,132 190,866 Home equity 707,017 1,102 352 59 10,472 719,002 Total residential mortgage 2,037,128 28,667 17,063 105,620 41,555 2,230,033 Personal 1,024,298 479 796 3 230 1,025,806 Total $ 21,308,989 $ 53,350 24,245 $ 106,899 $ 163,247 $ 21,656,730 A summary of loans currently performing, loans past due and accruing and nonaccrual loans as of December 31, 2017 is as follows (in thousands): Past Due Current 30 to 59 Days 60 to 89 Days 90 Days or More Nonaccrual Total Commercial: Energy $ 2,833,668 $ — 4,204 $ — $ 92,284 $ 2,930,156 Services 2,518,298 514 486 107 2,620 2,522,025 Wholesale/retail 1,468,284 398 — — 2,574 1,471,256 Manufacturing 490,739 — 73 — 5,962 496,774 Healthcare 2,213,504 15,218 — — 14,765 2,243,487 Public finance 541,775 — — — — 541,775 Other commercial and industrial 509,116 85 78 125 19,098 528,502 Total commercial 10,575,384 16,215 4,841 232 137,303 10,733,975 Commercial real estate: Residential construction and land development 115,213 200 — — 1,832 117,245 Retail 691,256 — — — 276 691,532 Office 831,118 254 — 123 275 831,770 Multifamily 979,625 22 370 — — 980,017 Industrial 573,014 — — — — 573,014 Other commercial real estate 285,937 — — — 472 286,409 Total commercial real estate 3,476,163 476 370 123 2,855 3,479,987 Residential mortgage: Permanent mortgage 1,014,588 3,435 219 — 25,193 1,043,435 Permanent mortgages guaranteed by U.S. government agencies 22,692 18,978 13,468 133,189 9,179 197,506 Home equity 717,007 2,206 440 17 13,075 732,745 Total residential mortgage 1,754,287 24,619 14,127 133,206 47,447 1,973,686 Personal 964,374 681 191 261 269 965,776 Total $ 16,770,208 $ 41,991 19,529 $ 133,822 $ 187,874 $ 17,153,424

Premises and Equipment Premises

Premises and Equipment Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Premises and Equipment [Table Text Block]	Premises and equipment at December 31 are summarized as follows (in thousands): December 31, 2018 2017 Land $ 70,575 $ 71,348 Buildings and improvements 266,733 249,139 Software 150,207 188,826 Furniture and equipment 129,988 223,163 Construction in progress 27,514 23,348 Premises and equipment 645,017 755,824 Less accumulated depreciation 314,984 438,489 Premises and equipment, net of accumulated depreciation $ 330,033 $ 317,335

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	A summary of the preliminary purchase price allocation and resulting goodwill at October 1, 2018 follows (in thousands): Cash and due from banks $ 80,827 Investment securities 17,287 Available for sale securities 546,776 Restricted equity securities 5,261 Loans (Unpaid principal balance - $3,066,521) 2,937,499 Premises and equipment 5,515 Receivables 24,893 Intangible assets 106,733 Real estate and other repossessed assets 5,155 Derivative contracts asset, net 8,197 Cash surrender value of bank-owned life insurance 55,740 Other assets 56,642 Total assets acquired 3,850,525 Deposits 3,289,071 Funds purchased and repurchase agreements 37,218 Subordinated debentures 131,197 Accrued interest, taxes and expense 33,122 Derivative contracts liability, net 12,303 Other liabilities 5,254 Total liabilities assumed 3,508,165 Net assets acquired 342,360 Less: Purchase price 944,193 Goodwill $ 601,833
Schedule of Finite-Lived Intangible Assets [Table Text Block]	The following table presents the original cost and accumulated amortization of intangible assets (in thousands): Dec. 31, 2018 2017 Core deposit premiums $ 103,200 $ 6,510 Less accumulated amortization 5,032 808 Net core deposit premiums 98,168 5,702 Other identifiable intangible assets 63,497 44,468 Less accumulated amortization 26,816 21,512 Net other identifiable intangible assets 36,681 22,956 Total intangible assets, net $ 134,849 $ 28,658
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	Expected amortization expense for intangible assets that will continue to be amortized (in thousands): Core Deposit Premiums Other Identifiable Intangible Assets Total 2019 $ 14,332 $ 6,149 $ 20,481 2020 12,892 6,304 19,196 2021 11,893 5,606 17,499 2022 10,981 4,238 15,219 2023 10,145 3,199 13,344 Thereafter 37,925 11,185 49,110 $ 98,168 $ 36,681 $ 134,849
Schedule of Goodwill [Table Text Block]	The changes in the carrying value of goodwill by operating segment are as follows (in thousands): Commercial Banking Consumer Banking Wealth Management Funds Management and Other Total Balance, December 31, 2016 272,196 39,023 71,520 66,160 448,899 Goodwill recognized during 2017 4,301 — — — 4,301 Sales of consolidated merchant banking investments during 2017 (5,219 ) — (25 ) — (5,244 ) Adjustment 1 41,992 4,435 19,207 (66,160 ) (526 ) Balance, December 31, 2017 313,270 43,458 90,702 — 447,430 Goodwill recognized during 2018 2 — — — 601,833 601,833 Balance, December 31, 2018 $ 313,270 $ 43,458 $ 90,702 $ 601,833 $ 1,049,263

Mortgage Banking Activities (Ta

Mortgage Banking Activities (Tables)	12 Months Ended
	Dec. 31, 2018
Mortgage Banking [Abstract]
Components of Residential Mortgage Loans Held For Sale [Table Text Block]	The unpaid principal balance of residential mortgage loans held for sale, notional amounts of derivative contracts related to residential mortgage loan commitments and forward contract sales and their related fair values included in Mortgage loans held for sale on the Consolidated Balance Sheets were (in thousands): December 31, 2018 December 31, 2017 Unpaid Principal Balance/ Notional Fair Value Unpaid Principal Balance/ Notional Fair Value Residential mortgage loans held for sale $ 145,057 $ 146,971 $ 212,525 $ 215,113 Residential mortgage loan commitments 160,848 5,378 222,919 6,523 Forward sales contracts 274,000 (3,128 ) 380,159 (258 ) $ 149,221 $ 221,378
Mortgage Banking Revenue [Table Text Block]	Mortgage banking revenue was as follows (in thousands): Year Ended 2018 2017 2016 Production revenue: Net realized gains on sales of mortgage loans $ 36,379 $ 45,128 $ 68,947 Net change in unrealized gain on mortgage loans held for sale (674 ) 2,031 (5,311 ) Net change in the fair value of mortgage loan commitments (1,145 ) (3,210 ) 1,599 Net change in the fair value of forward sales contracts (2,870 ) (5,451 ) 4,393 Total mortgage production revenue 31,690 38,498 69,628 Servicing revenue 66,097 66,221 64,286 Total mortgage banking revenue $ 97,787 $ 104,719 $ 133,914
Summary of Mortgage Servicing Rights [Table Text Block]	The following represents a summary of mortgage servicing rights (Dollars in thousands): December 31, 2018 2017 2016 Number of residential mortgage loans serviced for others 132,463,000 136,528,000 139,340,000 Outstanding principal balance of residential mortgage loans serviced for others $ 21,658,335 $ 22,046,632 $ 21,997,568 Weighted average interest rate 3.99 % 3.94 % 3.97 % Remaining contractual term (in months) 293 297 301
Activity in Capitalized Mortgage Servicing Rights [Table Text Block]	Activity in capitalized mortgage servicing rights during the three years ended December 31, 2018 is as follows (in thousands): Balance, December 31, 2015 $ 218,605 Additions, net 71,405 Change in fair value due to loan runoff (40,744 ) Change in fair value due to market changes (2,193 ) Balance, December 31, 2016 247,073 Additions, net 39,149 Change in fair value due to loan runoff (33,527 ) Change in fair value due to market changes 172 Balance, December 31, 2017 252,867 Additions, net 35,247 Change in fair value due to loan runoff (33,528 ) Change in fair value due to market changes 4,668 Balance, December 31, 2018 $ 259,254
Assumptions to Value Mortgage Servicing Rights [Table Text Block]	Significant assumptions used to determine fair value considered to be significant unobservable inputs were as follows: December 31, 2018 2017 Discount rate – risk-free rate plus a market premium 9.90% 9.84% Prepayment rate - based upon loan interest rate, original term and loan type 8.05% - 15.74% 8.72%-15.16% Loan servicing costs – annually per loan based upon loan type: Performing loans $67 - $93 $65 - $88 Delinquent loans $150 - $500 $150 - $500 Loans in foreclosure $1,000 - $4,000 $1,000 - $4,000 Primary/secondary mortgage rate spread 105 bps 105 bps Escrow earnings rate – indexed to rates paid on deposit accounts with comparable average life 2.57% 2.24%
Aging Status of Mortgage Loans Serviced For Others [Table Text Block]	The aging status of our mortgage loans serviced for others by investor at December 31, 2018 follows (in thousands): Past Due Current 30 to 59 Days 60 to 89 Days 90 Days or More Total FHLMC $ 7,798,790 $ 58,271 $ 11,139 $ 25,239 $ 7,893,439 FNMA 6,458,561 63,321 12,413 20,858 6,555,153 GNMA 6,568,459 200,747 56,024 15,996 6,841,226 Other 362,268 4,297 81 1,871 368,517 Total $ 21,188,078 $ 326,636 $ 79,657 $ 63,964 $ 21,658,335

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2018
Deposits [Abstract]
Interest Expense on Deposits Disclosure [Table Text Block]	Interest expense on deposits is summarized as follows (in thousands): Year Ended December 31, 2018 2017 2016 Transaction deposits $ 65,859 $ 28,627 $ 13,906 Savings 439 359 386 Time: Certificates of deposits under $100,000 5,751 7,702 8,776 Certificates of deposits $100,000 and over 19,739 12,393 10,123 Other time deposits 3,729 4,722 7,303 Total time 29,219 24,817 26,202 Total $ 95,517 $ 53,803 $ 40,494

Other Borrowings Other Borrowin

Other Borrowings Other Borrowings (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Other Borrowings [Table Text Block]	Information relating to other borrowings is summarized as follows (dollars in thousands): As of Year Ended December 31, 2018 December 31, 2018 Balance Rate Average Balance Rate Maximum Parent company and other non-bank subsidiaries: Other borrowings $ 5,207 1.57 % $ 2,660 1.35 % $ 5,335 Subordinated debentures 275,913 5.34 % 177,884 5.52 % 275,913 Total parent company and other non-bank subsidiaries 281,120 180,544 5.46 % Subsidiary banks: Funds purchased 402,450 2.34 % 419,322 1.89 % 949,531 Repurchase agreements 615,961 0.36 % 464,582 0.28 % 615,961 Other borrowings: Federal Home Loan Bank advances 6,100,000 2.65 % 6,207,142 2.06 % 6,500,000 GNMA repurchase liability 15,552 4.43 % 14,783 4.47 % 16,529 Other 3,631 4.80 % 11,856 4.45 % 15,096 Total other borrowings 6,119,183 6,233,781 2.07 % Subordinated debentures — — % — — % — Total Subsidiary banks 7,137,594 7,117,685 1.94 % Total other borrowed funds $ 7,418,714 $ 7,298,229 2.03 % As of Year Ended December 31, 2017 December 31, 2017 Balance Rate Average Balance Rate Maximum Parent company and other non-bank subsidiaries: Other borrowings $ — — % $ 935 11.11 % $ 3,104 Subordinated debentures 144,677 5.60 % 147,954 5.57 % 151,875 Total parent company and other non-bank subsidiaries 144,677 148,889 5.65 % Subsidiary banks: Funds purchased 58,628 1.00 % 58,064 0.73 % 80,967 Repurchase agreements 516,335 0.17 % 433,791 0.10 % 536,094 Other borrowings: Federal Home Loan Bank advances 5,100,000 1.47 % 5,882,466 1.13 % 6,200,000 GNMA repurchase liability 19,947 4.22 % 20,509 4.59 % 24,139 Other 14,950 2.61 % 15,382 2.38 % 15,506 Total other borrowings 5,134,897 5,918,357 1.14 % Subordinated debentures — — % — — % — Total Subsidiary banks 5,709,860 6,410,212 1.07 % Total other borrowed funds $ 5,854,537 $ 6,559,101 1.18 % As of Year Ended December 31, 2016 December 31, 2016 Balance Rate Average Balance Rate Maximum Parent company and other non-bank subsidiaries: Other borrowings $ 1,092 8.27 % $ 2,073 16.11 % $ 3,157 Subordinated debentures 151,857 5.49 % 75,039 5.57 % 151,857 Total parent company and other non-bank subsidiaries 152,949 77,112 5.86 % Subsidiary banks: Funds purchased 57,929 0.38 % 78,222 0.24 % 567,103 Repurchase agreements 668,661 0.02 % 589,145 0.04 % 668,661 Other borrowings: Federal Home Loan Bank advances 4,800,000 0.72 % 5,985,656 0.55 % 6,500,000 GNMA repurchase liability 22,471 4.26 % 15,637 4.74 % 22,471 Other 15,292 2.66 % 15,670 2.41 % 15,797 Total other borrowings 4,837,763 6,016,963 0.57 % Subordinated debentures — — % 140,414 1.35 % 226,434 Total Subsidiary banks 5,564,353 6,824,744 0.54 % Total other borrowed funds $ 5,717,302 $ 6,901,856 0.60 %
Schedule of Maturities of Other Borrowings [Table Text Block]	Aggregate annual principal repayments at December 31, 2018 are as follows (in thousands): Parent Company and Other Non-bank Subsidiaries Subsidiary Banks 2019 $ — $ 7,134,538 2020 — 575 2021 — 575 2022 — 575 2023 — 625 Thereafter 281,120 706 Total $ 281,120 $ 7,137,594
Schedule of Repurchase Agreements [Table Text Block]	Additional information relating to securities sold under agreements to repurchase and related liabilities at December 31, 2018 and 2017 is as follows (dollars in thousands): December 31, 2018 Amortized Fair Repurchase Average Security Sold/Maturity Cost Value Liability 1 Rate U.S. government agency mortgage-backed securities: Overnight 1 $ 636,864 $ 628,229 $ 615,961 0.36 % Long-term — — — — % Total Agency Securities $ 636,864 $ 628,229 $ 615,961 0.36 % December 31, 2017 Amortized Fair Repurchase Average Security Sold/Maturity Cost Value Liability 1 Rate U.S. government agency mortgage-backed securities: Overnight 1 $ 525,452 $ 523,914 $ 516,335 0.17 % Long-term — — — — % Total Agency Securities $ 525,452 $ 523,914 $ 516,335 0.17 % 1 BOK Financial maintains control over the securities underlying overnight repurchase agreements and generally transfers control over securities underlying longer-term dealer repurchase agreements to the respective counterparty.

Federal and State Income Taxes

Federal and State Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	The Tax Cuts and Jobs Act (the "Tax Reform Act"), which was enacted on December 22, 2017, reduced the federal corporate tax rate from 35% to 21% for periods beginning January 1, 2018. We completed our accounting during 2018 for uncertainties that resulted from the Tax Reform Act. Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of deferred tax assets and liabilities are as follows (in thousands): December 31, 2018 2017 Deferred tax assets: Available for sale securities mark to market $ 24,441 $ 12,083 Share-based compensation 4,434 7,598 Credit loss allowances 49,804 58,666 Valuation adjustments 9,619 8,102 Deferred compensation 25,608 12,215 Unearned fees 9,814 9,265 Purchased loan discount 27,283 — Other 31,812 30,859 Total deferred tax assets 182,815 138,788 Deferred tax liabilities: Depreciation 13,901 15,817 Mortgage servicing rights 61,844 63,112 Lease financing 10,040 9,973 Acquired identifiable intangible 28,620 — Other 32,954 34,880 Total deferred tax liabilities 147,359 123,782 Net deferred tax assets $ 35,456 $ 15,006
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	The significant components of the provision for income taxes attributable to continuing operations for BOK Financial are shown below (in thousands): Year Ended December 31, 2018 2017 2016 Current income tax expense: Federal $ 103,748 $ 141,607 $ 107,379 State 15,253 14,592 11,028 Total current income tax expense 119,001 156,199 118,407 Deferred income tax expense: Federal (190 ) 25,525 (11,340 ) State 250 869 (690 ) Total deferred income tax expense 60 26,394 (12,030 ) Total income tax expense $ 119,061 $ 182,593 $ 106,377
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The reconciliations of income attributable to continuing operations at the U.S. federal statutory tax rate to income tax expense are as follows (in thousands): Year Ended December 31, 2018 2017 2016 Amount: Federal statutory tax $ 118,752 $ 181,397 $ 118,530 Tax exempt revenue (8,311 ) (12,402 ) (10,544 ) Effect of state income taxes, net of federal benefit 12,430 10,701 6,478 Utilization of tax credits, net of proportional amortization of low-income housing limited partnership investments (4,559 ) (6,811 ) (6,256 ) Share-based compensation (2,105 ) (2,817 ) — Implementation of Tax Reform Act (1,728 ) 11,672 — Deposit insurance 3,099 — — Other, net 1,483 853 (1,831 ) Total income tax expense $ 119,061 $ 182,593 $ 106,377 Year Ended December 31, 2018 2017 2016 Percent of pretax income: Federal statutory tax 21.0 % 35.0 % 35.0 % Tax exempt revenue (1.5 ) (2.4 ) (3.1 ) Effect of state income taxes, net of federal benefit 2.2 2.0 1.9 Utilization of tax credits, net of proportional amortization of low-income housing limited partnership investments (0.8 ) (1.3 ) (1.8 ) Share-based compensation (0.4 ) (0.5 ) — Implementation of Tax Reform Act (0.3 ) 2.3 — Deposit insurance 0.5 — — Other, net 0.4 0.1 (0.6 ) Total 21.1 % 35.2 % 31.4 %
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): 2018 2017 2016 Balance as of January 1 $ 18,110 $ 15,841 $ 13,232 Additions for tax for current year positions 2,649 4,645 5,640 Settlements during the period — — — Lapses of applicable statute of limitations (1,890 ) (2,376 ) (3,031 ) Balance as of December 31 $ 18,869 $ 18,110 $ 15,841

Employee Benefits (Tables)

Employee Benefits (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Change in benefit obligation, plan assets funded status and net periodic pension cost (benefit) [Table Text Block]	The following table presents information regarding this plan (in thousands): December 31, 2018 2017 Change in projected benefit obligation: Projected benefit obligation at beginning of year $ 30,897 $ 34,964 Interest cost 973 1,153 Actuarial loss (gain) (1,417 ) 223 Benefits paid (6,033 ) (5,443 ) Projected benefit obligation at end of year 1,2 $ 24,547 $ 30,897 Change in plan assets: Plan assets at fair value at beginning of year $ 40,419 $ 41,769 Actual return on plan assets (804 ) 4,093 Benefits paid (6,033 ) (5,443 ) Plan assets at fair value at end of year $ 33,582 $ 40,419 Funded status of the plan $ 9,035 $ 9,522 Components of net periodic benefit: Interest cost $ 973 $ 1,153 Expected return on plan assets (2,065 ) (2,041 ) Other 509 184 Net periodic benefit cost (credit) $ (583 ) $ (704 ) 1 Projected benefit obligation equals accumulated benefit obligation. 2
Valuation assumptions used [Table Text Block]	Weighted-average assumptions as of December 31: 2018 2017 Discount rate 4.10 % 3.30 % Expected return on plan assets 5.50 % 5.50 %
Expected future benefit payments [Table Text Block]	As of December 31, 2018 , expected future benefit payments related to the Pension Plan were as follows (in thousands): 2019 $ 3,562 2020 2,257 2021 2,194 2022 2,299 2023 2,495 Thereafter 19,175 Total estimated future benefit payments $ 31,982

Share-Based Compensation Plans

Share-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation, Stock Options, Activity [Table Text Block]	The following table presents stock options outstanding under these plans (in thousands, except for per share data): Number Weighted- Average Exercise Price Aggregate Intrinsic Value Options outstanding at: December 31, 2016 218,524 51.95 6,793 December 31, 2017 117,551 53.26 4,592 December 31, 2018 63,058 $ 54.89 $ 1,163 Options vested at: December 31, 2016 93,117 $ 46.22 $ 3,429 December 31, 2017 51,286 48.62 2,241 December 31, 2018 33,573 53.09 679
Schedule of Nonvested Share Activity [Table Text Block]	The following represents a summary of the non-vested stock awards for the three years ended December 31, 2018 (in thousands): Shares Weighted Average Grant Date Fair Value Non-vested at January 1, 2016 791,109 Granted 256,670 $55.35 Vested (213,941 ) $55.87 Forfeited (47,132 ) $57.86 Non-vested at December 31, 2016 786,706 Granted 177,807 $86.95 Vested (194,419 ) $63.07 Forfeited (102,991 ) $78.70 Non-vested at December 31, 2017 667,103 Granted 150,419 $85.58 Vested (242,215 ) $74.85 Forfeited (47,700 ) $75.68 Non-vested at December 31, 2018 527,607

Related Parties Related Parties

Related Parties Related Parties (Tables)	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Schedule of Related Party Transactions [Table Text Block]	Activity in loans to related parties is summarized as follows (in thousands): Year Ended December 31, 2018 2017 Beginning balance $ 110,246 $ 136,945 Advances 1,479,735 1,559,291 Payments (1,514,841 ) (1,585,865 ) Adjustments 1 125 (125 ) Ending balance $ 75,265 $ 110,246 1

Commitments and Contingent Li_2

Commitments and Contingent Liabilities Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Variable Interest Entities [Table Text Block]	December 31, 2018 Loans Other Assets Other Liabilities Other Borrowings Non-controlling Interests Consolidated: Private equity funds $ — $ 9,516 $ — $ — $ 8,644 Tax credit entities — — — — — Other — 17,602 1,448 5,207 2,292 Total consolidated $ — $ 27,118 $ 1,448 $ 5,207 $ 10,936 Unconsolidated: Tax credit entities $ 58,981 $ 165,567 $ 53,198 $ — $ — Other — 62,406 20,687 — — Total unconsolidated $ 58,981 $ 227,973 $ 73,885 $ — $ — December 31, 2017 Loans Other Other Other Non-controlling Consolidated: Private equity funds $ — $ 14,783 $ — $ — $ 11,927 Tax credit entities 10,000 10,964 — 10,964 10,000 Other — 1,040 — — 1,040 Total consolidated $ 10,000 $ 26,787 $ — $ 10,964 $ 22,967 Unconsolidated: Tax credit entities $ 52,852 $ 153,506 $ 47,859 $ — $ — Other — 38,397 22,968 — — Total unconsolidated $ 52,852 $ 191,903 $ 70,827 $ — $ —

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share [Table Text Block]	The following table presents the computation of basic and diluted earnings per share (dollars in thousands, except per share data): Year Ended 2018 2017 2016 Numerator: Net income attributable to BOK Financial Corp. shareholders $ 445,646 $ 334,644 $ 232,668 Less: Earnings allocated to participating securities 3,737 3,561 2,883 Numerator for basic earnings per share – income available to common shareholders 441,909 331,083 229,785 Effect of reallocating undistributed earnings of participating securities 1 2 1 Numerator for diluted earnings per share – income available to common shareholders $ 441,910 $ 331,085 $ 229,786 Denominator: Weighted average shares outstanding 67,190,257 65,440,832 65,901,110 Less: Participating securities included in weighted average shares outstanding 561,617 695,468 815,483 Denominator for basic earnings per common share 66,628,640 64,745,364 65,085,627 Dilutive effect of employee stock compensation plans 1 33,633 60,920 58,271 Denominator for diluted earnings per common share 66,662,273 64,806,284 65,143,898 Basic earnings per share $ 6.63 $ 5.11 $ 3.53 Diluted earnings per share $ 6.63 $ 5.11 $ 3.53 1 Excludes employee stock options with exercise prices greater than current market price. — — —

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2018
Stockholders' Equity Note [Abstract]
Summary of Regulatory Capital Levels [Table Text Block]	A summary of regulatory capital minimum requirements and levels follows (dollars in thousands): Minimum Capital Requirement Capital Conservation Buffer 1 Minimum Capital Requirement Including Capital Conservation Buffer Well Capitalized Bank Requirement December 31, 2018 December 31, 2017 Common Equity Tier 1 Capital (to Risk Weighted Assets): Consolidated 4.50% 2.50% 7.00% N/A $ 3,356,524 10.92 % $ 3,074,981 12.05 % BOKF, NA 4.50% N/A 4.50% 6.50% 2,894,119 10.50 % 2,870,694 11.34 % CoBiz Bank 2 4.50% N/A 4.50% 6.50% 317,944 10.65 % 399,768 12.19 % Tier I Capital (to Risk Weighted Assets): Consolidated 6.00% 2.50% 8.50% N/A $ 3,356,524 10.92 % $ 3,074,981 12.05 % BOKF, NA 6.00% N/A 6.00% 8.00% 2,894,119 10.50 % 2,870,694 11.34 % CoBiz Bank 2 6.00% N/A 6.00% 8.00% 317,944 10.65 % 399,768 12.19 % Total Capital (to Risk Weighted Assets): Consolidated 8.00% 2.50% 10.50% N/A $ 3,841,684 12.50 % $ 3,455,709 13.54 % BOKF, NA 8.00% N/A 8.00% 10.00% 3,103,366 11.26 % 3,105,117 12.27 % CoBiz Bank 2 8.00% N/A 8.00% 10.00% 382,944 12.83 % 434,012 13.23 % Leverage (Tier I Capital to Average Assets): Consolidated 4.00% N/A 4.00% N/A $ 3,356,524 8.96 % $ 3,074,981 9.31 % BOKF, NA 4.00% N/A 4.00% 5.00% 2,894,119 8.56 % 2,870,694 8.73 % CoBiz Bank 2 4.00% N/A 4.00% 5.00% 317,944 8.25 % 399,768 10.47 % 1 Capital conservation buffer is effective January 1, 2016 and is phased in through 2019. The phased in capital conservation buffer was 1.875% at December 31, 2018 and 1.25% at December 31, 2017 . The fully phased in requirement of 2.50% is included in the table above. 2 CoBiz Bank was acquired by BOK Financial effective October 1, 2018.
Accumulated Other Comprehensive Income (Loss) [Table Text Block]	A rollforward of the components of accumulated other comprehensive income (loss) is included as follows (in thousands): Unrealized Gain (Loss) on Available for Sale Securities Investment Securities Transferred from AFS Employee Benefit Plans Total Balance, December 31, 2015 $ 23,284 $ 68 $ (1,765 ) $ 21,587 Net change in unrealized gain (loss) (41,333 ) — (188 ) (41,521 ) Reclassification adjustments included in earnings: Interest revenue, Investment securities, Taxable securities — (112 ) — (112 ) Gain on available for sale securities, net (11,675 ) — — (11,675 ) Other comprehensive income (loss), before income taxes (53,008 ) (112 ) (188 ) (53,308 ) Federal and state income tax 1 (20,637 ) (44 ) (73 ) (20,754 ) Other comprehensive income (loss), net of income taxes (32,371 ) (68 ) (115 ) (32,554 ) Balance, December 31, 2016 (9,087 ) — (1,880 ) (10,967 ) Net change in unrealized gain (loss) (28,170 ) — 2,018 (26,152 ) Reclassification adjustments included in earnings: Interest revenue, Investment securities, Taxable securities — — — — Gain on available for sale securities, net (4,428 ) — — (4,428 ) Other comprehensive income (loss), before income taxes (32,598 ) — 2,018 (30,580 ) Federal and state income tax 1 (12,708 ) — 785 (11,923 ) Other comprehensive income (loss), net of income taxes (19,890 ) — 1,233 (18,657 ) Reclassification of stranded accumulated other comprehensive loss related to tax reform (6,408 ) — (142 ) (6,550 ) Balance, December 31, 2017 (35,385 ) — (789 ) (36,174 ) Transition adjustment for net unrealized gains on equity securities (2,709 ) — — (2,709 ) Net change in unrealized gain (loss) (46,941 ) — (1,069 ) (48,010 ) Reclassification adjustments included in earnings: Interest revenue, Investment securities, Taxable securities — — — — Loss on available for sale securities, net 2,801 — — 2,801 Other comprehensive income (loss), before income taxes (44,140 ) — (1,069 ) (45,209 ) Federal and state income tax 2 (11,235 ) — (272 ) (11,507 ) Other comprehensive income (loss), net of income taxes (32,905 ) — (797 ) (33,702 ) Balance, December 31, 2018 $ (70,999 ) $ — $ (1,586 ) $ (72,585 ) 1 Calculated using a 39 percent blended federal and state statutory tax rate. 2

Reportable Segments (Tables)

Reportable Segments (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Reportable Segments [Table Text Block]	Reportable segments reconciliation to the Consolidated Financial Statements for the year ended December 31, 2018 is as follows (in thousands): Commercial Consumer Wealth Management Funds Management and Other BOK Financial Consolidated Net interest and dividend revenue from external sources $ 726,856 $ 83,231 $ 81,527 $ 93,253 $ 984,867 Net interest revenue (expense) from internal sources (156,254 ) 73,448 31,505 51,301 — Net interest and dividend revenue 570,602 156,679 113,032 144,554 984,867 Provision for credit losses 30,358 5,143 (288 ) (27,213 ) 8,000 Net interest and dividend revenue after provision for credit losses 540,244 151,536 113,320 171,767 976,867 Other operating revenue 162,701 178,123 296,369 (20,409 ) 616,784 Other operating expense 192,811 210,187 248,959 376,209 1,028,166 Net direct contribution 510,134 119,472 160,730 (224,851 ) 565,485 Gain (loss) on financial instruments, net 26 (25,021 ) 7 24,988 — Change in fair value of mortgage servicing rights — 4,668 — (4,668 ) — Gain (loss) on repossessed assets, net (6,532 ) 247 — 6,285 — Corporate expense allocations 45,818 63,700 44,190 (153,708 ) — Net income before taxes 457,810 35,666 116,547 (44,538 ) 565,485 Federal and state income taxes 121,434 9,085 30,003 (41,461 ) 119,061 Net income 336,376 26,581 86,544 (3,077 ) 446,424 Net income attributable to non-controlling interests — — — 778 778 Net income attributable to BOK Financial Corp. shareholders $ 336,376 $ 26,581 $ 86,544 $ (3,855 ) $ 445,646 Average assets $ 18,431,411 $ 8,303,262 $ 8,446,006 $ (243,149 ) $ 34,937,530 Reportable segments reconciliation to the Consolidated Financial Statements for the year ended December 31, 2017 is as follows (in thousands): Commercial Consumer Wealth Management Funds Management and Other BOK Financial Consolidated Net interest and dividend revenue from external sources $ 618,325 $ 84,286 $ 45,024 $ 94,066 $ 841,701 Net interest revenue (expense) from internal sources (89,106 ) 53,916 38,344 (3,154 ) — Net interest and dividend revenue 529,219 138,202 83,368 90,912 841,701 Provision for credit losses 13,877 4,786 (696 ) (24,967 ) (7,000 ) Net interest and dividend revenue after provision for credit losses 515,342 133,416 84,064 115,879 848,701 Other operating revenue 208,404 184,878 301,434 378 695,094 Other operating expense 228,119 221,679 246,626 329,093 1,025,517 Net direct contribution 495,627 96,615 138,872 (212,836 ) 518,278 Gain (loss) on financial instruments, net 52 (2,054 ) — 2,002 — Change in fair value of mortgage servicing rights — 172 — (172 ) — Gain (loss) on repossessed assets, net (2,681 ) 223 387 2,071 — Corporate expense allocations 34,253 67,320 40,562 (142,135 ) — Net income before taxes 458,745 27,636 98,697 (66,800 ) 518,278 Federal and state income taxes 188,241 10,750 38,848 (55,246 ) 182,593 Net income 270,504 16,886 59,849 (11,554 ) 335,685 Net income attributable to non-controlling interests — — — 1,041 1,041 Net income attributable to BOK Financial Corp. shareholders $ 270,504 $ 16,886 $ 59,849 $ (12,595 ) $ 334,644 Average assets $ 17,730,654 $ 8,544,117 $ 7,072,622 $ (399,899 ) $ 32,947,494 Reportable segments reconciliation to the Consolidated Financial Statements for the year ended December 31, 2016 is as follows (in thousands): Commercial Consumer Wealth Management Funds Management and Other BOK Financial Consolidated Net interest and dividend revenue from external sources $ 501,042 $ 77,283 $ 33,006 $ 135,897 $ 747,228 Net interest revenue (expense) from internal sources (62,655 ) 43,156 29,043 (9,544 ) — Net interest and dividend revenue 438,387 120,439 62,049 126,353 747,228 Provision for credit losses 32,961 4,925 (801 ) 27,915 65,000 Net interest and dividend revenue after provision for credit losses 405,426 115,514 62,850 98,438 682,228 Other operating revenue 198,902 216,285 283,222 (24,389 ) 674,020 Other operating expense 217,993 247,478 250,995 301,124 1,017,590 Net direct contribution 386,335 84,321 95,077 (227,075 ) 338,658 Gain (loss) on financial instruments, net 10 (26,252 ) (42 ) 26,284 — Change in fair value of mortgage servicing rights — (2,193 ) — 2,193 — Gain on repossessed assets, net 669 979 — (1,648 ) — Corporate expense allocations 36,134 65,567 42,378 (144,079 ) — Net income before taxes 350,880 (8,712 ) 52,657 (56,167 ) 338,658 Federal and state income taxes 146,740 (3,389 ) 20,976 (57,950 ) 106,377 Net income 204,140 (5,323 ) 31,681 1,783 232,281 Net loss attributable to non-controlling interests — — — (387 ) (387 ) Net income attributable to BOK Financial Corp. shareholders $ 204,140 $ (5,323 ) $ 31,681 $ 2,170 $ 232,668 Average assets $ 17,175,325 $ 8,254,666 $ 7,373,080 $ (524,669 ) $ 32,278,402

Fees and Commission Revenue Fee

Fees and Commission Revenue Fees and Commissions Revenue (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Fees and Commissions Revenue [Table Text Block]	Commercial Consumer Wealth Management Funds Management and Other Consolidated Out of Scope 1 In Scope 2 Trading revenue $ — $ — $ 28,077 $ — $ 28,077 $ 28,077 $ — Customer hedging revenue 7,748 — 27,512 3,574 38,834 38,834 — Retail brokerage revenue — — 19,030 3,120 22,150 — 22,150 Investment banking revenue 7,628 — 11,634 — 19,262 6,380 12,882 Brokerage and trading revenue 15,376 — 86,253 6,694 108,323 73,291 35,032 TransFund EFT network revenue 72,280 4,017 (82 ) 6 76,221 — 76,221 Merchant services revenue 7,666 59 — 79 7,804 — 7,804 Transaction card revenue 79,946 4,076 (82 ) 85 84,025 — 84,025 Personal trust revenue — — 96,839 — 96,839 — 96,839 Corporate trust revenue — — 22,292 — 22,292 — 22,292 Institutional trust & retirement plan services revenue — — 44,400 — 44,400 — 44,400 Investment management services and other — — 19,729 1,443 21,172 — 21,172 Fiduciary and asset management revenue — — 183,260 1,443 184,703 — 184,703 Commercial account service charge revenue 41,931 1,445 2,331 1,565 47,272 — 47,272 Overdraft fee revenue 370 36,177 134 (145 ) 36,536 — 36,536 Check card revenue — 20,967 — 339 21,306 — 21,306 Automated service charge and other deposit fee revenue 282 6,621 62 74 7,039 — 7,039 Deposit service charges and fees 42,583 65,210 2,527 1,833 112,153 — 112,153 Mortgage production revenue — 31,690 — — 31,690 31,690 — Mortgage servicing revenue — 67,980 — (1,883 ) 66,097 66,097 — Mortgage banking revenue — 99,670 — (1,883 ) 97,787 97,787 — Other revenue 24,044 9,218 24,507 (1,118 ) 56,651 38,306 18,345 Total fees and commissions revenue $ 161,949 $ 178,174 $ 296,465 $ 7,054 $ 643,642 $ 209,384 $ 434,258 1 Out of scope revenue generally relates to financial instruments or contractual rights and obligations within the scope of other applicable accounting guidance. 2 In scope revenue represents revenue subject to FASB ASC Topic 606,

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Assets And Liabilities Measured On A Recurring Basis [Table Text Block]	The fair value of financial assets and liabilities that are measured on a recurring basis is as follows as of December 31, 2018 (in thousands): Total Quoted Prices in Active Markets for Identical Instruments Significant Other Observable Inputs Significant Unobservable Inputs Assets: Trading securities: U.S. government agency debentures $ 63,765 $ — $ 63,765 $ — U.S. government agency residential mortgage-backed securities 1,791,584 — 1,791,584 — Municipal and other tax-exempt securities 34,507 — 34,507 — Asset-backed securities 42,656 — 42,656 — Other trading securities 24,411 — 24,411 — Total trading securities 1,956,923 — 1,956,923 — Available for sale securities: U.S. Treasury securities 493 493 — — Municipal and other tax-exempt securities 2,864 — 2,864 — U.S. government agency residential mortgage-backed securities 5,804,708 — 5,804,708 — Privately issued residential mortgage-backed securities 59,736 — 59,736 — Commercial mortgage-backed securities guaranteed by U.S. government agencies 2,953,889 — 2,953,889 — Other debt securities 35,430 — 34,958 472 Total available for sale securities 8,857,120 493 8,856,155 472 Fair value option securities – U.S. government agency residential mortgage-backed securities 283,235 — 283,235 — Residential mortgage loans held for sale 149,221 — 134,014 15,207 Mortgage servicing rights, net 1 259,254 — — 259,254 Derivative contracts, net of cash margin 2 320,929 44,074 276,855 — Liabilities: Derivative contracts, net of cash margin 2 362,306 — 362,306 — 1 A reconciliation of the beginning and ending fair value of mortgage servicing rights and disclosures of significant assumptions used to determine fair value are presented in Note 7 , Mortgage Banking Activities . 2 See Note 3 for detail of fair value of derivative contracts by contract type. Derivative contracts in a net asset position that were valued based on quoted prices in active markets or identical instruments (Level 1) are exchange-traded interest rate, energy and agricultural derivative contracts, net of cash margin. Derivative contracts in a net liability position that were valued using quoted prices in active markets for identical instruments (Level 1) are exchange-traded interest rate derivative contracts, fully offset by cash margin. The fair value of financial assets and liabilities that are measured on a recurring basis is as follows as of December 31, 2017 (in thousands): Total Quoted Prices in Active Markets for Identical Instruments Significant Other Observable Inputs Significant Unobservable Inputs Assets: Trading securities: U.S. government agency debentures $ 21,196 $ — $ 21,196 $ — U.S. government agency residential mortgage-backed securities 392,673 — 392,673 — Municipal and other tax-exempt securities 13,559 — 13,559 — Asset-backed securities 23,885 — 23,885 — Other trading securities 11,363 — 11,363 — Total trading securities 462,676 — 462,676 — Available for sale securities: U.S. Treasury securities 1,000 1,000 — — Municipal and other tax-exempt securities 27,080 — 22,278 4,802 U.S. government agency residential mortgage-backed securities 5,309,152 — 5,309,152 — Privately issued residential mortgage-backed securities 93,221 — 93,221 — Commercial mortgage-backed securities guaranteed by U.S. government agencies 2,834,961 — 2,834,961 — Other debt securities 25,481 — 25,009 472 Perpetual preferred stock 15,767 — 15,767 — Equity securities and mutual funds 14,916 — 14,916 — Total available for sale securities 8,321,578 1,000 8,315,304 5,274 Fair value option securities – U.S. government agency residential mortgage-backed securities 755,054 — 755,054 — Residential mortgage loans held for sale 221,378 — 209,079 12,299 Mortgage servicing rights, net 1 252,867 — — 252,867 Derivative contracts, net of cash margin 2 220,502 8,179 212,323 — Liabilities: Derivative contracts, net of cash margin 2 171,963 — 171,963 — 1 A reconciliation of the beginning and ending fair value of mortgage servicing rights and disclosures of significant assumptions used to determine fair value are presented in Note 7 , Mortgage Banking Activities. 2 See Note 3 for detail of fair value of derivative contracts by contract type. Derivative contracts in a net asset position that were valued based on quoted prices in active markets for identical instruments (Level 1) are exchange-traded interest rate, energy and agricultural derivative contracts, net of cash margin. Derivative contracts in a net liability position that were valued using quoted prices in active markets for identical instruments based on quoted prices in active markets for identical instruments (Level 1) are exchange-traded interest rate and energy derivative contracts, fully offset by cash margin.
Fair Value Assets Measured On Recurring Basis Significant Unobservable Inputs [Table Text Block]	The following represents the changes related to assets measured at fair value on a recurring basis using significant unobservable inputs (in thousands): Available for Sale Securities Residential mortgage loans held for sale Municipal and other tax-exempt securities Other debt securities Balance, December 31, 2016 $ 5,789 $ 4,152 $ 11,617 Transfer to Level 3 from Level 2 1 — — 3,507 Purchases and capital calls — — — Redemptions and distributions (1,100 ) — — Proceeds from sales — (3,900 ) (2,944 ) Gain (loss) recognized in earnings: Mortgage banking revenue — — 119 Other comprehensive income (loss): Net change in unrealized gain (loss) 113 220 — Balance, December 31, 2017 4,802 472 12,299 Transfer to Level 3 from Level 2 1 — — 6,183 Purchases and capital calls — — — Redemptions and distributions (5,095 ) — — Proceeds from sales — — (2,706 ) Gain (loss) recognized in earnings: Mortgage banking revenue — — (569 ) Other comprehensive income (loss): Net change in unrealized gain (loss) 293 — — Balance, December 31, 2018 $ — $ 472 $ 15,207 1 Recurring transfers to Level 3 from Level 2 consist of residential mortgage loans intended for sale to U.S. government agencies that fail to meet conforming standards.
Fair Value Inputs, Fair Value Measured On a Recurring Basis, Quantitative Information [Table Text Block]	A summary of quantitative information about assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3) as of December 31, 2018 follows (in thousands): Quantitative Information about Level 3 Recurring Fair Value Measurements Fair Value Valuation Technique(s) Significant Unobservable Input Range (Weighted Average) Available for sale securities: Other debt securities 472 Discounted cash flows 1 Interest rate spread 7.88%-7.88% (7.88%) 3 94.44%-94.44% (94.44%) 2 Residential mortgage loans held for sale 15,207 Quoted prices of loans sold in securitization transactions, with a liquidity discount applied Liquidity discount applied to the market value of mortgage loans qualifying for sale to U.S. government agencies 92.38% 1 Discounted cash flows developed using discount rates primarily based on reference to interest rate spreads for comparable securities of similar duration and credit rating as determined by the nationally-recognized rating agencies, adjusted for lack of trading volume. 2 Represents fair value as a percentage of par value. 3 Interest rate yields used to value investment grade taxable securities based on comparable short-term taxable securities which are generally yielding approximately 3% . A summary of quantitative information about Recurring Fair Value Measurements based on Significant Unobservable Inputs (Level 3) as of December 31, 2017 follows (in thousands): Quantitative Information about Level 3 Recurring Fair Value Measurements Fair Value Valuation Technique(s) Significant Unobservable Input Range (Weighted Average) Available for sale securities: Municipal and other tax-exempt securities $ 4,802 Discounted cash flows 1 Interest rate spread 6.60%-6.60% (6.60%) 2 92.25%-94.76% (93.75%) 3 Other debt securities 472 Discounted cash flows 1 Interest rate spread 6.85%-6.85% (6.85%) 4 94.39%-94.39% (94.39%) 3 Residential mortgage loans held for sale 12,299 Quoted prices of loans sold in securitization transactions, with a liquidity discount applied Liquidity discount applied to the market value of mortgage loans qualifying for sale to U.S. government agencies 94.75% 1 Discounted cash flows developed using discount rates primarily based on reference to interest rate spreads for comparable securities of similar duration and credit rating as determined by the nationally-recognized rating agencies, adjusted for lack of trading volume. 2 Interest rate yields used to value investment grade tax-exempt securities represent a spread of 372 to 466 basis points over average yields for comparable tax-exempt securities. 3 Represents fair value as a percentage of par value. 4 Interest rate yields used to value investment grade taxable securities based on comparable short-term taxable securities which are generally yielding less than 3%
Fair Value Assets Measured on Nonrecurring Basis [Table Text Block]	The following represents the carrying value of assets measured at fair value on a non-recurring basis and related losses recorded during the year. The carrying value represents only those assets with the balance sheet date for which the fair value was adjusted during the year: Carrying Value at December 31, 2018 Fair Value Adjustments for the Quoted Prices in Active Markets for Identical Instruments Significant Other Observable Inputs Significant Unobservable Inputs Gross charge-offs against allowance for loan losses Net losses and expenses of repossessed assets, net Impaired loans $ — $ 1,074 $ 17,401 $ 17,434 $ — Real estate and other repossessed assets — 4,795 6,366 — 7,269 Carrying Value at December 31, 2017 Fair Value Adjustments for the Quoted Prices in Active Markets for Identical Instruments Significant Other Observable Inputs Significant Unobservable Inputs Gross charge-offs against allowance for loan losses Net losses and expenses of repossessed assets, net Impaired loans $ — $ 7,436 $ 7,626 $ 12,145 $ — Real estate and other repossessed assets — 3,483 5,481 — 6,372
Fair Value Inputs, Fair Value Measured On a Nonrecurring Basis, Quantitative Information [Table Text Block]	A summary of quantitative information about Non-recurring Fair Value Measurements based on Significant Unobservable Inputs (Level 3) as of December 31, 2018 follows (in thousands): Quantitative Information about Level 3 Non-recurring Fair Value Measurements Fair Value Valuation Technique(s) Significant Unobservable Input Range (Weighted Average) Impaired loans $ 17,401 Discounted cash flows Management knowledge of industry and non-real estate collateral including but not limited to recoverable oil & gas reserves, forward looking commodity prices, and estimated operating costs 35% - 80% (50%) 1 Real estate and other repossessed assets 6,366 Discounted cash flows Recoverable oil and gas reserves, forward-looking commodity prices, estimated operating costs N/A 1 Represents fair value as a percentage of the unpaid principal balance. The table above excludes the initial measurement of assets and liabilities that were acquired as part of the CoBiz acquisition in October 1, 2018. These assets and liabilities were recorded at their fair value upon acquisition in accordance with U.S. GAAP and were not re-measured during the periods presented unless specifically required by U.S. GAAP. Acquisition date fair values represent either Level 2 fair value measurements (investment securities, deposits, property, equipment, and debt) or Level 3 fair value measurements (loans and core deposit intangible assets). Refer to Note 6, Goodwill and Intangible Assets, for further detail regarding the CoBiz acquisition. A summary of quantitative information about Non-recurring Fair Value Measurements based on Significant Unobservable Inputs (Level 3) as of December 31, 2017 follows (in thousands): Quantitative Information about Level 3 Non-recurring Fair Value Measurements Fair Value Valuation Technique(s) Significant Unobservable Input Range (Weighted Average) Impaired loans $ 7,626 Discounted cash flows Recoverable oil and gas reserves, forward-looking commodity prices and estimated operating costs 40% - 86% (59%) 1 Real estate and other repossessed assets 5,481 Discounted cash flows Recoverable oil and gas reserves, forward-looking commodity prices and estimated operating costs N/A 1 Represents fair value as a percentage of the unpaid principal balance.
Fair Value of Financial Instruments [Table Text Block]	The following table presents the carrying values and estimated fair values of all financial instruments, including those financial assets and liabilities that are not measured and reported at fair value on a recurring basis or non-recurring (dollars in thousands): December 31, 2018 Carrying Value Estimated Fair Value Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash and due from banks $ 741,749 $ 741,749 $ 741,749 $ — $ — Interest-bearing cash and cash equivalents 401,675 401,675 401,675 — — Trading securities: U.S. government agency debentures 63,765 63,765 — 63,765 — U.S. government agency residential mortgage-backed securities 1,791,584 1,791,584 — 1,791,584 — Municipal and other tax-exempt securities 34,507 34,507 — 34,507 — Asset-backed securities 42,656 42,656 — 42,656 — Other trading securities 24,411 24,411 — 24,411 — Total trading securities 1,956,923 1,956,923 — 1,956,923 — Investment securities: Municipal and other tax-exempt securities 137,296 138,562 — 138,562 — U.S. government agency residential mortgage-backed securities 12,612 12,770 — 12,770 — Other debt securities 205,279 215,966 — 7,905 208,061 Total investment securities 355,187 367,298 — 159,237 208,061 Available for sale securities: U.S. Treasury securities 493 493 493 — — Municipal and other tax-exempt securities 2,864 2,864 — 2,864 — U.S. government agency residential mortgage-backed securities 5,804,708 5,804,708 — 5,804,708 — Privately issued residential mortgage-backed securities 59,736 59,736 — 59,736 — Commercial mortgage-backed securities guaranteed by U.S. government agencies 2,953,889 2,953,889 — 2,953,889 — Other debt securities 35,430 35,430 — 34,958 472 Total available for sale securities 8,857,120 8,857,120 493 8,856,155 472 Fair value option securities – U.S. government agency residential mortgage-backed securities 283,235 283,235 — 283,235 — Residential mortgage loans held for sale 149,221 149,221 — 134,014 15,207 Loans: Commercial 13,636,078 13,526,162 — — 13,526,162 Commercial real estate 4,764,813 4,713,747 — — 4,713,747 Residential mortgage 2,230,033 2,213,951 — — 2,213,951 Personal 1,025,806 1,024,368 — — 1,024,368 Total loans 21,656,730 21,478,228 — — 21,478,228 Allowance for loan losses (207,457 ) — — — — Loans, net of allowance 21,449,273 21,478,228 — — 21,478,228 Mortgage servicing rights 259,254 259,254 — — 259,254 Derivative instruments with positive fair value, net of cash margin 320,929 320,929 44,074 276,855 — Deposits with no stated maturity 23,150,383 23,150,383 — — 23,150,383 Time deposits 2,113,380 2,073,538 — — 2,073,538 Other borrowed funds 7,142,801 6,771,953 — — 6,771,953 Subordinated debentures 275,913 261,977 — 261,977 — Derivative instruments with negative fair value, net of cash margin 362,306 362,306 — 362,306 — December 31, 2017 Carrying Value Estimated Fair Value Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash and due from banks $ 602,510 $ 602,510 $ 602,510 $ — $ — Interest-bearing cash and cash equivalents 1,714,544 1,714,544 1,714,544 — — Trading securities: U.S. government agency debentures 21,196 21,196 — 21,196 — U.S. government agency residential mortgage-backed securities 392,673 392,673 — 392,673 — Municipal and other tax-exempt securities 13,559 13,559 — 13,559 — Asset-backed securities 23,885 23,885 — 23,885 — Other trading securities 11,363 11,363 — 11,363 — Total trading securities 462,676 438,791 — 438,791 — Investment securities: Municipal and other tax-exempt securities 228,186 230,349 — 230,349 — U.S. government agency residential mortgage-backed securities 15,891 16,242 — 16,242 — Other debt securities 217,716 233,444 — 233,444 — Total investment securities 461,793 480,035 — 480,035 — Available for sale securities: U.S. Treasury securities 1,000 1,000 1,000 — — Municipal and other tax-exempt securities 27,080 27,080 — 22,278 4,802 U.S. government agency residential mortgage-backed securities 5,309,152 5,309,152 — 5,309,152 — Privately issued residential mortgage-backed securities 93,221 93,221 — 93,221 — Commercial mortgage-backed securities guaranteed by U.S. government agencies 2,834,961 2,834,961 — 2,834,961 — Other debt securities 25,481 25,481 — 25,009 472 Perpetual preferred stock 15,767 15,767 — 15,767 — Equity securities and mutual funds 14,916 14,916 — 14,916 — Total available for sale securities 8,321,578 8,321,578 1,000 8,315,304 5,274 Fair value option securities – U.S. government agency residential mortgage-backed securities 755,054 755,054 — 755,054 — Residential mortgage loans held for sale 221,378 221,378 — 208,946 12,432 Loans: Commercial 10,733,975 10,524,627 — — 10,524,627 Commercial real estate 3,479,987 3,428,733 — — 3,428,733 Residential mortgage 1,973,686 1,977,721 — — 1,977,721 Personal 965,776 956,706 — — 956,706 Total loans 17,153,424 16,887,787 — — 16,887,787 Allowance for loan losses (230,682 ) — — — — Loans, net of allowance 16,922,742 16,887,787 — — 16,887,787 Mortgage servicing rights 252,867 252,867 — — 252,867 Derivative instruments with positive fair value, net of cash margin 220,502 220,502 8,179 212,323 — Deposits with no stated maturity 19,962,889 19,962,889 — — 19,962,889 Time deposits 2,098,416 2,064,558 — — 2,064,558 Other borrowed funds 5,709,860 5,703,121 — — 5,703,121 Subordinated debentures 144,677 148,207 — 148,207 — Derivative instruments with negative fair value, net of cash margin 171,963 171,963 — 171,963 —

Parent Company Only Financial_2

Parent Company Only Financial Statements Parent Company Only Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Disclosure [Abstract]
Condensed Balance Sheet [Table Text Block]	Balance Sheets (In thousands) December 31, 2018 2017 Assets Cash and cash equivalents $ 167,093 $ 205,876 Available for sale securities — 16,185 Loan to bank subsidiary 65,228 — Investment in bank subsidiaries 4,236,654 3,255,912 Investment in non-bank subsidiaries 218,007 170,966 Other assets 32,999 4,065 Total assets $ 4,719,981 $ 3,653,004 Liabilities and Shareholders’ Equity Liabilities: Other liabilities $ 11,959 $ 12,960 Subordinated debentures 275,913 144,677 Total liabilities 287,872 157,637 Shareholders’ equity: Common stock 5 4 Capital surplus 1,334,030 1,035,895 Retained earnings 3,369,654 3,048,487 Treasury stock (72,585 ) (36,174 ) Accumulated other comprehensive loss (198,995 ) (552,845 ) Total shareholders’ equity 4,432,109 3,495,367 Total liabilities and shareholders’ equity $ 4,719,981 $ 3,653,004
Condensed Income Statement [Table Text Block]	Statements of Earnings (In thousands) Year Ended December 31, 2018 2017 2016 Dividends, interest and fees received from bank subsidiaries $ 426,071 $ 150,149 $ 15,237 Dividends, interest and fees received from non-bank subsidiaries 12,800 17,500 25,923 Other revenue 954 936 1,612 Total revenue 439,825 168,585 42,772 Interest expense 9,827 8,239 4,182 Other operating expense 12,110 2,014 1,978 Total expense 21,937 10,253 6,160 Net income before taxes, other losses, net, and equity in undistributed income of subsidiaries 417,888 158,332 36,612 Other losses, net (3,921 ) — — Net income before taxes and equity in undistributed income of subsidiaries 413,967 158,332 36,612 Federal and state income taxes (7,078 ) (4,305 ) (1,920 ) Net income before equity in undistributed income of subsidiaries 421,045 162,637 38,532 Equity in undistributed income of bank subsidiaries 37,515 181,552 216,120 Equity in undistributed income of non-bank subsidiaries (12,914 ) (9,545 ) (21,984 ) Net income attributable to BOK Financial Corp. shareholders $ 445,646 $ 334,644 $ 232,668
Condensed Cash Flow Statement [Table Text Block]	Statements of Cash Flows (In thousands) Year Ended December 31, 2018 2017 2016 Cash Flows From Operating Activities: Net income $ 445,646 $ 334,644 $ 232,668 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed income of bank subsidiaries (37,515 ) (181,552 ) (216,120 ) Equity in undistributed income of non-bank subsidiaries 12,914 9,545 21,984 Change in other assets (1,072 ) 12 (2,933 ) Change in other liabilities (13,434 ) 7,457 (1,285 ) Net cash provided by operating activities 406,539 170,106 34,314 Cash Flows From Investing Activities: Proceeds from sales of available for sale securities — 3,000 1,632 Investment in subsidiaries (31,901 ) (4,355 ) (26,000 ) Acquisitions, net of cash acquired (232,680 ) — (105,520 ) Net cash used in investing activities (264,581 ) (1,355 ) (129,888 ) Cash Flows From Financing Activities: Net change in other borrowed funds — (7,217 ) — Issuance of subordinated debentures, net of issuance costs — — 144,615 Issuance of common and treasury stock, net (88 ) 4,368 12,455 Dividends paid (127,188 ) (116,041 ) (113,455 ) Repurchase of common stock (53,465 ) (7,403 ) (66,792 ) Net cash used in financing activities (180,741 ) (126,293 ) (23,177 ) Net increase (decrease) in cash and cash equivalents (38,783 ) 42,458 (118,751 ) Cash and cash equivalents at beginning of period 205,876 163,418 282,169 Cash and cash equivalents at end of period $ 167,093 $ 205,876 $ 163,418 Cash paid for interest $ 11,457 $ 6,211 $ 4,127

Significant Accounting Polici_3

Significant Accounting Policies Goodwill and Intangible Assets (Details)	12 Months Ended
	Dec. 31, 2018
Minimum [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Maximum [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	20 years

Significant Accounting Polici_4

Significant Accounting Policies Cash Equivalents (Details)	12 Months Ended
	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Maturity of Federal Funds Sold Considered Cash Equivalents	1 day
Maturity of Resell Agreement Considered Cash Equivalents, Minimum	1 day
Maturity of Resell Agreements Considered Cash Equivalents, Maximum	30 days

Significant Accounting Polici_5

Significant Accounting Policies Loans (Details)	12 Months Ended
	Dec. 31, 2018
Loans [Abstract]
Loans, Number of Days Past Due for a Non-Risk Graded Loan to be Placed on Nonaccruing Status	90 days
Loans, Number of Days After Notification of Chapter 7 Bankruptcy Non-Risk Graded Loan is Placed on Nonaccruing Status	60 days
Loans, Minimum Number of Days After Which Past Due Non-Risk Graded Loans Are Charged Off	60 days
Loans, Maximum Number of Days After Which Past Due Non-Risk Graded Loans Are Charged Off	180 days
Loans, Number of Days After Notification of Chapter 7 Bankruptcy Non-Risk Graded Loan is Charged Off	60 days

Significant Accounting Polici_6

Significant Accounting Policies Premises and Equipment (Details)	12 Months Ended
	Dec. 31, 2018
Buildings and improvements | Minimum [Member]
Premises and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Buildings and improvements | Maximum [Member]
Premises and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	40 years
Software and Software Development Costs [Member] | Minimum [Member]
Premises and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Software and Software Development Costs [Member] | Maximum [Member]
Premises and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Furniture and equipment | Minimum [Member]
Premises and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Furniture and equipment | Maximum [Member]
Premises and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years

Significant Accounting Polici_7

Significant Accounting Policies Share-Based Compensation (Details)	12 Months Ended
	Dec. 31, 2018
Stock Options [Member]
Share-based Compensation Arrangements by Share-based Payment Award [Line Items]
Vesting period (in years)	7 years
Non-vested Common Stock [Member]
Share-based Compensation Arrangements by Share-based Payment Award [Line Items]
Vesting period (in years)	3 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Required Holding Period	2 years

Significant Accounting Polici_8

Significant Accounting Policies Newly Adopted and Pending Accounting Pronouncements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 2,700	$ (2,709)
Increase of reported right of use assets and liabilities	$ 137,000

Trading Securities (Details)

Trading Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Trading Securities [Line Items]
Trading securities	$ 1,956,923	$ 462,676
Trading Securities, Net Unrealized Gain (Loss)	10,969	(448)
U.S. government agency debentures [Member]
Schedule of Trading Securities [Line Items]
Trading securities	63,765	21,196
Trading Securities, Net Unrealized Gain (Loss)	254	8
U.S. government agency residential mortgage-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	1,791,584	392,673
Trading Securities, Net Unrealized Gain (Loss)	9,966	(517)
Municipal and other tax-exempt securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	34,507	13,559
Trading Securities, Net Unrealized Gain (Loss)	(1)	83
Asset-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	42,656	23,885
Trading Securities, Net Unrealized Gain (Loss)	685	(26)
Other trading securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	24,411	11,363
Trading Securities, Net Unrealized Gain (Loss)	$ 65	$ 4

Investment (Held-to-Maturity) S

Investment (Held-to-Maturity) Securities (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment securities		$ 355,187	$ 461,793
Investment Securities, Fair Value		367,298	480,035
Investment Securities, Gross Unrealized Gain		14,408	20,508
Investment Securities, Gross Unrealized Loss		(2,297)	(2,266)
Investment Securities, Debt Maturities, Net, Amortized Cost [Abstract]
Investment Securities, Debt Maturities, Amortized Cost		355,187	461,793
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Fair Value		$ 367,298	$ 480,035
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Nominal Yield		4.65%
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		146	150
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 31,627	$ 166,051
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		94,802	12,265
Investment Securities, Continuous Unrealized Loss Position, Fair Value		126,429	178,316
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Losses		133	1,881
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Losses		2,164	385
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		2,297	2,266
Fixed maturity securities [Member]
Investment Securities, Debt Maturities, Net, Amortized Cost [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		57,757
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		108,193
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		150,683
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		25,942
Investment Securities, Debt Maturities, Single Maturity Date, Carrying Value		342,575
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Fair Value		57,698
Investment Securities, Debt Maturities, One to Five Years, Fair Value		110,046
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		161,521
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		25,263
Investment Securities, Debt Maturities, Single Maturity Date, Fair value		$ 354,528
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield		2.71%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield		4.37%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield		5.82%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield		4.32%
Investment Securities, Debt Maturities, Nominal Yield		4.73%
Investment Securities, Debt Maturities, Weighted Average Maturity	[1]	5.19
Municipal and other tax-exempt securities [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment securities		$ 137,296	228,186
Investment Securities, Fair Value		138,562	230,349
Investment Securities, Gross Unrealized Gain		1,858	2,967
Investment Securities, Gross Unrealized Loss		(592)	(804)
Investment Securities, Debt Maturities, Net, Amortized Cost [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		41,475
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		46,363
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		35,077
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		14,381
Investment Securities, Debt Maturities, Single Maturity Date, Carrying Value		137,296
Investment Securities, Debt Maturities, Amortized Cost		137,296	228,186
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Fair Value		41,371
Investment Securities, Debt Maturities, One to Five Years, Fair Value		46,123
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		36,471
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		14,597
Investment Securities, Debt Maturities, Single Maturity Date, Fair value		138,562
Investment Securities, Fair Value		$ 138,562	$ 230,349
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield	[2]	2.25%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield	[2]	3.94%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield	[2]	6.00%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield	[2]	4.32%
Investment Securities, Debt Maturities, Nominal Yield	[2]	4.00%
Investment Securities, Debt Maturities, Weighted Average Maturity	[1]	4.73
Investment Securities, Debt Maturities, Effective tax rate for nominal yield calculation		25.00%
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		72	100
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 18,255	$ 145,960
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		66,141	5,833
Investment Securities, Continuous Unrealized Loss Position, Fair Value		84,396	151,793
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Losses		69	643
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Losses		523	161
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		592	804
Other debt securities [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment securities		205,279	217,716
Investment Securities, Fair Value		215,966	233,444
Investment Securities, Gross Unrealized Gain		12,257	17,095
Investment Securities, Gross Unrealized Loss		(1,570)	(1,367)
Investment Securities, Debt Maturities, Net, Amortized Cost [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		16,282
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		61,830
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		115,606
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		11,561
Investment Securities, Debt Maturities, Single Maturity Date, Carrying Value		205,279
Investment Securities, Debt Maturities, Amortized Cost		205,279	217,716
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Fair Value		16,327
Investment Securities, Debt Maturities, One to Five Years, Fair Value		63,923
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		125,050
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		10,666
Investment Securities, Debt Maturities, Single Maturity Date, Fair value		215,966
Investment Securities, Fair Value		$ 215,966	$ 233,444
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield		3.88%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield		4.69%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield		5.76%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield		4.33%
Investment Securities, Debt Maturities, Nominal Yield		5.21%
Investment Securities, Debt Maturities, Weighted Average Maturity	[1]	5.50
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		72	49
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 13,372	$ 20,091
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		23,028	3,076
Investment Securities, Continuous Unrealized Loss Position, Fair Value		36,400	23,167
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Losses		64	1,238
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Losses		1,506	129
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		1,570	1,367
U.S. government agency residential mortgage-backed securities [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment securities		12,612	15,891
Investment Securities, Fair Value		12,770	16,242
Investment Securities, Gross Unrealized Gain		293	446
Investment Securities, Gross Unrealized Loss		(135)	(95)
Investment Securities, Debt Maturities, Net, Amortized Cost [Abstract]
Investment Securities, Debt Maturities, without Single Maturity Date, Net Carrying value		12,612
Investment Securities, Debt Maturities, Amortized Cost		12,612	15,891
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, without Single Maturity Date, Fair value		12,770
Investment Securities, Fair Value		$ 12,770	$ 16,242
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Nominal Yield		2.77%
Investment Securities, Debt Maturities, Average Expected Life of Mortgage-backed Securities		4 years 8 months 12 days
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		2	1
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 0	$ 0
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		5,633	3,356
Investment Securities, Continuous Unrealized Loss Position, Fair Value		5,633	3,356
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Losses		0	0
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Losses		135	95
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 135	$ 95
[1]	Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without penalty.
[2]	Calculated on a taxable equivalent basis using a 25 percent

Available for Sale Securities (

Available for Sale Securities (Details)		3 Months Ended		12 Months Ended
		Dec. 31, 2018USD ($)		Dec. 31, 2018USD ($)		Dec. 31, 2017USD ($)		Dec. 31, 2016USD ($)
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost		$ 8,952,391,000		$ 8,952,391,000		$ 8,369,075,000
Available for sale securities, Fair Value		8,857,120,000		8,857,120,000		8,321,578,000
Available for sale securities, Gross Unrealized Gain		42,986,000		42,986,000		41,519,000
Available for sale securities, Gross Unrealized Loss		138,257,000		138,257,000		88,625,000
Available for sale securities, OTTI		0		0		(391,000)
Available for sale securities, Pledged as Collateral, Fair Value		$ 9,100,000,000		$ 9,100,000,000		7,300,000,000
Available for Sale Securities, Debt Maturities, Nominal Yield [Abstract]
Available for Sale Securities, Debt Maturities, Nominal Yield		2.37%		2.37%
Available for Sale Securities, Realized Gain (Loss) [Abstract]
Proceeds from sales of available for sale securities				$ 745,643,000		1,309,215,000		$ 899,381,000
Available for Sale Securities, Gross realized gains				7,117,000		10,223,000		11,696,000
Available for Sale Securities, Gross realized losses				(9,918,000)		(5,795,000)		(21,000)
Available for Sale Securities, Related federal and state income tax expense				$ (713,000)		$ 1,722,000		$ 4,542,000
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions		490		490		534
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months		$ 700,064,000		$ 700,064,000		$ 3,773,942,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer		5,631,803,000		5,631,803,000		2,118,360,000
Available for Sale Securities, Unrealized Loss Position		6,331,867,000		6,331,867,000		5,892,302,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		1,615,000		1,615,000		30,648,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		136,642,000		136,642,000		58,368,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss		138,257,000		138,257,000		89,016,000
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net [Abstract]
Other-than-temporary Impairment Loss, Available for Sale Securities, Recognized in Earnings				0		0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Cumulative Credit Losses on Debt Securities Held		45,000,000		45,000,000		55,000,000
Fixed maturity securities [Member]
Available for Sale Securities, Debt Maturities, Amortized Cost, Rolling Maturity [Abstract]
Available for Sale Securities, Debt Maturities, Less than One Year, Amortized Cost		78,615,000		78,615,000
Available for Sale Securities, Debt Maturities, One to Five Years, Amortized Cost		1,109,788,000		1,109,788,000
Available for Sale Securities, Debt Maturities, Six to Ten Years, Amortized Cost		1,497,468,000		1,497,468,000
Available for Sale Securities, Debt Maturities, Over Ten Years, Amortized Cost		339,249,000		339,249,000
Available for Sale Securities, Maturity, Allocated and Single Maturity Date, Amortized Cost		3,025,120,000		3,025,120,000
Available for Sale Securities, Maturity, Fair Value, Rolling Maturity [Abstract]
Available for Sale Securities, Debt Maturities, Less Than One Year, Fair Value		77,965,000		77,965,000
Available for Sale Securities, Debt Maturities, One to Five Years, Fair Value		1,091,285,000		1,091,285,000
Available for Sale Securities, Debt Maturities, Six to Ten Years, Fair Value		1,486,939,000		1,486,939,000
Available for Sale Securities, Debt Maturities, Over Ten Years, Fair Value		336,487,000		336,487,000
Available for Sale Securities, Debt Maturities, Single Maturity Date, Fair value		$ 2,992,676,000		$ 2,992,676,000
Available for Sale Securities, Debt Maturities, Nominal Yield [Abstract]
Available for Sale Securities, Debt Maturities, Less than one year, Nominal Yield		1.73%		1.73%
Available for Sale Securities, Debt Maturities, One to five years, Nominal Yield		2.07%		2.07%
Available for Sale Securities, Debt Maturities, Six to ten years, Nominal Yield		2.44%		2.44%
Available for Sale Securities, Debt Maturities, Over ten years, Nominal Yield		2.48%		2.48%
Available for Sale Securities, Debt Maturities, Nominal Yield		2.29%		2.29%
Available for Sale Securities, Debt Maturities, Weighted Average Maturity	[1]	6.98		6.98
U.S. Treasury [Member]
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost		$ 496,000		$ 496,000		1,000,000
Available for sale securities, Fair Value		493,000		493,000		1,000,000
Available for sale securities, Gross Unrealized Gain		0		0		0
Available for sale securities, Gross Unrealized Loss		3,000		3,000		0
Available for sale securities, OTTI		0		0		$ 0
Available for Sale Securities, Debt Maturities, Amortized Cost, Rolling Maturity [Abstract]
Available for Sale Securities, Debt Maturities, Less than One Year, Amortized Cost		0		0
Available for Sale Securities, Debt Maturities, One to Five Years, Amortized Cost		496,000		496,000
Available for Sale Securities, Debt Maturities, Six to Ten Years, Amortized Cost		0		0
Available for Sale Securities, Debt Maturities, Over Ten Years, Amortized Cost		0		0
Available for Sale Securities, Maturity, Allocated and Single Maturity Date, Amortized Cost		496,000		496,000
Available for Sale Securities, Maturity, Fair Value, Rolling Maturity [Abstract]
Available for Sale Securities, Debt Maturities, Less Than One Year, Fair Value		0		0
Available for Sale Securities, Debt Maturities, One to Five Years, Fair Value		493,000		493,000
Available for Sale Securities, Debt Maturities, Six to Ten Years, Fair Value		0		0
Available for Sale Securities, Debt Maturities, Over Ten Years, Fair Value		0		0
Available for Sale Securities, Debt Maturities, Single Maturity Date, Fair value		$ 493,000		$ 493,000
Available for Sale Securities, Debt Maturities, Nominal Yield [Abstract]
Available for Sale Securities, Debt Maturities, Less than one year, Nominal Yield		0.00%		0.00%
Available for Sale Securities, Debt Maturities, One to five years, Nominal Yield		1.99%		1.99%
Available for Sale Securities, Debt Maturities, Six to ten years, Nominal Yield		0.00%		0.00%
Available for Sale Securities, Debt Maturities, Over ten years, Nominal Yield		0.00%		0.00%
Available for Sale Securities, Debt Maturities, Nominal Yield		1.99%		1.99%
Available for Sale Securities, Debt Maturities, Weighted Average Maturity	[1]	1.08		1.08
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions		1		1		0
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months		$ 0		$ 0		$ 0
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer		493,000		493,000		0
Available for Sale Securities, Unrealized Loss Position		493,000		493,000		0
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0		0		0
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		3,000		3,000		0
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss		3,000		3,000		0
Municipal and other tax-exempt securities [Member]
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost		2,782,000		2,782,000		27,182,000
Available for sale securities, Fair Value		2,864,000		2,864,000		27,080,000
Available for sale securities, Gross Unrealized Gain		82,000		82,000		181,000
Available for sale securities, Gross Unrealized Loss		0		0		283,000
Available for sale securities, OTTI		0		0		$ 0
Available for Sale Securities, Debt Maturities, Amortized Cost, Rolling Maturity [Abstract]
Available for Sale Securities, Debt Maturities, Less than One Year, Amortized Cost		1,057,000		1,057,000
Available for Sale Securities, Debt Maturities, One to Five Years, Amortized Cost		1,725,000		1,725,000
Available for Sale Securities, Debt Maturities, Six to Ten Years, Amortized Cost		0		0
Available for Sale Securities, Debt Maturities, Over Ten Years, Amortized Cost		0		0
Available for Sale Securities, Maturity, Allocated and Single Maturity Date, Amortized Cost		2,782,000		2,782,000
Available for Sale Securities, Maturity, Fair Value, Rolling Maturity [Abstract]
Available for Sale Securities, Debt Maturities, Less Than One Year, Fair Value		1,063,000		1,063,000
Available for Sale Securities, Debt Maturities, One to Five Years, Fair Value		1,801,000		1,801,000
Available for Sale Securities, Debt Maturities, Six to Ten Years, Fair Value		0		0
Available for Sale Securities, Debt Maturities, Over Ten Years, Fair Value		0		0
Available for Sale Securities, Debt Maturities, Single Maturity Date, Fair value		$ 2,864,000		$ 2,864,000
Available for Sale Securities, Debt Maturities, Nominal Yield [Abstract]
Available for Sale Securities, Debt Maturities, Less than one year, Nominal Yield	[2]	6.69%		6.69%
Available for Sale Securities, Debt Maturities, One to five years, Nominal Yield	[2]	6.45%		6.45%
Available for Sale Securities, Debt Maturities, Six to ten years, Nominal Yield	[2]	0.00%		0.00%
Available for Sale Securities, Debt Maturities, Over ten years, Nominal Yield	[2]	0.00%		0.00%
Available for Sale Securities, Debt Maturities, Nominal Yield	[2]	6.54%		6.54%
Available for Sale Securities, Debt Maturities, Weighted Average Maturity	[1]	1.67		1.67
Available for Sale Securities, Debt Maturities, Effective tax rate for nominal yield calculation		25.00%		25.00%
Available for Sale Securities, Debt Maturities, Number of days for interest rates to reset		35 days
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions		0		0		19
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months		$ 0		$ 0		$ 12,765,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer		0		0		4,802,000
Available for Sale Securities, Unrealized Loss Position		0		0		17,567,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0		0		18,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0		0		265,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss		0		0		283,000
Residential Mortgage Backed Securities [Member]
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost		5,927,271,000		5,927,271,000		5,429,459,000
Available for sale securities, Fair Value		5,864,444,000		5,864,444,000		5,402,373,000
Available for sale securities, Gross Unrealized Gain		34,937,000		34,937,000		35,605,000
Available for sale securities, Gross Unrealized Loss		97,764,000		97,764,000		62,300,000
Available for sale securities, OTTI		0		0		$ (391,000)
Available for Sale Securities, Debt Maturities, Amortized Cost, Rolling Maturity [Abstract]
Available for Sale Securities, Maturity, without Single Maturity Date, Amortized Cost		5,927,271,000		5,927,271,000
Available for Sale Securities, Maturity, Fair Value, Rolling Maturity [Abstract]
Available for Sale Securities, Debt Maturities, without Single Maturity Date, Fair value		$ 5,864,444,000		$ 5,864,444,000
Available for Sale Securities, Debt Maturities, Nominal Yield [Abstract]
Available for Sale Securities, Debt Maturities, Nominal Yield	[3]	2.41%		2.41%
Available for Sale Securities, Debt Maturities, Average Expected Life of Mortgage-backed Securities				4 years 1 month 6 days
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions		289		289		217
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months		$ 510,824,000		$ 510,824,000		$ 2,274,604,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer		3,641,370,000		3,641,370,000		1,458,587,000
Available for Sale Securities, Unrealized Loss Position		4,152,194,000		4,152,194,000		3,733,191,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		1,158,000		1,158,000		18,758,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		96,606,000		96,606,000		43,933,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss		97,764,000		97,764,000		62,691,000
U.S. government agency residential mortgage-backed securities [Member]
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost		5,886,323,000		5,886,323,000		5,355,148,000
Available for sale securities, Fair Value		5,804,708,000		5,804,708,000		5,309,152,000
Available for sale securities, Gross Unrealized Gain		16,149,000		16,149,000		16,304,000
Available for sale securities, Gross Unrealized Loss		97,764,000		97,764,000		62,300,000
Available for sale securities, OTTI		$ 0		$ 0		$ 0
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions		289		289		209
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months		$ 510,824,000		$ 510,824,000		$ 2,268,706,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer		3,641,370,000		3,641,370,000		1,458,587,000
Available for Sale Securities, Unrealized Loss Position		4,152,194,000		4,152,194,000		3,727,293,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		1,158,000		1,158,000		18,367,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		96,606,000		96,606,000		43,933,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss		97,764,000		97,764,000		62,300,000
U.S. government agency residential mortgage-backed securities [Member] | FNMA [Member]
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost		3,414,573,000		3,414,573,000		3,021,551,000
Available for sale securities, Fair Value		3,367,124,000		3,367,124,000		2,997,563,000
Available for sale securities, Gross Unrealized Gain		10,559,000		10,559,000		11,549,000
Available for sale securities, Gross Unrealized Loss		58,008,000		58,008,000		35,537,000
Available for sale securities, OTTI		$ 0		$ 0		$ 0
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions		162		162		113
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months		$ 161,089,000		$ 161,089,000		$ 1,203,041,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer		2,135,377,000		2,135,377,000		824,029,000
Available for Sale Securities, Unrealized Loss Position		2,296,466,000		2,296,466,000		2,027,070,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		542,000		542,000		9,618,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		57,466,000		57,466,000		25,919,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss		58,008,000		58,008,000		35,537,000
U.S. government agency residential mortgage-backed securities [Member] | FHLMC [Member]
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost		1,723,399,000		1,723,399,000		1,545,971,000
Available for sale securities, Fair Value		1,699,779,000		1,699,779,000		1,531,009,000
Available for sale securities, Gross Unrealized Gain		5,189,000		5,189,000		3,148,000
Available for sale securities, Gross Unrealized Loss		28,809,000		28,809,000		18,110,000
Available for sale securities, OTTI		$ 0		$ 0		$ 0
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions		85		85		69
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months		$ 71,205,000		$ 71,205,000		$ 863,778,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer		1,129,730,000		1,129,730,000		385,816,000
Available for Sale Securities, Unrealized Loss Position		1,200,935,000		1,200,935,000		1,249,594,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		328,000		328,000		7,297,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		28,481,000		28,481,000		10,813,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss		28,809,000		28,809,000		18,110,000
U.S. government agency residential mortgage-backed securities [Member] | GNMA [Member]
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost		748,351,000		748,351,000		787,626,000
Available for sale securities, Fair Value		737,805,000		737,805,000		780,580,000
Available for sale securities, Gross Unrealized Gain		401,000		401,000		1,607,000
Available for sale securities, Gross Unrealized Loss		10,947,000		10,947,000		8,653,000
Available for sale securities, OTTI		$ 0		$ 0		$ 0
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions		42		42		27
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months		$ 278,530,000		$ 278,530,000		$ 201,887,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer		376,263,000		376,263,000		248,742,000
Available for Sale Securities, Unrealized Loss Position		654,793,000		654,793,000		450,629,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		288,000		288,000		1,452,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		10,659,000		10,659,000		7,201,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss		10,947,000		10,947,000		8,653,000
Privately issued residential mortgage-backed securities [Member]
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost		40,948,000		40,948,000		74,311,000
Available for sale securities, Fair Value		59,736,000		59,736,000		93,221,000
Available for sale securities, Gross Unrealized Gain		18,788,000		18,788,000		19,301,000
Available for sale securities, Gross Unrealized Loss		0		0		0
Available for sale securities, OTTI		$ 0		$ 0		$ (391,000)
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions		0	[4]	0	[4]	8	[5]
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months		$ 0	[4]	$ 0	[4]	$ 5,898,000	[5]
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer		0	[4]	0	[4]	0	[5]
Available for Sale Securities, Unrealized Loss Position		0	[4]	0	[4]	5,898,000	[5]
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0	[4]	0	[4]	391,000	[5]
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0	[4]	0	[4]	0	[5]
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss		0	[4]	0	[4]	391,000	[5]
Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost		2,986,297,000		2,986,297,000		2,858,885,000
Available for sale securities, Fair Value		2,953,889,000		2,953,889,000		2,834,961,000
Available for sale securities, Gross Unrealized Gain		7,955,000		7,955,000		1,963,000
Available for sale securities, Gross Unrealized Loss		40,363,000		40,363,000		25,887,000
Available for sale securities, OTTI		0		0		$ 0
Available for Sale Securities, Debt Maturities, Amortized Cost, Rolling Maturity [Abstract]
Available for Sale Securities, Debt Maturities, Less than One Year, Amortized Cost		77,558,000		77,558,000
Available for Sale Securities, Debt Maturities, One to Five Years, Amortized Cost		1,107,567,000		1,107,567,000
Available for Sale Securities, Debt Maturities, Six to Ten Years, Amortized Cost		1,497,468,000		1,497,468,000
Available for Sale Securities, Debt Maturities, Over Ten Years, Amortized Cost		303,704,000		303,704,000
Available for Sale Securities, Maturity, Allocated and Single Maturity Date, Amortized Cost		2,986,297,000		2,986,297,000
Available for Sale Securities, Maturity, Fair Value, Rolling Maturity [Abstract]
Available for Sale Securities, Debt Maturities, Less Than One Year, Fair Value		76,902,000		76,902,000
Available for Sale Securities, Debt Maturities, One to Five Years, Fair Value		1,088,991,000		1,088,991,000
Available for Sale Securities, Debt Maturities, Six to Ten Years, Fair Value		1,486,939,000		1,486,939,000
Available for Sale Securities, Debt Maturities, Over Ten Years, Fair Value		301,057,000		301,057,000
Available for Sale Securities, Debt Maturities, Single Maturity Date, Fair value		$ 2,953,889,000		$ 2,953,889,000
Available for Sale Securities, Debt Maturities, Nominal Yield [Abstract]
Available for Sale Securities, Debt Maturities, Less than one year, Nominal Yield		1.66%		1.66%
Available for Sale Securities, Debt Maturities, One to five years, Nominal Yield		2.06%		2.06%
Available for Sale Securities, Debt Maturities, Six to ten years, Nominal Yield		2.44%		2.44%
Available for Sale Securities, Debt Maturities, Over ten years, Nominal Yield		2.54%		2.54%
Available for Sale Securities, Debt Maturities, Nominal Yield		2.29%		2.29%
Available for Sale Securities, Debt Maturities, Weighted Average Maturity	[1]	6.90		6.90
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions		197		197		185
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months		$ 179,258,000		$ 179,258,000		$ 1,465,703,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer		1,969,504,000		1,969,504,000		652,296,000
Available for Sale Securities, Unrealized Loss Position		2,148,762,000		2,148,762,000		2,117,999,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		394,000		394,000		11,824,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		39,969,000		39,969,000		14,063,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss		40,363,000		40,363,000		25,887,000
Perpetual preferred stock [Member]
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost						12,562,000
Available for sale securities, Fair Value						15,767,000
Available for sale securities, Gross Unrealized Gain						3,205,000
Available for sale securities, Gross Unrealized Loss						0
Available for sale securities, OTTI						$ 0
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions						0
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months						$ 0
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer						0
Available for Sale Securities, Unrealized Loss Position						0
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss						0
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss						0
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss						0
Equity securities and mutual funds [Member]
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost						14,487,000
Available for sale securities, Fair Value						14,916,000
Available for sale securities, Gross Unrealized Gain						515,000
Available for sale securities, Gross Unrealized Loss						86,000
Available for sale securities, OTTI						$ 0
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions						111
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months						$ 911,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer						2,203,000
Available for Sale Securities, Unrealized Loss Position						3,114,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss						7,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss						79,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss						86,000
Other debt securities [Member]
Available for Sale Securities [Line Items]
Available for sale securities, Amortized Cost		35,545,000		35,545,000		25,500,000
Available for sale securities, Fair Value		35,430,000		35,430,000		25,481,000
Available for sale securities, Gross Unrealized Gain		12,000		12,000		50,000
Available for sale securities, Gross Unrealized Loss		127,000		127,000		69,000
Available for sale securities, OTTI		0		0		$ 0
Available for Sale Securities, Debt Maturities, Amortized Cost, Rolling Maturity [Abstract]
Available for Sale Securities, Debt Maturities, Less than One Year, Amortized Cost		0		0
Available for Sale Securities, Debt Maturities, One to Five Years, Amortized Cost		0		0
Available for Sale Securities, Debt Maturities, Six to Ten Years, Amortized Cost		0		0
Available for Sale Securities, Debt Maturities, Over Ten Years, Amortized Cost		35,545,000		35,545,000
Available for Sale Securities, Maturity, Allocated and Single Maturity Date, Amortized Cost		35,545,000		35,545,000
Available for Sale Securities, Maturity, Fair Value, Rolling Maturity [Abstract]
Available for Sale Securities, Debt Maturities, Less Than One Year, Fair Value		0		0
Available for Sale Securities, Debt Maturities, One to Five Years, Fair Value		0		0
Available for Sale Securities, Debt Maturities, Six to Ten Years, Fair Value		0		0
Available for Sale Securities, Debt Maturities, Over Ten Years, Fair Value		35,430,000		35,430,000
Available for Sale Securities, Debt Maturities, Single Maturity Date, Fair value		$ 35,430,000		$ 35,430,000
Available for Sale Securities, Debt Maturities, Nominal Yield [Abstract]
Available for Sale Securities, Debt Maturities, Less than one year, Nominal Yield		0.00%		0.00%
Available for Sale Securities, Debt Maturities, One to five years, Nominal Yield		0.00%		0.00%
Available for Sale Securities, Debt Maturities, Six to ten years, Nominal Yield		0.00%		0.00%
Available for Sale Securities, Debt Maturities, Over ten years, Nominal Yield	[6]	1.94%		1.94%
Available for Sale Securities, Debt Maturities, Nominal Yield		1.94%		1.94%
Available for Sale Securities, Debt Maturities, Weighted Average Maturity	[1]	13.61		13.61
Available for Sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available for Sale Securities, Unrealized Loss Position, Number of Positions		3		3		2
Available for Sale Securities, Unrealized Loss Position [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months		$ 9,982,000		$ 9,982,000		$ 19,959,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer		20,436,000		20,436,000		472,000
Available for Sale Securities, Unrealized Loss Position		30,418,000		30,418,000		20,431,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for Sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		63,000		63,000		41,000
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		64,000		64,000		28,000
Available for Sale Securities, Unrealized Loss Position, Accumulated Loss		$ 127,000		$ 127,000		$ 69,000
[1]	Expected maturities may differ from contractual maturities, because borrowers may have the right to call or prepay obligations with or without penalty.
[2]	Calculated on a taxable equivalent basis using a 25 percent
[3]	The nominal yield on mortgage-backed securities is based upon prepayment assumptions at the purchase date. Actual yields earned may differ significantly based upon actual prepayments. See Quarterly Financial Summary –– Unaudited following for current yields on available for sale securities portfolio.
[4]	Includes securities for which an unrealized loss remains in AOCI after an other-than-temporary credit loss has been recognized in income.
[5]	Includes securities for which an unrealized loss remains in AOCI after an other-than-temporary credit loss has been recognized in income.
[6]	Nominal yield on other debt securities with contractual maturity dates over ten years are based on variable rates which generally are reset within 35 days

Securities Fair Value Option Se

Securities Fair Value Option Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Fair Value Option Securities [Line Items]
Fair Value Option Securities, Fair Value	$ 283,235	$ 755,054
U.S. government agency residential mortgage-backed securities [Member]
Schedule of Fair Value Option Securities [Line Items]
Fair Value Option Securities, Fair Value	283,235	755,054
Fair Value Option Securities, Net Unrealized Gain (Loss)	$ 2,766	$ (1,877)

Derivatives, Fair Value of Deri

Derivatives, Fair Value of Derivatives Contracts (Details) - USD ($) $ in Thousands	Dec. 31, 2018		Dec. 31, 2017
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Fair Value, Net of Cash Collateral	$ 320,929		$ 220,502
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Fair Value, Net of Cash Collateral	362,306		171,963
Not Designated as Hedging Instrument [Member]
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	30,272,764	[1]	20,038,522	[2]
Derivative Liabilities, Notional	33,838,893	[1]	20,186,467	[2]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	571,793		301,052
Derivative Assets, Netting Adjustments	(135,530)		(74,022)
Derivative Assets, Net Fair Value Before Cash Collateral	436,263		227,030
Derivative Assets, Cash Collateral	(115,334)		(6,528)
Derivative Assets, Fair Value, Net of Cash Collateral	320,929		220,502
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	574,347		302,405
Derivative Liabilities, Netting Adjustments	(135,530)		(74,022)
Derivative Liabilities, Net Fair Value Before Cash Collateral	438,817		228,383
Derivative Liabilities, Cash Collateral	(76,511)		(56,420)
Derivative Liabilities, Fair Value, Net of Cash Collateral	362,306		171,963
Not Designated as Hedging Instrument [Member] | Total customer risk management programs [Member]
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	14,362,776	[1]	15,301,821	[2]
Derivative Liabilities, Notional	14,204,251	[1]	14,458,046	[2]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	521,383		291,558
Derivative Assets, Netting Adjustments	(94,659)		(66,929)
Derivative Assets, Net Fair Value Before Cash Collateral	426,724		224,629
Derivative Assets, Cash Collateral	(115,334)		(6,528)
Derivative Assets, Fair Value, Net of Cash Collateral	311,390		218,101
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	507,925		280,643
Derivative Liabilities, Netting Adjustments	(94,659)		(66,929)
Derivative Liabilities, Net Fair Value Before Cash Collateral	413,266		213,714
Derivative Liabilities, Cash Collateral	(69,196)		(56,420)
Derivative Liabilities, Fair Value, Net of Cash Collateral	344,070		157,294
Not Designated as Hedging Instrument [Member] | To-be-announced residential mortgage-backed securities [Member]
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	10,671,151	[1]	12,347,542	[2]
Derivative Liabilities, Notional	10,558,151	[1]	11,537,742	[2]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	92,231		23,606
Derivative Assets, Netting Adjustments	(26,787)		(18,096)
Derivative Assets, Net Fair Value Before Cash Collateral	65,444		5,510
Derivative Assets, Cash Collateral	0		0
Derivative Assets, Fair Value, Net of Cash Collateral	65,444		5,510
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	90,388		20,367
Derivative Liabilities, Netting Adjustments	(26,787)		(18,096)
Derivative Liabilities, Net Fair Value Before Cash Collateral	63,601		2,271
Derivative Liabilities, Cash Collateral	(63,596)		(704)
Derivative Liabilities, Fair Value, Net of Cash Collateral	5		1,567
Not Designated as Hedging Instrument [Member] | Interest rate swaps [Member]
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	1,924,131	[1]	1,478,944	[2]
Derivative Liabilities, Notional	1,924,131	[1]	1,478,944	[2]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	36,112		28,278
Derivative Assets, Netting Adjustments	(6,688)		0
Derivative Assets, Net Fair Value Before Cash Collateral	29,424		28,278
Derivative Assets, Cash Collateral	(7,934)		(4,964)
Derivative Assets, Fair Value, Net of Cash Collateral	21,490		23,314
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	36,288		28,298
Derivative Liabilities, Netting Adjustments	(6,688)		0
Derivative Liabilities, Net Fair Value Before Cash Collateral	29,600		28,298
Derivative Liabilities, Cash Collateral	(4,110)		(12,896)
Derivative Liabilities, Fair Value, Net of Cash Collateral	25,490		15,402
Not Designated as Hedging Instrument [Member] | Energy contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	1,472,209	[1]	1,190,067	[2]
Derivative Liabilities, Notional	1,434,247	[1]	1,166,924	[2]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	206,418		103,044
Derivative Assets, Netting Adjustments	(60,983)		(47,873)
Derivative Assets, Net Fair Value Before Cash Collateral	145,435		55,171
Derivative Assets, Cash Collateral	(106,752)		(196)
Derivative Assets, Fair Value, Net of Cash Collateral	38,683		54,975
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	202,494		101,603
Derivative Liabilities, Netting Adjustments	(60,983)		(47,873)
Derivative Liabilities, Net Fair Value Before Cash Collateral	141,511		53,730
Derivative Liabilities, Cash Collateral	(1,490)		(42,767)
Derivative Liabilities, Fair Value, Net of Cash Collateral	140,021		10,963
Not Designated as Hedging Instrument [Member] | Agricultural contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	21,210	[1]	53,238	[2]
Derivative Liabilities, Notional	21,214	[1]	48,552	[2]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	842		1,576
Derivative Assets, Netting Adjustments	(201)		(960)
Derivative Assets, Net Fair Value Before Cash Collateral	641		616
Derivative Assets, Cash Collateral	0		0
Derivative Assets, Fair Value, Net of Cash Collateral	641		616
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	812		1,551
Derivative Liabilities, Netting Adjustments	(201)		(960)
Derivative Liabilities, Net Fair Value Before Cash Collateral	611		591
Derivative Liabilities, Cash Collateral	0		0
Derivative Liabilities, Fair Value, Net of Cash Collateral	611		591
Not Designated as Hedging Instrument [Member] | Foreign exchange contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	184,990	[1]	132,397	[2]
Derivative Liabilities, Notional	177,423	[1]	126,251	[2]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	183,759		129,551
Derivative Assets, Netting Adjustments	0		0
Derivative Assets, Net Fair Value Before Cash Collateral	183,759		129,551
Derivative Assets, Cash Collateral	0		(448)
Derivative Assets, Fair Value, Net of Cash Collateral	183,759		129,103
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	175,922		123,321
Derivative Liabilities, Netting Adjustments	0		0
Derivative Liabilities, Net Fair Value Before Cash Collateral	175,922		123,321
Derivative Liabilities, Cash Collateral	0		(53)
Derivative Liabilities, Fair Value, Net of Cash Collateral	175,922		123,268
Not Designated as Hedging Instrument [Member] | Equity option contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	89,085	[1]	99,633	[2]
Derivative Liabilities, Notional	89,085	[1]	99,633	[2]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	2,021		5,503
Derivative Assets, Netting Adjustments	0		0
Derivative Assets, Net Fair Value Before Cash Collateral	2,021		5,503
Derivative Assets, Cash Collateral	(648)		(920)
Derivative Assets, Fair Value, Net of Cash Collateral	1,373		4,583
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	2,021		5,503
Derivative Liabilities, Netting Adjustments	0		0
Derivative Liabilities, Net Fair Value Before Cash Collateral	2,021		5,503
Derivative Liabilities, Cash Collateral	0		0
Derivative Liabilities, Fair Value, Net of Cash Collateral	2,021		5,503
Not Designated as Hedging Instrument [Member] | Internal risk management programs [Member]
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	15,909,988	[1]	4,736,701	[2]
Derivative Liabilities, Notional	19,634,642	[1]	5,728,421	[2]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	50,410		9,494
Derivative Assets, Netting Adjustments	(40,871)		(7,093)
Derivative Assets, Net Fair Value Before Cash Collateral	9,539		2,401
Derivative Assets, Cash Collateral	0		0
Derivative Assets, Fair Value, Net of Cash Collateral	9,539		2,401
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	66,422		21,762
Derivative Liabilities, Netting Adjustments	(40,871)		(7,093)
Derivative Liabilities, Net Fair Value Before Cash Collateral	25,551		14,669
Derivative Liabilities, Cash Collateral	(7,315)		0
Derivative Liabilities, Fair Value, Net of Cash Collateral	$ 18,236		$ 14,669
[1]	Notional amounts for commodity contracts are converted into dollar-equivalent amounts based on dollar prices at the inception of the contract.
[2]	Notional amounts for commodity contracts are converted into dollar-equivalent amounts based on dollar prices at the inception of the contract.

Loans and Allowances for Cred_3

Loans and Allowances for Credit Losses, Loans by Portfolio Segment (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Loans receivables disclosure [Abstract]
Loans receivables with fixed rate of interest		$ 5,749,373	$ 4,529,296
Loans receivables with variable rate of interest		15,744,110	12,436,254
Loan receivable non-accrual		163,247	187,874
Total		21,656,730	17,153,424
Accruing loans past due (90 days)	[1]	1,338	633
Foregone interest on nonaccrual loans		15,502	16,496
Purchase Credit Imapired Loans [Abstract]
Purchase Credit Impaired Loans, Carrying Amount, Net		31,000
Purchase Credit Impaired Loans, Outstanding Balance		47,000
Purchase Credit Impaired Loans, Accretable Yield		843
Credit Commitments [Abstract]
Outstanding commitments to extend credit		12,000,000
Outstanding standby letters of credit		582,000
Geographic Concentration Risk [Member] | Texas [Member]
Loans receivables disclosure [Abstract]
Total		$ 6,400,000	$ 5,800,000
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in Texas (in hundredths)		30.00%	34.00%
Geographic Concentration Risk [Member] | Oklahoma [Member]
Loans receivables disclosure [Abstract]
Total		$ 3,500,000	$ 3,300,000
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in Oklahoma (in hundredths)		16.00%	19.00%
Geographic Concentration Risk [Member] | Colorado [Member]
Loans receivables disclosure [Abstract]
Total		$ 3,300,000
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in Colorado (in hundredths)		15.00%
Commercial [Member]
Loans receivables disclosure [Abstract]
Loans receivables with fixed rate of interest		$ 2,251,188	$ 2,217,432
Loans receivables with variable rate of interest		11,285,049	8,379,240
Loan receivable non-accrual		99,841	137,303
Total		13,636,078	10,733,975
Credit Commitments [Abstract]
Outstanding commercial letters of credit		1,900
Commercial [Member] | Geographic Concentration Risk [Member] | Texas [Member]
Loans receivables disclosure [Abstract]
Total		$ 4,100,000	$ 3,600,000
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in Texas (in hundredths)		30.00%	34.00%
Commercial [Member] | Geographic Concentration Risk [Member] | Oklahoma [Member]
Loans receivables disclosure [Abstract]
Total		$ 2,200,000	$ 2,000,000
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in Oklahoma (in hundredths)		16.00%	18.00%
Commercial [Member] | Geographic Concentration Risk [Member] | Colorado [Member]
Loans receivables disclosure [Abstract]
Total		$ 2,000,000
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in Colorado (in hundredths)		15.00%
Commercial [Member] | Services [Member]
Loans receivables disclosure [Abstract]
Total		$ 3,252,146	$ 2,522,025
Commercial [Member] | Services [Member] | Credit Concentration Risk [Member]
Loans receivables disclosure [Abstract]
Total		$ 3,300,000	$ 2,500,000
Loans receivable, other information [Abstract]
Percentage of loan class to total loans		15.00%	15.00%
Amount of loans with individual balances less than $10 million		$ 2,300,000	$ 1,500,000
Maximum loan amount for certain individual loans in category		10,000	10,000
Commercial [Member] | Energy [Member]
Loans receivables disclosure [Abstract]
Total		3,590,333	2,930,156
Commercial [Member] | Energy [Member] | Credit Concentration Risk [Member]
Loans receivables disclosure [Abstract]
Total		$ 3,600,000	$ 2,900,000
Loans receivable, other information [Abstract]
Percentage of loan class to total loans		17.00%	17.00%
Commercial [Member] | Energy Producers [Member] | Credit Concentration Risk [Member]
Loans receivables disclosure [Abstract]
Total		$ 2,900,000	$ 2,500,000
Loans receivable, other information [Abstract]
Percentage of committed energy production loans secured by oil		57.00%	57.00%
Percentage of committed energy production loans secured by natural gas		43.00%	43.00%
Commercial [Member] | Healthcare [Member]
Loans receivables disclosure [Abstract]
Total		$ 2,733,537	$ 2,243,487
Commercial [Member] | Healthcare [Member] | Credit Concentration Risk [Member]
Loans receivables disclosure [Abstract]
Total		$ 2,700,000	$ 2,200,000
Loans receivable, other information [Abstract]
Percentage of loan class to total loans		13.00%	13.00%
Commercial Real Estate [Member]
Loans receivables disclosure [Abstract]
Loans receivables with fixed rate of interest		$ 1,477,274	$ 548,692
Loans receivables with variable rate of interest		3,265,918	2,928,440
Loan receivable non-accrual		21,621	2,855
Total		$ 4,764,813	$ 3,479,987
Commercial Real Estate [Member] | Geographic Concentration Risk [Member] | Texas [Member]
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in Texas (in hundredths)		26.00%	35.00%
Commercial Real Estate [Member] | Geographic Concentration Risk [Member] | Oklahoma [Member]
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in Oklahoma (in hundredths)			12.00%
Commercial Real Estate [Member] | Geographic Concentration Risk [Member] | Colorado [Member]
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in Colorado (in hundredths)		16.00%
Residential Mortgage [Member]
Loans receivables disclosure [Abstract]
Loans receivables with fixed rate of interest		$ 1,830,224	$ 1,608,655
Loans receivables with variable rate of interest		358,254	317,584
Loan receivable non-accrual		41,555	47,447
Total		$ 2,230,033	$ 1,973,686
Residential Mortgage [Member] | Geographic Concentration Risk [Member] | Texas [Member]
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in Texas (in hundredths)		28.00%	30.00%
Residential Mortgage [Member] | Geographic Concentration Risk [Member] | Oklahoma [Member]
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in Oklahoma (in hundredths)		26.00%	31.00%
Percentage of loan portfolio secured by property in Colorado (in hundredths)			11.00%
Residential Mortgage [Member] | Geographic Concentration Risk [Member] | New Mexico [Memnber]
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in New Mexico (in hundredths)			9.00%
Residential Mortgage [Member] | Geographic Concentration Risk [Member] | Colorado [Member]
Loans receivable, other information [Abstract]
Percentage of loan portfolio secured by property in Colorado (in hundredths)		19.00%
Residential Mortgage [Member] | Permanent mortgage [Member]
Loans receivables disclosure [Abstract]
Total		$ 1,320,165	$ 1,043,435
Loans receivable, other information [Abstract]
Minimum FICO required for jumbo loan approval		720
Maximum debt-to-income ratio on jumbo loans (in hundredths)		38.00%
Minimum loan-to-value ratio on jumbo loans (in hundredths)		60.00%
Maximum loan-to-value ratio on jumbo loans (in hundredths)		100.00%
Minimum period for fixed rate on variable rate jumbo loans (in years)		3 years
Maximum period for fixed rate on variable rate jumbo loans (in years)		10 years
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Loans receivables disclosure [Abstract]
Total		$ 190,866	197,506
Residential Mortgage [Member] | Home equity [Member]
Loans receivables disclosure [Abstract]
Total		719,002	$ 732,745
Loans receivable, other information [Abstract]
Maximum loan amount for certain individual loans in category		$ 400
Percentage of home equity portfolio comprised of first lien loans		59.00%	64.00%
Percentage of home equity portfolio comprised of junior lien loans		41.00%	36.00%
Percentage of junior lien home equity loans that are amortizing term loans		40.00%	46.00%
Percentage of junior lien home equity loans that are revolving lines of credit		60.00%	54.00%
Home equity loans, description		Home equity loans generally require a minimum FICO score of 700 and a maximum DTI of 40%.
Home equity loans, revolving period		5 years
Home equity loans, amortization period following revolving period		15 years
Home equity loans, discretionary additional revolving period		5 years
Personal [Member]
Loans receivables disclosure [Abstract]
Loans receivables with fixed rate of interest		$ 190,687	$ 154,517
Loans receivables with variable rate of interest		834,889	810,990
Loan receivable non-accrual		230	269
Total		$ 1,025,806	$ 965,776
[1]	Excludes residential mortgage loans guaranteed by agencies of the U.S. government

Derivatives, Derivatives Instru

Derivatives, Derivatives Instruments Gain (Loss) in Income Statement (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Trading Activity, Gains and Losses, Net [Line Items]
Brokerage and Trading Revenue	$ 25,192	$ 48,761	$ 42,603
Gain (Loss) on Derivatives, Net	(422)	779	(15,685)
To-be-announced residential mortgage-backed securities [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokerage and Trading Revenue	27,190	34,532	38,523
Gain (Loss) on Derivatives, Net	0	0	0
Interest rate swaps [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokerage and Trading Revenue	2,614	2,647	2,589
Gain (Loss) on Derivatives, Net	0	0	0
Energy contracts [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokerage and Trading Revenue	8,443	5,536	5,027
Gain (Loss) on Derivatives, Net	0	0	0
Agricultural contracts [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokerage and Trading Revenue	53	79	111
Gain (Loss) on Derivatives, Net	0	0	0
Foreign exchange contracts [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokerage and Trading Revenue	535	1,352	945
Gain (Loss) on Derivatives, Net	0	0	0
Equity option contracts [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokerage and Trading Revenue	0	0	0
Gain (Loss) on Derivatives, Net	0	0	0
Total customer risk management programs [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokerage and Trading Revenue	38,835	44,146	47,195
Gain (Loss) on Derivatives, Net	0	0	0
Internal risk management programs [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokerage and Trading Revenue	(13,643)	4,615	(4,592)
Gain (Loss) on Derivatives, Net	$ (422)	$ 779	$ (15,685)

Loans and Allowances for Cred_4

Loans and Allowances for Credit Losses, Activity in Allowance for Credit Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017
Allowance for loan losses [Roll Forward]
Beginning balance	$ 230,682	$ 246,159	$ 225,524
Provision for loan losses	9,944	510	55,467
Loans charged off	(43,583)	(25,599)	(42,588)
Recoveries	10,414	9,612	7,756
Ending balance	207,457	230,682	246,159
Accrual for off-balance sheet credit losses [Roll Forward]
Beginning balance	3,734	11,244	1,711
Provision for off-balance sheet credit risk	(1,944)	(7,510)	9,533
Ending balance	1,790	3,734	11,244
Total provision for credit losses	8,000	(7,000)	65,000
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment				$ 21,493,483	$ 16,965,550
Individually measured for impairment, recorded investment				163,247	187,874
Total				21,656,730	17,153,424
Related allowance [Abstract]
Collectively measured for impairment, related allowance				180,957	199,634
Individually measured for impairment, related allowance				8,732	8,831
Total measured for impairment, related allowance	230,682	246,159	246,159	207,457	230,682
Commercial [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	124,269	140,213	130,334
Provision for loan losses	12,521	(595)	43,980
Loans charged off	(37,880)	(19,810)	(35,828)
Recoveries	3,316	4,461	1,727
Ending balance	102,226	124,269	140,213
Accrual for off-balance sheet credit losses [Roll Forward]
Beginning balance	3,644	11,063	1,506
Provision for off-balance sheet credit risk	(1,989)	(7,419)	9,557
Ending balance	1,655	3,644	11,063
Total provision for credit losses	10,532	(8,014)	53,537
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment				13,536,237	10,596,672
Individually measured for impairment, recorded investment				99,841	137,303
Total				13,636,078	10,733,975
Related allowance [Abstract]
Collectively measured for impairment, related allowance				93,494	115,438
Individually measured for impairment, related allowance				8,732	8,831
Total measured for impairment, related allowance	124,269	124,269	130,334	102,226	124,269
Commercial Real Estate [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	56,621	50,749	41,391
Provision for loan losses	(147)	4,008	8,075
Loans charged off	0	(76)	0
Recoveries	3,552	1,940	1,283
Ending balance	60,026	56,621	50,749
Accrual for off-balance sheet credit losses [Roll Forward]
Beginning balance	45	123	153
Provision for off-balance sheet credit risk	7	(78)	(30)
Ending balance	52	45	123
Total provision for credit losses	(140)	3,930	8,045
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment				4,743,192	3,477,132
Individually measured for impairment, recorded investment				21,621	2,855
Total				4,764,813	3,479,987
Related allowance [Abstract]
Collectively measured for impairment, related allowance				60,026	56,621
Individually measured for impairment, related allowance				0	0
Total measured for impairment, related allowance	56,621	56,621	41,391	60,026	56,621
Residential Mortgage [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	18,451	18,224	19,509
Provision for loan losses	(1,156)	116	(1,972)
Loans charged off	(378)	(649)	(1,312)
Recoveries	1,047	760	1,999
Ending balance	17,964	18,451	18,224
Accrual for off-balance sheet credit losses [Roll Forward]
Beginning balance	43	50	30
Provision for off-balance sheet credit risk	9	(7)	20
Ending balance	52	43	50
Total provision for credit losses	(1,147)	109	(1,952)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment				2,188,478	1,926,239
Individually measured for impairment, recorded investment				41,555	47,447
Total				2,230,033	1,973,686
Related allowance [Abstract]
Collectively measured for impairment, related allowance				17,964	18,451
Individually measured for impairment, related allowance				0	0
Total measured for impairment, related allowance	18,451	18,451	18,224	17,964	18,451
Personal [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	9,124	8,773	4,164
Provision for loan losses	3,175	2,964	7,310
Loans charged off	(5,325)	(5,064)	(5,448)
Recoveries	2,499	2,451	2,747
Ending balance	9,473	9,124	8,773
Accrual for off-balance sheet credit losses [Roll Forward]
Beginning balance	2	8	22
Provision for off-balance sheet credit risk	29	(6)	(14)
Ending balance	31	2	8
Total provision for credit losses	3,204	2,958	7,296
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment				1,025,576	965,507
Individually measured for impairment, recorded investment				230	269
Total				1,025,806	965,776
Related allowance [Abstract]
Collectively measured for impairment, related allowance				9,473	9,124
Individually measured for impairment, related allowance				0	0
Total measured for impairment, related allowance	9,473	8,773	8,773	9,473	9,124
Specific Allowance [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	208,465
Ending balance	189,689	208,465
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment				21,493,483	16,965,550
Individually measured for impairment, recorded investment				163,247	187,874
Total				21,656,730	17,153,424
Related allowance [Abstract]
Collectively measured for impairment, related allowance				180,957	199,634
Individually measured for impairment, related allowance				8,732	8,831
Total measured for impairment, related allowance	189,689	208,465		189,689	208,465
Nonspecific Allowance [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	22,217	28,200	30,126
Provision for loan losses	(4,449)	(5,983)	(1,926)
Loans charged off	0	0	0
Recoveries	0	0	0
Ending balance	17,768	22,217	28,200
Accrual for off-balance sheet credit losses [Roll Forward]
Beginning balance	0	0	0
Provision for off-balance sheet credit risk	0	0	0
Ending balance	0	0	0
Total provision for credit losses	(4,449)	(5,983)	(1,926)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment				0	0
Individually measured for impairment, recorded investment				0	0
Total				0	0
Related allowance [Abstract]
Collectively measured for impairment, related allowance				0	0
Individually measured for impairment, related allowance				0	0
Total measured for impairment, related allowance	$ 17,768	$ 28,200	$ 30,126	$ 17,768	$ 22,217

Loans and Allowances for Cred_5

Loans and Allowances for Credit Losses, Credit Quality Indicators (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	$ 19,805,403,000	$ 15,297,889,000
Non-Graded, Recorded Investment	1,851,327,000	1,855,535,000
Total	21,656,730,000	17,153,424,000
Related Allowance [Abstract]
Internally Risk Graded, Related Allowance	171,272,000	189,412,000
Non-Graded, Related Allowance	18,417,000	19,053,000
Total, Related Allowance	207,457,000	230,682,000	$ 246,159,000	$ 225,524,000
Commercial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	13,586,654,000	10,706,035,000
Non-Graded, Recorded Investment	49,424,000	27,940,000
Total	13,636,078,000	10,733,975,000
Related Allowance [Abstract]
Internally Risk Graded, Related Allowance	101,303,000	123,383,000
Non-Graded, Related Allowance	923,000	886,000
Total, Related Allowance	102,226,000	124,269,000	140,213,000	130,334,000
Commercial [Member] | Energy [Member]
Recorded Investment [Abstract]
Total	3,590,333,000	2,930,156,000
Commercial [Member] | Services [Member]
Recorded Investment [Abstract]
Total	3,252,146,000	2,522,025,000
Commercial [Member] | Wholesale/retail [Member]
Recorded Investment [Abstract]
Total	1,621,158,000	1,471,256,000
Commercial [Member] | Manufacturing [Member]
Recorded Investment [Abstract]
Total	730,521,000	496,774,000
Commercial [Member] | Healthcare [Member]
Recorded Investment [Abstract]
Total	2,733,537,000	2,243,487,000
Commercial [Member] | Public finance [Member]
Recorded Investment [Abstract]
Total	876,336,000	541,775,000
Commercial [Member] | Other commercial and industrial [Member]
Recorded Investment [Abstract]
Total	832,047,000	528,502,000
Commercial Real Estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,764,813,000	3,479,987,000
Non-Graded, Recorded Investment	0	0
Total	4,764,813,000	3,479,987,000
Related Allowance [Abstract]
Internally Risk Graded, Related Allowance	60,026,000	56,621,000
Non-Graded, Related Allowance	0	0
Total, Related Allowance	60,026,000	56,621,000	50,749,000	41,391,000
Commercial Real Estate [Member] | Residential construction and land development [Member]
Recorded Investment [Abstract]
Total	148,584,000	117,245,000
Commercial Real Estate [Member] | Retail [Member]
Recorded Investment [Abstract]
Total	919,082,000	691,532,000
Commercial Real Estate [Member] | Office [Member]
Recorded Investment [Abstract]
Total	1,072,920,000	831,770,000
Commercial Real Estate [Member] | Multifamily [Member]
Recorded Investment [Abstract]
Total	1,288,065,000	980,017,000
Commercial Real Estate [Member] | Industrial [Member]
Recorded Investment [Abstract]
Total	778,106,000	573,014,000
Commercial Real Estate [Member] | Other commercial real estate [Member]
Recorded Investment [Abstract]
Total	558,056,000	286,409,000
Residential Mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	505,046,000	234,477,000
Non-Graded, Recorded Investment	1,724,987,000	1,739,209,000
Total	2,230,033,000	1,973,686,000
Related Allowance [Abstract]
Internally Risk Graded, Related Allowance	3,310,000	2,947,000
Non-Graded, Related Allowance	14,654,000	15,504,000
Total, Related Allowance	17,964,000	18,451,000	18,224,000	19,509,000
Residential Mortgage [Member] | Permanent mortgage [Member]
Recorded Investment [Abstract]
Total	1,320,165,000	1,043,435,000
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Recorded Investment [Abstract]
Total	190,866,000	197,506,000
Residential Mortgage [Member] | Home equity [Member]
Recorded Investment [Abstract]
Total	719,002,000	732,745,000
Personal [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	948,890,000	877,390,000
Non-Graded, Recorded Investment	76,916,000	88,386,000
Total	1,025,806,000	965,776,000
Related Allowance [Abstract]
Internally Risk Graded, Related Allowance	6,633,000	6,461,000
Non-Graded, Related Allowance	2,840,000	2,663,000
Total, Related Allowance	9,473,000	9,124,000	8,773,000	4,164,000
Specific Allowance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	19,805,403,000	15,297,889,000
Non-Graded, Recorded Investment	1,851,327,000	1,855,535,000
Total	21,656,730,000	17,153,424,000
Related Allowance [Abstract]
Internally Risk Graded, Related Allowance	171,272,000	189,412,000
Non-Graded, Related Allowance	18,417,000	19,053,000
Total, Related Allowance	189,689,000	208,465,000
Nonspecific Allowance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0
Non-Graded, Recorded Investment	0	0
Total	0	0
Related Allowance [Abstract]
Internally Risk Graded, Related Allowance	0	0
Non-Graded, Related Allowance	0	0
Total, Related Allowance	17,768,000	22,217,000	$ 28,200,000	$ 30,126,000
Performing Financial Instruments [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	1,811,557,000	1,808,995,000
Performing Financial Instruments [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	184,000,000	188,000,000
Performing Financial Instruments [Member] | Commercial [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	49,371,000	27,870,000
Performing Financial Instruments [Member] | Commercial [Member] | Energy [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Commercial [Member] | Services [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Commercial [Member] | Wholesale/retail [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Commercial [Member] | Manufacturing [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Commercial [Member] | Healthcare [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Commercial [Member] | Public finance [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Commercial [Member] | Other commercial and industrial [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	49,371,000	27,870,000
Performing Financial Instruments [Member] | Commercial Real Estate [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Commercial Real Estate [Member] | Residential construction and land development [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Commercial Real Estate [Member] | Retail [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Commercial Real Estate [Member] | Office [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Commercial Real Estate [Member] | Multifamily [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Commercial Real Estate [Member] | Industrial [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Commercial Real Estate [Member] | Other commercial real estate [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Residential Mortgage [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	1,685,424,000	1,692,925,000
Performing Financial Instruments [Member] | Residential Mortgage [Member] | Permanent mortgage [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	819,199,000	784,928,000
Performing Financial Instruments [Member] | Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	183,734,000	188,327,000
Performing Financial Instruments [Member] | Residential Mortgage [Member] | Home equity [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	682,491,000	719,670,000
Performing Financial Instruments [Member] | Personal [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	76,762,000	88,200,000
Performing Financial Instruments [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	19,285,126,000	14,797,279,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	13,135,068,000	10,226,089,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial [Member] | Energy [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	3,414,039,000	2,632,986,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial [Member] | Services [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	3,161,157,000	2,478,945,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial [Member] | Wholesale/retail [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,593,902,000	1,443,917,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial [Member] | Manufacturing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	668,438,000	472,869,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial [Member] | Healthcare [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,664,381,000	2,182,231,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial [Member] | Public finance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	876,336,000	541,775,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial [Member] | Other commercial and industrial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	756,815,000	473,366,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial Real Estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,712,826,000	3,463,002,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial Real Estate [Member] | Residential construction and land development [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	148,234,000	113,190,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial Real Estate [Member] | Retail [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	885,588,000	686,915,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial Real Estate [Member] | Office [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,059,334,000	824,408,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial Real Estate [Member] | Multifamily [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,287,471,000	979,969,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial Real Estate [Member] | Industrial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	776,898,000	573,014,000
Performing Financial Instruments [Member] | Pass [Member] | Commercial Real Estate [Member] | Other commercial real estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	555,301,000	285,506,000
Performing Financial Instruments [Member] | Pass [Member] | Residential Mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	492,976,000	232,492,000
Performing Financial Instruments [Member] | Pass [Member] | Residential Mortgage [Member] | Permanent mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	467,233,000	232,492,000
Performing Financial Instruments [Member] | Pass [Member] | Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Pass [Member] | Residential Mortgage [Member] | Home equity [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	25,743,000	0
Performing Financial Instruments [Member] | Pass [Member] | Personal [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	944,256,000	875,696,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	181,960,000	118,175,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	157,866,000	103,324,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial [Member] | Energy [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	42,176,000	60,288,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial [Member] | Services [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	49,761,000	13,927,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial [Member] | Wholesale/retail [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	18,809,000	19,263,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial [Member] | Manufacturing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	30,934,000	6,653,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial [Member] | Healthcare [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	14,920,000	3,186,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial [Member] | Public finance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial [Member] | Other commercial and industrial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,266,000	7,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial Real Estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	23,927,000	13,303,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial Real Estate [Member] | Residential construction and land development [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	1,828,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial Real Estate [Member] | Retail [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	11,926,000	4,243,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial Real Estate [Member] | Office [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,532,000	7,087,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial Real Estate [Member] | Multifamily [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	281,000	0
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial Real Estate [Member] | Industrial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Commercial Real Estate [Member] | Other commercial real estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,188,000	145,000
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Residential Mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	52,000	0
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Residential Mortgage [Member] | Permanent mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	52,000	0
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Residential Mortgage [Member] | Home equity [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Other Loans Especially Mentioned [Member] | Personal [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	115,000	1,548,000
Performing Financial Instruments [Member] | Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	214,840,000	241,101,000
Performing Financial Instruments [Member] | Substandard [Member] | Commercial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	193,932,000	239,389,000
Performing Financial Instruments [Member] | Substandard [Member] | Commercial [Member] | Energy [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	86,624,000	144,598,000
Performing Financial Instruments [Member] | Substandard [Member] | Commercial [Member] | Services [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	32,661,000	26,533,000
Performing Financial Instruments [Member] | Substandard [Member] | Commercial [Member] | Wholesale/retail [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	7,131,000	5,502,000
Performing Financial Instruments [Member] | Substandard [Member] | Commercial [Member] | Manufacturing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	22,230,000	11,290,000
Performing Financial Instruments [Member] | Substandard [Member] | Commercial [Member] | Healthcare [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	37,698,000	43,305,000
Performing Financial Instruments [Member] | Substandard [Member] | Commercial [Member] | Public finance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Substandard [Member] | Commercial [Member] | Other commercial and industrial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	7,588,000	8,161,000
Performing Financial Instruments [Member] | Substandard [Member] | Commercial Real Estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	6,439,000	827,000
Performing Financial Instruments [Member] | Substandard [Member] | Commercial Real Estate [Member] | Residential construction and land development [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	395,000
Performing Financial Instruments [Member] | Substandard [Member] | Commercial Real Estate [Member] | Retail [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,289,000	98,000
Performing Financial Instruments [Member] | Substandard [Member] | Commercial Real Estate [Member] | Office [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	3,054,000	0
Performing Financial Instruments [Member] | Substandard [Member] | Commercial Real Estate [Member] | Multifamily [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	12,000	48,000
Performing Financial Instruments [Member] | Substandard [Member] | Commercial Real Estate [Member] | Industrial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,208,000	0
Performing Financial Instruments [Member] | Substandard [Member] | Commercial Real Estate [Member] | Other commercial real estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	876,000	286,000
Performing Financial Instruments [Member] | Substandard [Member] | Residential Mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,026,000	822,000
Performing Financial Instruments [Member] | Substandard [Member] | Residential Mortgage [Member] | Permanent mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	9,730,000	822,000
Performing Financial Instruments [Member] | Substandard [Member] | Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0
Performing Financial Instruments [Member] | Substandard [Member] | Residential Mortgage [Member] | Home equity [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	296,000	0
Performing Financial Instruments [Member] | Substandard [Member] | Personal [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,443,000	63,000
Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	123,476,000	141,334,000
Non-Graded, Recorded Investment	39,771,000	46,540,000
Nonaccrual [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment	7,100,000	9,200,000
Nonaccrual [Member] | Commercial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	99,788,000	137,233,000
Non-Graded, Recorded Investment	53,000	70,000
Nonaccrual [Member] | Commercial [Member] | Energy [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	47,494,000	92,284,000
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Commercial [Member] | Services [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	8,567,000	2,620,000
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Commercial [Member] | Wholesale/retail [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,316,000	2,574,000
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Commercial [Member] | Manufacturing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	8,919,000	5,962,000
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Commercial [Member] | Healthcare [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	16,538,000	14,765,000
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Commercial [Member] | Public finance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Commercial [Member] | Other commercial and industrial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	16,954,000	19,028,000
Non-Graded, Recorded Investment	53,000	70,000
Nonaccrual [Member] | Commercial Real Estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	21,621,000	2,855,000
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Commercial Real Estate [Member] | Residential construction and land development [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	350,000	1,832,000
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Commercial Real Estate [Member] | Retail [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	20,279,000	276,000
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Commercial Real Estate [Member] | Office [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	275,000
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Commercial Real Estate [Member] | Multifamily [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	301,000	0
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Commercial Real Estate [Member] | Industrial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Commercial Real Estate [Member] | Other commercial real estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	691,000	472,000
Non-Graded, Recorded Investment	0	0
Nonaccrual [Member] | Residential Mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,991,000	1,163,000
Non-Graded, Recorded Investment	39,564,000	46,284,000
Nonaccrual [Member] | Residential Mortgage [Member] | Permanent mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,991,000	1,163,000
Non-Graded, Recorded Investment	21,960,000	24,030,000
Nonaccrual [Member] | Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0
Non-Graded, Recorded Investment	7,132,000	9,179,000
Nonaccrual [Member] | Residential Mortgage [Member] | Home equity [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0
Non-Graded, Recorded Investment	10,472,000	13,075,000
Nonaccrual [Member] | Personal [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	76,000	83,000
Non-Graded, Recorded Investment	$ 154,000	$ 186,000

Loans and Allowances for Cred_6

Loans and Allowances for Credit Losses, Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	$ 423,787		$ 438,459
Impaired loans, recorded investment, total	346,981		376,201
Impaired loans, recorded investment with no related allowance	311,526		324,867
Impaired loans, recorded investment with related allowance	35,455		51,334
Impaired loans, related allowance	8,732		8,831
Impaired loans, average recorded investment	345,107		398,161
Impaired loans, interest income recognized	8,405		8,861
Commercial [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	156,163		184,604
Impaired loans, recorded investment, total	99,841		137,303
Impaired loans, recorded investment with no related allowance	64,386		85,969
Impaired loans, recorded investment with related allowance	35,455		51,334
Impaired loans, related allowance	8,732		8,831
Impaired loans, average recorded investment	115,460		158,127
Impaired loans, interest income recognized	0		0
Commercial [Member] | Energy [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	79,675		111,011
Impaired loans, recorded investment, total	47,494		92,284
Impaired loans, recorded investment with no related allowance	18,639		40,968
Impaired loans, recorded investment with related allowance	28,855		51,316
Impaired loans, related allowance	5,362		8,814
Impaired loans, average recorded investment	69,645		112,392
Impaired loans, interest income recognized	0		0
Commercial [Member] | Services [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	13,437		5,324
Impaired loans, recorded investment, total	8,567		2,620
Impaired loans, recorded investment with no related allowance	8,489		2,620
Impaired loans, recorded investment with related allowance	78		0
Impaired loans, related allowance	74		0
Impaired loans, average recorded investment	4,509		5,396
Impaired loans, interest income recognized	0		0
Commercial [Member] | Wholesale/retail [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	1,722		9,099
Impaired loans, recorded investment, total	1,316		2,574
Impaired loans, recorded investment with no related allowance	1,015		2,574
Impaired loans, recorded investment with related allowance	301		0
Impaired loans, related allowance	101		0
Impaired loans, average recorded investment	1,784		6,990
Impaired loans, interest income recognized	0		0
Commercial [Member] | Manufacturing [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	10,055		6,073
Impaired loans, recorded investment, total	8,919		5,962
Impaired loans, recorded investment with no related allowance	8,673		5,962
Impaired loans, recorded investment with related allowance	246		0
Impaired loans, related allowance	246		0
Impaired loans, average recorded investment	7,249		5,446
Impaired loans, interest income recognized	0		0
Commercial [Member] | Healthcare [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	24,319		25,140
Impaired loans, recorded investment, total	16,538		14,765
Impaired loans, recorded investment with no related allowance	10,563		14,765
Impaired loans, recorded investment with related allowance	5,975		0
Impaired loans, related allowance	2,949		0
Impaired loans, average recorded investment	14,297		7,795
Impaired loans, interest income recognized	0		0
Commercial [Member] | Public finance [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	0		0
Impaired loans, recorded investment, total	0		0
Impaired loans, recorded investment with no related allowance	0		0
Impaired loans, recorded investment with related allowance	0		0
Impaired loans, related allowance	0		0
Impaired loans, average recorded investment	0		0
Impaired loans, interest income recognized	0		0
Commercial [Member] | Other commercial and industrial [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	26,955		27,957
Impaired loans, recorded investment, total	17,007		19,098
Impaired loans, recorded investment with no related allowance	17,007		19,080
Impaired loans, recorded investment with related allowance	0		18
Impaired loans, related allowance	0		17
Impaired loans, average recorded investment	17,976		20,108
Impaired loans, interest income recognized	0		0
Commercial Real Estate [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	30,138		4,751
Impaired loans, recorded investment, total	21,621		2,855
Impaired loans, recorded investment with no related allowance	21,621		2,855
Impaired loans, recorded investment with related allowance	0		0
Impaired loans, related allowance	0		0
Impaired loans, average recorded investment	12,238		4,189
Impaired loans, interest income recognized	0		0
Commercial Real Estate [Member] | Residential construction and land development [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	1,306		3,285
Impaired loans, recorded investment, total	350		1,832
Impaired loans, recorded investment with no related allowance	350		1,832
Impaired loans, recorded investment with related allowance	0		0
Impaired loans, related allowance	0		0
Impaired loans, average recorded investment	1,091		2,633
Impaired loans, interest income recognized	0		0
Commercial Real Estate [Member] | Retail [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	27,680		509
Impaired loans, recorded investment, total	20,279		276
Impaired loans, recorded investment with no related allowance	20,279		276
Impaired loans, recorded investment with related allowance	0		0
Impaired loans, related allowance	0		0
Impaired loans, average recorded investment	10,278		301
Impaired loans, interest income recognized	0		0
Commercial Real Estate [Member] | Office [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	0		287
Impaired loans, recorded investment, total	0		275
Impaired loans, recorded investment with no related allowance	0		275
Impaired loans, recorded investment with related allowance	0		0
Impaired loans, related allowance	0		0
Impaired loans, average recorded investment	137		351
Impaired loans, interest income recognized	0		0
Commercial Real Estate [Member] | Multifamily [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	301		0
Impaired loans, recorded investment, total	301		0
Impaired loans, recorded investment with no related allowance	301		0
Impaired loans, recorded investment with related allowance	0		0
Impaired loans, related allowance	0		0
Impaired loans, average recorded investment	151		19
Impaired loans, interest income recognized	0		0
Commercial Real Estate [Member] | Industrial [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	0		0
Impaired loans, recorded investment, total	0		0
Impaired loans, recorded investment with no related allowance	0		0
Impaired loans, recorded investment with related allowance	0		0
Impaired loans, related allowance	0		0
Impaired loans, average recorded investment	0		38
Impaired loans, interest income recognized	0		0
Commercial Real Estate [Member] | Other commercial real estate [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	851		670
Impaired loans, recorded investment, total	691		472
Impaired loans, recorded investment with no related allowance	691		472
Impaired loans, recorded investment with related allowance	0		0
Impaired loans, related allowance	0		0
Impaired loans, average recorded investment	581		847
Impaired loans, interest income recognized	0		0
Residential Mortgage [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	237,208		248,797
Impaired loans, recorded investment, total	225,289		235,774
Impaired loans, recorded investment with no related allowance	225,289		235,774
Impaired loans, recorded investment with related allowance	0		0
Impaired loans, related allowance	0		0
Impaired loans, average recorded investment	217,159		235,565
Impaired loans, interest income recognized	8,405		8,861
Residential Mortgage [Member] | Permanent mortgage [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	28,716		30,435
Impaired loans, recorded investment, total	23,951		25,193
Impaired loans, recorded investment with no related allowance	23,951		25,193
Impaired loans, recorded investment with related allowance	0		0
Impaired loans, related allowance	0		0
Impaired loans, average recorded investment	24,572		24,024
Impaired loans, interest income recognized	1,233		1,229
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	196,296	[1]	203,814	[2]
Impaired loans, recorded investment, total	190,866	[1]	197,506	[2]
Impaired loans, recorded investment with no related allowance	190,866	[1]	197,506	[2]
Impaired loans, recorded investment with related allowance	0	[1]	0	[2]
Impaired loans, related allowance	0	[1]	0	[2]
Impaired loans, average recorded investment	180,813	[1]	199,244	[2]
Impaired loans, interest income recognized	7,172	[1]	7,632	[2]
Residential Mortgage [Member] | Home equity [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	12,196		14,548
Impaired loans, recorded investment, total	10,472		13,075
Impaired loans, recorded investment with no related allowance	10,472		13,075
Impaired loans, recorded investment with related allowance	0		0
Impaired loans, related allowance	0		0
Impaired loans, average recorded investment	11,774		12,297
Impaired loans, interest income recognized	0		0
Personal [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	278		307
Impaired loans, recorded investment, total	230		269
Impaired loans, recorded investment with no related allowance	230		269
Impaired loans, recorded investment with related allowance	0		0
Impaired loans, related allowance	0		0
Impaired loans, average recorded investment	250		280
Impaired loans, interest income recognized	$ 0		$ 0
[1]	All permanent mortgage loans guaranteed by U.S. government agencies are considered impaired as we do not expect full collection of contractual principal and interest. At December 31, 2018 , $7.1 million of these loans are nonaccruing and $184 million
[2]	All permanent mortgage loans guaranteed by U.S. government agencies are considered impaired as we do not expect full collection of contractual principal and interest. At December 31, 2017 , $9.2 million of these loans are nonaccruing and $188 million

Loans and Allowances for Cred_7

Loans and Allowances for Credit Losses, Troubled Debt Restructurings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	$ 166,000	$ 126,000
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	71,000	48,000
Troubled Debt Restructuring, Charge-offs	16,100	117
Troubled Debt Restructurings, Recorded Balance Modified During The Period	75,000	57,000
Residential Mortgage [Member] | Accruing [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	$ 86,000	$ 74,000

Loans and Allowances for Cred_8

Loans and Allowances for Credit Losses, By Aging Category (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing receivable, recorded investment, aging [Abstract]
Current	$ 21,308,989	$ 16,770,208
Nonaccrual	163,247	187,874
Total	21,656,730	17,153,424
Commercial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	13,521,894	10,575,384
Nonaccrual	99,841	137,303
Total	13,636,078	10,733,975
Commercial [Member] | Energy [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	3,542,839	2,833,668
Nonaccrual	47,494	92,284
Total	3,590,333	2,930,156
Commercial [Member] | Services [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	3,231,532	2,518,298
Nonaccrual	8,567	2,620
Total	3,252,146	2,522,025
Commercial [Member] | Wholesale/retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,619,290	1,468,284
Nonaccrual	1,316	2,574
Total	1,621,158	1,471,256
Commercial [Member] | Manufacturing [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	721,204	490,739
Nonaccrual	8,919	5,962
Total	730,521	496,774
Commercial [Member] | Healthcare [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,716,204	2,213,504
Nonaccrual	16,538	14,765
Total	2,733,537	2,243,487
Commercial [Member] | Public finance [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	876,336	541,775
Nonaccrual	0	0
Total	876,336	541,775
Commercial [Member] | Other commercial and industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	814,489	509,116
Nonaccrual	17,007	19,098
Total	832,047	528,502
Commercial Real Estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	4,725,669	3,476,163
Nonaccrual	21,621	2,855
Total	4,764,813	3,479,987
Commercial Real Estate [Member] | Residential construction and land development [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	147,705	115,213
Nonaccrual	350	1,832
Total	148,584	117,245
Commercial Real Estate [Member] | Retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	884,424	691,256
Nonaccrual	20,279	276
Total	919,082	691,532
Commercial Real Estate [Member] | Office [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,072,920	831,118
Nonaccrual	0	275
Total	1,072,920	831,770
Commercial Real Estate [Member] | Multifamily [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,287,483	979,625
Nonaccrual	301	0
Total	1,288,065	980,017
Commercial Real Estate [Member] | Industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	776,898	573,014
Nonaccrual	0	0
Total	778,106	573,014
Commercial Real Estate [Member] | Other commercial real estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	556,239	285,937
Nonaccrual	691	472
Total	558,056	286,409
Residential Mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,037,128	1,754,287
Nonaccrual	41,555	47,447
Total	2,230,033	1,973,686
Residential Mortgage [Member] | Permanent mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,292,652	1,014,588
Nonaccrual	23,951	25,193
Total	1,320,165	1,043,435
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	37,459	22,692
Nonaccrual	7,132	9,179
Total	190,866	197,506
Residential Mortgage [Member] | Home equity [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	707,017	717,007
Nonaccrual	10,472	13,075
Total	719,002	732,745
Personal [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,024,298	964,374
Nonaccrual	230	269
Total	1,025,806	965,776
30 to 59 Days Past Due [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	53,350	41,991
30 to 59 Days Past Due [Member] | Commercial [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	7,675	16,215
30 to 59 Days Past Due [Member] | Commercial [Member] | Energy [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
30 to 59 Days Past Due [Member] | Commercial [Member] | Services [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	6,009	514
30 to 59 Days Past Due [Member] | Commercial [Member] | Wholesale/retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	515	398
30 to 59 Days Past Due [Member] | Commercial [Member] | Manufacturing [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	392	0
30 to 59 Days Past Due [Member] | Commercial [Member] | Healthcare [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	241	15,218
30 to 59 Days Past Due [Member] | Commercial [Member] | Public finance [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
30 to 59 Days Past Due [Member] | Commercial [Member] | Other commercial and industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	518	85
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	16,529	476
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] | Residential construction and land development [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	249	200
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] | Retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	14,379	0
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] | Office [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	254
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] | Multifamily [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	281	22
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] | Industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	1,208	0
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] | Other commercial real estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	412	0
30 to 59 Days Past Due [Member] | Residential Mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	28,667	24,619
30 to 59 Days Past Due [Member] | Residential Mortgage [Member] | Permanent mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	3,196	3,435
30 to 59 Days Past Due [Member] | Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	24,369	18,978
30 to 59 Days Past Due [Member] | Residential Mortgage [Member] | Home equity [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	1,102	2,206
30 to 59 Days Past Due [Member] | Personal [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	479	681
60 to 89 Days Past Due [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	24,245	19,529
60 to 89 Days Past Due [Member] | Commercial [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	6,106	4,841
60 to 89 Days Past Due [Member] | Commercial [Member] | Energy [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	4,204
60 to 89 Days Past Due [Member] | Commercial [Member] | Services [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	6,038	486
60 to 89 Days Past Due [Member] | Commercial [Member] | Wholesale/retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	37	0
60 to 89 Days Past Due [Member] | Commercial [Member] | Manufacturing [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	6	73
60 to 89 Days Past Due [Member] | Commercial [Member] | Healthcare [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
60 to 89 Days Past Due [Member] | Commercial [Member] | Public finance [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
60 to 89 Days Past Due [Member] | Commercial [Member] | Other commercial and industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	25	78
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	280	370
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] | Residential construction and land development [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	280	0
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] | Retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] | Office [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] | Multifamily [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	370
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] | Industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] | Other commercial real estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
60 to 89 Days Past Due [Member] | Residential Mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	17,063	14,127
60 to 89 Days Past Due [Member] | Residential Mortgage [Member] | Permanent mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	366	219
60 to 89 Days Past Due [Member] | Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	16,345	13,468
60 to 89 Days Past Due [Member] | Residential Mortgage [Member] | Home equity [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	352	440
60 to 89 Days Past Due [Member] | Personal [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	796	191
90 Days or More [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	106,899	133,822
90 Days or More [Member] | Commercial [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	562	232
90 Days or More [Member] | Commercial [Member] | Energy [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
90 Days or More [Member] | Commercial [Member] | Services [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	107
90 Days or More [Member] | Commercial [Member] | Wholesale/retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
90 Days or More [Member] | Commercial [Member] | Manufacturing [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
90 Days or More [Member] | Commercial [Member] | Healthcare [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	554	0
90 Days or More [Member] | Commercial [Member] | Public finance [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
90 Days or More [Member] | Commercial [Member] | Other commercial and industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	8	125
90 Days or More [Member] | Commercial Real Estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	714	123
90 Days or More [Member] | Commercial Real Estate [Member] | Residential construction and land development [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
90 Days or More [Member] | Commercial Real Estate [Member] | Retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
90 Days or More [Member] | Commercial Real Estate [Member] | Office [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	123
90 Days or More [Member] | Commercial Real Estate [Member] | Multifamily [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
90 Days or More [Member] | Commercial Real Estate [Member] | Industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
90 Days or More [Member] | Commercial Real Estate [Member] | Other commercial real estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	714	0
90 Days or More [Member] | Residential Mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	105,620	133,206
90 Days or More [Member] | Residential Mortgage [Member] | Permanent mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	0	0
90 Days or More [Member] | Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	105,561	133,189
90 Days or More [Member] | Residential Mortgage [Member] | Home equity [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	59	17
90 Days or More [Member] | Personal [Member]
Financing receivable, recorded investment, aging [Abstract]
Past Due	$ 3	$ 261

Premises and Equipment Premis_2

Premises and Equipment Premises and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Premises and Equipment [Line Items]
Premises and equipment	$ 645,017	$ 755,824
Less accumulated depreciation	314,984	438,489
Premises and equipment, net of accumulated depreciation	330,033	317,335
Depreciation Expense	51,000	48,000	$ 40,000
Land
Premises and Equipment [Line Items]
Premises and equipment	70,575	71,348
Buildings and improvements
Premises and Equipment [Line Items]
Premises and equipment	266,733	249,139
Software
Premises and Equipment [Line Items]
Premises and equipment	150,207	188,826
Furniture and equipment
Premises and Equipment [Line Items]
Premises and equipment	129,988	223,163
Construction in progress
Premises and Equipment [Line Items]
Premises and equipment	$ 27,514	$ 23,348

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets Acquisitions (Details) - USD ($) $ in Thousands, shares in Millions	Oct. 01, 2018	May 01, 2018	Dec. 01, 2016	Dec. 31, 2018	Dec. 31, 2016	Dec. 31, 2017
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Goodwill				$ 1,049,263	$ 448,899	$ 447,430
CoBiz Financial Inc. [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Oct. 1, 2018
Name of Acquired Entity				CoBiz Financial, Inc. ("CoBiz")
Consideration Transferred				$ 944,193
Cash payments to acquire businesses				$ 243,000
Stock Issued During Period, Shares, Acquisitions				7.2
Equity interests issued				$ 701,000
Goodwill Recognized, Description				synergies expected to be gained through consolidation of administrative functions resulting in cost savings.
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Cash and due from banks	$ 80,827
Investment securities	17,287
Available for sale securities	546,776
Restricted equity securities	5,261
Loans	2,937,499
Unpaid principal balance of loans	3,066,521
Premises and equipment	5,515
Receivables	24,893
Intangible assets	106,733
Real estate and other repossessed assets	5,155
Derivative contracts asset, net	8,197
Cash surrender value of bank-owned life insurance	55,740
Other assets	56,642
Total assets acquired	3,850,525
Deposits	3,289,071
Funds purchased and repurchase agreements	37,218
Subordinated debentures	131,197
Accrued interest, taxes and expense	33,122
Derivative contracts liability, Net	12,303
Other liabilities	5,254
Total liabilities assumed	3,508,165
Net assets acquired	342,360
Goodwill	$ 601,833
Switchgrass Holdings LLC [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition		May 1, 2018
Name of Acquired Entity				Switchgrass Holdings, LLC
Cash payments to acquire businesses				$ 14,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Intangible assets				$ 6,700
MBT Bancshares [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition			Dec. 1, 2016
Name of Acquired Entity					MBT Bancshares (“MBT”)
Cash payments to acquire businesses					$ 103,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Intangible assets						15,000
Goodwill						$ 66,000

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net		$ 134,849		$ 28,658
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2,019		20,481
2,020		19,196
2,021		17,499
2,022		15,219
2,023		13,344
Thereafter		49,110
Goodwill [Roll Forward]
Goodwill, Beginning Balance		447,430		448,899
Goodwill recognized during period		601,833	[1]	4,301
Goodwill, decrease due to sale of consolidated merchant banking investments				(5,244)
Adjustment	[2]			(526)
Goodwill, Ending Balance		1,049,263		447,430
Commercial [Member]
Goodwill [Roll Forward]
Goodwill, Beginning Balance		313,270		272,196
Goodwill recognized during period		0	[1]	4,301
Goodwill, decrease due to sale of consolidated merchant banking investments				(5,219)
Adjustment	[2]			41,992
Goodwill, Ending Balance		313,270		313,270
Consumer [Member]
Goodwill [Roll Forward]
Goodwill, Beginning Balance		43,458		39,023
Goodwill recognized during period		0	[1]	0
Goodwill, decrease due to sale of consolidated merchant banking investments				0
Adjustment	[2]			4,435
Goodwill, Ending Balance		43,458		43,458
Wealth Management [Member]
Goodwill [Roll Forward]
Goodwill, Beginning Balance		90,702		71,520
Goodwill recognized during period		0	[1]	0
Goodwill, decrease due to sale of consolidated merchant banking investments				(25)
Adjustment	[2]			19,207
Goodwill, Ending Balance		90,702		90,702
Funds Management and Other [Member]
Goodwill [Roll Forward]
Goodwill, Beginning Balance		0		66,160
Goodwill recognized during period		601,833	[1]	0
Goodwill, decrease due to sale of consolidated merchant banking investments				0
Adjustment	[2]			(66,160)
Goodwill, Ending Balance		601,833		0
Core deposits premiums [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		103,200		6,510
Accumulated amortization		5,032		808
Finite-lived intangible assets, net		98,168		5,702
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2,019		14,332
2,020		12,892
2,021		11,893
2,022		10,981
2,023		10,145
Thereafter		37,925
Other identifiable intangible assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		63,497		44,468
Accumulated amortization		26,816		21,512
Finite-lived intangible assets, net		36,681		$ 22,956
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2,019		6,149
2,020		6,304
2,021		5,606
2,022		4,238
2,023		3,199
Thereafter		$ 11,185
[1]	Goodwill related to the CoBiz acquisition was not yet allocated to the operating segments as of December 31, 2018 and is included in Funds Management and Other above.
[2]	Goodwill from Mobank acquisition was not yet allocated to the segments as of December 31, 2016. Adjustment was made in 2017 for final purchase price adjustments and to allocate to the segments.

Mortgage Banking Activities, Co

Mortgage Banking Activities, Components of Loans Held For Sale (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Schedule of Residential Mortgage Loans Held For Sale [Line Items]
Number of days for past due for a residential mortgage loan to be considered nonperforming (in days)	90 days	90 days
Residential mortgage loans held for sale, nonperforming	$ 0	$ 0
Credit losses recognized on residential mortgage loans held for sale	0	0
Components of Residential Mortgage Loans Held for Sale [Abstract]
Unpaid principal balance	145,057	212,525
Residential mortgage loans held for sale, Fair value	146,971	215,113
Total residential mortgages loans held for sale and mortgage loan commitments, net of forward sales contracts	$ 149,221	$ 221,378
Not Designated as Hedging Instrument [Member] | Residential mortgage loan commitments [Member]
Schedule of Residential Mortgage Loans Held For Sale [Line Items]
General number of days outstanding for residential mortgage commitments, minimum (in days)	60 days	60 days
General number of days outstanding for residential mortgage commitments, maximum (in days)	90 days	90 days
Components of Residential Mortgage Loans Held for Sale [Abstract]
Notional	$ 160,848	$ 222,919
Derivative, Net fair value	$ 5,378	$ 6,523
Not Designated as Hedging Instrument [Member] | Forward sales contracts [Member]
Schedule of Residential Mortgage Loans Held For Sale [Line Items]
General number of days for delivery of loans, for which the price is set by forward sales contracts, minimum (in days)	60 days	60 days
General number of days for delivery of loans, for which the price is set by forward sales contracts, maximum (in days)	90 days	90 days
Components of Residential Mortgage Loans Held for Sale [Abstract]
Notional	$ 274,000	$ 380,159
Derivative, Net fair value	$ (3,128)	$ (258)

Mortgage Banking Activities, Mo

Mortgage Banking Activities, Mortgage Banking Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Mortgage Banking Revenue [Abstract]
Net realized gains on sales of mortgage loans	$ 36,379	$ 45,128	$ 68,947
Net change in unrealized gain on mortgage loans held for sale	(674)	2,031	(5,311)
Net change in fair value of mortgage loan commitments	(1,145)	(3,210)	1,599
Net change in the fair value of forward sales contracts	(2,870)	(5,451)	4,393
Total mortgage Production Revenue	31,690	38,498	69,628
Mortgage Servicing Fees	66,097	66,221	64,286
Mortgage banking revenue	$ 97,787	$ 104,719	$ 133,914

Mortgage Banking Activities, _2

Mortgage Banking Activities, Mortgage Servicing Rights (Details)	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Summary of Mortgage Servicing Rights [Abstract]
Number of residential mortgage loans serviced for others	132,463,000	136,528,000	139,340,000
Outstanding principal balance of residential mortgage loans serviced for others	$ 21,658,335,000	$ 22,046,632,000	$ 21,997,568,000
Weighted average interest rate (in hundredths)	3.99%	3.94%	3.97%
Remaining contractual term (in months)	293 months	297 months	301 months
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	$ 252,867,000	$ 247,073,000	$ 218,605,000
Additions, net	35,247,000	39,149,000	71,405,000
Change in fair value due to loan runoff	(33,528,000)	(33,527,000)	(40,744,000)
Change in fair value due to market changes	4,668,000	172,000	(2,193,000)
Ending balance	$ 259,254,000	$ 252,867,000	$ 247,073,000
Servicing Assets at Fair Value, Assumptions Used to Estimate Fair Value [Abstract]
Discount rate - risk-free rate plus a market premium (in hundredths)	9.90%	9.84%
Prepayment rate - based upon loan interest rate, original term and loan type, minimum	8.05%	8.72%
Prepayment rate - based upon loan interest rate, original term and loan type, maximum	15.74%	15.16%
Loan servicing costs - annually per loan based upon loan type, performing, minimum (in dollars per loan)	$ 67	$ 65
Loan servicing costs - annually per loan based upon loan type, performing, maximum (in dollars per loan)	93	88
Loan servicing costs - annually per loan based upon loan type, delinquent, minimum (in dollars per loan)	150	150
Loan servicing costs - annually per loan based upon loan type, delinquent, maximum (in dollars per loan)	500	500
Loan servicing costs - annually per loan based upon loan type, foreclosure, minimum (in dollars per loan)	1,000	1,000
Loan servicing costs - annually per loan based upon loan type, foreclosure, maximum (in dollars per loan)	$ 4,000	$ 4,000
Primary secondary mortgage rate spread (in basis points)	105	105
Escrow earnings rate - indexed to rates paid on deposit accounts with comparable average life	2.57%	2.24%

Mortgage Banking Activities, Lo

Mortgage Banking Activities, Loans Serviced for Others (Details) $ in Thousands	Dec. 31, 2018USD ($)
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	$ 21,188,078
30 To 59 Days Past Due	326,636
60 To 89 Days Past Due	79,657
90 Days or More Past Due	63,964
Total	21,658,335
FHLMC [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	7,798,790
30 To 59 Days Past Due	58,271
60 To 89 Days Past Due	11,139
90 Days or More Past Due	25,239
Total	7,893,439
FNMA [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	6,458,561
30 To 59 Days Past Due	63,321
60 To 89 Days Past Due	12,413
90 Days or More Past Due	20,858
Total	6,555,153
GNMA [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	6,568,459
30 To 59 Days Past Due	200,747
60 To 89 Days Past Due	56,024
90 Days or More Past Due	15,996
Total	6,841,226
Other [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	362,268
30 To 59 Days Past Due	4,297
60 To 89 Days Past Due	81
90 Days or More Past Due	1,871
Total	$ 368,517

Deposits (Details)

Deposits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest expense on deposits [Abstract]
Transaction deposits	$ 65,859	$ 28,627	$ 13,906
Savings	439	359	386
Time Deposit, Interest Expense [Abstract]
Certificates of deposits under $100,000	5,751	7,702	8,776
Certificates of deposits $100,000 and over	19,739	12,393	10,123
Other time deposits	3,729	4,722	7,303
Total time	29,219	24,817	26,202
Total	95,517	53,803	$ 40,494
Time Deposit Information [Abstract]
Time deposits in denomination of $250,000 or more	756,000	797,000
Time Deposit Maturities [Abstract]
2,019	1,300,000
2,020	262,000
2,021	98,000
2,022	115,000
2,023	130,000
Thereafter	211,000
Other Deposits Information [Abstract]
Overdrawn customer transaction deposits reclassified as loan balances	$ 27,000	$ 5,900

Other Borrowings (Details)

Other Borrowings (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Borrowings [Line Items]
Balance		$ 7,418,714	$ 5,854,537	$ 5,717,302
Average Balance		$ 7,298,229	$ 6,559,101	$ 6,901,856
Rate		2.03%	1.18%	0.60%
U.S. government agency mortgage-backed securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Amortized Cost		$ 636,864	$ 525,452
Fair Value		628,229	523,914
Repurchase Liability	[1]	$ 615,961	$ 516,335
Average Rate (in hundredths)		0.36%	0.17%
U.S. government agency mortgage-backed securities [Member] | Overnight [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Amortized Cost		$ 636,864	$ 525,452
Fair Value		628,229	523,914
Repurchase Liability	[1]	$ 615,961	$ 516,335
Average Rate (in hundredths)		0.36%	0.17%
U.S. government agency mortgage-backed securities [Member] | Long-term [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Amortized Cost		$ 0	$ 0
Fair Value		0	0
Repurchase Liability	[1]	$ 0	$ 0
Average Rate (in hundredths)		0.00%	0.00%
Parent Company [Member]
Other Borrowings [Line Items]
Balance		$ 281,120	$ 144,677	$ 152,949
Average Balance		$ 180,544	$ 148,889	$ 77,112
Rate		5.46%	5.65%	5.86%
Other borrowings, Maturities [Abstract]
2,019		$ 0
2,020		0
2,021		0
2,022		0
2,023		0
Thereafter		281,120
Parent Company [Member] | Other Borrowings [Member]
Other Borrowings [Line Items]
Balance		$ 5,207	$ 0	$ 1,092
Rate		1.57%	0.00%	8.27%
Average Balance		$ 2,660	$ 935	$ 2,073
Rate		1.35%	11.11%	16.11%
Maximum Outstanding At Any Month End		$ 5,335	$ 3,104	$ 3,157
Parent Company [Member] | Subordinated debentures [Member]
Other Borrowings [Line Items]
Balance		$ 275,913	$ 144,677	$ 151,857
Rate		5.34%	5.60%	5.49%
Average Balance		$ 177,884	$ 147,954	$ 75,039
Rate		5.52%	5.57%	5.57%
Maximum Outstanding At Any Month End		$ 275,913	$ 151,875	$ 151,857
Parent Company [Member] | Subordinated debentures, 2016 issuance [Member]
Other borrowings, Other Disclosures [Abstract]
Amount of debt issuance		$ 150,000
Maturity date		Jun. 30, 2056
Stated interest rate		5.375%
Debt Instrument, Call Date, Earliest		Jun. 30, 2021
Parent Company [Member] | Subordinated debentures-acquired, 2015 Issuance [Member]
Other borrowings, Other Disclosures [Abstract]
Amount of debt issuance		$ 60,000
Maturity date		Jun. 25, 2030
Interest rate description		three-month LIBOR plus 3.17%
Stated interest rate		5.625%
Debt Instrument, Call Date, Earliest		Jun. 25, 2025
Parent Company [Member] | Junior subordinated debentures-acquired, 2003 issuance [Member]
Other borrowings, Other Disclosures [Abstract]
Amount of debt issuance		$ 21,000
Maturity date		Sep. 17, 2033
Interest rate description		three-month LIBOR plus 2.95%
Parent Company [Member] | Junior subordinated debentures-acquired, 2004 issuance [Member]
Other borrowings, Other Disclosures [Abstract]
Amount of debt issuance		$ 31,000
Maturity date		Jul. 23, 2034
Interest rate description		three-month LIBOR plus 2.60%
Parent Company [Member] | Junior subordinated debentures-acquired, 2005 issuance [Member]
Other borrowings, Other Disclosures [Abstract]
Amount of debt issuance		$ 20,000
Maturity date		Sep. 30, 2035
Interest rate description		three-month LIBOR plus 1.45%
Parent Company [Member] | Trust preferred debt [Member]
Other Borrowings [Line Items]
Balance			7,200
Parent Company [Member] | Trust preferred debt, 2003 issuance [Member]
Other Borrowings [Line Items]
Balance			$ 3,100
Other borrowings, Other Disclosures [Abstract]
Interest rate description			three-month LIBOR plus 2.95%
Parent Company [Member] | Trust preferred debt, 2006 issuance [Member]
Other Borrowings [Line Items]
Balance			$ 4,100
Other borrowings, Other Disclosures [Abstract]
Interest rate description			three-month LIBOR plus 1.82%
Subsidiaries [Member] | BOKF, NA [Member]
Other Borrowings [Line Items]
Balance		$ 7,137,594	$ 5,709,860	5,564,353
Average Balance		$ 7,117,685	$ 6,410,212	$ 6,824,744
Rate		1.94%	1.07%	0.54%
Other borrowings, Maturities [Abstract]
2,019		$ 7,134,538
2,020		575
2,021		575
2,022		575
2,023		625
Thereafter		706
Subsidiaries [Member] | BOKF, NA [Member] | Funds purchased [Member]
Other Borrowings [Line Items]
Balance		$ 402,450	$ 58,628	$ 57,929
Rate		2.34%	1.00%	0.38%
Average Balance		$ 419,322	$ 58,064	$ 78,222
Rate		1.89%	0.73%	0.24%
Maximum Outstanding At Any Month End		$ 949,531	$ 80,967	$ 567,103
Other borrowings, Other Disclosures [Abstract]
Number of days to maturity, minimum		1 day
Number of days to maturity, maximum		90 days
Subsidiaries [Member] | BOKF, NA [Member] | Repurchase agreements [Member]
Other Borrowings [Line Items]
Balance		$ 615,961	$ 516,335	$ 668,661
Rate		0.36%	0.17%	0.02%
Average Balance		$ 464,582	$ 433,791	$ 589,145
Rate		0.28%	0.10%	0.04%
Maximum Outstanding At Any Month End		$ 615,961	$ 536,094	$ 668,661
Other borrowings, Other Disclosures [Abstract]
Number of days to maturity, maximum		90 days
Subsidiaries [Member] | BOKF, NA [Member] | Other Borrowings [Member]
Other Borrowings [Line Items]
Balance		$ 6,119,183	5,134,897	4,837,763
Average Balance		$ 6,233,781	$ 5,918,357	$ 6,016,963
Rate		2.07%	1.14%	0.57%
Subsidiaries [Member] | BOKF, NA [Member] | Federal Home Loan Bank advances [Member]
Other Borrowings [Line Items]
Balance		$ 6,100,000	$ 5,100,000	$ 4,800,000
Rate		2.65%	1.47%	0.72%
Average Balance		$ 6,207,142	$ 5,882,466	$ 5,985,656
Rate		2.06%	1.13%	0.55%
Maximum Outstanding At Any Month End		$ 6,500,000	$ 6,200,000	$ 6,500,000
Other borrowings, Other Disclosures [Abstract]
Federal Home Loan Banks, Letters of credit issued to secure public funds		266,000
Unused credit available pursuant to the FHLB's collateral policies		1,900,000
Subsidiaries [Member] | BOKF, NA [Member] | GNMA repurchase liability [Member]
Other Borrowings [Line Items]
Balance		$ 15,552	$ 19,947	$ 22,471
Rate		4.43%	4.22%	4.26%
Average Balance		$ 14,783	$ 20,509	$ 15,637
Rate		4.47%	4.59%	4.74%
Maximum Outstanding At Any Month End		$ 16,529	$ 24,139	$ 22,471
Subsidiaries [Member] | BOKF, NA [Member] | Other [Member]
Other Borrowings [Line Items]
Balance		$ 3,631	$ 14,950	$ 15,292
Rate		4.80%	2.61%	2.66%
Average Balance		$ 11,856	$ 15,382	$ 15,670
Rate		4.45%	2.38%	2.41%
Maximum Outstanding At Any Month End		$ 15,096	$ 15,506	$ 15,797
Subsidiaries [Member] | BOKF, NA [Member] | Subordinated debentures [Member]
Other Borrowings [Line Items]
Balance		$ 0	$ 0	$ 0
Rate		0.00%	0.00%	0.00%
Average Balance		$ 0	$ 0	$ 140,414
Rate		0.00%	0.00%	1.35%
Maximum Outstanding At Any Month End		$ 0	$ 0	$ 226,434
Subsidiaries [Member] | BOKF, NA [Member] | Subordinated debentures, 2007 issuance [Member]
Other borrowings, Other Disclosures [Abstract]
Amount of debt issuance				$ 250,000
Maturity date				May 15, 2017
Interest rate description				fixed rate of 5.75% through May 14, 2012 and is based on a floating rate of three-month LIBOR plus 0.69% thereafter
Subsidiaries [Member] | BOK Financial Securities, Inc. [Member] | Other [Member]
Other Borrowings [Line Items]
Balance		$ 0
[1]	BOK Financial maintains control over the securities underlying overnight repurchase agreements and generally transfers control over securities underlying longer-term dealer repurchase agreements to the respective counterparty.

Federal and State Income Taxe_2

Federal and State Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets [Abstract]
Available for sale securities mark to market	$ 24,441	$ 12,083
Share-based compensation	4,434	7,598
Credit loss allowances	49,804	58,666
Valuation adjustments	9,619	8,102
Deferred compensation	25,608	12,215
Unearned fees	9,814	9,265
Purchased loan discount	27,283	0
Other	31,812	30,859
Total deferred tax assets	182,815	138,788
Valuation Allowance [Abstract]
Valuation allowance	0	0
Deferred tax liabilities [Abstract]
Depreciation	13,901	15,817
Mortgage servicing rights	61,844	63,112
Lease financing	10,040	9,973
Acquired identifiable intangible	28,620	0
Other	32,954	34,880
Total deferred tax liabilities	147,359	123,782
Net deferred tax assets	35,456	15,006
Current income tax expense [Abstract]
Federal	103,748	141,607	$ 107,379
State	15,253	14,592	11,028
Total current income tax expense	119,001	156,199	118,407
Deferred income tax expense [Abstract]
Federal	(190)	25,525	(11,340)
State	250	869	(690)
Total deferred income tax expense	60	26,394	(12,030)
Federal and state income taxes	119,061	182,593	106,377
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Federal statutory tax	118,752	181,397	118,530
Tax exempt revenue	(8,311)	(12,402)	(10,544)
Effect of state income taxes, net of federal benefit	12,430	10,701	6,478
Utilization of tax credits, net of proportional amortization of low-income housing limited partnership investments	4,559	6,811	6,256
Share-based compensation	(2,105)	(2,817)	0
Implementation of Tax Reform Act	(1,728)	11,672	0
Deposit insurance	3,099	0	0
Other, net	1,483	853	(1,831)
Federal and state income taxes	$ 119,061	$ 182,593	$ 106,377
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory tax (in thousandths)	21.00%	35.00%	35.00%
Tax exempt revenue (in thousandths)	(1.50%)	(2.40%)	(3.10%)
Effect of state income taxes, net of federal benefit (in thousandths)	2.20%	2.00%	1.90%
Utilization of tax credits, net of proportional amortization of low-income housing limited partnership investments (in thousandths)	0.80%	1.30%	1.80%
Share-based compensation (in thousandths)	(0.40%)	(0.50%)	0.00%
Implementation of Tax Reform Act (in thousandths)	(0.30%)	2.30%	0.00%
Deposit insurance (in thousandths)	0.50%	0.00%	0.00%
Other, net (in thousandths)	0.40%	0.10%	(0.60%)
Total (in thousandths)	21.10%	35.20%	31.40%
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of January 1	$ 18,110	$ 15,841	$ 13,232
Additions for tax for current year positions	2,649	4,645	5,640
Settlements during the period	0	0	0
Lapses of applicable statute of limitations	(1,890)	(2,376)	(3,031)
Balance as of December 31	18,869	18,110	15,841
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	12,900
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	1,700	1,200	$ 1,000
Unrecognized Tax Benefits, Penalties and Interest Accrued	$ 5,000	$ 4,000
Unrecognized Tax Benefits, Number of Reporting Periods Open for Examination, Federal	3
Unrecognized Tax Benefits, Number of Reporting Periods Open for Examination, State, Minimum	3
Unrecognized Tax Benefits, Number of Reporting Periods Open for Examination, State, Maximum	6

Employee Benefits (Details)

Employee Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest percentage added to the five-year trailing average of five-year Treasury Securities	1.50%
Interest percentage accrued on employee account balances, Minimum	3.00%
Interest percentage accrued on employee account balances, Maximum	5.00%
Quarterly variable interest percentage accrued on employee account balances, minimum	3.00%
Quarterly variable interest percentage accrued on employee account balances, maximum	3.24%
Change in projected benefit obligation [Roll Forward]
Projected benefit obligation at beginning of year	$ 30,897,000	[1],[2]	$ 34,964,000
Interest cost	973,000		1,153,000
Actuarial loss (gain)	(1,417,000)		223,000
Benefits paid	(6,033,000)		(5,443,000)
Projected benefit obligation at end of year	24,547,000	[1],[2]	30,897,000	[1],[2]	$ 34,964,000
Change in plan assets [Roll Forward]
Plan assets at fair value at beginning of year	40,419,000		41,769,000
Actual return on plan assets	(804,000)		4,093,000
Benefits paid	(6,033,000)		(5,443,000)
Plan assets at fair value at end of year	33,582,000		40,419,000		41,769,000
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Funded status of the plan	9,035,000		9,522,000
Components of net periodic benefit costs [Abstract]
Interest cost	973,000		1,153,000
Expected return on plan assets	(2,065,000)		(2,041,000)
Other	509,000		184,000
Net periodic benefit cost (credit)	$ (583,000)		$ (704,000)
Weighted-average assumptions [Abstract]
Discount rate (in hundredths)	4.10%		3.30%
Expected return on plan assets (in hundredths)	5.50%		5.50%
Estimated Future Benefit Payments [Abstract]
2,019	$ 3,562,000
2,020	2,257,000
2,021	2,194,000
2,022	2,299,000
2,023	2,495,000
Thereafter	19,175,000
Total estimated future benefit payments	31,982,000
Defined Benefit Plan, Information about Plan Assets [Abstract]
Maximum tax deductible contributions to defined benefit plan	$ 6,600,000
Thrift Plan - Defined Contribution [Abstract]
Employee base compensation company match employee contributions (in hundredths)	6.00%
Employer matching rate for employee contributions minimum (in hundredths)	50.00%
Minimum years of service for employees to obtain maximum employer matching (in years)	4 years
Employer matching rate for employee contributions maximum (in hundredths)	200.00%
Maximum years of service for employees to obtain minimum employer matching (in years)	15 years
Non-elective annual contribution for qualified employees	$ 750
Annual base employee compensation to qualify for non-elective employer contributions maximum	$ 40,000
Vesting period for employer contributions (in years)	5 years
Thrift Plan expenses	$ 25,100,000		$ 22,800,000		$ 22,400,000
Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	60.00%
Bonds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	40.00%
[1]	Projected benefit obligation equals accumulated benefit obligation.
[2]	Projected benefit obligation is based on January 1 measurement date.

Share-Based Compensation Plan_2

Share-Based Compensation Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock Options [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Outstanding, Number of Options [Abstract]
Number of options outstanding, Ending balance (in shares)	63,058	117,551	218,524
Options shares vested (in shares)	33,573	51,286	93,117
Share-based Compensation Arrangements by Share-based Payment Award, Options, Weighted Average Exercise Price [Abstract]
Options outstanding, weighted average exercise price, ending balance (in dollars per share)	$ 54.89	$ 53.26	$ 51.95
Options vested, weighted average exercise price (in dollars per share)	$ 53.09	$ 48.62	$ 46.22
Share-based Compensation Arrangements by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options outstanding, aggregate intrinsic value	$ 1,163	$ 4,592	$ 6,793
Options vested, aggregate intrinsic value	679	2,241	3,429
Options exercised, aggregate intrinsic value	$ 2,300	$ 3,500	$ 6,200
Weighted average remaining contractual life of options outstanding (in years)	2 years 1 month 13 days
Weighted average remaining contractual life of options vested (in years)	1 year 14 days
Non-vested Common Stock [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Restricted Stock, Nonvested, Number of Shares [Roll Forward]
Non-vested common shares awarded, beginning of period (in shares)	667,103	786,706	791,109
Non-vested shares that were granted during the period (in shares)	150,419	177,807	256,670
Non-vested shares that vested during period (in shares)	(242,215)	(194,419)	(213,941)
Non-vested shares that forfeited during period (in shares)	(47,700)	(102,991)	(47,132)
Non-vested common shares awarded, end of period (in shares)	527,607	667,103	786,706
Share-based Compensation Arrangements by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted Average Grant Date Fair Value, Granted	$ 85.58	$ 86.95	$ 55.35
Weighted Average Grant Date Fair Value, Vested	74.85	63.07	55.87
Weighted average grant date fair value non-vested stock awards forfeited (in dollars per share)	$ 75.68	$ 78.70	$ 57.86
Share-based Compensation Costs, Including Costs That May Be Recognized As Future Expense [Abstract]
Share-based Compensation Expense Recognized	$ 3,600	$ 23,200	$ 10,200
Unrecognized compensation cost of unvested awards, for future periods	14,200
Unrecognized compensation cost of unvested awards, Amount to be expensed in 2019	9,700
Unrecognized compensation cost of unvested awards, Amount to be expensed in 2020	4,300
Unrecognized compensation cost of unvested awards, Amount to be expensed in 2021	$ 138
Total shares awarded under executive incentive plan (in shares)	189,179
Number of shares with required performance obligations	188,827

Related Parties Related Parti_2

Related Parties Related Parties (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loans and Leases Receivable, Related Parties [Roll Forward]
Lease payments on office space in facilities owned by related party afffiliates		$ 28,500	$ 27,500	$ 25,800
Commercial [Member] | Manufacturing [Member]
Loans and Leases Receivable, Related Parties [Roll Forward]
Impaired Affiliated Loans		4,700
Directors and Senior Management [Member]
Loans and Leases Receivable, Related Parties [Roll Forward]
Beginning balance		110,246	136,945
Advances		1,479,735	1,559,291
Payments		(1,514,841)	(1,585,865)
Adjustments	[1]	125	(125)
Ending balance		75,265	110,246	136,945
Board of Directors Chairman [Member]
Loans and Leases Receivable, Related Parties [Roll Forward]
Lease payments on office space in facilities owned by related party afffiliates		683	1,000	$ 1,100
Related Party Transaction, Amounts of Transaction		3,100	580
Director [Member]
Loans and Leases Receivable, Related Parties [Roll Forward]
Related Party Transaction, Expenses from Transactions with Related Party		$ 9,200
Executive Officer [Member]
Loans and Leases Receivable, Related Parties [Roll Forward]
Percentage of investment funds' assets held by clients		89.00%
Assets Held in Cavanal Hill Funds		$ 3,400,000
Subsidiaries [Member] | BOKF, NA [Member] | Affiliated Entity [Member]
Loan Commitments and Equity Investments [Abstract]
Maximum percentage of unimpaired capital on loan commitments and equity investments to a single affiliate (in hundredths)		10.00%
Maximum percentage of unimpaired capital on loan commitments and equity investments to all affiliates (in hundredths)		20.00%
Maximum loan commitments and equity investments to a single affiliate		$ 310,000
Maximum loan commitments and equity investments to all affiliates		621,000
Largest loan commitment and equity investment to a single affiliate		253,000
Aggregate loan commitment and equity investment to all affiliates		313,000	323,000
Outstanding amounts to all affiliates		883	$ 16,000
Largest amount outstanding to a single affiliate		$ 883
[1]	Adjustments generally consist of changes in status as a related party.

Commitments and Contingent Li_3

Commitments and Contingent Liabilities (Details)	12 Months Ended
	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Other Commitments [Abstract]
The Net Asset Value of Units in Mutual Funds (per unit)	1
Minimum Average Cash Balance Required to be Maintained at Federal Reserve by Subsidiary Bank	$ 1,200,000,000	$ 1,900,000,000
Operating Leases, Rent Expense, Net [Abstract]
Operating Leases, Rent Expense, Net	28,500,000	$ 27,500,000	$ 25,800,000
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating Leases, Future Minimum Payments, Due in 2019	25,800,000
Operating Leases, Future Minimum Payments, Due in 2020	24,800,000
Operating Leases, Future Minimum Payments, Due in 2021	21,300,000
Operating Leases, Future Minimum Payments, Due in 2022	15,200,000
Operating Leases, Future Minimum Payments, Due in 2023	13,000,000
Operating Leases, Future Minimum Payments, Due Thereafter	$ 78,600,000
Visa Membership [Member]
Loss Contingencies [Line Items]
Number of Visa Class B Shares Owned by Entity (in shares) | shares	252,233
Number of Visa Class A Shares Visa Class B Shares Are Convertible To (in shares) | shares	411,089
Misuse of Revenues Pledged to Municipal Bonds [Member] | Judicial Ruling [Member]
Litigation Settlement [Abstract]
Outstanding principal, accrued interest and other amounts required by bond documents	$ 40,000,000
Disgorged fees	1,067,721
Litigation Settlement, Expense	$ 600,000
Misuse of Revenues Pledged to Municipal Bonds [Member] | Pending Litigation [Member]
Litigation Settlement [Abstract]
Loss Contingency, Number of Plaintiffs	2
Alleged total of judgment against nursing home operator	$ 8,000,000
Bank Participation in Fraudulent Sale of Securities by Principals [Member] | Pending Litigation [Member]
Litigation Settlement [Abstract]
Loss Contingency, Number of Plaintiffs	19
Purchase of facilities from principals subject to SEC New Jersey proceedings [Member] | Pending Litigation [Member]
Litigation Settlement [Abstract]
Outstanding principal, accrued interest and other amounts required by bond documents	$ 60,000,000
Number of individuals who purchased facilities from the principals subject to SEC New Jersey proceedings	2
Number of principals in SEC New Jersey proceedings	2

Commitments and Contingent Li_4

Commitments and Contingent Liabilities Variable Interest Entities (Details) $ in Thousands	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
BOKF Equity, LLC [Member]
Variable Interest Entity [Line Items]
Number of Private Equity Funds of which the Entity is a General Partner	2
Loans [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	$ 0	$ 10,000
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	58,981	52,852
Other Assets [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	27,118	26,787
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	227,973	191,903
Other Liabilities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	1,448	0
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	73,885	70,827
Other Borrowings [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	5,207	10,964
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Non-Controlling Interests [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	10,936	22,967
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Private equity funds [Member] | Loans [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Private equity funds [Member] | Other Assets [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	9,516	14,783
Private equity funds [Member] | Other Liabilities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Private equity funds [Member] | Other Borrowings [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Private equity funds [Member] | Non-Controlling Interests [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	8,644	11,927
Tax credit entities [Member] | Loans [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	0	10,000
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	58,981	52,852
Tax credit entities [Member] | Other Assets [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	0	10,964
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	165,567	153,506
Tax credit entities [Member] | Other Liabilities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	53,198	47,859
Tax credit entities [Member] | Other Borrowings [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	0	10,964
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Tax credit entities [Member] | Non-Controlling Interests [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	0	10,000
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Other [Member] | Loans [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Other [Member] | Other Assets [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	17,602	1,040
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	62,406	38,397
Other [Member] | Other Liabilities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	1,448	0
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	20,687	22,968
Other [Member] | Other Borrowings [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	5,207	0
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Other [Member] | Non-Controlling Interests [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	2,292	1,040
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	$ 0	$ 0

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator: [Abstract]:
Net income attributable to BOK Financial Corp. shareholders			$ 445,646	$ 334,644	$ 232,668
Less: Earnings allocated to participating securities			3,737	3,561	2,883
Numerator for basic earnings per share - income available to common shareholders			441,909	331,083	229,785
Effect of reallocating undistributed earnings of participating securities			1	2	1
Numerator for diluted earnings per share - income available to common shareholders			$ 441,910	$ 331,085	$ 229,786
Denominator: [Abstract]
Weighted average shares outstanding			67,190,257	65,440,832	65,901,110
Less: Participating securities included in weighted average shares outstanding (in shares)			561,617	695,468	815,483
Denominator for basic earnings per common share (in shares)			66,628,640	64,745,364	65,085,627
Dilutive effect of employee stock compensation plans (in shares)			33,633	60,920	58,271
Denominator for diluted earnings per common share (in shares)			66,662,273	64,806,284	65,143,898
Basic (in dollars per share)	$ 1.50	$ 1.11	$ 6.63	$ 5.11	$ 3.53
Diluted earnings per share (per share)	$ 1.50	$ 1.11	$ 6.63	$ 5.11	$ 3.53
Excludes employee stock options with exercise prices greater than current market price.			0	0	0

Shareholders' Equity (Details)

Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock [Abstract]
Common stock, shares authorized (in shares)	2,500,000,000	2,500,000,000
Common stock, par value (in dollars per share)	$ 0.00006	$ 0.00006
Perpetual preferred stock [Member]
Preferred Stock [Abstract]
Preferred stock, authorized (in shares)	1,000,000,000
Preferred stock at par value (in dollars per share)	$ 0.00005
Preferred stock conversion rate	one share of Common Stock for each 36 shares of Series A Preferred Stock at the option of the holder
Preferred stock, Rate of annual cumulative dividends (in hundredths)	10.00%
Preferred stock, Liquidation preference per share	$ 0.06
Preferred stock, Aggregate liquidation preference	$ 15
Preferred Stock, Shares Outstanding	0	0	0
Common Stock [Member]
Common Stock [Abstract]
Common stock, shares authorized (in shares)	2,500,000,000
Common stock, par value (in dollars per share)	$ 0.00006
Common stock, number of vote per share	$ 1

Shareholders' Equity Regulatory

Shareholders' Equity Regulatory Capital (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Common Equity Tier 1 Capital [Abstract]
Minimum Capital Requirements, Common Equity Tier 1 to Risk Weighted Assets		4.50%	4.50%
Capital Conservation Buffer, Common Equity Tier 1 to Risk Weighted Assets	[1]	2.50%	2.50%
Minimum Capital Requirement Including Capital Conservation Buffer, Common Equity Tier 1 to Risk Weighted Assets		7.00%	7.00%
Common Equity Tier 1 Capital		$ 3,356,524	$ 3,074,981
Common Equity Tier 1 Capital to Risk Weighted Assets		10.92%	12.05%
Tier I Capital (to Risk Weighted Assets) [Abstract]
Minimum Capital Requirement, Tier 1 Capital to Risk Weighted Assets		6.00%	6.00%
Capital Conservation Buffer, Tier 1 Capital to Risk Weighted Assets	[1]	2.50%	2.50%
Minimum Capital Requirement Including Capital Conservation Buffer, Tier One to Risk Weighted Assets		8.50%	8.50%
Tier 1 Capital		$ 3,356,524	$ 3,074,981
Tier 1 Capital to Risk Weighted Assets		10.92%	12.05%
Total Capital (to Risk Weighted Assets) [Abstract]
Minimum Capital Requirement, Total Capital to Risk Weighted Assets		8.00%	8.00%
Capital Conservation Buffer, Total Capital to Risk Weighted Assets	[1]	2.50%	2.50%
Minimum Capital Requirement Including Capital Conservation Buffer, Total Capital to Risk Weighted Assets		10.50%	10.50%
Total Capital		$ 3,841,684	$ 3,455,709
Total Capital to Risk Weighted Assets		12.50%	13.54%
Tier 1 Capital (to Average Assets) [Abstract]
Minimum Capital Requirement, Tier 1 Capital to Average Assets		4.00%	4.00%
Minimum Capital Requirements Including Capital Conservation Buffer, Tier 1 Capital to Average Assets		4.00%	4.00%
Tier 1 Leverage Capital		$ 3,356,524	$ 3,074,981
Tier 1 Capital to Average Assets		8.96%	9.31%
Phased in Capital Conservation Buffer		1.875%	1.25%
Fully Phased In Capital Conservation Buffer		2.50%
Subsidiaries [Member] | BOKF, NA [Member]
Common Equity Tier 1 Capital [Abstract]
Common Equity Tier 1 Capital Ratio Required to be Well Capitalized		6.50%	6.50%
Minimum Capital Requirements, Common Equity Tier 1 to Risk Weighted Assets		4.50%	4.50%
Minimum Capital Requirement Including Capital Conservation Buffer, Common Equity Tier 1 to Risk Weighted Assets		4.50%	4.50%
Common Equity Tier 1 Capital		$ 2,894,119	$ 2,870,694
Common Equity Tier 1 Capital to Risk Weighted Assets		10.50%	11.34%
Tier I Capital (to Risk Weighted Assets) [Abstract]
Tier I Capital Ratio Required to be Well Capitalized		8.00%	8.00%
Minimum Capital Requirement, Tier 1 Capital to Risk Weighted Assets		6.00%	6.00%
Minimum Capital Requirement Including Capital Conservation Buffer, Tier One to Risk Weighted Assets		6.00%	6.00%
Tier 1 Capital		$ 2,894,119	$ 2,870,694
Tier 1 Capital to Risk Weighted Assets		10.50%	11.34%
Total Capital (to Risk Weighted Assets) [Abstract]
Total Capital Ratio Required to be Well Capitalized		10.00%	10.00%
Minimum Capital Requirement, Total Capital to Risk Weighted Assets		8.00%	8.00%
Minimum Capital Requirement Including Capital Conservation Buffer, Total Capital to Risk Weighted Assets		8.00%	8.00%
Total Capital		$ 3,103,366	$ 3,105,117
Total Capital to Risk Weighted Assets		11.26%	12.27%
Tier 1 Capital (to Average Assets) [Abstract]
Leverage Ratio Required to be Well Capitalized		5.00%	5.00%
Minimum Capital Requirement, Tier 1 Capital to Average Assets		4.00%	4.00%
Minimum Capital Requirements Including Capital Conservation Buffer, Tier 1 Capital to Average Assets		4.00%	4.00%
Tier 1 Leverage Capital		$ 2,894,119	$ 2,870,694
Tier 1 Capital to Average Assets		8.56%	8.73%
Subsidiaries [Member] | CoBiz [Member]
Common Equity Tier 1 Capital [Abstract]
Common Equity Tier 1 Capital Ratio Required to be Well Capitalized	[2]	6.50%	6.50%
Minimum Capital Requirements, Common Equity Tier 1 to Risk Weighted Assets	[2]	4.50%	4.50%
Minimum Capital Requirement Including Capital Conservation Buffer, Common Equity Tier 1 to Risk Weighted Assets	[2]	4.50%	4.50%
Common Equity Tier 1 Capital	[2]	$ 317,944	$ 399,768
Common Equity Tier 1 Capital to Risk Weighted Assets	[2]	10.65%	12.19%
Tier I Capital (to Risk Weighted Assets) [Abstract]
Tier I Capital Ratio Required to be Well Capitalized	[2]	8.00%	8.00%
Minimum Capital Requirement, Tier 1 Capital to Risk Weighted Assets	[2]	6.00%	6.00%
Minimum Capital Requirement Including Capital Conservation Buffer, Tier One to Risk Weighted Assets	[2]	6.00%	6.00%
Tier 1 Capital	[2]	$ 317,944	$ 399,768
Tier 1 Capital to Risk Weighted Assets	[2]	10.65%	12.19%
Total Capital (to Risk Weighted Assets) [Abstract]
Total Capital Ratio Required to be Well Capitalized	[2]	10.00%	10.00%
Minimum Capital Requirement, Total Capital to Risk Weighted Assets	[2]	8.00%	8.00%
Minimum Capital Requirement Including Capital Conservation Buffer, Total Capital to Risk Weighted Assets	[2]	8.00%	8.00%
Total Capital	[2]	$ 382,944	$ 434,012
Total Capital to Risk Weighted Assets	[2]	12.83%	13.23%
Tier 1 Capital (to Average Assets) [Abstract]
Leverage Ratio Required to be Well Capitalized	[2]	5.00%	5.00%
Minimum Capital Requirement, Tier 1 Capital to Average Assets	[2]	4.00%	4.00%
Minimum Capital Requirements Including Capital Conservation Buffer, Tier 1 Capital to Average Assets	[2]	4.00%	4.00%
Tier 1 Leverage Capital	[2]	$ 317,944	$ 399,768
Tier 1 Capital to Average Assets	[2]	8.25%	10.47%
[1]	Capital conservation buffer is effective January 1, 2016 and is phased in through 2019. The phased in capital conservation buffer was 1.875% at December 31, 2018 and 1.25% at December 31, 2017 . The fully phased in requirement of 2.50%
[2]	CoBiz Bank was acquired by BOK Financial effective October 1, 2018.

Shareholders' Equity Accumulate

Shareholders' Equity Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (36,174)		$ (10,967)		$ 21,587
Reclassification of stranded accumulated other comprehensive loss to retained earnings related to tax reform			(6,550)
Transition adjustment of net unrealized gains on equity securities	2,700		(2,709)
Net change in unrealized gain (loss)	(48,010)		(26,152)		(41,521)
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities, Taxable securities	0		0		(112)
Loss (gain) on available for sale securities, net	2,801		(4,428)		(11,675)
Other comprehensive income (loss), before income taxes	(45,209)		(30,580)		(53,308)
Federal and state income taxes	(11,507)	[1]	(11,923)	[2]	(20,754)	[2]
Other comprehensive income (loss), net of income taxes	(33,702)		(18,657)		(32,554)
Ending balance	(72,585)		(36,174)		(10,967)
Unrealized Gain (Loss) on Available for Sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(35,385)		(9,087)		23,284
Reclassification of stranded accumulated other comprehensive loss to retained earnings related to tax reform			(6,408)
Transition adjustment of net unrealized gains on equity securities			(2,709)
Net change in unrealized gain (loss)	(46,941)		(28,170)		(41,333)
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities, Taxable securities	0		0		0
Loss (gain) on available for sale securities, net	2,801		(4,428)		(11,675)
Other comprehensive income (loss), before income taxes	(44,140)		(32,598)		(53,008)
Federal and state income taxes	(11,235)	[1]	(12,708)	[2]	(20,637)	[2]
Other comprehensive income (loss), net of income taxes	(32,905)		(19,890)		(32,371)
Ending balance	(70,999)		(35,385)		(9,087)
Unrealized Gain (Loss) on Investment Securities Transferred from AFS [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0		0		68
Reclassification of stranded accumulated other comprehensive loss to retained earnings related to tax reform			0
Transition adjustment of net unrealized gains on equity securities			0
Net change in unrealized gain (loss)	0		0		0
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities, Taxable securities	0		0		(112)
Loss (gain) on available for sale securities, net	0		0		0
Other comprehensive income (loss), before income taxes	0		0		(112)
Federal and state income taxes	0	[1]	0	[2]	(44)	[2]
Other comprehensive income (loss), net of income taxes	0		0		(68)
Ending balance	0		0		0
Unrealized Gain (Loss) on Employee Benefit Plans [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(789)		(1,880)		(1,765)
Reclassification of stranded accumulated other comprehensive loss to retained earnings related to tax reform			(142)
Transition adjustment of net unrealized gains on equity securities			0
Net change in unrealized gain (loss)	(1,069)		2,018		(188)
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities, Taxable securities	0		0		0
Loss (gain) on available for sale securities, net	0		0		0
Other comprehensive income (loss), before income taxes	(1,069)		2,018		(188)
Federal and state income taxes	(272)	[1]	785	[2]	(73)	[2]
Other comprehensive income (loss), net of income taxes	(797)		1,233		(115)
Ending balance	$ (1,586)		$ (789)		$ (1,880)
[1]	Calculated using a 25 percent blended federal and state statutory tax rate.
[2]	Calculated using a 39 percent blended federal and state statutory tax rate.

Reportable Segments (Details)

Reportable Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net interest and dividend revenue from external sources	$ 984,867	$ 841,701	$ 747,228
Net interest revenue (expense) from internal sources	0	0	0
Net interest and dividend revenue	984,867	841,701	747,228
Provision for credit losses	8,000	(7,000)	65,000
Net interest and dividend revenue after provision for credit losses	976,867	848,701	682,228
Other operating revenue	616,784	695,094	674,020
Other operating expense	1,028,166	1,025,517	1,017,590
Net direct contribution	565,485	518,278	338,658
Gain (loss) on financial instruments, net	0	0	0
Change in fair value of mortgage servicing rights	0	0	0
Gain (loss) on repossessed assets, net	0	0	0
Corporate expense allocations	0	0	0
Net income before taxes	565,485	518,278	338,658
Federal and state income taxes	119,061	182,593	106,377
Net income	446,424	335,685	232,281
Net income (loss) attributable to non-controlling interests	778	1,041	(387)
Net income attributable to BOK Financial Corp. shareholders	445,646	334,644	232,668
Average assets	34,937,530	32,947,494	32,278,402
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net interest and dividend revenue from external sources	726,856	618,325	501,042
Net interest revenue (expense) from internal sources	(156,254)	(89,106)	(62,655)
Net interest and dividend revenue	570,602	529,219	438,387
Provision for credit losses	30,358	13,877	32,961
Net interest and dividend revenue after provision for credit losses	540,244	515,342	405,426
Other operating revenue	162,701	208,404	198,902
Other operating expense	192,811	228,119	217,993
Net direct contribution	510,134	495,627	386,335
Gain (loss) on financial instruments, net	26	52	10
Change in fair value of mortgage servicing rights	0	0	0
Gain (loss) on repossessed assets, net	(6,532)	(2,681)	669
Corporate expense allocations	45,818	34,253	36,134
Net income before taxes	457,810	458,745	350,880
Federal and state income taxes	121,434	188,241	146,740
Net income	336,376	270,504	204,140
Net income (loss) attributable to non-controlling interests	0	0	0
Net income attributable to BOK Financial Corp. shareholders	336,376	270,504	204,140
Average assets	18,431,411	17,730,654	17,175,325
Operating Segments [Member] | Consumer [Member]
Segment Reporting Information [Line Items]
Net interest and dividend revenue from external sources	83,231	84,286	77,283
Net interest revenue (expense) from internal sources	73,448	53,916	43,156
Net interest and dividend revenue	156,679	138,202	120,439
Provision for credit losses	5,143	4,786	4,925
Net interest and dividend revenue after provision for credit losses	151,536	133,416	115,514
Other operating revenue	178,123	184,878	216,285
Other operating expense	210,187	221,679	247,478
Net direct contribution	119,472	96,615	84,321
Gain (loss) on financial instruments, net	(25,021)	(2,054)	(26,252)
Change in fair value of mortgage servicing rights	4,668	172	(2,193)
Gain (loss) on repossessed assets, net	247	223	979
Corporate expense allocations	63,700	67,320	65,567
Net income before taxes	35,666	27,636	(8,712)
Federal and state income taxes	9,085	10,750	(3,389)
Net income	26,581	16,886	(5,323)
Net income (loss) attributable to non-controlling interests	0	0	0
Net income attributable to BOK Financial Corp. shareholders	26,581	16,886	(5,323)
Average assets	8,303,262	8,544,117	8,254,666
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest and dividend revenue from external sources	81,527	45,024	33,006
Net interest revenue (expense) from internal sources	31,505	38,344	29,043
Net interest and dividend revenue	113,032	83,368	62,049
Provision for credit losses	(288)	(696)	(801)
Net interest and dividend revenue after provision for credit losses	113,320	84,064	62,850
Other operating revenue	296,369	301,434	283,222
Other operating expense	248,959	246,626	250,995
Net direct contribution	160,730	138,872	95,077
Gain (loss) on financial instruments, net	7	0	(42)
Change in fair value of mortgage servicing rights	0	0	0
Gain (loss) on repossessed assets, net	0	387	0
Corporate expense allocations	44,190	40,562	42,378
Net income before taxes	116,547	98,697	52,657
Federal and state income taxes	30,003	38,848	20,976
Net income	86,544	59,849	31,681
Net income (loss) attributable to non-controlling interests	0	0	0
Net income attributable to BOK Financial Corp. shareholders	86,544	59,849	31,681
Average assets	8,446,006	7,072,622	7,373,080
Funds Management and Other [Member]
Segment Reporting Information [Line Items]
Net interest and dividend revenue from external sources	93,253	94,066	135,897
Net interest revenue (expense) from internal sources	51,301	(3,154)	(9,544)
Net interest and dividend revenue	144,554	90,912	126,353
Provision for credit losses	(27,213)	(24,967)	27,915
Net interest and dividend revenue after provision for credit losses	171,767	115,879	98,438
Other operating revenue	(20,409)	378	(24,389)
Other operating expense	376,209	329,093	301,124
Net direct contribution	(224,851)	(212,836)	(227,075)
Gain (loss) on financial instruments, net	24,988	2,002	26,284
Change in fair value of mortgage servicing rights	(4,668)	(172)	2,193
Gain (loss) on repossessed assets, net	6,285	2,071	(1,648)
Corporate expense allocations	(153,708)	(142,135)	(144,079)
Net income before taxes	(44,538)	(66,800)	(56,167)
Federal and state income taxes	(41,461)	(55,246)	(57,950)
Net income	(3,077)	(11,554)	1,783
Net income (loss) attributable to non-controlling interests	778	1,041	(387)
Net income attributable to BOK Financial Corp. shareholders	(3,855)	(12,595)	2,170
Average assets	$ (243,149)	$ (399,899)	$ (524,669)

Fees and Commission Revenue F_2

Fees and Commission Revenue Fees and Commissions (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		$ 643,642	$ 681,235	$ 685,831
Fees and commissions revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		643,642
Fees and commissions revenue not from contracts with customers	[1]	209,384
Fees and commissions revenue from contracts with customers	[2]	434,258
Brokerage and trading revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		108,323	131,601	138,377
Fees and commissions revenue not from contracts with customers	[1]	73,291
Fees and commissions revenue from contracts with customers	[2]	35,032
Trading Revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		28,077
Fees and commissions revenue not from contracts with customers	[1]	28,077
Fees and commissions revenue from contracts with customers	[2]	0
Customer hedging revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		38,834
Fees and commissions revenue not from contracts with customers	[1]	38,834
Fees and commissions revenue from contracts with customers	[2]	0
Retail brokerage revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		22,150
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	22,150
Investment banking revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		19,262
Fees and commissions revenue not from contracts with customers	[1]	6,380
Fees and commissions revenue from contracts with customers	[2]	12,882
Transaction card revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		84,025	119,988	116,452
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	84,025
TransFund EFT network revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		76,221
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	76,221
Merchant services revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		7,804
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	7,804
Fiduciary and asset management revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		184,703	162,889	135,387
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	184,703
Personal trust revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		96,839
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	96,839
Corporate trust revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		22,292
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	22,292
Institutional trust & retirement plan services revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		44,400
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	44,400
Investment management services and other [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		21,172
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	21,172
Deposit service charges and fees [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		112,153	112,079	111,589
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	112,153
Commercial account service charge revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		47,272
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	47,272
Overdraft fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		36,536
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	36,536
Check card fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		21,306
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	21,306
Automated service charge and other deposit fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		7,039
Fees and commissions revenue not from contracts with customers	[1]	0
Fees and commissions revenue from contracts with customers	[2]	7,039
Mortgage banking revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		97,787	104,719	133,914
Fees and commissions revenue not from contracts with customers	[1]	97,787
Fees and commissions revenue from contracts with customers	[2]	0
Mortgage production revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		31,690
Fees and commissions revenue not from contracts with customers	[1]	31,690
Fees and commissions revenue from contracts with customers	[2]	0
Mortgage servicing revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		66,097
Fees and commissions revenue not from contracts with customers	[1]	66,097
Fees and commissions revenue from contracts with customers	[2]	0
Other revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		56,651	$ 49,959	$ 50,112
Fees and commissions revenue not from contracts with customers	[1]	38,306
Fees and commissions revenue from contracts with customers	[2]	18,345
Operating Segments [Member] | Commercial [Member] | Fees and commissions revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		161,949
Operating Segments [Member] | Commercial [Member] | Brokerage and trading revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		15,376
Operating Segments [Member] | Commercial [Member] | Trading Revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Commercial [Member] | Customer hedging revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		7,748
Operating Segments [Member] | Commercial [Member] | Retail brokerage revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Commercial [Member] | Investment banking revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		7,628
Operating Segments [Member] | Commercial [Member] | Transaction card revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		79,946
Operating Segments [Member] | Commercial [Member] | TransFund EFT network revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		72,280
Operating Segments [Member] | Commercial [Member] | Merchant services revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		7,666
Operating Segments [Member] | Commercial [Member] | Fiduciary and asset management revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Commercial [Member] | Personal trust revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Commercial [Member] | Corporate trust revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Commercial [Member] | Institutional trust & retirement plan services revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Commercial [Member] | Investment management services and other [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Commercial [Member] | Deposit service charges and fees [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		42,583
Operating Segments [Member] | Commercial [Member] | Commercial account service charge revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		41,931
Operating Segments [Member] | Commercial [Member] | Overdraft fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		370
Operating Segments [Member] | Commercial [Member] | Check card fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Commercial [Member] | Automated service charge and other deposit fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		282
Operating Segments [Member] | Commercial [Member] | Mortgage banking revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Commercial [Member] | Mortgage production revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Commercial [Member] | Mortgage servicing revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Commercial [Member] | Other revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		24,044
Operating Segments [Member] | Consumer [Member] | Fees and commissions revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		178,174
Operating Segments [Member] | Consumer [Member] | Brokerage and trading revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Consumer [Member] | Trading Revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Consumer [Member] | Customer hedging revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Consumer [Member] | Retail brokerage revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Consumer [Member] | Investment banking revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Consumer [Member] | Transaction card revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		4,076
Operating Segments [Member] | Consumer [Member] | TransFund EFT network revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		4,017
Operating Segments [Member] | Consumer [Member] | Merchant services revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		59
Operating Segments [Member] | Consumer [Member] | Fiduciary and asset management revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Consumer [Member] | Personal trust revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Consumer [Member] | Corporate trust revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Consumer [Member] | Institutional trust & retirement plan services revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Consumer [Member] | Investment management services and other [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Consumer [Member] | Deposit service charges and fees [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		65,210
Operating Segments [Member] | Consumer [Member] | Commercial account service charge revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		1,445
Operating Segments [Member] | Consumer [Member] | Overdraft fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		36,177
Operating Segments [Member] | Consumer [Member] | Check card fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		20,967
Operating Segments [Member] | Consumer [Member] | Automated service charge and other deposit fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		6,621
Operating Segments [Member] | Consumer [Member] | Mortgage banking revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		99,670
Operating Segments [Member] | Consumer [Member] | Mortgage production revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		31,690
Operating Segments [Member] | Consumer [Member] | Mortgage servicing revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		67,980
Operating Segments [Member] | Consumer [Member] | Other revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		9,218
Operating Segments [Member] | Wealth Management [Member] | Fees and commissions revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		296,465
Operating Segments [Member] | Wealth Management [Member] | Brokerage and trading revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		86,253
Operating Segments [Member] | Wealth Management [Member] | Trading Revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		28,077
Operating Segments [Member] | Wealth Management [Member] | Customer hedging revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		27,512
Operating Segments [Member] | Wealth Management [Member] | Retail brokerage revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		19,030
Operating Segments [Member] | Wealth Management [Member] | Investment banking revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		11,634
Operating Segments [Member] | Wealth Management [Member] | Transaction card revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		(82)
Operating Segments [Member] | Wealth Management [Member] | TransFund EFT network revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		(82)
Operating Segments [Member] | Wealth Management [Member] | Merchant services revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Wealth Management [Member] | Fiduciary and asset management revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		183,260
Operating Segments [Member] | Wealth Management [Member] | Personal trust revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		96,839
Operating Segments [Member] | Wealth Management [Member] | Corporate trust revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		22,292
Operating Segments [Member] | Wealth Management [Member] | Institutional trust & retirement plan services revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		44,400
Operating Segments [Member] | Wealth Management [Member] | Investment management services and other [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		19,729
Operating Segments [Member] | Wealth Management [Member] | Deposit service charges and fees [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		2,527
Operating Segments [Member] | Wealth Management [Member] | Commercial account service charge revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		2,331
Operating Segments [Member] | Wealth Management [Member] | Overdraft fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		134
Operating Segments [Member] | Wealth Management [Member] | Check card fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Wealth Management [Member] | Automated service charge and other deposit fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		62
Operating Segments [Member] | Wealth Management [Member] | Mortgage banking revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Wealth Management [Member] | Mortgage production revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Wealth Management [Member] | Mortgage servicing revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Operating Segments [Member] | Wealth Management [Member] | Other revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		24,507
Funds Management and Other [Member] | Fees and commissions revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		7,054
Funds Management and Other [Member] | Brokerage and trading revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		6,694
Funds Management and Other [Member] | Trading Revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Funds Management and Other [Member] | Customer hedging revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		3,574
Funds Management and Other [Member] | Retail brokerage revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		3,120
Funds Management and Other [Member] | Investment banking revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Funds Management and Other [Member] | Transaction card revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		85
Funds Management and Other [Member] | TransFund EFT network revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		6
Funds Management and Other [Member] | Merchant services revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		79
Funds Management and Other [Member] | Fiduciary and asset management revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		1,443
Funds Management and Other [Member] | Personal trust revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Funds Management and Other [Member] | Corporate trust revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Funds Management and Other [Member] | Institutional trust & retirement plan services revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Funds Management and Other [Member] | Investment management services and other [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		1,443
Funds Management and Other [Member] | Deposit service charges and fees [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		1,833
Funds Management and Other [Member] | Commercial account service charge revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		1,565
Funds Management and Other [Member] | Overdraft fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		(145)
Funds Management and Other [Member] | Check card fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		339
Funds Management and Other [Member] | Automated service charge and other deposit fee revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		74
Funds Management and Other [Member] | Mortgage banking revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		(1,883)
Funds Management and Other [Member] | Mortgage production revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		0
Funds Management and Other [Member] | Mortgage servicing revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		(1,883)
Funds Management and Other [Member] | Other revenue [Member]
Disaggregation of Revenue [Line Items]
Fess and commissions revenue		$ (1,118)
[1]	Out of scope revenue generally relates to financial instruments or contractual rights and obligations within the scope of other applicable accounting guidance.
[2]	In scope revenue represents revenue subject to FASB ASC Topic 606, Revenue from Contracts with Customers.

Fair Value Measurements, Fair V

Fair Value Measurements, Fair Value Of Financial Instruments as Measured On a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Assets [Abstract]
Trading securities	$ 1,956,923		$ 462,676
Available for sale securities	8,857,120		8,321,578
Fair value option securities	283,235		755,054
Mortgage servicing rights	259,254		252,867		$ 247,073	$ 218,605
Derivative contracts, net of cash margin, Assets, Fair Value	320,929		220,502
Liabilities [Abstract]
Derivative contracts, net of cash margin, Liabilities, Fair Value	362,306		171,963
U.S. government agency debentures [Member]
Assets [Abstract]
Trading securities	63,765		21,196
U.S. government agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	1,791,584		392,673
Available for sale securities	5,804,708		5,309,152
Fair value option securities	283,235		755,054
Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	34,507		13,559
Available for sale securities	2,864		27,080
Asset-backed securities [Member]
Assets [Abstract]
Trading securities	42,656		23,885
U.S. Treasury [Member]
Assets [Abstract]
Available for sale securities	493		1,000
Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	59,736		93,221
Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	2,953,889		2,834,961
Other debt securities [Member]
Assets [Abstract]
Available for sale securities	35,430		25,481
Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities			15,767
Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities			14,916
Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Trading securities	1,956,923		462,676
Available for sale securities	8,857,120		8,321,578
Residential mortgage loans held for sale	149,221		221,378
Mortgage servicing rights	259,254	[1]	252,867	[2]
Derivative contracts, net of cash margin, Assets, Fair Value	320,929	[3]	220,502	[4]
Liabilities [Abstract]
Derivative contracts, net of cash margin, Liabilities, Fair Value	362,306	[3]	171,963	[4]
Fair Value, Measurements, Recurring [Member] | U.S. government agency debentures [Member]
Assets [Abstract]
Trading securities	63,765		21,196
Fair Value, Measurements, Recurring [Member] | U.S. government agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	1,791,584		392,673
Available for sale securities	5,804,708		5,309,152
Fair value option securities	283,235		755,054
Fair Value, Measurements, Recurring [Member] | Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	34,507		13,559
Available for sale securities	2,864		27,080
Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member]
Assets [Abstract]
Trading securities	42,656		23,885
Fair Value, Measurements, Recurring [Member] | U.S. Treasury [Member]
Assets [Abstract]
Available for sale securities	493		1,000
Fair Value, Measurements, Recurring [Member] | Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	59,736		93,221
Fair Value, Measurements, Recurring [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	2,953,889		2,834,961
Fair Value, Measurements, Recurring [Member] | Other debt securities [Member]
Assets [Abstract]
Trading securities	24,411		11,363
Available for sale securities	35,430		25,481
Fair Value, Measurements, Recurring [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities			15,767
Fair Value, Measurements, Recurring [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities			14,916
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets [Abstract]
Trading securities	0		0
Available for sale securities	493		1,000
Residential mortgage loans held for sale	0		0
Mortgage servicing rights	0	[1]	0	[2]
Derivative contracts, net of cash margin, Assets, Fair Value	44,074	[3]	8,179	[4]
Liabilities [Abstract]
Derivative contracts, net of cash margin, Liabilities, Fair Value	0	[3]	0	[4]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. government agency debentures [Member]
Assets [Abstract]
Trading securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. government agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	0		0
Available for sale securities	0		0
Fair value option securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	0		0
Available for sale securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Asset-backed securities [Member]
Assets [Abstract]
Trading securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Treasury [Member]
Assets [Abstract]
Available for sale securities	493		1,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other debt securities [Member]
Assets [Abstract]
Trading securities	0		0
Available for sale securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities			0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities			0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets [Abstract]
Trading securities	1,956,923		462,676
Available for sale securities	8,856,155		8,315,304
Residential mortgage loans held for sale	134,014		209,079
Mortgage servicing rights	0	[1]	0	[2]
Derivative contracts, net of cash margin, Assets, Fair Value	276,855	[3]	212,323	[4]
Liabilities [Abstract]
Derivative contracts, net of cash margin, Liabilities, Fair Value	362,306	[3]	171,963	[4]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. government agency debentures [Member]
Assets [Abstract]
Trading securities	63,765		21,196
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. government agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	1,791,584		392,673
Available for sale securities	5,804,708		5,309,152
Fair value option securities	283,235		755,054
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	34,507		13,559
Available for sale securities	2,864		22,278
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Asset-backed securities [Member]
Assets [Abstract]
Trading securities	42,656		23,885
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Treasury [Member]
Assets [Abstract]
Available for sale securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	59,736		93,221
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	2,953,889		2,834,961
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other debt securities [Member]
Assets [Abstract]
Trading securities	24,411		11,363
Available for sale securities	34,958		25,009
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities			15,767
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities			14,916
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets [Abstract]
Trading securities	0		0
Available for sale securities	472		5,274
Residential mortgage loans held for sale	15,207		12,299
Mortgage servicing rights	259,254	[1]	252,867	[2]
Derivative contracts, net of cash margin, Assets, Fair Value	0	[3]	0	[4]
Liabilities [Abstract]
Derivative contracts, net of cash margin, Liabilities, Fair Value	0	[3]	0	[4]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. government agency debentures [Member]
Assets [Abstract]
Trading securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. government agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	0		0
Available for sale securities	0		0
Fair value option securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	0		0
Available for sale securities			4,802
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Asset-backed securities [Member]
Assets [Abstract]
Trading securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Treasury [Member]
Assets [Abstract]
Available for sale securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other debt securities [Member]
Assets [Abstract]
Trading securities	0		0
Available for sale securities	$ 472		472
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities			0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities			$ 0
[1]	A reconciliation of the beginning and ending fair value of mortgage servicing rights and disclosures of significant assumptions used to determine fair value are presented in Note 7 , Mortgage Banking Activities
[2]	A reconciliation of the beginning and ending fair value of mortgage servicing rights and disclosures of significant assumptions used to determine fair value are presented in Note 7
[3]	See Note 3 for detail of fair value of derivative contracts by contract type. Derivative contracts in a net asset position that were valued based on quoted prices in active markets or identical instruments (Level 1) are exchange-traded interest rate, energy and agricultural derivative contracts, net of cash margin. Derivative contracts in a net liability position that were valued using quoted prices in active markets for identical instruments (Level 1) are exchange-traded interest rate derivative contracts, fully offset by cash margin.
[4]	See Note 3

Fair Value Measurements, Measur

Fair Value Measurements, Measured On Recurring Basis Significant Unobservable Inputs (Details) - Fair Value, Measurements, Recurring [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Available for sale securities [Member] | Municipal and other tax-exempt securities [Member]
Fair Value Assets Measured on Recurring Basis Unobservable Reconciliation [Roll Forward]
Balance at beginning of period	$ 4,802	$ 5,789
Transfers to Level 3 from Level 2	0	0
Purchases and capital calls	0	0
Redemptions and distributions	(5,095)	(1,100)
Proceeds from sales	0	0
Other comprehensive income (loss)	293	113
Balance at end of period	0	4,802
Available for sale securities [Member] | Municipal and other tax-exempt securities [Member] | Mortgage banking revenue [Member]
Fair Value Assets Measured on Recurring Basis Unobservable Reconciliation [Roll Forward]
Gain (loss) recognized in earnings	0	0
Available for sale securities [Member] | Other debt securities [Member]
Fair Value Assets Measured on Recurring Basis Unobservable Reconciliation [Roll Forward]
Balance at beginning of period	472	4,152
Transfers to Level 3 from Level 2	0	0
Purchases and capital calls	0	0
Redemptions and distributions	0	0
Proceeds from sales	0	(3,900)
Other comprehensive income (loss)	0	220
Balance at end of period	472	472
Available for sale securities [Member] | Other debt securities [Member] | Mortgage banking revenue [Member]
Fair Value Assets Measured on Recurring Basis Unobservable Reconciliation [Roll Forward]
Gain (loss) recognized in earnings	0	0
Residential mortgage loans held for sale [Member]
Fair Value Assets Measured on Recurring Basis Unobservable Reconciliation [Roll Forward]
Balance at beginning of period	12,299	11,617
Transfers to Level 3 from Level 2	6,183	3,507
Purchases and capital calls	0	0
Redemptions and distributions	0	0
Proceeds from sales	(2,706)	(2,944)
Other comprehensive income (loss)	0	0
Balance at end of period	15,207	12,299
Residential mortgage loans held for sale [Member] | Mortgage banking revenue [Member]
Fair Value Assets Measured on Recurring Basis Unobservable Reconciliation [Roll Forward]
Gain (loss) recognized in earnings	$ (569)	$ 119

Fair Value Measurements Fair Va

Fair Value Measurements Fair Value Measurements, Financial Instruments Measured On a Recurring Basis, Quantitative Information (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale securities	$ 8,857,120	$ 8,321,578
Municipal and other tax-exempt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale securities	2,864	27,080
Other debt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale securities	35,430	25,481
Fair Value, Measurements, Recurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale securities	8,857,120	8,321,578
Residential mortgage loans held for sale	149,221	221,378
Fair Value, Measurements, Recurring [Member] | Municipal and other tax-exempt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale securities	2,864	27,080
Fair Value, Measurements, Recurring [Member] | Other debt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale securities	35,430	25,481
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale securities	472	5,274
Residential mortgage loans held for sale	15,207	12,299
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Municipal and other tax-exempt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale securities		4,802
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other debt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale securities	$ 472	$ 472
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Available for sale securities [Member] | Municipal and other tax-exempt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment Grade Tax Exempt Securities Yield Spread Over Comparable Securities, Minimum		372
Investment Grade Tax Exempt Securities Yield Spread Over Comparable Securities, Maximum		466
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Available for sale securities [Member] | Other debt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Average Yields On Comparable Short-term Taxable Securities	3.00%	3.00%
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Residential mortgage loans held for sale [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Liquidity Discount on Mortgage Loans Qualifying for Sale to US Govt Agencies	92.38%	94.75%
Discounted Cash Flow [Member] | Interest Rate Spread [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Available for sale securities [Member] | Municipal and other tax-exempt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale securities		$ 4,802
Discounted Cash Flow [Member] | Interest Rate Spread [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Available for sale securities [Member] | Other debt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale securities	$ 472	472
Quoted prices of loans sold in securitization transactions, with a liquidity discount applied [Member] | Liquidity discount [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Residential mortgage loans held for sale [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Residential mortgage loans held for sale	$ 15,207	$ 12,299
Minimum [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Available for sale securities [Member] | Municipal and other tax-exempt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of fair value as a percentage of par value	0.00%	92.25%
Range of interest rates used to value securities	0.00%	6.60%
Minimum [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Available for sale securities [Member] | Other debt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of fair value as a percentage of par value	94.44%	94.39%
Range of interest rates used to value securities	7.88%	6.85%
Maximum [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Available for sale securities [Member] | Municipal and other tax-exempt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of fair value as a percentage of par value	0.00%	94.76%
Range of interest rates used to value securities	0.00%	6.60%
Maximum [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Available for sale securities [Member] | Other debt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of fair value as a percentage of par value	94.44%	94.39%
Range of interest rates used to value securities	7.88%	6.85%
Weighted Average [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Available for sale securities [Member] | Municipal and other tax-exempt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of fair value as a percentage of par value	0.00%	93.75%
Range of interest rates used to value securities	0.00%	6.60%
Weighted Average [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Available for sale securities [Member] | Other debt securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of fair value as a percentage of par value	94.44%	94.39%
Range of interest rates used to value securities	7.88%	6.85%

Fair Value Measurements, Fair_2

Fair Value Measurements, Fair Value Measured On a Nonrecurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 33,582	$ 40,419	$ 41,769
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross charge-offs against allowance for loan losses	17,434	12,145
Net losses and expenses of repossessed assets, net	0	0
Fair Value, Measurements, Nonrecurring [Member] | Real estate and other repossessed assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross charge-offs against allowance for loan losses	0	0
Net losses and expenses of repossessed assets, net	7,269	6,372
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Real estate and other repossessed assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined Benefit Plan, Plan Assets, Amount	34,000	40,000
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	1,074	7,436
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Real estate and other repossessed assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	4,795	3,483
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	17,401	7,626
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Real estate and other repossessed assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 6,366	$ 5,481

Fair Value Measurements Fair _2

Fair Value Measurements Fair Value Measurement, Measured On Non-Recurring Basis, Signfiicant Unobservable Inputs, Quantitative Information (Details) - Fair Value, Measurements, Nonrecurring [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Impaired Loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	$ 17,401	$ 7,626
Real estate and other repossessed assets [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	6,366	5,481
Discounted Cash Flow [Member] | Impaired Loans [Member] | Management knowledge of Industry [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	17,401
Discounted Cash Flow [Member] | Impaired Loans [Member] | Recoverable oil and gas reserves, forward-looking commodity prices, and estimated operating costs [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure		7,626
Discounted Cash Flow [Member] | Real estate and other repossessed assets [Member] | Recoverable oil and gas reserves, forward-looking commodity prices, and estimated operating costs [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	$ 6,366	$ 5,481
Minimum [Member] | Impaired Loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value of Impaired Loans as Percentage of Unpaid Principal Balance	35.00%	40.00%
Maximum [Member] | Impaired Loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value of Impaired Loans as Percentage of Unpaid Principal Balance	80.00%	86.00%
Weighted Average [Member] | Impaired Loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value of Impaired Loans as Percentage of Unpaid Principal Balance	50.00%	59.00%

Fair Value Measurements, Financ

Fair Value Measurements, Financial Instruments (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	$ 1,956,923,000	$ 462,676,000
Investment securities	355,187,000	461,793,000
Available for sale securities	8,857,120,000	8,321,578,000
Fair value option securities	283,235,000	755,054,000
Residential mortgage loans held for sale	149,221,000	221,378,000
Loans	21,656,730,000	17,153,424,000
Allowance for loan losses	(207,457,000)	(230,682,000)	$ (246,159,000)	$ (225,524,000)
Loans, net of allowance	21,449,273,000	16,922,742,000
Mortgage servicing rights	259,254,000	252,867,000	247,073,000	218,605,000
Derivative contracts, net of cash margin, Assets, Fair Value	320,929,000	220,502,000
Time deposits	2,113,380,000	2,098,416,000
Subordinated debentures	275,913,000	144,677,000
Derivative contracts, net of cash margin, Liabilities, Fair Value	362,306,000	171,963,000
Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	13,636,078,000	10,733,975,000
Allowance for loan losses	(102,226,000)	(124,269,000)	(140,213,000)	(130,334,000)
Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	4,764,813,000	3,479,987,000
Allowance for loan losses	(60,026,000)	(56,621,000)	(50,749,000)	(41,391,000)
Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,230,033,000	1,973,686,000
Allowance for loan losses	(17,964,000)	(18,451,000)	(18,224,000)	(19,509,000)
Personal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	1,025,806,000	965,776,000
Allowance for loan losses	(9,473,000)	(9,124,000)	$ (8,773,000)	$ (4,164,000)
U.S. government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	63,765,000	21,196,000
U.S. government agency residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	1,791,584,000	392,673,000
Investment securities	12,612,000	15,891,000
Available for sale securities	5,804,708,000	5,309,152,000
Fair value option securities	283,235,000	755,054,000
Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	34,507,000	13,559,000
Investment securities	137,296,000	228,186,000
Available for sale securities	2,864,000	27,080,000
Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	24,411,000	11,363,000
U.S. Treasury [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	493,000	1,000,000
Privately issued residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	59,736,000	93,221,000
Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	2,953,889,000	2,834,961,000
Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	205,279,000	217,716,000
Available for sale securities	35,430,000	25,481,000
Perpetual preferred stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		15,767,000
Equity securities and mutual funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		14,916,000
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	741,749,000	602,510,000
Interest-bearing cash and cash equivalents	401,675,000	1,714,544,000
Trading securities	1,956,923,000	462,676,000
Investment securities	355,187,000	461,793,000
Available for sale securities	8,857,120,000	8,321,578,000
Residential mortgage loans held for sale	149,221,000	221,378,000
Loans	21,656,730,000	17,153,424,000
Allowance for loan losses	(207,457,000)	(230,682,000)
Loans, net of allowance	21,449,273,000	16,922,742,000
Mortgage servicing rights	259,254,000	252,867,000
Derivative contracts, net of cash margin, Assets, Fair Value	320,929,000	220,502,000
Deposits with no stated maturity	23,150,383,000	19,962,889,000
Time deposits	2,113,380,000	2,098,416,000
Other borrowed funds	7,142,801,000	5,709,860,000
Subordinated debentures	275,913,000	144,677,000
Derivative contracts, net of cash margin, Liabilities, Fair Value	362,306,000	171,963,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	13,636,078,000	10,733,975,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	4,764,813,000	3,479,987,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,230,033,000	1,973,686,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Personal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	1,025,806,000	965,776,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | U.S. government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	63,765,000	21,196,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | U.S. government agency residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	1,791,584,000	392,673,000
Investment securities	12,612,000	15,891,000
Available for sale securities	5,804,708,000	5,309,152,000
Fair value option securities	283,235,000	755,054,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	34,507,000	13,559,000
Investment securities	137,296,000	228,186,000
Available for sale securities	2,864,000	27,080,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	42,656,000	23,885,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	24,411,000	11,363,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | U.S. Treasury [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	493,000	1,000,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Privately issued residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	59,736,000	93,221,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	2,953,889,000	2,834,961,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	205,279,000	217,716,000
Available for sale securities	35,430,000	25,481,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Perpetual preferred stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		15,767,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Equity securities and mutual funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		14,916,000
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	741,749,000	602,510,000
Interest-bearing cash and cash equivalents	401,675,000	1,714,544,000
Trading securities	1,956,923,000	438,791,000
Investment securities	367,298,000	480,035,000
Available for sale securities	8,857,120,000	8,321,578,000
Residential mortgage loans held for sale	149,221,000	221,378,000
Loans	21,478,228,000	16,887,787,000
Allowance for loan losses	0	0
Loans, net of allowance	21,478,228,000	16,887,787,000
Mortgage servicing rights	259,254,000	252,867,000
Derivative contracts, net of cash margin, Assets, Fair Value	320,929,000	220,502,000
Deposits with no stated maturity	23,150,383,000	19,962,889,000
Time deposits	2,073,538,000	2,064,558,000
Other borrowed funds	6,771,953,000	5,703,121,000
Subordinated debentures	261,977,000	148,207,000
Derivative contracts, net of cash margin, Liabilities, Fair Value	362,306,000	171,963,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	13,526,162,000	10,524,627,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	4,713,747,000	3,428,733,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,213,951,000	1,977,721,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Personal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	1,024,368,000	956,706,000
Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	63,765,000	21,196,000
Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. government agency residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	1,791,584,000	392,673,000
Investment securities	12,770,000	16,242,000
Available for sale securities	5,804,708,000	5,309,152,000
Fair value option securities	283,235,000	755,054,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	34,507,000	13,559,000
Investment securities	138,562,000	230,349,000
Available for sale securities	2,864,000	27,080,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	42,656,000	23,885,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	24,411,000	11,363,000
Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. Treasury [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	493,000	1,000,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Privately issued residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	59,736,000	93,221,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	2,953,889,000	2,834,961,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	215,966,000	233,444,000
Available for sale securities	35,430,000	25,481,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Perpetual preferred stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		15,767,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Equity securities and mutual funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		14,916,000
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	741,749,000	602,510,000
Interest-bearing cash and cash equivalents	401,675,000	1,714,544,000
Trading securities	0	0
Investment securities	0	0
Available for sale securities	493,000	1,000,000
Residential mortgage loans held for sale	0	0
Loans	0	0
Allowance for loan losses	0	0
Loans, net of allowance	0	0
Mortgage servicing rights	0	0
Derivative contracts, net of cash margin, Assets, Fair Value	44,074,000	8,179,000
Deposits with no stated maturity	0	0
Time deposits	0	0
Other borrowed funds	0	0
Subordinated debentures	0	0
Derivative contracts, net of cash margin, Liabilities, Fair Value	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Personal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. government agency residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities	0	0
Available for sale securities	0	0
Fair value option securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities	0	0
Available for sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. Treasury [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	493,000	1,000,000
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Privately issued residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	0	0
Available for sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Perpetual preferred stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Equity securities and mutual funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	0	0
Interest-bearing cash and cash equivalents	0	0
Trading securities	1,956,923,000	438,791,000
Investment securities	159,237,000	480,035,000
Available for sale securities	8,856,155,000	8,315,304,000
Residential mortgage loans held for sale	134,014,000	208,946,000
Loans	0	0
Allowance for loan losses	0	0
Loans, net of allowance	0	0
Mortgage servicing rights	0	0
Derivative contracts, net of cash margin, Assets, Fair Value	276,855,000	212,323,000
Deposits with no stated maturity	0	0
Time deposits	0	0
Other borrowed funds	0	0
Subordinated debentures	261,977,000	148,207,000
Derivative contracts, net of cash margin, Liabilities, Fair Value	362,306,000	171,963,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Personal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	63,765,000	21,196,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. government agency residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	1,791,584,000	392,673,000
Investment securities	12,770,000	16,242,000
Available for sale securities	5,804,708,000	5,309,152,000
Fair value option securities	283,235,000	755,054,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	34,507,000	13,559,000
Investment securities	138,562,000	230,349,000
Available for sale securities	2,864,000	22,278,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	42,656,000	23,885,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	24,411,000	11,363,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. Treasury [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Privately issued residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	59,736,000	93,221,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	2,953,889,000	2,834,961,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	7,905,000	233,444,000
Available for sale securities	34,958,000	25,009,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Perpetual preferred stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		15,767,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Equity securities and mutual funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		14,916,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	0	0
Interest-bearing cash and cash equivalents	0	0
Trading securities	0	0
Investment securities	208,061,000	0
Available for sale securities	472,000	5,274,000
Residential mortgage loans held for sale	15,207,000	12,432,000
Loans	21,478,228,000	16,887,787,000
Allowance for loan losses	0	0
Loans, net of allowance	21,478,228,000	16,887,787,000
Mortgage servicing rights	259,254,000	252,867,000
Derivative contracts, net of cash margin, Assets, Fair Value	0	0
Deposits with no stated maturity	23,150,383,000	19,962,889,000
Time deposits	2,073,538,000	2,064,558,000
Other borrowed funds	6,771,953,000	5,703,121,000
Subordinated debentures	0	0
Derivative contracts, net of cash margin, Liabilities, Fair Value	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	13,526,162,000	10,524,627,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	4,713,747,000	3,428,733,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,213,951,000	1,977,721,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Personal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	1,024,368,000	956,706,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. government agency residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities	0	0
Available for sale securities	0	0
Fair value option securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities	0	0
Available for sale securities	0	4,802,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. Treasury [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Privately issued residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	208,061,000	0
Available for sale securities	$ 472,000	472,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Perpetual preferred stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Equity securities and mutual funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		$ 0

Parent Company Only Financial_3

Parent Company Only Financial Statements Parent Company Only Financial Statements, Condensed Balance Sheet Statement (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets [Abstract]
Cash and cash equivalents	$ 1,143,424	$ 2,317,054	$ 2,537,497	$ 2,643,599
Available for sale securities	8,857,120	8,321,578
Loan to bank subsidiary	21,449,273	16,922,742
Other assets	446,891	359,092
Total assets	38,020,504	32,272,160
Liabilities [Abstract]
Other liabilities	183,480	162,381
Subordinated debentures	275,913	144,677
Total liabilities	33,577,459	28,753,826
Shareholders' equity: [Abstract]
Common stock	5	4
Capital surplus	1,334,030	1,035,895
Retained earnings	3,369,654	3,048,487
Treasury stock	(198,995)	(552,845)
Accumulated other comprehensive loss	(72,585)	(36,174)	(10,967)	21,587
Total shareholders’ equity	4,432,109	3,495,367
Total liabilities and shareholders’ equity	38,020,504	32,272,160
Parent Company [Member]
Assets [Abstract]
Cash and cash equivalents	167,093	205,876	$ 163,418	$ 282,169
Available for sale securities	0	16,185
Loan to bank subsidiary	65,228	0
Investment in bank subsidiaries	4,236,654	3,255,912
Investment in non-bank subsidiaries	218,007	170,966
Other assets	32,999	4,065
Total assets	4,719,981	3,653,004
Liabilities [Abstract]
Other liabilities	11,959	12,960
Subordinated debentures	275,913	144,677
Total liabilities	287,872	157,637
Shareholders' equity: [Abstract]
Common stock	5	4
Capital surplus	1,334,030	1,035,895
Retained earnings	3,369,654	3,048,487
Treasury stock	72,585	36,174
Accumulated other comprehensive loss	(198,995)	(552,845)
Total shareholders’ equity	4,432,109	3,495,367
Total liabilities and shareholders’ equity	$ 4,719,981	$ 3,653,004

Parent Company Only Financial_4

Parent Company Only Financial Statements Parent Company Only Financial Statements, Condensed Income Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Income Statements, Captions [Line Items]
Interest expense	$ 243,559	$ 131,050	$ 81,889
Other operating expense	1,028,166	1,025,517	1,017,590
Other losses, net	(2,731)	11,213	4,947
Federal and state income taxes	119,061	182,593	106,377
Net income attributable to BOK Financial Corp. shareholders	445,646	334,644	232,668
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Total revenue	439,825	168,585	42,772
Interest expense	9,827	8,239	4,182
Other operating expense	12,110	2,014	1,978
Total expense	21,937	10,253	6,160
Net income before taxes, other losses, net, and equity in undistributed income of subsidiaries	417,888	158,332	36,612
Other losses, net	3,921	0	0
Net income before taxes, other losses, net, and equity in undistributed income of subsidiaries	413,967	158,332	36,612
Federal and state income taxes	(7,078)	(4,305)	(1,920)
Net income before equity in undistributed income of subsidiaries	421,045	162,637	38,532
Equity in undistributed income of bank subsidiaries	37,515	181,552	216,120
Equity in undistributed income of non-bank subsidiaries	(12,914)	(9,545)	(21,984)
Net income attributable to BOK Financial Corp. shareholders	445,646	334,644	232,668
Parent Company [Member] | Dividends, interest and fees received from bank susidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Total revenue	426,071	150,149	15,237
Parent Company [Member] | Diviidends, interest and fees received from non-bank subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Total revenue	12,800	17,500	25,923
Parent Company [Member] | Other revenue [Member]
Condensed Income Statements, Captions [Line Items]
Total revenue	$ 954	$ 936	$ 1,612

Parent Company Only Financial_5

Parent Company Only Financial Statements Parent Company Only Financial Statements, Condensed Cash Flow Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows From Operating Activities: [Abstract]
Net income	$ 446,424	$ 335,685	$ 232,281
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Change in other assets	27,507	(5,506)	(49,565)
Change in other liabilities	(139,346)	182,184	(11,413)
Net cash provided by operating activities	(552,006)	214,931	(91,949)
Cash Flows From Investing Activities: [Abstract]
Proceeds from sales of available for sale securities	745,643	1,309,215	899,381
Acquisitions, net of cash acquired	(175,755)	0	56,017
Net cash used in investing activities	(1,807,631)	739,556	(286,007)
Cash Flows From Financing Activities: [Abstract]
Net change in other borrowed funds	1,295,484	(10,909)	(606,476)
Issuance of subordinated debentures, net of issuance costs	0	0	144,615
Issuance of common and treasury stock, net	(88)	4,368	12,455
Dividends paid	(127,188)	(116,041)	(113,455)
Repurchase of common stock	(53,465)	(7,403)	(66,792)
Net cash used in financing activities	1,186,007	(1,174,930)	271,854
Net increase (decrease) in cash and cash equivalents	(1,173,630)	(220,443)	(106,102)
Cash and cash equivalents at beginning of period	2,317,054	2,537,497	2,643,599
Cash and cash equivalents at end of period	1,143,424	2,317,054	2,537,497
Cash paid for interest	243,121	127,513	82,876
Parent Company [Member]
Cash Flows From Operating Activities: [Abstract]
Net income	445,646	334,644	232,668
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Equity in undistributed income of bank subsidiaries	(37,515)	(181,552)	(216,120)
Equity in undistributed income of non-bank subsidiaries	(12,914)	(9,545)	(21,984)
Change in other assets	1,072	(12)	2,933
Change in other liabilities	(13,434)	7,457	(1,285)
Net cash provided by operating activities	406,539	170,106	34,314
Cash Flows From Investing Activities: [Abstract]
Proceeds from sales of available for sale securities	0	3,000	1,632
Investment in subsidiaries	(31,901)	(4,355)	(26,000)
Acquisitions, net of cash acquired	(232,680)	0	(105,520)
Net cash used in investing activities	(264,581)	(1,355)	(129,888)
Cash Flows From Financing Activities: [Abstract]
Net change in other borrowed funds	0	(7,217)	0
Issuance of subordinated debentures, net of issuance costs	0	0	144,615
Issuance of common and treasury stock, net	(88)	4,368	12,455
Dividends paid	127,188	116,041	113,455
Repurchase of common stock	53,465	7,403	66,792
Net cash used in financing activities	(180,741)	(126,293)	(23,177)
Net increase (decrease) in cash and cash equivalents	(38,783)	42,458	(118,751)
Cash and cash equivalents at beginning of period	205,876	163,418	282,169
Cash and cash equivalents at end of period	167,093	205,876	163,418
Cash paid for interest	$ 11,457	$ 6,211	$ 4,127