Western Alliance Bancorporation (WAL) 10-Q 30 Oct 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 26, 2018
Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	WAL
Entity Registrant Name	WESTERN ALLIANCE BANCORPORATION
Entity Central Index Key	1,212,545
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		105,858,808

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets:
Cash and due from banks	$ 148,545	$ 181,191
Interest-bearing deposits in other financial institutions	482,019	235,577
Federal Funds Sold	70,000	0
Cash, cash equivalents, and restricted cash	700,564	416,768
Money Market Funds, at Carrying Value	5	0
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	3,107,076	3,499,519
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	288,290	255,050
Investment securities - equity	172,294	0
Investments in restricted stock, at cost	65,993	65,785
Loans:
Loans, net of deferred loan fees and costs	16,732,765	15,093,935
Less: Allowance for credit losses	(150,011)	(140,050)
Net loans held for investment	16,582,754	14,953,885
Premises and equipment, net	119,211	118,719
Other assets acquired through foreclosure, net	20,028	28,540
Bank owned life insurance	169,162	167,764
Goodwill	289,895	289,895
Other intangible assets, net	9,658	10,853
Deferred tax assets, net	43,483	5,780
Amortization Method Qualified Affordable Housing Project Investments	295,116	267,023
Other assets	312,618	249,504
Total assets	22,176,147	20,329,085
Deposits:
Non-interest-bearing demand	8,014,715	7,433,962
Interest-bearing	10,893,865	9,538,570
Total deposits	18,908,580	16,972,532
Customer repurchase agreements	20,969	26,017
Other borrowings	0	390,000
Qualifying debt	359,082	376,905
Other liabilities	399,123	333,933
Total liabilities	19,687,754	18,099,387
Commitments and Contingencies
Stockholders’ equity:
Common stock - par value $0.0001; 200,000,000 authorized; 107,633,006 shares issued at September 30, 2018 and 107,057,520 at December 31, 2017	10	10
Treasury stock, at cost (1,771,509 shares at September 30, 2018 and 1,570,155 shares at December 31, 2017)	(52,035)	(40,173)
Additional paid in capital	1,444,555	1,424,540
Accumulated other comprehensive (loss) income	(70,363)	(3,145)
Retained earnings	1,166,226	848,466
Total stockholders’ equity	2,488,393	2,229,698
Total liabilities and stockholders’ equity	$ 22,176,147	$ 20,329,085

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale, Amortized Cost	$ 3,211,440	$ 3,515,401
Amortized cost of investment securities available for sale		3,515,401
Debt Securities, Held-to-maturity, Fair Value	$ 279,033	$ 256,314
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	107,633,006	107,057,520
Common stock, shares outstanding	105,861,497	105,487,365

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Interest income:
Loans, including fees	$ 234,709	$ 191,096	$ 662,703	$ 547,306
Investment securities	26,100	22,152	77,847	58,010
Dividends	1,831	2,005	5,506	6,154
Other	2,576	2,583	5,459	5,584
Total interest income	265,216	217,836	751,515	617,054
Interest expense:
Deposits	25,266	11,449	59,288	29,506
Qualifying debt	5,794	4,708	16,458	13,539
Other borrowings	90	84	3,352	333
Other	28	12	51	41
Total interest expense	31,178	16,253	79,149	43,419
Net interest income	234,038	201,583	672,366	573,635
Provision for credit losses	6,000	5,000	17,000	12,250
Net interest income after provision for credit losses	228,038	196,583	655,366	561,385
Non-interest income:
Service charges and fees	5,267	5,248	16,684	15,189
Card Income	2,138	1,509	6,143	4,517
Income from equity investments	1,440	967	5,417	2,977
Lending related income and gains (losses) on sale of loans, net	1,422	97	3,447	746
Foreign currency income	1,092	756	3,475	2,630
Income from bank owned life insurance	868	975	2,963	2,896
Other income	635	585	1,579	1,795
Total non-interest income	4,418	10,456	29,505	31,656
Non-interest expense:
Salaries and employee benefits	64,762	52,747	188,680	156,640
Legal, professional, and directors' fees	7,907	6,038	21,856	23,324
Occupancy	7,406	7,507	21,671	21,328
Data processing	5,895	4,524	16,688	14,163
Deposit costs	4,848	2,904	11,888	6,778
Insurance	3,712	3,538	11,466	10,355
Business development	1,381	1,439	4,523	4,949
Card expense	1,282	966	3,305	2,558
Loan and repossessed asset expenses	1,230	1,263	2,830	3,639
Marketing	687	776	2,429	2,628
Intangible amortization	398	489	1,195	1,666
Net (gain) loss on sales / valuations of repossessed and other assets	(67)	266	(1,474)	(46)
Other expense	14,400	6,839	29,481	17,561
Total non-interest expense	113,841	89,296	314,538	265,543
Income before provision for income taxes	118,615	117,743	370,333	327,498
Income tax expense	7,492	34,899	53,631	91,352
Net income	$ 111,123	$ 82,844	$ 316,702	$ 236,146
Earnings per share:
Basic	$ 1.06	$ 0.79	$ 3.03	$ 2.27
Diluted	$ 1.05	$ 0.79	$ 3	$ 2.25
Weighted average number of common shares outstanding:
Basic	104,768	104,221	104,664	104,124
Diluted	105,448	104,942	105,398	104,941
(Gains) / Losses on:	$ (7,232)	$ 319	$ (7,232)	$ 907
Equity Securities, FV-NI, Unrealized Gain (Loss)	$ (1,212)	$ 0	$ (2,971)	$ (1)

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 111,123	$ 82,844	$ 316,702	$ 236,146
Other comprehensive (loss) income, net:
Unrealized (loss) gain on AFS securities, net of tax effect of $7,337, $(689), $23,438, and $(9,894), respectively	(22,462)	1,116	(71,765)	15,947
Unrealized (loss) gain on SERP, net of tax effect of $4, $(71), $10, and $(93), respectively	(12)	114	(35)	150
Unrealized (loss) gain on junior subordinated debt, net of tax effect of $661, $(394), $(61), and $1,649, respectively	(2,028)	641	186	(2,677)
Realized loss (gain) on sale of AFS securities included in income, net of tax effect of $(1,778), $122, $(1,778), and $346, respectively	5,454	(197)	5,454	(561)
Net other comprehensive (loss) income	(19,048)	1,674	(66,160)	12,859
Comprehensive income	$ 92,075	$ 84,518	$ 250,542	$ 249,005

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Unrealized gain on securities available-for-sale securities, tax	$ (7,337)	$ 689	$ (23,438)	$ 9,894
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	4	(71)	10	(93)
Unrealized (loss) gain on junior subordinated debt, net of tax effect of $661, $(394), $(61), and $1,649, respectively	661	(394)	(61)	1,649
Realized gain on sale of securities, tax	$ (1,778)	$ 122	$ (1,778)	$ 346

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated (Deficit) [Member]	Restricted Stock [Member]	Performance Shares [Member]	Executive Officer [Member]Restricted Stock [Member]
Allocated Share-based Compensation Expense							$ 11,300	$ 4,500	$ 1,600
Beginning balance at Dec. 31, 2016	$ 1,891,529	$ 10	$ 1,400,140	$ (26,362)	$ (4,695)	$ 522,436
Beginning balance, shares at Dec. 31, 2016		105,071,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	236,146					236,146
Exercise of stock options, shares		36,000
Exercise of stock options	786		786
Restricted stock grants, net, shares		653,000
Restricted stock grants, net	$ 17,909		17,909
Treasury Stock, Shares, Acquired	(266,883)	(267,000)
Treasury Stock Acquired, Average Cost Per Share	$ 51.10
Restricted Stock Award, Forfeitures	$ (13,642)			13,642
Other comprehensive (loss) income, net	12,859				12,859
Ending balance at Sep. 30, 2017	2,146,125	$ 10	1,418,835	(40,004)	8,164	759,120
Ending balance, shares at Sep. 30, 2017		105,493,000
Retained earnings	848,466
Stock Granted, Value, Share-based Compensation, Gross							23,700
Allocated Share-based Compensation Expense							$ 12,400	$ 4,800	$ 1,900
Beginning balance at Dec. 31, 2017	2,229,698	$ 10	1,424,540	(40,173)	(3,145)	848,466
Beginning balance, shares at Dec. 31, 2017		105,487,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	316,702					316,702
Exercise of stock options, shares		21,000
Exercise of stock options	534		534
Restricted stock grants, net, shares		554,000
Restricted stock grants, net	$ 19,481		19,481
Treasury Stock, Shares, Acquired	(201,354)	(201,000)
Treasury Stock Acquired, Average Cost Per Share	$ 58.91
Restricted Stock Award, Forfeitures	$ (11,862)			(11,862)
Other comprehensive (loss) income, net	(66,160)				(66,160)
Ending balance at Sep. 30, 2018	2,488,393	$ 10	$ 1,444,555	$ (52,035)	$ (70,363)	$ 1,166,226
Ending balance, shares at Sep. 30, 2018		105,861,000
Retained earnings	$ 1,166,226

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 316,702	$ 236,146
Adjustments to reconcile net income to cash provided by operating activities:
Provision for credit losses	17,000	12,250
Depreciation and amortization	10,460	9,956
Stock-based compensation	19,481	17,909
Deferred income taxes	(16,107)	3,371
Amortization of net premiums for investment securities	10,795	14,926
Amortization of tax credit investments	26,546	19,524
Accretion of fair market value adjustments on loans acquired from business combinations	(14,099)	(20,994)
Accretion and amortization of fair market value adjustments on other assets and liabilities acquired from business combinations	1,427	1,898
Income from bank owned life insurance	(2,963)	(2,896)
(Gains) / Losses on:
(Gains) / Losses on:	(7,232)	907
Assets measured at fair value, net	2,971	1
Sale of loans	(2,434)	117
Other assets acquired through foreclosure, net	(1,464)	(233)
Valuation adjustments of other repossessed assets, net	32	120
Sale of premises, equipment, and other assets, net	(42)	67
Changes in:
Other assets	17,419	(12,958)
Other liabilities	3,324	(7,214)
Net cash provided by operating activities	396,280	271,083
Investment securities - trading
Proceeds from sales	0	994
Investment securities - AFS
Purchases	(251,413)	(1,361,908)
Principal pay downs and maturities	329,958	370,231
Proceeds from sales	44,308	87,853
Purchases	34,275	62,489
Principal pay downs and maturities	754	0
Purchases	(71,727)	0
Purchase of investment tax credits	(66,456)	(19,916)
Purchase of SBIC investments	3,063	0
(Purchase) sale of money market investments, net	(5)	(175)
(Purchase) sale of money market investments, net	1,655	607
(Purchase) liquidation of restricted stock, net	208	430
Loan fundings and principal collections, net	(1,591,733)	(1,179,494)
Purchase of premises, equipment, and other assets, net	(8,319)	(7,644)
Proceeds from sale of other real estate owned and repossessed assets, net	8,793	20,748
Net cash used in investing activities	(1,642,157)	(2,151,623)
Net cash used in investing activities
Net increase (decrease) in deposits	1,936,048	2,354,920
Net increase (decrease) in borrowings	(395,047)	(95,661)
Proceeds from exercise of common stock options	534	786
Cash paid for tax withholding on vested restricted stock	(11,862)	(13,642)
Net cash provided by financing activities	1,529,673	2,246,403
Net increase (decrease) in cash, cash equivalents, and restricted cash	283,796	365,863
Cash, cash equivalents, and restricted cash at beginning of period	416,768	284,491
Cash, cash equivalents, and restricted cash at end of period	700,564	650,354
Cash paid during the period for:
Interest	81,247	47,815
Income taxes	14,658	79,522
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Foreclosure	5,744	1,812
Noncash Contribution Expense	6,895	0
Non-cash operating, investing, and financing activity:
Unfunded commitments originated	65,639	103,012
Change in unrealized (loss) gain on AFS securities, net of tax	(66,311)	15,386
Unrealized (loss) gain on junior subordinated debt, net of tax effect of $661, $(394), $(61), and $1,649, respectively	186	(2,677)
Change in unfunded obligations	82,270	140,217
Reinvestments of dividend proceeds	$ (426)	$ 0

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of operation WAL is a bank holding company headquartered in Phoenix, Arizona, incorporated under the laws of the state of Delaware. WAL provides a full spectrum of deposit, lending, treasury management, international banking, and online banking products and services through its wholly-owned banking subsidiary, WAB. WAB operates the following full-service banking divisions: ABA, BON, FIB, Bridge, and TPB. The Company also serves business customers through a national platform of specialized financial services. In addition, the Company has two non-bank subsidiaries, LVSP, which holds and manages certain OREO properties and a captive insurance company formed and licensed under the laws of the State of Arizona, CSI. CSI was established as part of the Company's overall enterprise risk management strategy. Basis of presentation The accounting and reporting policies of the Company are in accordance with GAAP and conform to practices within the financial services industry. The accounts of the Company and its consolidated subsidiaries are included in the Consolidated Financial Statements. Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management's estimates and judgments are ongoing and are based on experience, current and expected future conditions, third-party evaluations and various other assumptions that management believes are reasonable under the circumstances. The results of these estimates form the basis for making judgments about the carrying values of assets and liabilities, as well as identifying and assessing the accounting treatment with respect to commitments and contingencies. Actual results may differ from those estimates and assumptions used in the Consolidated Financial Statements and related notes. Material estimates that are particularly susceptible to significant changes in the near term relate to the determination of the allowance for credit losses; estimated cash flows related to PCI loans; fair value determinations related to acquisitions and certain assets and liabilities carried at fair value; and accounting for income taxes. Principles of consolidation As of September 30, 2018 , WAL has the following significant wholly-owned subsidiaries: WAB, LVSP, and eight unconsolidated subsidiaries used as business trusts in connection with the issuance of trust-preferred securities. The Bank has the following significant wholly-owned subsidiaries: WABT, which holds certain investment securities, municipal and nonprofit loans, and leases; WA PWI, which holds certain limited partnerships invested primarily in low income housing tax credits and small business investment corporations; and BW Real Estate, Inc., which operates as a real estate investment trust and holds certain of WAB's real estate loans and related securities. The Company does not have any other significant entities that should be considered for consolidation. All significant intercompany balances and transactions have been eliminated in consolidation. Reclassifications Certain amounts reported in prior periods may have been reclassified in the Consolidated Financial Statements to conform to the current presentation. The reclassifications have no effect on net income or stockholders’ equity as previously reported. Interim financial information The accompanying Unaudited Consolidated Financial Statements as of and for the three and nine months ended September 30, 2018 and 2017 have been prepared in condensed format and, therefore, do not include all of the information and footnotes required by GAAP for complete financial statements. These statements have been prepared on a basis that is substantially consistent with the accounting principles applied to the Company's audited Consolidated Financial Statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 . The information furnished in these interim statements reflects all adjustments which are, in the opinion of management, necessary for a fair statement of the results for each respective period presented. Such adjustments are of a normal, recurring nature. The results of operations in the interim statements are not necessarily indicative of the results that may be expected for any other quarter or for the full year. The interim financial information should be read in conjunction with the Company's audited Consolidated Financial Statements. Investment securities Investment securities include debt securities and equity securities. Debt securities may be classified as HTM, AFS, or measured at fair value. The appropriate classification is initially decided at the time of purchase. Securities classified as HTM are those debt securities that the Company has both the intent and ability to hold to maturity regardless of changes in market conditions, liquidity needs, or general economic conditions. These securities are carried at amortized cost. The sale of an HTM security within three months of its maturity date or after the majority of the principal outstanding has been collected is considered a maturity for purposes of classification and disclosure. Securities classified as AFS or trading securities are reported as an asset in the Consolidated Balance Sheet at their estimated fair value. As the fair value of AFS debt securities changes, the changes are reported net of income tax as an element of OCI, except for other-than-temporarily-impaired securities. When AFS debt securities are sold, the unrealized gain or loss is reclassified from OCI to non-interest income. The changes in the fair values of trading securities are reported in non-interest income. Securities classified as AFS are securities that the Company intends to hold for an indefinite period of time, but not necessarily to maturity. Any decision to sell a security classified as AFS would be based on various factors, including significant movements in interest rates, changes in the maturity mix of the Company’s assets and liabilities, liquidity needs, decline in credit quality, and regulatory capital considerations. For periods prior to January 1, 2018, equity securities were classified as AFS and reported at fair value with unrealized gains and losses included as a separate component of AOCI, net of tax. Upon adoption of ASU 2016-01, the fair value changes in equity securities are recognized as part of non-interest income, see "Recently adopted accounting guidance" below for further discussion. Interest income is recognized based on the coupon rate and increased by accretion of discounts earned or decreased by the amortization of premiums paid over the contractual life of the security, adjusted for prepayment estimates, using the interest method. In estimating whether there are any OTTI losses, management considers the 1) length of time and the extent to which the fair value has been less than amortized cost; 2) financial condition and near term prospects of the issuer; 3) impact of changes in market interest rates; and 4) intent and ability of the Company to retain its investment for a period of time sufficient to allow for any anticipated recovery in fair value and whether it is not more likely than not the Company would be required to sell the security. Declines in the fair value of individual AFS securities that are deemed to be other-than-temporary are reflected in earnings when identified. The fair value of the debt security then becomes the new cost basis. For individual debt securities where the Company does not intend to sell the security and it is not more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis, the other-than-temporary decline in fair value of the debt security related to 1) credit loss is recognized in earnings; and 2) interest rate, market, or other factors is recognized in other comprehensive income or loss. For individual debt securities where the Company either intends to sell the security or more likely than not will not recover all of its amortized cost, the OTTI is recognized in earnings equal to the entire difference between the security's cost basis and its fair value at the balance sheet date. For individual debt securities for which a credit loss has been recognized in earnings, interest accruals and amortization and accretion of premiums and discounts are suspended when the credit loss is recognized. Interest received after accruals have been suspended is recognized on a cash basis. Restricted stock WAB is a member of the Federal Reserve System and, as part of its membership, is required to maintain stock in the FRB in a specified ratio to its capital. In addition, WAB is a member of the FHLB system and, accordingly, maintains an investment in capital stock of the FHLB based on the borrowing capacity used. The Bank also maintains an investment in its primary correspondent bank. All of these investments are considered equity securities with no actively traded market. Therefore, the shares are considered restricted investment securities. These investments are carried at cost, which is equal to the value at which they may be redeemed. The dividend income received from the stock is reported in interest income. The Company conducts a periodic review and evaluation of its restricted stock to determine if any impairment exists. No impairment has been recorded to date. Loans, held for investment The Company generally holds loans for investment and has the intent and ability to hold loans until their maturity. Therefore, they are reported at book value. Net loans are stated at the amount of unpaid principal, adjusted for net deferred fees and costs, purchase accounting fair value adjustments, and an allowance for credit losses. In addition, the book values of loans subject to a fair value hedge are adjusted for changes in value attributable to the effective portion of the hedged benchmark interest rate risk. The Company may also acquire loans through a business combination. These acquired loans are recorded at estimated fair value on the date of purchase, which is comprised of unpaid principal adjusted for estimated credit losses and interest rate fair value adjustments. Loans are evaluated individually at the acquisition date to determine if there has been credit deterioration since origination. Such loans may then be aggregated and accounted for as a pool of loans based on common characteristics. When the Company acquires such loans, the yield that may be accreted (accretable yield) is limited to the excess of the Company’s estimate of undiscounted cash flows expected to be collected over the Company’s initial investment in the loan. The excess of contractual cash flows over the cash flows expected to be collected may not be recognized as an adjustment to yield, loss, or a valuation allowance. Subsequent increases in cash flows expected to be collected generally are recognized prospectively through adjustment of the loan’s yield over the remaining life. Subsequent decreases to cash flows expected to be collected are recognized as impairment. The Company may not carry over or create a valuation allowance in the initial accounting for loans acquired under these circumstances. For purchased loans that are not deemed impaired at the acquisition date, fair value adjustments attributable to both credit and interest rates are accreted (or amortized) over the contractual life of the individual loan. For additional information, see " Note 3. Loans, Leases and Allowance for Credit Losses " of these Notes to Unaudited Consolidated Financial Statements. Loan fees collected for the origination of loans less direct loan origination costs (net deferred loan fees) are amortized over the contractual life of the loan through interest income. If a loan has scheduled payments, the amortization of the net deferred loan fee is calculated using the interest method over the contractual life of the loan. If a loan does not have scheduled payments, such as a line of credit, the net deferred loan fee is recognized as interest income on a straight-line basis over the contractual life of the loan commitment. Commitment fees based on a percentage of a customer’s unused line of credit and fees related to standby letters of credit are recognized over the commitment period. When loans are repaid, any remaining unamortized balances of premiums, discounts, or net deferred fees are recognized as interest income. Non-accrual loans: When a borrower discontinues making payments as contractually required by the note, the Company must determine whether it is appropriate to continue to accrue interest. The Company ceases accruing interest income when the loan has become delinquent by more than 90 days or when management determines that the full repayment of principal and collection of interest according to contractual terms is no longer likely. The Company may decide to continue to accrue interest on certain loans more than 90 days delinquent if the loans are well secured by collateral and in the process of collection. For all loan types, when a loan is placed on non-accrual status, all interest accrued but uncollected is reversed against interest income in the period in which the status is changed, and the Company makes a loan-level decision to apply either the cash basis or cost recovery method. The Company recognizes income on a cash basis only for those non-accrual loans for which the collection of the remaining principal balance is not in doubt. Under the cost recovery method, subsequent payments received from the customer are applied to principal and generally no further interest income is recognized until the principal has been paid in full or until circumstances have changed such that payments are again consistently received as contractually required. Impaired loans: A loan is identified as impaired when it is no longer probable that interest and principal will be collected according to the contractual terms of the original loan agreement. Generally, impaired loans are classified as non-accrual. However, in certain instances, impaired loans may continue on an accrual basis, if full repayment of all principal and interest is expected and the loan is both well secured and in the process of collection. Impaired loans are measured for reserve requirements in accordance with ASC 310, Receivables, based on the present value of expected future cash flows discounted at the loan's effective interest rate or, as a practical expedient, at the loan's observable market price or the fair value of the collateral less applicable disposition costs if the loan is collateral dependent. The amount of an impairment reserve, if any, and any subsequent changes are recorded as a provision for credit losses. Losses are recorded as a charge-off when losses are confirmed. In addition to management's internal loan review process, regulators may from time to time direct the Company to modify loan grades, loan impairment calculations, or loan impairment methodology. Troubled Debt Restructured Loans : A TDR loan is a loan on which the Company, for reasons related to a borrower’s financial difficulties, grants a concession to the borrower that the Company would not otherwise consider. The loan terms that have been modified or restructured due to a borrower’s financial situation include, but are not limited to, a reduction in the stated interest rate, an extension of the maturity or renewal of the loan at an interest rate below current market, a reduction in the face amount of the debt, a reduction in the accrued interest, or deferral of interest payments. A TDR loan is also considered impaired. A TDR loan may be returned to accrual status when the loan is brought current, has performed in accordance with the contractual restructured terms for a reasonable period of time (generally six months) and the ultimate collectability of the total contractual restructured principal and interest is no longer in doubt. However, such loans continue to be considered impaired. Consistent with regulatory guidance, a TDR loan that is subsequently modified in another restructuring agreement but has shown sustained performance and classification as a TDR, will be removed from TDR status provided that the modified terms were market-based at the time of modification. Allowance for credit losses Credit risk is inherent in the business of extending loans and leases to borrowers, for which the Company must maintain an adequate allowance for credit losses. The allowance for credit losses is established through a provision for credit losses recorded to expense. Loans are charged against the allowance for credit losses when management believes that the contractual principal or interest will not be collected. Subsequent recoveries, if any, are credited to the allowance. The allowance is an amount believed adequate to absorb estimated probable losses on existing loans that may become uncollectable, based on evaluation of the collectability of loans and prior credit loss experience, together with other factors. The Company formally re-evaluates and establishes the appropriate level of the allowance for credit losses on a quarterly basis. The allowance consists of specific and general components. The specific allowance applies to impaired loans. For impaired collateral dependent loans, the reserve is calculated based on the collateral value, net of estimated disposition costs. Generally, the Company obtains independent collateral valuation analysis for each loan every twelve months. Loans not collateral dependent are evaluated based on the expected future cash flows discounted at the original contractual interest rate. The general allowance covers all non-impaired loans and incorporates several quantitative and qualitative factors, which are used for all of the Company's portfolio segments. Quantitative factors include company-specific, ten-year historical net charge-offs stratified by loans with similar characteristics. Qualitative factors include: 1) levels of and trends in delinquencies and impaired loans; 2) levels of and trends in charge-offs and recoveries; 3) trends in volume and terms of loans; 4) changes in underwriting standards or lending policies; 5) experience, ability, depth of lending staff; 6) national and local economic trends and conditions; 7) changes in credit concentrations; 8) out-of-market exposures; 9) changes in quality of loan review system; and 10) changes in the value of underlying collateral. Due to the credit concentration of the Company's loan portfolio in real estate secured loans, the value of collateral is heavily dependent on real estate values in Arizona, Nevada, and California. While management uses the best information available to make its evaluation, future adjustments to the allowance may be necessary if there are significant changes in economic or other conditions. In addition, regulators, as an integral part of their examination processes, periodically review the Bank's allowance for credit losses, and may require the Bank to make additions to the allowance based on their judgment about information available to them at the time of their examination. Management regularly reviews the assumptions and formulae used in determining the allowance and makes adjustments if required to reflect the current risk profile of the portfolio. Goodwill and other intangible assets The Company records as goodwill the excess of the purchase price over the fair value of the identifiable net assets acquired in accordance with applicable guidance. The Company performs its annual goodwill and intangibles impairment tests as of October 1 each year, or more often if events or circumstances indicate that the carrying value may not be recoverable. The Company can first elect to assess, through qualitative factors, whether it is more likely than not that goodwill is impaired. If the qualitative assessment indicates potential impairment, a quantitative impairment test is necessary. If, based on the quantitative test, a reporting unit's carrying amount exceeds its fair value, a goodwill impairment charge for this difference is recorded to current period earnings as non-interest expense. The Company’s intangible assets consist primarily of core deposit intangible assets that are amortized over periods ranging from 5 to 10 years. The Company considers the remaining useful lives of its core deposit intangible assets each reporting period, as required by ASC 350, Intangibles—Goodwill and Other, to determine whether events and circumstances warrant a revision to the remaining period of amortization. If the estimate of an intangible asset’s remaining useful life has changed, the remaining carrying amount of the intangible asset is amortized prospectively over the revised remaining useful life. The Company has not revised its estimates of the useful lives of its core deposit intangibles during the three and nine months ended September 30, 2018 and 2017 . Other assets acquired through foreclosure Other assets acquired through foreclosure consist primarily of properties acquired as a result of, or in-lieu-of, foreclosure. Properties or other assets (primarily repossessed assets formerly leased) are classified as OREO and other repossessed property and are initially reported at fair value of the asset less estimated selling costs. Subsequent adjustments are based on the lower of carrying value or fair value less estimated costs to sell the property. Costs related to the development or improvement of the assets are capitalized and costs related to holding the assets are charged to non-interest expense. Property is evaluated regularly to ensure the recorded amount is supported by its current fair value and valuation allowances. Treasury shares The Company separately presents treasury shares, which represent shares surrendered to the Company equal in value to the statutory payroll tax withholding obligations arising from the vesting of employee restricted stock awards. Treasury shares are carried at cost. Derivative financial instruments The Company uses interest-rate swaps to mitigate interest-rate risk associated with changes to the fair value of certain fixed-rate financial instruments (fair value hedges). The Company recognizes derivatives as assets or liabilities in the Consolidated Balance Sheet at their fair value in accordance with ASC 815, Derivatives and Hedging . The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and further, on the type of hedging relationship. Derivative instruments designated in a hedge relationship to mitigate exposure to changes in the fair value of an asset or liability attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Changes in the fair value of a derivative that is designated and qualifies as a fair value hedge, along with changes in the fair value of the hedged asset or liability that are attributable to the hedged risk are recorded in current-period earnings. Changes in the fair value of derivatives not considered to be highly effective in hedging the change in fair value of the hedged item are recognized in earnings as non-interest income during the period of the change. The Company documents its hedge relationships, including identification of the hedging instruments and the hedged items, as well as its risk management objectives and strategies for undertaking the hedge transaction after the derivative contract is executed. At inception, the Company performs a quantitative assessment to determine whether the derivatives used in hedging transactions are highly effective (as defined in the guidance) in offsetting changes in the fair value of the hedged item. Retroactive effectiveness is assessed, as well as the continued expectation that the hedge will remain effective prospectively. After the initial quantitative assessment is performed, on a quarterly basis, the Company performs a qualitative hedge effectiveness assessment. This assessment takes into consideration any adverse developments related to the counterparty's risk of default and any negative events or circumstances that affect the factors that originally enabled the Company to assess that it could reasonably support, qualitatively, an expectation that the hedging relationship was and will continue to be highly effective. The Company discontinues hedge accounting prospectively when it is determined that a hedge is no longer highly effective. When hedge accounting is discontinued on a fair value hedge that no longer qualifies as an effective hedge, the derivative continues to be reported at fair value in the Consolidated Balance Sheet, but the carrying amount of the hedged item is no longer adjusted for future changes in fair value. The adjustment to the carrying amount of the hedged item that existed at the date hedge accounting is discontinued is amortized over the remaining life of the hedged item into earnings. Derivative instruments that are not designated as hedges, so called free-standing derivatives, are reported in the Consolidated Balance Sheet at fair value and the changes in fair value are recognized in earnings as non-interest income during the period of change. The Company may in the normal course of business purchase a financial instrument or originate a loan that contains an embedded derivative instrument. Upon purchasing the instrument or originating the loan, the Company assesses whether the economic characteristics of the embedded derivative are clearly and closely related to the economic characteristics of the remaining component of the financial instrument (i.e., the host contract) and whether a separate instrument with the same terms as the embedded instrument would meet the definition of a derivative instrument. When it is determined that the embedded derivative possesses economic characteristics that are not clearly and closely related to the economic characteristics of the host contract and a separate instrument with the same terms would qualify as a derivative instrument, the embedded derivative is separated from the host contract and carried at fair value. However, in cases where the host contract is measured at fair value, with changes in fair value reported in current earnings, or the Company is unable to reliably identify and measure an embedded derivative for separation from its host contract, the entire contract is carried in the Consolidated Balance Sheet at fair value and is not designated as a hedging instrument. Off-balance sheet instruments In the ordinary course of business, the Company has entered into off-balance sheet financial instrument arrangements consisting of commitments to extend credit and standby letters of credit. Such financial instruments are recorded in the Consolidated Financial Statements when they are funded. They involve, to varying degrees, elements of credit risk in excess of amounts recognized in the Consolidated Balance Sheet. Losses would be experienced when the Company is contractually obligated to make a payment under these instruments and must seek repayment from the borrower, which may not be as financially sound in the current period as they were when the commitment was originally made. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. The Company enters into credit arrangements that generally provide for the termination of advances in the event of a covenant violation or other event of default. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer’s creditworthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the Company upon extension of credit, is based on management’s credit evaluation of the party. The commitments are collateralized by the same types of assets used as loan collateral. As with outstanding loans, the Company applies qualitative factors and utilization rates to its off-balance sheet obligations in determining an estimate of losses inherent in these contractual obligations. The estimate for credit losses on off-balance sheet instruments is included in other liabilities and the charge to income that establishes this liability is included in non-interest expense. The Company also has off-balance sheet arrangements related to its derivative instruments. Derivative instruments are recognized in the Consolidated Financial Statements at fair value and their notional values are carried off-balance sheet. See " Note 9. Derivatives and Hedging Activities " of these Notes to Unaudited Consolidated Financial Statements for further discussion. Business combinations Business combinations are accounted for under the acquisition method of accounting in accordance with ASC 805, Business Combinations. Under the acquisition method, the acquiring entity in a business combination recognizes all of the acquired assets and assumed liabilities at their estimated fair values as of the date of acquisition. Any excess of the purchase price over the fair value of net assets and other identifiable intangible assets acquired is recorded as goodwill. To the extent the fair value of net assets acquired, including identified intangible assets, exceeds the purchase price, a bargain purchase gain is recognized. Changes to estimated fair values from a business combination are recognized as an adjustment to goodwill during the measurement period and are recognized in the proper reporting period in which the adjustment amounts are determined. Results of operations of an acquired business are included in the Consolidated Income Statement from the date of acquisition. Acquisition-related costs, including conversion and restructuring charges, are expensed as incurred. Fair values of financial instruments The Company uses fair value measurements to record fair value adjustments to certain assets and liabilities. ASC 820, Fair Value Measurement , establishes a framework for measuring fair value and a three-level valuation hierarchy for disclosure of fair value measurement, as well as enhances disclosure requirements for fair value measurements. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. The Company uses various valuation approaches, including market, income, and/or cost approaches. ASC 820 establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability developed based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the factors market participants would consider in pricing the asset or liability developed based on the best information available in the circumstances. The hierarchy is broken down into three levels based on the reliability of inputs, as follows: • Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. • Level 2 - Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. These might include quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (such as interest rates, prepayment speeds, volatilities, etc.) or model-based valuation techniques where all significant assumptions are observable, either directly or indirectly, in the market. • Level 3 - Valuation is generated from model-based techniques where one or more significant inputs are not observable, either directly or indirectly, in the market. These unobservable a

Investment Securities

Investment Securities	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Investment Securities	The carrying amounts and fair values of investment securities at September 30, 2018 and December 31, 2017 are summarized as follows: September 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (in thousands) Held-to-maturity debt securities Tax-exempt $ 288,290 $ 773 $ (10,030 ) $ 279,033 Available-for-sale debt securities CDO $ 50 $ 19,098 $ — $ 19,148 Commercial MBS issued by GSEs 107,915 42 (7,014 ) 100,943 Corporate debt securities 105,033 119 (5,768 ) 99,384 Private label residential MBS 887,581 42 (31,681 ) 855,942 Residential MBS issued by GSEs 1,515,408 167 (65,516 ) 1,450,059 Tax-exempt 511,957 4,015 (11,065 ) 504,907 Trust preferred securities 32,000 — (3,383 ) 28,617 U.S. government sponsored agency securities 49,000 — (3,399 ) 45,601 U.S. treasury securities 2,496 — (21 ) 2,475 Total AFS debt securities $ 3,211,440 $ 23,483 $ (127,847 ) $ 3,107,076 Equity securities (1) CRA investments $ 52,058 $ — $ (1,314 ) $ 50,744 Preferred stock 122,699 880 (2,029 ) 121,550 Total equity securities $ 174,757 $ 880 $ (3,343 ) $ 172,294 December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (in thousands) Held-to-maturity debt securities Tax-exempt $ 255,050 $ 4,514 $ (3,250 ) $ 256,314 Available-for-sale debt securities CDO $ 50 $ 21,807 $ — $ 21,857 Commercial MBS issued by GSEs 113,069 46 (4,038 ) 109,077 Corporate debt securities 105,044 261 (1,822 ) 103,483 Private label residential MBS 874,261 756 (6,493 ) 868,524 Residential MBS issued by GSEs 1,719,188 810 (30,703 ) 1,689,295 Tax-exempt 501,988 10,893 (1,971 ) 510,910 Trust preferred securities 32,000 — (3,383 ) 28,617 U.S. government sponsored agency securities 64,000 — (2,538 ) 61,462 U.S. treasury securities 2,496 — (14 ) 2,482 Available-for-sale equity securities (1) CRA investments 51,133 — (517 ) 50,616 Preferred stock 52,172 1,160 (136 ) 53,196 Total AFS securities $ 3,515,401 $ 35,733 $ (51,615 ) $ 3,499,519 ( 1) The Company's equity securities consist of CRA investments and preferred stock. Effective January 1, 2018, the Company adopted the amendments within ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities, which requires that fair value changes in equity securities be recognized as part of non-interest income. Prior to January 1, 2018, equity securities were classified as part of AFS securities. On a prospective basis, equity securities will be reported separately. The Company conducts an OTTI analysis on a quarterly basis. The initial indication of OTTI for both debt and equity securities is a decline in the market value below the amount recorded for an investment, and taking into account the severity and duration of the decline. Another potential indication of OTTI is a downgrade below investment grade. In determining whether an impairment is OTTI, the Company considers the length of time and the extent to which the market value has been below cost, recent events specific to the issuer, including investment downgrades by rating agencies and economic conditions of its industry, and the Company’s ability and intent to hold the investment for a period of time sufficient to allow for any anticipated recovery. For marketable equity securities, the Company also considers the issuer’s financial condition, capital strength, and near-term prospects. For debt securities, for the purpose of an OTTI analysis, the Company also considers the cause of the price decline (general level of interest rates, credit spreads, and industry and issuer-specific factors), whether downgrades by bond rating agencies have occurred, the issuer’s financial condition, near-term prospects, and current ability to make future payments in a timely manner, as well as the issuer’s ability to service debt, and any change in agencies’ ratings at the evaluation date from the acquisition date and any likely imminent action. At September 30, 2018 and December 31, 2017 , the Company’s unrealized losses relate primarily to market interest rate increases since the securities' original purchase date. The total number of AFS securities in an unrealized loss position at September 30, 2018 is 409 , compared to 302 at December 31, 2017 . The Company has reviewed securities for which there is an unrealized loss in accordance with its accounting policy for OTTI described above and determined that there are no impairment charges for the three and nine months ended September 30, 2018 and 2017 . The Company does not consider any securities to be other-than-temporarily impaired as of September 30, 2018 and December 31, 2017 . No assurance can be made that OTTI will not occur in future periods. Information pertaining to securities with gross unrealized losses at September 30, 2018 and December 31, 2017 , aggregated by investment category and length of time that individual securities have been in a continuous loss position follows: September 30, 2018 Less Than Twelve Months More Than Twelve Months Total Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (in thousands) Held-to-maturity debt securities Tax-exempt $ 10,030 $ 215,827 $ — $ — $ 10,030 $ 215,827 Available-for-sale debt securities Commercial MBS issued by GSEs $ — $ — $ 7,014 $ 99,134 $ 7,014 $ 99,134 Corporate debt securities 766 19,234 5,002 74,998 5,768 94,232 Private label residential MBS 13,004 463,026 18,677 374,504 31,681 837,530 Residential MBS issued by GSEs 16,624 563,642 48,892 878,925 65,516 1,442,567 Tax-exempt 6,337 227,531 4,728 66,047 11,065 293,578 Trust preferred securities — — 3,383 28,617 3,383 28,617 U.S. government sponsored agency securities 151 4,849 3,248 40,752 3,399 45,601 U.S. treasury securities 16 978 5 1,497 21 2,475 Total AFS securities $ 36,898 $ 1,279,260 $ 90,949 $ 1,564,474 $ 127,847 $ 2,843,734 December 31, 2017 Less Than Twelve Months More Than Twelve Months Total Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (in thousands) Held-to-maturity debt securities Tax-exempt $ 3,250 $ 107,921 $ — $ — $ 3,250 $ 107,921 Available-for-sale debt securities Commercial MBS issued by GSEs $ 161 $ 13,565 $ 3,877 $ 93,641 $ 4,038 $ 107,206 Corporate debt securities 1,398 78,602 424 19,576 1,822 98,178 Private label residential MBS 3,115 480,885 3,378 188,710 6,493 669,595 Residential MBS issued by GSEs 13,875 999,478 16,828 523,270 30,703 1,522,748 Tax-exempt 17 6,159 1,954 69,674 1,971 75,833 Trust preferred securities — — 3,383 28,617 3,383 28,617 U.S. government sponsored agency securities 14 4,986 2,524 56,476 2,538 61,462 U.S. treasury securities 14 2,482 — — 14 2,482 Available-for-sale equity securities CRA investments — — 517 50,616 517 50,616 Preferred stock 136 7,357 — — 136 7,357 Total AFS securities $ 18,730 $ 1,593,514 $ 32,885 $ 1,030,580 $ 51,615 $ 2,624,094 The portion of unrealized gains and losses related to equity securities still held at the reporting date is calculated as follows: Three Months Ended September 30, 2018 Nine Months Ended September 30, 2018 (in thousands) Net (losses) gains on equity securities $ (1,212 ) $ (2,971 ) Less: Net gains (losses) recognized on equity securities sold — — Unrealized (losses) gains on equity securities still held at the reporting date $ (1,212 ) $ (2,971 ) The amortized cost and fair value of securities as of September 30, 2018 , by contractual maturities, are shown below. MBS are shown separately as individual MBS are comprised of pools of loans with varying maturities. Therefore, these securities are listed separately in the maturity summary. September 30, 2018 Amortized Cost Estimated Fair Value (in thousands) Held-to-maturity Due in one year or less $ 1,200 $ 1,236 After one year through five years 10,100 10,122 After five years through ten years 14,602 14,351 After ten years 262,388 253,324 Total HTM securities $ 288,290 $ 279,033 Available-for-sale Due in one year or less $ 4,001 $ 3,996 After one year through five years 17,355 17,571 After five years through ten years 223,060 215,580 After ten years 456,120 462,985 Mortgage-backed securities 2,510,904 2,406,944 Total AFS securities $ 3,211,440 $ 3,107,076 The following tables summarize the carrying amount of the Company’s investment ratings position as of September 30, 2018 and December 31, 2017 : September 30, 2018 AAA Split-rated AAA/AA+ AA+ to AA- A+ to A- BBB+ to BBB- BB+ and below Unrated Totals (in thousands) Held-to-maturity debt securities Tax-exempt $ — $ — $ — $ — $ — $ — $ 288,290 $ 288,290 Available-for-sale debt securities CDO $ — $ — $ — $ — $ — $ 19,148 $ — $ 19,148 Commercial MBS issued by GSEs — 100,943 — — — — — 100,943 Corporate debt securities — — — 71,685 27,699 — — 99,384 Private label residential MBS 818,046 — 34,957 395 1,019 1,525 — 855,942 Residential MBS issued by GSEs — 1,450,059 — — — — — 1,450,059 Tax-exempt 61,443 20,636 244,696 170,409 — — 7,723 504,907 Trust preferred securities — — — — 28,617 — — 28,617 U.S. government sponsored agency securities — 45,601 — — — — — 45,601 U.S. treasury securities — 2,475 — — — — — 2,475 Total AFS securities (1) $ 879,489 $ 1,619,714 $ 279,653 $ 242,489 $ 57,335 $ 20,673 $ 7,723 $ 3,107,076 Equity securities CRA investments $ — $ 26,291 $ — $ — $ — $ — $ 24,453 $ 50,744 Preferred stock — — — — 72,991 39,032 9,527 121,550 Total equity securities (1) $ — $ 26,291 $ — $ — $ 72,991 $ 39,032 $ 33,980 $ 172,294 (1) Where ratings differ, the Company uses an average of the available ratings by major credit agencies. December 31, 2017 AAA Split-rated AAA/AA+ AA+ to AA- A+ to A- BBB+ to BBB- BB+ and below Unrated Totals (in thousands) Held-to-maturity debt securities Tax-exempt $ — $ — $ — $ — $ — $ — $ 255,050 $ 255,050 Available-for-sale debt securities CDO $ — $ — $ — $ — $ — $ 21,857 $ — $ 21,857 Commercial MBS issued by GSEs — 109,077 — — — — — 109,077 Corporate debt securities — — — 74,293 29,190 — — 103,483 Private label residential MBS 809,242 — 55,161 1,350 931 1,840 — 868,524 Residential MBS issued by GSEs — 1,689,295 — — — — — 1,689,295 Tax-exempt 64,893 25,280 249,200 167,994 — — 3,543 510,910 Trust preferred securities — — — — 28,617 — — 28,617 U.S. government sponsored agency securities — 61,462 — — — — — 61,462 U.S. treasury securities — 2,482 — — — — — 2,482 Available-for-sale equity securities CRA investments — 25,349 — — — — 25,267 50,616 Preferred stock — — — 10,388 23,822 4,104 14,882 53,196 Total AFS securities (1) $ 874,135 $ 1,912,945 $ 304,361 $ 254,025 $ 82,560 $ 27,801 $ 43,692 $ 3,499,519 (1) Where ratings differ, the Company uses an average of the available ratings by major credit agencies. Securities with carrying amounts of approximately $814.1 million and $913.7 million at September 30, 2018 and December 31, 2017 , respectively, were pledged for various purposes as required or permitted by law. The following table presents gross gains and losses on sales of investment securities: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Gross gains $ — $ 468 $ — $ 1,181 Gross losses (7,232 ) (149 ) (7,232 ) (274 ) Net (losses) gains on sales of investment securities $ (7,232 ) $ 319 $ (7,232 ) $ 907 During the three months ended September 30, 2018 , the Company sold certain available-for-sale securities with a carrying value of $111.9 million and recognized a net loss on sale of these securities of $7.2 million . The sale resulted from management’s review of its investment portfolio, which led to its decision to sell lower yielding securities and reinvest in securities with higher yields and shorter durations. With the exception of these transactions, management does not intend to sell any of its debt securities in an unrealized loss position in the foreseeable future and it is more-likely-than-not that the Company will not be required to sell these securities prior to recovery.

Loans, Leases and Allowance for

Loans, Leases and Allowance for Credit Losses	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Loans, Leases and Allowance for Credit Losses	The composition of the Company’s held for investment loan portfolio is as follows: September 30, 2018 December 31, 2017 (in thousands) Commercial and industrial $ 7,487,725 $ 6,841,381 Commercial real estate - non-owner occupied 3,952,966 3,904,011 Commercial real estate - owner occupied 2,288,156 2,241,613 Construction and land development 2,107,631 1,632,204 Residential real estate 827,073 425,940 Consumer 69,214 48,786 Loans, net of deferred loan fees and costs 16,732,765 15,093,935 Allowance for credit losses (150,011 ) (140,050 ) Total loans HFI $ 16,582,754 $ 14,953,885 Net deferred loan fees and costs as of September 30, 2018 and December 31, 2017 total $31.0 million and $25.3 million , respectively, which is a reduction in the carrying value of loans. Net unamortized purchase discounts on secondary market loan purchases total $3.3 million and $8.5 million as of September 30, 2018 and December 31, 2017 , respectively. Total loans held for investment are also net of interest rate and credit marks on acquired loans, which are a net reduction in the carrying value of loans. Interest rate marks were $8.7 million and $14.1 million as of September 30, 2018 and December 31, 2017 , respectively. Credit marks were $17.2 million and $27.0 million as of September 30, 2018 and December 31, 2017 , respectively. The following table presents the contractual aging of the recorded investment in past due loans held for investment by class of loans: September 30, 2018 Current 30-59 Days 60-89 Days Over 90 Days Past Due Total Total (in thousands) Commercial and industrial $ 7,477,017 $ 8,870 $ 254 $ 1,584 $ 10,708 $ 7,487,725 Commercial real estate Owner occupied 2,287,826 — 330 — 330 2,288,156 Non-owner occupied 3,787,571 — 531 — 531 3,788,102 Multi-family 164,864 — — — — 164,864 Construction and land development Construction 1,412,161 — — — — 1,412,161 Land 695,470 — — — — 695,470 Residential real estate 811,516 5,865 1,338 8,354 15,557 827,073 Consumer 68,881 — — 333 333 69,214 Total loans $ 16,705,306 $ 14,735 $ 2,453 $ 10,271 $ 27,459 $ 16,732,765 December 31, 2017 Current 30-59 Days 60-89 Days Over 90 days Total Total (in thousands) Commercial and industrial $ 6,835,385 $ 2,245 $ 669 $ 3,082 $ 5,996 $ 6,841,381 Commercial real estate Owner occupied 2,240,457 1,026 — 130 1,156 2,241,613 Non-owner occupied 3,696,729 2,993 — 2,847 5,840 3,702,569 Multi-family 201,442 — — — — 201,442 Construction and land development Construction 1,090,176 — — — — 1,090,176 Land 536,917 — — 5,111 5,111 542,028 Residential real estate 411,857 6,874 1,487 5,722 14,083 425,940 Consumer 48,408 83 213 82 378 48,786 Total loans $ 15,061,371 $ 13,221 $ 2,369 $ 16,974 $ 32,564 $ 15,093,935 The following table presents the recorded investment in non-accrual loans and loans past due ninety days or more and still accruing interest by class of loans: September 30, 2018 December 31, 2017 Non-accrual loans Loans past due 90 days or more and still accruing Non-accrual loans Loans past due 90 days or more and still accruing Current Past Due/ Total Current Past Due/ Total (in thousands) Commercial and industrial $ 14,894 $ 9,083 $ 23,977 $ — $ 17,913 $ 4,113 $ 22,026 $ 43 Commercial real estate Owner occupied — — — — 1,089 792 1,881 — Non-owner occupied — — — — — 5,840 5,840 — Multi-family — — — — — — — — Construction and land development Construction — — — — — — — — Land — — — — 868 5,111 5,979 — Residential real estate 4,204 8,354 12,558 — 2,039 6,078 8,117 — Consumer — 333 333 — — 82 82 — Total $ 19,098 $ 17,770 $ 36,868 $ — $ 21,909 $ 22,016 $ 43,925 $ 43 The reduction in interest income associated with loans on non-accrual status was approximately $0.6 million and $0.7 million for the three months ended September 30, 2018 and 2017 , respectively. For each of the nine months ended September 30, 2018 and 2017 , the reduction in interest income associated with loans on non-accrual status was approximately $1.8 million . The Company utilizes an internal asset classification system as a means of reporting problem and potential problem loans. Under the Company’s risk rating system, the Company classifies problem and potential problem loans as Special Mention, Substandard, Doubtful, and Loss. Substandard loans include those characterized by well-defined weaknesses and carry the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. Loans classified as Doubtful, or risk rated nine, have all the weaknesses inherent in those classified as Substandard with the added characteristic that the weaknesses present make collection or liquidation in full, on the basis of currently existing facts, conditions and values, highly questionable and improbable. The final rating of Loss covers loans considered uncollectible and having such little recoverable value that it is not practical to defer writing off the asset. Loans that do not currently expose the Company to sufficient risk to warrant classification in one of the aforementioned categories, but possess weaknesses that warrant management’s close attention, are deemed to be Special Mention. Risk ratings are updated, at a minimum, quarterly. The following tables present gross loans by risk rating: September 30, 2018 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Commercial and industrial $ 7,273,634 $ 83,886 $ 129,183 $ 1,022 $ — $ 7,487,725 Commercial real estate Owner occupied 2,214,765 18,713 54,678 — — 2,288,156 Non-owner occupied 3,765,340 14,666 8,096 — — 3,788,102 Multi-family 164,864 — — — — 164,864 Construction and land development Construction 1,404,619 1,233 6,309 — — 1,412,161 Land 694,596 266 608 — — 695,470 Residential real estate 808,065 5,884 13,124 — — 827,073 Consumer 68,599 41 574 — — 69,214 Total $ 16,394,482 $ 124,689 $ 212,572 $ 1,022 $ — $ 16,732,765 September 30, 2018 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Current (up to 29 days past due) $ 16,386,286 $ 124,056 $ 194,118 $ 846 $ — $ 16,705,306 Past due 30 - 59 days 5,991 393 8,351 — — 14,735 Past due 60 - 89 days 1,870 240 343 — — 2,453 Past due 90 days or more 335 — 9,760 176 — 10,271 Total $ 16,394,482 $ 124,689 $ 212,572 $ 1,022 $ — $ 16,732,765 December 31, 2017 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Commercial and industrial $ 6,675,574 $ 85,781 $ 76,328 $ 3,698 $ — $ 6,841,381 Commercial real estate Owner occupied 2,149,465 43,122 48,397 629 — 2,241,613 Non-owner occupied 3,676,711 11,166 14,692 — — 3,702,569 Multi-family 201,442 — — — — 201,442 Construction and land development Construction 1,072,342 4,477 13,357 — — 1,090,176 Land 535,412 637 5,979 — — 542,028 Residential real estate 408,527 8,971 8,442 — — 425,940 Consumer 47,824 878 84 — — 48,786 Total $ 14,767,297 $ 155,032 $ 167,279 $ 4,327 $ — $ 15,093,935 December 31, 2017 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Current (up to 29 days past due) $ 14,758,149 $ 154,295 $ 145,934 $ 2,993 $ — $ 15,061,371 Past due 30 - 59 days 7,966 518 4,737 — — 13,221 Past due 60 - 89 days 1,182 219 968 — — 2,369 Past due 90 days or more — — 15,640 1,334 — 16,974 Total $ 14,767,297 $ 155,032 $ 167,279 $ 4,327 $ — $ 15,093,935 The table below reflects the recorded investment in loans classified as impaired: September 30, 2018 December 31, 2017 (in thousands) Impaired loans with a specific valuation allowance under ASC 310 (1) $ 3,601 $ 19,315 Impaired loans without a specific valuation allowance under ASC 310 (2) 121,968 79,239 Total impaired loans $ 125,569 $ 98,554 Valuation allowance related to impaired loans (3) $ (1,171 ) $ (5,606 ) (1) Includes TDR loans of $2.6 million and $3.7 million at September 30, 2018 and December 31, 2017 , respectively. (2) Includes TDR loans of $49.5 million and $48.8 million at September 30, 2018 and December 31, 2017 , respectively. (3) Includes valuation allowance related to TDR loans of $0.7 million and $1.2 million at September 30, 2018 and December 31, 2017 , respectively. The following table presents impaired loans by class: September 30, 2018 December 31, 2017 (in thousands) Commercial and industrial $ 76,185 $ 34,156 Commercial real estate Owner occupied 6,660 10,430 Non-owner occupied 12,544 21,251 Multi-family — — Construction and land development Construction — — Land 9,128 15,426 Residential real estate 20,686 17,170 Consumer 366 121 Total $ 125,569 $ 98,554 A valuation allowance is established for an impaired loan when the fair value of the loan is less than the recorded investment. In certain cases, portions of impaired loans are charged-off to realizable value instead of establishing a valuation allowance and are included, when applicable, in the table above as “Impaired loans without a specific valuation allowance under ASC 310.” However, before concluding that an impaired loan needs no associated valuation allowance, an assessment is made to consider all available and relevant information for the method used to evaluate impairment and the type of loan being assessed. The valuation allowance disclosed above is included in the allowance for credit losses reported in the Consolidated Balance Sheets as of September 30, 2018 and December 31, 2017 . The following table presents the average investment in impaired loans and income recognized on impaired loans: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Average balance on impaired loans $ 104,652 $ 108,033 $ 100,712 $ 106,456 Interest income recognized on impaired loans 1,114 1,040 3,109 3,075 Interest recognized on non-accrual loans, cash basis 569 694 1,443 1,372 The following table presents the average investment in impaired loans by loan class: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Commercial and industrial $ 55,026 $ 40,074 $ 47,083 $ 33,358 Commercial real estate Owner occupied 6,698 17,779 8,053 20,136 Non-owner occupied 12,597 20,789 16,349 22,446 Multi-family — — — — Construction and land development Construction — — — — Land 9,218 12,503 9,701 13,297 Residential real estate 20,746 16,692 19,217 17,011 Consumer 367 196 309 208 Total $ 104,652 $ 108,033 $ 100,712 $ 106,456 The average investment in TDR loans was $52.2 million and $52.0 million for the three months ended September 30, 2018 and 2017 , respectively, and $51.9 million and $56.6 million for the nine months ended September 30, 2018 and 2017 , respectively. The following table presents interest income on impaired loans by class: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Commercial and industrial $ 537 $ 307 $ 1,276 $ 788 Commercial real estate Owner occupied 118 166 376 530 Non-owner occupied 218 279 744 798 Multi-family — — — — Construction and land development Construction — — — — Land 146 163 425 551 Residential real estate 95 124 287 406 Consumer — 1 1 2 Total $ 1,114 $ 1,040 $ 3,109 $ 3,075 The Company is not committed to lend significant additional funds on these impaired loans. The following table summarizes nonperforming assets: September 30, 2018 December 31, 2017 (in thousands) Non-accrual loans (1) $ 36,868 $ 43,925 Loans past due 90 days or more on accrual status (2) — 43 Accruing troubled debt restructured loans 42,567 42,431 Total nonperforming loans 79,435 86,399 Other assets acquired through foreclosure, net 20,028 28,540 Total nonperforming assets $ 99,463 $ 114,939 (1) Includes non-accrual TDR loans of $9.6 million and $10.1 million at September 30, 2018 and December 31, 2017 , respectively. (2) Includes less than $0.1 million from loans acquired with deteriorated credit quality at December 31, 2017 . Loans Acquired with Deteriorated Credit Quality Changes in the accretable yield for loans acquired with deteriorated credit quality are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Balance, at beginning of period $ 4,828 $ 14,247 $ 9,324 $ 15,177 Reclassifications from non-accretable to accretable yield (1) — — 683 2,086 Accretion to interest income (224 ) (690 ) (801 ) (2,374 ) Reversal of fair value adjustments upon disposition of loans (563 ) (2,199 ) (5,165 ) (3,531 ) Balance, at end of period $ 4,041 $ 11,358 $ 4,041 $ 11,358 (1) The primary drivers of reclassification from non-accretable to accretable yield resulted from changes in estimated cash flows. Allowance for Credit Losses The following table summarizes the changes in the allowance for credit losses by portfolio type: Three Months Ended September 30, Construction and Land Development Commercial Real Estate Residential Real Estate Commercial and Industrial Consumer Total (in thousands) 2018 Beginning Balance $ 22,159 $ 31,979 $ 6,849 $ 85,244 $ 852 $ 147,083 Charge-offs — — 46 4,610 109 4,765 Recoveries (24 ) (856 ) (440 ) (362 ) (11 ) (1,693 ) Provision 473 (1,250 ) 832 5,652 293 6,000 Ending balance $ 22,656 $ 31,585 $ 8,075 $ 86,648 $ 1,047 $ 150,011 2017 Beginning Balance $ 20,852 $ 28,593 $ 4,838 $ 76,734 $ 794 $ 131,811 Charge-offs — 175 — 2,921 61 3,157 Recoveries (226 ) (1,781 ) (108 ) (619 ) (33 ) (2,767 ) Provision (619 ) (1,474 ) (141 ) 7,192 42 5,000 Ending balance $ 20,459 $ 28,725 $ 4,805 $ 81,624 $ 808 $ 136,421 Nine Months Ended September 30, Construction and Land Development Commercial Real Estate Residential Real Estate Commercial and Industrial Consumer Total (in thousands) 2018 Beginning Balance $ 19,511 $ 31,495 $ 5,478 $ 82,793 $ 773 $ 140,050 Charge-offs 1 233 1,038 10,904 114 12,290 Recoveries (1,420 ) (1,228 ) (831 ) (1,737 ) (35 ) (5,251 ) Provision 1,726 (905 ) 2,804 13,022 353 17,000 Ending balance $ 22,656 $ 31,585 $ 8,075 $ 86,648 $ 1,047 $ 150,011 2017 Beginning Balance $ 21,175 $ 25,673 $ 3,851 $ 73,333 $ 672 $ 124,704 Charge-offs — 1,994 447 6,166 103 8,710 Recoveries (1,011 ) (2,719 ) (1,659 ) (2,705 ) (83 ) (8,177 ) Provision (1,727 ) 2,327 (258 ) 11,752 156 12,250 Ending balance $ 20,459 $ 28,725 $ 4,805 $ 81,624 $ 808 $ 136,421 The following table presents impairment method information related to loans and allowance for credit losses by loan portfolio segment: Commercial Real Estate-Owner Occupied Commercial Real Estate-Non-Owner Occupied Commercial and Industrial Residential Real Estate Construction and Land Development Consumer Total Loans (in thousands) Loans as of September 30, 2018; Recorded Investment Impaired loans with an allowance recorded $ — $ — $ 3,238 $ 363 $ — $ — $ 3,601 Impaired loans with no allowance recorded 6,660 12,544 72,947 20,323 9,128 366 121,968 Total loans individually evaluated for impairment 6,660 12,544 76,185 20,686 9,128 366 125,569 Loans collectively evaluated for impairment 2,276,847 3,859,914 7,411,540 805,800 2,098,503 68,848 16,521,452 Loans acquired with deteriorated credit quality 4,649 80,508 — 587 — — 85,744 Total recorded investment $ 2,288,156 $ 3,952,966 $ 7,487,725 $ 827,073 $ 2,107,631 $ 69,214 $ 16,732,765 Unpaid Principal Balance Impaired loans with an allowance recorded $ — $ — $ 5,520 $ 363 $ — $ — $ 5,883 Impaired loans with no allowance recorded 13,164 18,292 108,469 29,312 25,756 10,726 205,719 Total loans individually evaluated for impairment 13,164 18,292 113,989 29,675 25,756 10,726 211,602 Loans collectively evaluated for impairment 2,276,847 3,859,914 7,411,540 805,800 2,098,503 68,848 16,521,452 Loans acquired with deteriorated credit quality 6,351 96,840 4,357 706 — — 108,254 Total unpaid principal balance $ 2,296,362 $ 3,975,046 $ 7,529,886 $ 836,181 $ 2,124,259 $ 79,574 $ 16,841,308 Related Allowance for Credit Losses Impaired loans with an allowance recorded $ — $ — $ 1,111 $ 60 $ — $ — $ 1,171 Impaired loans with no allowance recorded — — — — — — — Total loans individually evaluated for impairment — — 1,111 60 — — 1,171 Loans collectively evaluated for impairment 13,946 17,497 85,528 8,015 22,656 1,047 148,689 Loans acquired with deteriorated credit quality — 142 9 — — — 151 Total allowance for credit losses $ 13,946 $ 17,639 $ 86,648 $ 8,075 $ 22,656 $ 1,047 $ 150,011 Commercial Real Estate-Owner Occupied Commercial Real Estate-Non-Owner Occupied Commercial and Industrial Residential Real Estate Construction and Land Development Consumer Total Loans (in thousands) Loans as of December 31, 2017; Recorded Investment Impaired loans with an allowance recorded $ — $ — $ 19,315 $ — $ — $ — $ 19,315 Impaired loans with no allowance recorded 10,430 21,250 14,842 17,170 15,426 121 79,239 Total loans individually evaluated for impairment 10,430 21,250 34,157 17,170 15,426 121 98,554 Loans collectively evaluated for impairment 2,221,614 3,777,219 6,807,181 408,169 1,616,778 48,665 14,879,626 Loans acquired with deteriorated credit quality 9,569 105,542 43 601 — — 115,755 Total recorded investment $ 2,241,613 $ 3,904,011 $ 6,841,381 $ 425,940 $ 1,632,204 $ 48,786 $ 15,093,935 Unpaid Principal Balance Impaired loans with an allowance recorded $ — $ — $ 20,795 $ — $ — $ — $ 20,795 Impaired loans with no allowance recorded 17,459 28,028 42,261 26,057 32,289 10,695 156,789 Total loans individually evaluated for impairment 17,459 28,028 63,056 26,057 32,289 10,695 177,584 Loans collectively evaluated for impairment 2,221,614 3,777,219 6,807,181 408,169 1,616,778 48,665 14,879,626 Loans acquired with deteriorated credit quality 12,619 128,440 3,146 720 — — 144,925 Total unpaid principal balance $ 2,251,692 $ 3,933,687 $ 6,873,383 $ 434,946 $ 1,649,067 $ 59,360 $ 15,202,135 Related Allowance for Credit Losses Impaired loans with an allowance recorded $ — $ — $ 5,606 $ — $ — $ — $ 5,606 Impaired loans with no allowance recorded — — — — — — — Total loans individually evaluated for impairment — — 5,606 — — — 5,606 Loans collectively evaluated for impairment 13,884 16,135 76,919 5,500 19,599 776 132,813 Loans acquired with deteriorated credit quality — 1,629 2 — — — 1,631 Total allowance for credit losses $ 13,884 $ 17,764 $ 82,527 $ 5,500 $ 19,599 $ 776 $ 140,050 Troubled Debt Restructurings A TDR loan is a loan on which the Company, for reasons related to a borrower’s financial difficulties, grants a concession to the borrower that the Company would not otherwise consider. The loan terms that have been modified or restructured due to a borrower’s financial situation include, but are not limited to, a reduction in the stated interest rate, an extension of the maturity or renewal of the loan at an interest rate below current market, a reduction in the face amount of the debt, a reduction in the accrued interest, or deferral of interest payments. The majority of the Company's modifications are extensions in terms or deferral of payments which result in no lost principal or interest followed by reductions in interest rates or accrued interest. A TDR loan is also considered impaired. Consistent with regulatory guidance, a TDR loan that is subsequently modified in another restructuring agreement but has shown sustained performance and classification as a TDR, will be removed from TDR status provided that the modified terms were market-based at the time of modification. During the three months ended September 30, 2018 , the Company had four new TDR loans with a recorded investment of $2.8 million and two new TDR loans during the three months ended September 30, 2017 with a recorded investment of $ 1.9 million . During the nine months ended September 30, 2018 , the Company had eleven new TDR loans with a recorded investment of $34.4 million and three new TDR loans with a recorded investment of $6.8 million during the nine months ended September 30, 2017 . No principal amounts were forgiven and there were no waived fees or other expenses resulting from these TDRs. During the three and nine months ended September 30, 2018 , there were no TDR loans for which there was a payment default. During the three months ended September 30, 2017 , there was one CRE, non-owner occupied TDR loan with a recorded investment of $0.1 million for which there was a payment default. During the nine months ended September 30, 2017 , there were three TDR loans with a recorded investment of $0.5 million for which there was a payment default. A TDR loan is deemed to have a payment default when it becomes past due 90 days, goes on non-accrual, or is restructured again. Payment defaults, along with other qualitative indicators, are considered by management in the determination of the allowance for credit losses. At September 30, 2018 , commitments outstanding on TDR loans totaled $0.3 million . There were no loan commitments outstanding on TDR loans at December 31, 2017 . Loan Purchases and Sales For the three months ended September 30, 2018 and 2017 , secondary market loan purchases totaled $482.8 million and $216.8 million , respectively. For the nine months ended September 30, 2018 and 2017 , secondary market loan purchases totaled $1.01 billion and $666.8 million , respectively. For 2018 , these purchased loans consisted of $511.5 million of commercial and industrial loans, $471.7 million of residential real estate loans, and $27.1 million of construction loans. For 2017 , these purchased loans consisted of $520.4 million of commercial and industrial loans and $146.4 million of residential real estate loans. During the three months ended September 30, 2018 , the Company sold loans which primarily consisted of commercial and industrial loans with a carrying value of $12.4 million and recognized a net gain of $1.0 million . During the three months ended September 30, 2017 , the Company sold commercial and industrial loans with a carrying value of $41.3 million and did not recognize a significant net gain or loss on the sales. During the nine months ended September 30, 2018 , the Company sold loans which primarily consisted of commercial and industrial loans with a carrying value of $46.5 million and recognized a gain of $2.4 million on the sales. During the nine months ended September 30, 2017 , the Company sold loans, which consisted primarily of commercial and industrial loans with a carrying value of $50.5 million and recognized a loss of $0.1 million on the sales.

Other Assets Acquired Through F

Other Assets Acquired Through Foreclosure	9 Months Ended
	Sep. 30, 2018
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Other Assets Acquired Through Foreclosure	The following table represents the changes in other assets acquired through foreclosure: Three Months Ended September 30, 2018 Gross Balance Valuation Allowance Net Balance (in thousands) Balance, beginning of period $ 31,145 $ (3,604 ) $ 27,541 Proceeds from sale of other real estate owned and repossessed assets, net (1,093 ) 401 (692 ) Charitable contribution (1) (6,895 ) — (6,895 ) Valuation adjustments, net — — — Gains (losses), net (2) 74 — 74 Balance, end of period $ 23,231 $ (3,203 ) $ 20,028 2017 Balance, beginning of period $ 35,037 $ (4,049 ) $ 30,988 Transfers to other assets acquired through foreclosure, net 430 — 430 Proceeds from sale of other real estate owned and repossessed assets, net (2,491 ) 330 (2,161 ) Valuation adjustments, net — (343 ) (343 ) Gains (losses), net (2) 78 — 78 Balance, end of period $ 33,054 $ (4,062 ) $ 28,992 Nine Months Ended September 30, 2018 Gross Balance Valuation Allowance Net Balance (in thousands) Balance, beginning of period $ 32,552 $ (4,012 ) $ 28,540 Transfers to other assets acquired through foreclosure, net 5,744 — 5,744 Proceeds from sale of other real estate owned and repossessed assets, net (9,634 ) 841 (8,793 ) Charitable contribution (1) (6,895 ) — (6,895 ) Valuation adjustments, net — (32 ) (32 ) Gains (losses), net (3) 1,464 — 1,464 Balance, end of period $ 23,231 $ (3,203 ) $ 20,028 2017 Balance, beginning of period $ 54,138 $ (6,323 ) $ 47,815 Transfers to other assets acquired through foreclosure, net 1,812 — 1,812 Proceeds from sale of other real estate owned and repossessed assets, net (23,129 ) 2,381 (20,748 ) Valuation adjustments, net — (120 ) (120 ) Gains (losses), net (3) 233 — 233 Balance, end of period $ 33,054 $ (4,062 ) $ 28,992 (1) Represents a contribution of OREO property to the Company's charitable foundation. See Note 16. Related Party Transactions for further discussion. (2) There were no net gains related to initial transfers to other assets during the three months ended September 30, 2018 and 2017 , respectively. (3) There were $1.0 million and $0.1 million in net gains related to initial transfers to other assets during the nine months ended September 30, 2018 and 2017 , respectively. At September 30, 2018 and 2017 , the majority of the Company’s repossessed assets consisted of properties located in Nevada. The Company held 12 properties at September 30, 2018 , compared to 19 at December 31, 2017 , and 20 at September 30, 2017 .

Other Borrowings

Other Borrowings	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Other Borrowings	The following table summarizes the Company’s borrowings as of September 30, 2018 and December 31, 2017 : September 30, 2018 December 31, 2017 (in thousands) Short-Term: FHLB advances $ — $ 390,000 Total short-term borrowings $ — $ 390,000 The Company maintains other lines of credit with correspondent banks totaling $306.0 million . These lines of credit are unsecured, of which $45.0 million have a floating interest rate of one-month LIBOR plus 3.25% and $261.0 million have a rate equivalent to the federal funds effective rate. As of September 30, 2018 and December 31, 2017 , there were no outstanding balances on the Company's lines of credit. The Company maintains lines of credit with the FHLB and the FRB. The Company’s borrowing capacity is determined based on collateral pledged, generally consisting of investment securities and loans, at the time of the borrowing. At September 30, 2018 , the Company had no short-term FHLB overnight advances. At December 31, 2017 , short-term FHLB advances of $390.0 million had an interest rate of 1.41% . Other short-term borrowing sources available to the Company include Federal funds purchased from correspondent banks and customer repurchase agreements. Federal funds purchased have a rate equivalent to the federal funds effective rate plus 0.10% to 0.20% and customer repurchase agreements have an average rate of 0.15%. There were no outstanding balances on Federal funds purchased as of September 30, 2018 and December 31, 2017 . At September 30, 2018 and December 31, 2017 , customer repurchase agreements totaled $21.0 million and $26.0 million , respectively. As of September 30, 2018 and December 31, 2017 , the Company had additional available credit with the FHLB of approximately $2.84 billion and $1.91 billion , respectively, and with the FRB of approximately $1.40 billion and $1.11 billion , respectively.

Qualifying Debt

Qualifying Debt	9 Months Ended
	Sep. 30, 2018
Qualifying Debt Disclosure [Abstract]
Qualifying Debt	Subordinated Debt The Parent has $175.0 million of subordinated debentures, which were recorded net of issuance costs of $5.5 million , and mature July 1, 2056. Beginning on or after July 1, 2021, the Company may redeem the debentures, in whole or in part, at their principal amount plus any accrued and unpaid interest. The debentures have a fixed interest rate of 6.25% per annum. WAB has $150.0 million of subordinated debt, which was recorded net of debt issuance costs of $1.8 million , and matures July 15, 2025. The subordinated debt has a fixed interest rate of 5.00% through June 30, 2020 and then converts to a variable rate of 3.20% plus three-month LIBOR through maturity. To hedge the interest rate risk on the Company's subordinated debt issuances, the Company entered into fair value interest rate hedges with receive fixed/pay variable swaps. The carrying value of all subordinated debt issuances, which includes the fair value of the related hedges, totals $290.8 million and $308.6 million at September 30, 2018 and December 31, 2017 , respectively. Junior Subordinated Debt The Company has formed or acquired through acquisition eight statutory business trusts, which exist for the exclusive purpose of issuing Cumulative Trust Preferred Securities. With the exception of debt issued by Bridge Capital Trust I and Bridge Capital Trust II, junior subordinated debt is recorded at fair value at each reporting date due to the FVO election made by the Company under ASC 825. The Company did not make the FVO election for the junior subordinated debt acquired as part of the Bridge acquisition. Accordingly, the carrying value of these trusts does not reflect the current fair value of the debt and includes a fair market value adjustment established at acquisition that is being accreted over the remaining life of the trusts. The carrying value of junior subordinated debt was $68.3 million at each of the periods ended September 30, 2018 and December 31, 2017 , respectively. The weighted average interest rate of all junior subordinated debt as of September 30, 2018 was 4.74% , which is three-month LIBOR plus the contractual spread of 2.34%, compared to a weighted average interest rate of 4.03% at December 31, 2017 .

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2018
Stockholders' Equity Note [Abstract]
Stockholder's Equity	Stock-Based Compensation Restricted Stock Awards Restricted stock awards granted to employees generally vest over a three -year period. Stock grants made to non-employee WAL directors in 2018 became fully vested at June 30, 2018. The Company estimates the compensation expense for stock grants based upon the grant date fair value. Stock compensation expense is recognized on a straight-line basis over the requisite service period for the entire award. The aggregate grant date fair value for the restricted stock awards granted during the three and nine months ended September 30, 2018 was $0.7 million and $23.7 million , respectively. Stock compensation expense related to restricted stock awards and stock options granted to employees are included in Salaries and employee benefits in the Consolidated Income Statement. For restricted stock awards granted to WAL directors, the related stock compensation expense is included in Legal, professional, and directors' fees. For the three and nine months ended September 30, 2018 , the Company recognized $3.4 million and $12.4 million , respectively, in stock-based compensation expense related to all restricted stock award grants, compared to $2.7 million and $11.3 million for the three and nine months ended September 30, 2017 , respectively. In addition, the Company previously granted shares of restricted stock to certain members of executive management that had both performance and service conditions that affect vesting. There were no such grants made during the three and nine months ended September 30, 2018 , however expense is still being recognized for the grants made in 2016 and 2017 as they also have a three -year vesting period. For the three and nine months ended September 30, 2018 , the Company recognized $0.6 million and $1.9 million , respectively, in stock-based compensation expense related to these performance-based restricted stock grants, compared to $0.8 million and $1.6 million for the three and nine months ended September 30, 2017 , respectively. Performance Stock Units The Company grants members of its executive management performance stock units that do not vest unless the Company achieves a specified cumulative EPS target over a three-year performance period. The number of shares issued will vary based on the cumulative EPS target that is achieved. The Company estimates the cost of performance stock units based upon the grant date fair value and expected vesting percentage over the three-year performance period. For the three and nine months ended September 30, 2018 , the Company recognized $1.5 million and $4.8 million , respectively, in stock-based compensation expense related to these performance stock units, compared to $1.9 million and $4.5 million for the three and nine months ended September 30, 2017 , respectively. The three-year performance period for the 2015 grant ended on December 31, 2017, and the Company's cumulative EPS for the performance period exceeded the level required for a maximum award under the terms of the grant. As a result, executive management members were entitled to the maximum award of 202,074 shares, which was paid out in the first quarter of 2018 . Treasury Shares Treasury share purchases represent shares surrendered to the Company equal in value to the statutory payroll tax withholding obligations arising from the vesting of employee restricted stock awards. During the three and nine months ended September 30, 2018 , the Company purchased treasury shares of 18,402 and 201,354 , respectively, at a weighted average price of $57.81 and $58.91 per share, respectively. During the three and nine months ended September 30, 2017 , the Company purchased treasury shares of 64,705 and 266,883 , respectively, at a weighted average price of $51.82 and $51.10 per share, respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Accumulated Other Comprehensive Income	The following table summarizes the changes in accumulated other comprehensive income (loss) by component, net of tax, for the periods indicated: Three Months Ended September 30, Unrealized holding (losses) gains on AFS Unrealized holding gains (losses) on SERP Unrealized holding gains (losses) on junior subordinated debt Impairment loss on securities Total (in thousands) Balance, June 30, 2018 $ (61,859 ) $ 446 $ 9,954 $ 144 $ (51,315 ) Other comprehensive (loss) income before reclassifications (22,462 ) (12 ) (2,028 ) — (24,502 ) Amounts reclassified from AOCI 5,454 — — — 5,454 Net current-period other comprehensive (loss) income (17,008 ) (12 ) (2,028 ) — (19,048 ) Balance, September 30, 2018 $ (78,867 ) $ 434 $ 7,926 $ 144 $ (70,363 ) Balance, June 30, 2017 $ (449 ) $ 157 $ 6,638 $ 144 $ 6,490 Other comprehensive income (loss) before reclassifications 1,116 114 641 — 1,871 Amounts reclassified from AOCI (197 ) — — — (197 ) Net current-period other comprehensive income (loss) 919 114 641 — 1,674 Balance, September 30, 2017 $ 470 $ 271 $ 7,279 $ 144 $ 8,164 Nine Months Ended September 30, Unrealized holding (losses) gains on AFS Unrealized holding gains (losses) on SERP Unrealized holding gains (losses) on junior subordinated debt Impairment loss on securities Total (in thousands) Balance, December 31, 2017 $ (10,026 ) $ 385 $ 6,352 $ 144 $ (3,145 ) Balance, January 1, 2018 (1) (12,556 ) 469 7,740 144 (4,203 ) Other comprehensive (loss) income before reclassifications (71,765 ) (35 ) 186 — (71,614 ) Amounts reclassified from AOCI 5,454 — — — 5,454 Net current-period other comprehensive (loss) income (66,311 ) (35 ) 186 — (66,160 ) Balance, September 30, 2018 $ (78,867 ) $ 434 $ 7,926 $ 144 $ (70,363 ) Balance, December 31, 2016 $ (14,916 ) $ 121 $ 9,956 $ 144 $ (4,695 ) Other comprehensive income (loss) before reclassifications 15,947 150 (2,677 ) — 13,420 Amounts reclassified from AOCI (561 ) — — — (561 ) Net current-period other comprehensive income (loss) 15,386 150 (2,677 ) — 12,859 Balance, September 30, 2017 $ 470 $ 271 $ 7,279 $ 144 $ 8,164 (1) As adjusted for adoption of ASU 2016-01 and ASU 2018-02, see " Note 1. Summary of Significant Accounting Policies " for further discussion. The following table presents reclassifications out of accumulated other comprehensive income (loss): Three Months Ended September 30, Nine Months Ended September 30, Income Statement Classification 2018 2017 2018 2017 (in thousands) (Loss) gain on sales of investment securities, net $ (7,232 ) $ 319 $ (7,232 ) $ 907 Income tax expense (benefit) 1,778 (122 ) 1,778 (346 ) Net of tax $ (5,454 ) $ 197 $ (5,454 ) $ 561

Derivatives and Hedging

Derivatives and Hedging	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging Activities	The Company is a party to various derivative instruments. Derivative instruments are contracts between two or more parties that have a notional amount and an underlying variable, require a small or no initial investment, and allow for the net settlement of positions. A derivative’s notional amount serves as the basis for the payment provision of the contract and takes the form of units, such as shares or dollars. A derivative’s underlying variable is a specified interest rate, security price, commodity price, foreign exchange rate, index, or other variable. The interaction between the notional amount and the underlying variable determines the number of units to be exchanged between the parties and influences the fair value of the derivative contract. The primary type of derivatives that the Company uses are interest rate swaps. Generally, these instruments are used to help manage the Company's exposure to interest rate risk and meet client financing and hedging needs. Derivatives are recorded at fair value in the Consolidated Balance Sheets, after taking into account the effects of bilateral collateral and master netting agreements. These agreements allow the Company to settle all derivative contracts held with the same counterparty on a net basis, and to offset net derivative positions with related cash collateral, where applicable. As of September 30, 2018 , December 31, 2017 , and September 30, 2017 , the Company does not have any outstanding cash flow hedges. Derivatives Designated in Hedge Relationships The Company utilizes derivatives that have been designated as part of a hedge relationship in accordance with the applicable accounting guidance to minimize the exposure to changes in benchmark interest rates and volatility of net interest income and EVE to interest rate fluctuations. The primary derivative instruments used to manage interest rate risk are interest rate swaps, which convert the contractual interest rate index of agreed-upon amounts of assets and liabilities (i.e., notional amounts) to another interest rate index. The Company has entered into pay fixed/receive variable interest rate swaps designated as fair value hedges of certain fixed rate loans. As a result, the Company receives variable-rate interest payments in exchange for making fixed-rate payments over the lives of the contracts without exchanging the notional amounts. The Company has also entered into receive fixed/pay variable interest rate swaps, designated as fair value hedges on its fixed rate subordinated debt offerings. As a result, the Company is paying a floating rate of three-month LIBOR plus 3.16% and is receiving semi-annual fixed payments of 5.00% to match the payments on the $150.0 million subordinated debt. For the fair value hedge on the Parent's $175.0 million subordinated debentures issued on June 16, 2016, the Company is paying a floating rate of three-month LIBOR plus 3.25% and is receiving quarterly fixed payments of 6.25% to match the payments on the debt. Derivatives Not Designated in Hedge Relationships Management also enters into certain foreign exchange derivative contracts and back-to-back interest rate swaps which are not designated as accounting hedges. Foreign exchange derivative contracts include spot, forward, and forward window contracts. The purpose of these derivative contracts is to mitigate foreign currency risk on transactions entered into, or on behalf of customers. Contracts with customers, along with the related derivative trades the Company places, are both remeasured at fair value, and are referred to as economic hedges since they economically offset the Company's exposure. The Company's back-to-back interest rate swaps are used to manage long-term interest rate risk. As of each of the periods ended September 30, 2018 , December 31, 2017 , and September 30, 2017 , derivatives not designated as hedging instruments were in a net asset position of $0.2 million . For the three months ended September 30, 2018 and 2017 , net changes in the fair value related to these derivative contracts totaled $1.1 million and $0.8 million , respectively, and $3.5 million and $2.6 million for the nine months ended September 30, 2018 and 2017 , respectively, and are included as part of Foreign currency income in the Consolidated Income Statements. As of September 30, 2018 and December 31, 2017 , the following amounts are reflected in the Consolidated Balance Sheet related to cumulative basis adjustments for fair value hedges: September 30, 2018 December 31, 2017 Carrying Value of Hedged Assets/(Liabilities) Cumulative Amount of the Fair Value Hedging Adjustment (1) Carrying Value of Hedged Assets/(Liabilities) Cumulative Amount of the Fair Value Hedging Adjustment (1) (in thousands) Loans - HFI, net of deferred loan fees and costs $ 635,184 $ 1,997 $ 699,452 $ 41,919 Qualifying debt (290,801 ) 28,160 (308,608 ) 9,959 (1) Included in the carrying value of the hedged assets/(liabilities). For the Company's derivative instruments that are designated and qualify as a fair value hedge, the gain or loss on the derivative instrument as well as the offsetting loss or gain on the hedged item attributable to the hedged risk are recognized in current earnings in the same line item as the offsetting loss or gain on the related interest rate swaps. For loans, the gain or loss on the hedged item is included in interest income and for subordinated debt, the gain or loss on the hedged item is included in interest expense. Fair Values, Volume of Activity, and Gain/Loss Information Related to Derivative Instruments The following table summarizes the fair values of the Company's derivative instruments on a gross and net basis as of September 30, 2018 , December 31, 2017 , and September 30, 2017 . The derivative asset and liability balances are presented on a gross basis, prior to the application of bilateral collateral and master netting agreements. Total derivative assets and liabilities are adjusted to take into account the impact of legally enforceable master netting agreements that allow the Company to settle all derivative contracts with the same counterparty on a net basis and to offset the net derivative position with the related collateral. Where master netting agreements are not in effect or are not enforceable under bankruptcy laws, the Company does not adjust those derivative amounts with counterparties. The fair value of derivative contracts, after taking into account the effects of master netting agreements, is included in other assets or other liabilities in the Consolidated Balance Sheets, as indicated in the following table: September 30, 2018 December 31, 2017 September 30, 2017 Fair Value Fair Value Fair Value Notional Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities (in thousands) Derivatives designated as hedging instruments: Fair value hedges Interest rate swaps $ 971,408 $ 7,883 $ 38,040 $ 993,432 $ 1,703 $ 53,581 $ 1,016,694 $ 1,656 $ 59,346 Total 971,408 7,883 38,040 993,432 1,703 53,581 1,016,694 1,656 59,346 Netting adjustments (1) — 6,119 6,119 — 896 896 — 1,588 1,588 Net derivatives in the balance sheet $ 971,408 $ 1,764 $ 31,921 $ 993,432 $ 807 $ 52,685 $ 1,016,694 $ 68 $ 57,758 Derivatives not designated as hedging instruments: Foreign currency contracts (2) $ 47,349 $ 1,003 $ 841 $ 85,335 $ 1,232 $ 983 $ 68,122 $ 494 $ 291 Interest rate swaps 2,348 92 92 36,969 776 776 35,578 641 641 Total $ 49,697 $ 1,095 $ 933 $ 122,304 $ 2,008 $ 1,759 $ 103,700 $ 1,135 $ 932 (1) Netting adjustments represent the amounts recorded to convert the Company's derivative balances from a gross basis to a net basis in accordance with the applicable accounting guidance. (2) Prior period derivative asset / liability netting adjustments have been made to conform to current presentation. Counterparty Credit Risk Like other financial instruments, derivatives contain an element of credit risk. This risk is measured as the expected positive replacement value of the contracts. Management generally enters into bilateral collateral and master netting agreements that provide for the net settlement of all contracts with the same counterparty. Additionally, management monitors counterparty credit risk exposure on each contract to determine appropriate limits on the Company's total credit exposure across all product types. In general, the Company has a zero credit threshold with regard to derivative exposure with counterparties. Management reviews the Company's collateral positions on a daily basis and exchanges collateral with counterparties in accordance with standard ISDA documentation and other related agreements. The Company generally holds collateral in the form of cash deposits or highly rated securities issued by the U.S. Treasury or government-sponsored enterprises, such as GNMA, FNMA, and FHLMC. The total collateral netted against net derivative liabilities totaled $34.7 million at September 30, 2018 , $53.6 million at December 31, 2017 , and $59.3 million at September 30, 2017 . The following table summarizes the Company's largest exposure to an individual counterparty at the dates indicated: September 30, 2018 December 31, 2017 September 30, 2017 (in thousands) Largest gross exposure (derivative asset) to an individual counterparty $ 5,802 $ 893 $ 945 Collateral posted by this counterparty — — — Derivative liability with this counterparty 9,567 40,340 44,053 Collateral pledged to this counterparty 22,179 60,476 65,051 Net exposure after netting adjustments and collateral $ — $ — $ — Credit Risk Contingent Features Management has entered into certain derivative contracts that require the Company to post collateral to the counterparties when these contracts are in a net liability position. Conversely, the counterparties may be required to post collateral when these contracts are in a net asset position. The amount of collateral to be posted is based on the amount of the net liability and exposure thresholds. As of September 30, 2018 , December 31, 2017 , and September 30, 2017 the aggregate fair value of all derivative contracts with credit risk contingent features (i.e., those containing collateral posting provisions) held by the Company that were in a net liability position totaled $31.9 million , $52.7 million , and $57.8 million , respectively. As of September 30, 2018 , the Company was in an over-collateralized net position of $17.7 million after considering $52.4 million of collateral held in the form of cash and securities. As of December 31, 2017 and September 30, 2017 , the Company was in an over-collateralized position of $25.0 million and $25.1 million , respectively.

Earnings per Share

Earnings per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share	Diluted EPS is based on the weighted average outstanding common shares during each period, including common stock equivalents. Basic EPS is based on the weighted average outstanding common shares during the period. The following table presents the calculation of basic and diluted EPS: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands, except per share amounts) Weighted average shares - basic 104,768 104,221 104,664 104,124 Dilutive effect of stock awards 680 721 734 817 Weighted average shares - diluted 105,448 104,942 105,398 104,941 Net income $ 111,123 $ 82,844 $ 316,702 $ 236,146 Earnings per share - basic 1.06 0.79 3.03 2.27 Earnings per share - diluted 1.05 0.79 3.00 2.25 The Company had no anti-dilutive stock options outstanding at each of the periods ended September 30, 2018 and 2017 .

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	The effective tax rate was 6.32% and 29.64% for the three months ended September 30, 2018 and 2017 , respectively. For the nine months ended September 30, 2018 and 2017 , the Company's effective tax rate was 14.48% and 27.89% , respectively. The decrease in the effective tax rate from the three and nine months ended September 30, 2017 is due primarily to the decrease in the Federal statutory rate effective in 2018 and management's decision during the quarter to carryback its 2017 federal NOLs. These federal NOLs resulted from the acceleration of deductions into and deferral of revenue from 2017. As the federal income tax rate was higher in the years to which the carryback is applicable, a larger tax benefit results from the decision to carryback the 2017 federal NOLs, rather than carryforward these losses to future taxable years. As of September 30, 2018 , the net deferred tax asset was $43.5 million , an increase of $37.7 million from December 31, 2017 . This overall increase in the net deferred tax asset was primarily the result of the deferral of WAB's dividend from the real estate investment trust from 2017 to 2018 and decreases in the fair market value of AFS securities, which were not fully offset by the utilization of NOL and credit carryovers. Although realization is not assured, the Company believes that the realization of the recognized deferred tax asset of $43.5 million at September 30, 2018 is more-likely-than-not based on expectations as to future taxable income and based on available tax planning strategies that could be implemented if necessary to prevent a carryover from expiring. At September 30, 2018 and December 31, 2017 , the Company had no deferred tax valuation allowance. As of September 30, 2018 , the Company’s gross federal NOL carryovers, all of which are subject to limitations under Section 382 of the IRC, totaled approximately $49.8 million for which an ending deferred tax asset of $6.3 million has been recorded reflecting the expected benefit of these federal NOL carryovers remaining. The Company also has varying gross amounts of state NOL carryovers, primarily with California and Arizona. The ending gross California and Arizona NOL carryovers totaled approximately $7.3 million and $5.0 million , respectively. A deferred tax asset of $1.1 million has been recorded to reflect the expected benefit of all state NOL carryovers remaining. Investments in LIHTC The Company invests in LIHTC funds that are designed to generate a return primarily through the realization of federal tax credits. Investments in LIHTC total $295.1 million and $267.0 million as of September 30, 2018 and December 31, 2017 , respectively. Unfunded LIHTC obligations are included as part of other liabilities in the Consolidated Balance Sheets and total $139.4 million and $151.3 million as of September 30, 2018 and December 31, 2017 , respectively. For the three months ended September 30, 2018 and 2017 , $9.0 million and $6.8 million , respectively, of amortization related to LIHTC investments was recognized as a component of income tax expense. For the nine months ended September 30, 2018 and 2017 , $26.5 million and $19.5 million , respectively, of amortization related to LIHTC investments was recognized as a component of income tax expense.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Unfunded Commitments and Letters of Credit The Company is party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit and standby letters of credit. They involve, to varying degrees, elements of credit risk in excess of amounts recognized in the Consolidated Balance Sheets. Lines of credit are obligations to lend money to a borrower. Credit risk arises when the borrower's current financial condition may indicate less ability to pay than when the commitment was originally made. In the case of standby letters of credit, the risk arises from the potential failure of the customer to perform according to the terms of a contract. In such a situation, the third party might draw on the standby letter of credit to pay for completion of the contract and the Company would look to its customer to repay these funds with interest. To minimize the risk, the Company uses the same credit policies in making commitments and conditional obligations as it would for a loan to that customer. Standby letters of credit and financial guarantees are commitments issued by the Company to guarantee the performance of a customer to a third party in borrowing arrangements. The Company generally has recourse to recover from the customer any amounts paid under the guarantees. Typically, letters of credit issued have expiration dates within one year. A summary of the contractual amounts for unfunded commitments and letters of credit are as follows: September 30, 2018 December 31, 2017 (in thousands) Commitments to extend credit, including unsecured loan commitments of $594,074 at September 30, 2018 and $364,638 at December 31, 2017 $ 6,798,062 $ 5,851,158 Credit card commitments and financial guarantees 218,993 153,752 Standby letters of credit, including unsecured letters of credit of $16,940 at September 30, 2018 and $11,664 at December 31, 2017 216,636 161,966 Total $ 7,233,691 $ 6,166,876 Commitments to extend credit are agreements to lend to a customer provided that there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. The Company enters into credit arrangements that generally provide for the termination of advances in the event of a covenant violation or other event of default. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer’s creditworthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the Company upon extension of credit, is based on management’s credit evaluation of the party. The commitments are collateralized by the same types of assets used as loan collateral. The Company has exposure to credit losses from unfunded commitments and letters of credit. As funds have not been disbursed on these commitments, they are not reported as loans outstanding. Credit losses related to these commitments are included in other liabilities as a separate loss contingency and are not included in the allowance for credit losses reported in " Note 3. Loans, Leases and Allowance for Credit Losses " of these Unaudited Consolidated Financial Statements. This loss contingency for unfunded loan commitments and letters of credit was $7.6 million and $6.2 million as of September 30, 2018 and December 31, 2017 , respectively. Changes to this liability are adjusted through other expense in the Consolidated Income Statement. Concentrations of Lending Activities The Company’s lending activities are driven in large part by the customers served in the market areas where the Company has branch offices in the states of Arizona, Nevada, and California. Despite the geographic concentration of lending activities, the Company does not have a single external customer from which it derives 10% or more of its revenues. The Company monitors concentrations within four broad categories: geography, industry, product, and collateral. The Company's loan portfolio includes significant credit exposure to the CRE market. As of September 30, 2018 and December 31, 2017 , CRE related loans accounted for approximately 50% and 52% of total loans, respectively. Substantially all of these loans are secured by first liens with an initial loan to value ratio of generally not more than 75% . Approximately 37% and 36% of these CRE loans, excluding construction and land loans, were owner-occupied at September 30, 2018 and December 31, 2017 , respectively. Contingencies The Company is involved in various lawsuits of a routine nature that are being handled and defended in the ordinary course of the Company’s business. Expenses are being incurred in connection with these lawsuits, but in the opinion of management, based in part on consultation with outside legal counsel, the resolution of these lawsuits and associated defense costs will not have a material impact on the Company’s financial position, results of operations, or cash flows. Lease Commitments The Company leases the majority of its office locations and many of these leases contain multiple renewal options and provisions for increased rents. Total rent expense of $2.8 million for each of the three months ended September 30, 2018 and 2017 was included in Occupancy expense in these Unaudited Consolidated Financial Statements. For the nine months ended September 30, 2018 and 2017 , total rent expense was $8.1 million and $8.2 million , respectively.

Fair Value Accounting

Fair Value Accounting	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Accounting	The fair value of an asset or liability is the price that would be received to sell that asset or paid to transfer that liability in an orderly transaction occurring in the principal market (or most advantageous market in the absence of a principal market) for such asset or liability. In estimating fair value, the Company utilizes valuation techniques that are consistent with the market approach, the income approach, and/or the cost approach. Such valuation techniques are consistently applied. Inputs to valuation techniques include the assumptions that market participants would use in pricing an asset or liability. ASC 825 establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy under ASC 825 are described in " Note 1. Summary of Significant Accounting Policies " of these Notes to Unaudited Consolidated Financial Statements. In general, fair value is based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally-developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. These adjustments may include amounts to reflect counterparty credit quality and the Company’s creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. The Company’s valuation methodologies may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. While management believes the Company’s valuation methodologies are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different estimate of fair value at the reporting date. Furthermore, the reported fair value amounts have not been comprehensively revalued since the presentation dates, and therefore, estimates of fair value after the balance sheet date may differ significantly from the amounts presented herein. A more detailed description of the valuation methodologies used for assets and liabilities measured at fair value is set forth below. Transfers between levels in the fair value hierarchy are recognized as of the end of the month following the event or change in circumstances that caused the transfer. Under ASC 825, the Company elected the FVO treatment for junior subordinated debt issued by WAL. This election is irrevocable and results in the recognition of unrealized gains and losses on these items at each reporting date. These unrealized gains and losses are recognized as part of other comprehensive income rather than earnings. The Company did not elect FVO treatment for the junior subordinated debt assumed in the Bridge Capital Holdings acquisition. For the three and nine months ended September 30, 2018 and 2017 , gains and losses from fair value changes on junior subordinated debt and trading securities were as follows: Changes in Fair Values for Items Measured at Fair Value Unrealized Gain/(Loss) on Assets and Liabilities Measured at Fair Value, Net Interest Income on Securities Interest Expense on Junior Subordinated Debt Total Changes Included in Current-Period Earnings Changes Included in OCI (in thousands) Three Months Ended September 30, 2018 Junior subordinated debt $ (2,689 ) $ — $ 1,056 $ 1,056 $ (2,028 ) Nine Months Ended September 30, 2018 Junior subordinated debt $ 247 $ — $ 2,979 $ 2,979 $ 186 Three Months Ended September 30, 2017 Junior subordinated debt $ 1,035 $ — $ (835 ) $ (835 ) $ 641 Nine Months Ended September 30, 2017 Trading securities $ — $ 9 $ — $ 9 $ — Junior subordinated debt (4,327 ) — (2,376 ) (2,376 ) (2,677 ) Total $ (4,327 ) $ 9 $ (2,376 ) $ (2,367 ) $ (2,677 ) During the year ended December 31, 2017, the Company sold all of its trading securities. No significant gain or loss was recognized upon sale of these securities. Fair value on a recurring basis Financial assets and financial liabilities measured at fair value on a recurring basis include the following: Trading securities: All of the Company’s trading securities, which consisted of MBS, were reported at fair value utilizing Level 2 inputs in the same manner as described above for AFS securities. AFS securities: Securities classified as AFS are reported at fair value utilizing Level 2 inputs. For these securities, the Company obtains fair value measurements from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information, and the bond’s terms and conditions, among other things. Equity securities: Preferred stock and CRA investments are reported at fair value utilizing Level 1 inputs. Independent pricing service: The Company's independent pricing service provides pricing information on the majority of the Company's Level 1 and 2 securities. Management independently evaluates the fair value measurements received from the Company's third party pricing service through multiple review steps. First, management reviews what has transpired in the marketplace with respect to interest rates, credit spreads, volatility, and mortgage rates, among other things, and develops an expectation of changes to the securities' valuations from the previous quarter. Then, management obtains market values from additional sources. The pricing service provides management with observable market data including interest rate curves and mortgage prepayment speed grids, as well as dealer quote sheets, new bond offering sheets, and historical trade documentation. Management reviews the assumptions and decides whether they are reasonable. Management may compare interest rates, credit spreads, and prepayments speeds used as part of the assumptions to those that management believes are reasonable. Management may price securities using the provided assumptions to determine whether they can develop similar prices on like securities. Any discrepancies between management’s review and the prices provided by the vendor are discussed with the vendor and the Company’s other valuation advisors. Lastly, management selects a sample of investment securities and compares the values provided by its primary third party pricing service to the market values obtained from secondary sources and evaluates those with notable variances. Interest rate swaps: Interest rate swaps are reported at fair value utilizing Level 2 inputs. The Company obtains dealer quotations to value its interest rate swaps. Junior subordinated debt: The Company estimates the fair value of its junior subordinated debt using a discounted cash flow model which incorporates the effect of the Company’s own credit risk in the fair value of the liabilities (Level 3). The Company’s cash flow assumptions are based on contractual cash flows as the Company anticipates that it will pay the debt according to its contractual terms. As of September 30, 2018 , the Company estimates the discount rate at 6.20% , which represents an implied credit spread of 3.80% plus three-month LIBOR ( 2.40% ). As of December 31, 2017 , the Company estimated the discount rate at 5.61% , which was a 3.92% credit spread plus three-month LIBOR ( 1.69% ). The fair value of assets and liabilities measured at fair value on a recurring basis was determined using the following inputs as of the periods presented: Fair Value Measurements at the End of the Reporting Period Using: Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Fair Value (in thousands) September 30, 2018 Assets: Available-for-sale debt securities CDO $ — $ 19,148 $ — $ 19,148 Commercial MBS issued by GSEs — 100,943 — 100,943 Corporate debt securities — 99,384 — 99,384 Private label residential MBS — 855,942 — 855,942 Residential MBS issued by GSEs — 1,450,059 — 1,450,059 Tax-exempt — 504,907 — 504,907 Trust preferred securities — 28,617 — 28,617 U.S. government sponsored agency securities — 45,601 — 45,601 U.S. treasury securities — 2,475 — 2,475 Total AFS debt securities $ — $ 3,107,076 $ — $ 3,107,076 Equity securities CRA investments 50,744 — — 50,744 Preferred stock 121,550 — — 121,550 Total equity securities $ 172,294 $ — $ — $ 172,294 Derivative assets (1) $ — $ 8,978 $ — $ 8,978 Liabilities: Junior subordinated debt (2) $ — $ — $ 55,987 $ 55,987 Derivative liabilities (1) — 38,973 — 38,973 (1) Derivative assets and liabilities relate to interest rate swaps, see " Note 9. Derivatives and Hedging Activities ." In addition, the carrying value of loans is decreased by $1,997 and the net carrying value of subordinated debt is increased by $28,160 as of September 30, 2018 for the effective portion of the hedge, which relates to the fair value of the hedges put in place to mitigate against fluctuations in interest rates. (2) Includes only the portion of junior subordinated debt that is recorded at fair value at each reporting period pursuant to the election of FVO treatment. Fair Value Measurements at the End of the Reporting Period Using: Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Fair Value (in thousands) December 31, 2017 Assets: Available-for-sale debt securities CDO $ — $ 21,857 $ — $ 21,857 Commercial MBS issued by GSEs — 109,077 — 109,077 Corporate debt securities — 103,483 — 103,483 Private label residential MBS — 868,524 — 868,524 Residential MBS issued by GSEs — 1,689,295 — 1,689,295 Tax-exempt — 510,910 — 510,910 Trust preferred securities — 28,617 — 28,617 U.S. government sponsored agency securities — 61,462 — 61,462 U.S. treasury securities — 2,482 — 2,482 Available-for-sale equity securities CRA investments 50,616 — — 50,616 Preferred stock 53,196 — — 53,196 Total AFS securities $ 103,812 $ 3,395,707 $ — $ 3,499,519 Derivative assets (1) $ — $ 3,711 $ — $ 3,711 Liabilities: Junior subordinated debt (2) $ — $ — $ 56,234 $ 56,234 Derivative liabilities (1) — 55,340 — 55,340 (1) Derivative assets and liabilities relate to interest rate swaps, see " Note 9. Derivatives and Hedging Activities ." In addition, the carrying value of loans is increased by $41,919 and the net carrying value of subordinated debt is decreased by $9,959 as of December 31, 2017 for the effective portion of the hedge, which relates to the fair value of the hedges put in place to mitigate against fluctuations in interest rates. (2) Includes only the portion of junior subordinated debt that is recorded at fair value at each reporting period pursuant to the election of FVO treatment. For the three and nine months ended September 30, 2018 and 2017 , the change in Level 3 liabilities measured at fair value on a recurring basis was as follows: Junior Subordinated Debt Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Beginning balance $ (53,298 ) $ (55,772 ) $ (56,234 ) $ (50,410 ) Change in fair value (2,689 ) 1,035 247 (4,327 ) Ending balance $ (55,987 ) $ (54,737 ) $ (55,987 ) $ (54,737 ) For Level 3 liabilities measured at fair value on a recurring basis as of September 30, 2018 and December 31, 2017 , the significant unobservable inputs used in the fair value measurements were as follows: September 30, 2018 Valuation Technique Significant Unobservable Inputs Input Value (in thousands) Junior subordinated debt $ 55,987 Discounted cash flow Implied credit rating of the Company 6.20 % December 31, 2017 Valuation Technique Significant Unobservable Inputs Input Value (in thousands) Junior subordinated debt $ 56,234 Discounted cash flow Implied credit rating of the Company 5.61 % The significant unobservable inputs used in the fair value measurement of the Company’s junior subordinated debt as of September 30, 2018 and December 31, 2017 was the implied credit risk for the Company, calculated as the difference between the 20-year 'BB' rated financial index over the corresponding swap index. Fair value on a nonrecurring basis Certain assets are measured at fair value on a nonrecurring basis. That is, the assets are not measured at fair value on an ongoing basis, but are subject to fair value adjustments in certain circumstances (for example, when there is evidence of impairment). The following table presents such assets carried on the Balance Sheet by caption and by level within the ASC 825 hierarchy: Fair Value Measurements at the End of the Reporting Period Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Active Markets for Similar Assets (Level 2) Unobservable Inputs (Level 3) (in thousands) As of September 30, 2018; Impaired loans with specific valuation allowance $ 2,430 $ — $ — $ 2,430 Impaired loans without specific valuation allowance (1) 81,445 — — 81,445 Other assets acquired through foreclosure 20,028 — — 20,028 As of December 31, 2017: Impaired loans with specific valuation allowance $ 13,709 $ — $ — $ 13,709 Impaired loans without specific valuation allowance (1) 63,607 — — 63,607 Other assets acquired through foreclosure 28,540 — — 28,540 (1) Net of loan balances with charge-offs of $40.5 million and $15.6 million as of September 30, 2018 and December 31, 2017 , respectively. For Level 3 assets measured at fair value on a nonrecurring basis as of September 30, 2018 and December 31, 2017 , the significant unobservable inputs used in the fair value measurements were as follows: September 30, 2018 Valuation Technique(s) Significant Unobservable Inputs Range (in thousands) Impaired loans $ 83,875 Collateral method Third party appraisal Costs to sell 4.0% to 10.0% Discounted cash flow method Discount rate Contractual loan rate 4.0% to 7.0% Scheduled cash collections Probability of default 0% to 20.0% Proceeds from non-real estate collateral Loss given default 0% to 70.0% Other assets acquired through foreclosure 20,028 Collateral method Third party appraisal Costs to sell 4.0% to 10.0% December 31, 2017 Valuation Technique(s) Significant Unobservable Inputs Range (in thousands) Impaired loans $ 77,316 Collateral method Third party appraisal Costs to sell 4.0% to 10.0% Discounted cash flow method Discount rate Contractual loan rate 4.0% to 7.0% Scheduled cash collections Probability of default 0% to 20.0% Proceeds from non-real estate collateral Loss given default 0% to 70.0% Other assets acquired through foreclosure 28,540 Collateral method Third party appraisal Costs to sell 4.0% to 10.0% Impaired loans: The specific reserves for collateral dependent impaired loans are based on collateral value, net of estimated disposition costs and other identified quantitative inputs. Collateral value is determined based on independent third-party appraisals or internally-developed discounted cash flow analyses. Appraisals may utilize a single valuation approach or a combination of approaches, including comparable sales and the income approach. Fair value is determined, where possible, using market prices derived from an appraisal or evaluation, which are considered to be Level 2. However, certain assumptions and unobservable inputs are often used by the appraiser, therefore qualifying the assets as Level 3 in the fair value hierarchy. In addition, when adjustments are made to an appraised value to reflect various factors such as the age of the appraisal or known changes in the market or the collateral, such valuation inputs are considered unobservable and the fair value measurement is categorized as a Level 3 measurement. Internal discounted cash flow analyses are also utilized to estimate the fair value of impaired loans, which considers internally-developed, unobservable inputs such as discount rates, default rates, and loss severity. Total Level 3 impaired loans had an estimated fair value of $83.9 million and $77.3 million at September 30, 2018 and December 31, 2017 , respectively. Impaired loans with a specific valuation allowance had a gross estimated fair value of $3.6 million and $19.3 million at September 30, 2018 and December 31, 2017 , respectively, which was reduced by a specific valuation allowance of $1.2 million and $5.6 million , respectively. Other assets acquired through foreclosure: Other assets acquired through foreclosure consist of properties acquired as a result of, or in-lieu-of, foreclosure. These assets are initially reported at the fair value determined by independent appraisals using appraised value less estimated cost to sell. Such properties are generally re-appraised every twelve months. There is risk for subsequent volatility. Costs relating to the development or improvement of the assets are capitalized and costs relating to holding the assets are charged to expense. Fair value is determined, where possible, using market prices derived from an appraisal or evaluation, which are considered to be Level 2. However, certain assumptions and unobservable inputs are often used by the appraiser, therefore qualifying the assets as Level 3 in the fair value hierarchy. When significant adjustments are based on unobservable inputs, such as when a current appraised value is not available or management determines the fair value of the collateral is further impaired below the appraised value and there is no observable market price, the resulting fair value measurement has been categorized as a Level 3 measurement. The Company had $20.0 million and $28.5 million of such assets at September 30, 2018 and December 31, 2017 , respectively. Credit vs. non-credit losses Under the provisions of ASC 320, Investments-Debt and Equity Securities , OTTI is separated into the amount of total impairment related to the credit loss and the amount of the total impairment related to all other factors. The amount of the total OTTI related to the credit loss is recognized in earnings. The amount of the total impairment related to all other factors is recognized in OCI. For the three and nine months ended September 30, 2018 and 2017 , the Company determined that no securities experienced credit losses. There is no OTTI balance recognized in comprehensive income as of September 30, 2018 and 2017 . Fair Value of Financial Instruments The estimated fair value of the Company’s financial instruments is as follows: September 30, 2018 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (in thousands) Financial assets: Federal funds sold $ 70,000 $ — $ 70,000 $ — $ 70,000 Investment securities: HTM 288,290 — 279,033 — 279,033 AFS 3,107,076 — 3,107,076 — 3,107,076 Equity 172,294 172,294 — — 172,294 Derivative assets 8,978 — 8,978 — 8,978 Loans, net 16,582,754 — 15,964,980 83,875 16,048,855 Accrued interest receivable 88,847 — 88,847 — 88,847 Financial liabilities: Deposits $ 18,908,580 $ — $ 18,918,956 $ — $ 18,918,956 Customer repurchase agreements 20,969 — 20,969 — 20,969 Qualifying debt 359,082 — 328,448 67,013 395,461 Derivative liabilities 38,973 — 38,973 — 38,973 Accrued interest payable 14,268 — 14,268 — 14,268 December 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (in thousands) Financial assets: Investment securities: HTM $ 255,050 $ — $ 256,314 $ — $ 256,314 AFS 3,499,519 103,812 3,395,707 — 3,499,519 Derivative assets 3,711 — 3,711 — 3,711 Loans, net 14,953,885 — 14,577,010 77,316 14,654,326 Accrued interest receivable 85,517 — 85,517 — 85,517 Financial liabilities: Deposits $ 16,972,532 $ — $ 16,980,066 $ — $ 16,980,066 Customer repurchase agreements 26,017 — 26,017 — 26,017 FHLB advances 390,000 — 390,000 — 390,000 Qualifying debt 376,905 — 336,803 67,210 404,013 Derivative liabilities 55,340 — 55,340 — 55,340 Accrued interest payable 16,366 — 16,366 — 16,366 Interest rate risk The Company assumes interest rate risk (the risk to the Company’s earnings and capital from changes in interest rate levels) as a result of its normal operations. As a result, the fair values of the Company’s financial instruments, as well as its future net interest income will change when interest rate levels change and that change may be either favorable or unfavorable to the Company. Interest rate risk exposure is measured using interest rate sensitivity analysis to determine the Company's change in EVE and net interest income resulting from hypothetical changes in interest rates. If potential changes to EVE and net interest income resulting from hypothetical interest rate changes are not within the limits established by the BOD, the BOD may direct management to adjust the asset and liability mix to bring interest rate risk within BOD-approved limits. WAB has an ALCO charged with managing interest rate risk within the BOD-approved limits. Limits are structured to preclude an interest rate risk profile that does not conform to both management and BOD risk tolerances without ALCO approval. There is also ALCO reporting at the Parent level for reviewing interest rate risk for the Company, which gets reported to the BOD and its Finance and Investment Committee. Fair value of commitments The estimated fair value of standby letters of credit outstanding at September 30, 2018 and December 31, 2017 is insignificant. Loan commitments on which the committed interest rates are less than the current market rate are also insignificant at September 30, 2018 and December 31, 2017 .

Segments

Segments	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segments	The Company's reportable segments are aggregated based primarily on geographic location, services offered, and markets served. The Company's regional segments, which include Arizona, Nevada, Southern California, and Northern California, provide full service banking and related services to their respective markets. The operations from the regional segments correspond to the following banking divisions: ABA in Arizona, BON and FIB in Nevada, TPB in Southern California, and Bridge in Northern California. The Company's NBL segments provide specialized banking services to niche markets. The Company's NBL reportable segments include HOA Services, Public & Nonprofit Finance, Technology & Innovation, HFF, and Other NBLs. These NBLs are managed centrally and are broader in geographic scope than the Company's other segments, though still predominately located within the Company's core market areas. The Corporate & Other segment consists of corporate-related items, income and expense items not allocated to the Company's other reportable segments, and inter-segment eliminations. The Company's segment reporting process begins with the assignment of all loan and deposit accounts directly to the segments where these products are originated and/or serviced. Equity capital is assigned to each segment based on the risk profile of their assets and liabilities. With the exception of goodwill, which is assigned a 100% weighting, equity capital allocations ranged from 0% to 12% during the year, with a funds credit provided for the use of this equity as a funding source. Any excess or deficient equity not allocated to segments based on risk is assigned to the Corporate & Other segment. Net interest income, provision for credit losses, and non-interest expense amounts are recorded in their respective segment to the extent that the amounts are directly attributable to those segments. Net interest income is recorded in each segment on a TEB with a corresponding increase in income tax expense, which is eliminated in the Corporate & Other segment. Further, net interest income of a reportable segment includes a funds transfer pricing process that matches assets and liabilities with similar interest rate sensitivity and maturity characteristics. Using this funds transfer pricing methodology, liquidity is transferred between users and providers. A net user of funds has lending/investing in excess of deposits/borrowings and a net provider of funds has deposits/borrowings in excess of lending/investing. A segment that is a user of funds is charged for the use of funds, while a provider of funds is credited through funds transfer pricing, which is determined based on the average life of the assets or liabilities in the portfolio. The net income amount for each reportable segment is further derived by the use of expense allocations. Certain expenses not directly attributable to a specific segment are allocated across all segments based on key metrics, such as number of employees, average loan balances, and average deposit balances. These types of expenses include information technology, operations, human resources, finance, risk management, credit administration, legal, and marketing. Income taxes are applied to each segment based on the effective tax rate for the geographic location of the segment. Any difference in the corporate tax rate and the aggregate effective tax rates in the segments are adjusted in the Corporate & Other segment. The following is a summary of operating segment information for the periods indicated: Regional Segments Balance Sheet: Consolidated Company Arizona Nevada Southern California Northern California At September 30, 2018 (in millions) Assets: Cash, cash equivalents, and investment securities $ 4,334.2 $ 2.0 $ 8.5 $ 2.1 $ 1.8 Loans, net of deferred loan fees and costs 16,732.8 3,593.5 1,936.7 2,116.3 1,332.3 Less: allowance for credit losses (150.0 ) (33.1 ) (18.6 ) (20.2 ) (11.3 ) Total loans 16,582.8 3,560.4 1,918.1 2,096.1 1,321.0 Other assets acquired through foreclosure, net 20.0 1.7 14.1 — — Goodwill and other intangible assets, net 299.5 — 23.2 — 155.8 Other assets 939.6 46.3 58.0 15.1 18.8 Total assets $ 22,176.1 $ 3,610.4 $ 2,021.9 $ 2,113.3 $ 1,497.4 Liabilities: Deposits $ 18,908.6 $ 5,331.7 $ 3,847.3 $ 2,550.7 $ 1,951.5 Borrowings and qualifying debt 359.1 — — — — Other liabilities 420.0 13.5 16.3 1.9 12.3 Total liabilities 19,687.7 5,345.2 3,863.6 2,552.6 1,963.8 Allocated equity: 2,488.4 439.8 270.7 242.4 308.7 Total liabilities and stockholders' equity $ 22,176.1 $ 5,785.0 $ 4,134.3 $ 2,795.0 $ 2,272.5 Excess funds provided (used) — 2,174.6 2,112.4 681.7 775.1 Income Statement: Three Months Ended September 30, 2018 (in thousands) Net interest income $ 234,038 $ 56,701 $ 37,933 $ 29,572 $ 23,825 Provision for (recovery of) credit losses 6,000 (297 ) (38 ) 1,467 482 Net interest income after provision for credit losses 228,038 56,998 37,971 28,105 23,343 Non-interest income 4,418 2,230 2,573 931 2,312 Non-interest expense (113,841 ) (23,231 ) (16,471 ) (14,332 ) (13,207 ) Income (loss) before income taxes 118,615 35,997 24,073 14,704 12,448 Income tax expense (benefit) 7,492 8,999 5,055 4,117 3,486 Net income $ 111,123 $ 26,998 $ 19,018 $ 10,587 $ 8,962 Nine Months Ended September 30, 2018 (in thousands) Net interest income $ 672,366 $ 169,233 $ 109,898 $ 85,038 $ 69,081 Provision for (recovery of) credit losses 17,000 1,655 (2,005 ) 1,921 2,043 Net interest income after provision for credit losses 655,366 167,578 111,903 83,117 67,038 Non-interest income 29,505 5,902 8,585 2,898 7,281 Non-interest expense (314,538 ) (67,154 ) (46,486 ) (42,470 ) (39,139 ) Income (loss) before income taxes 370,333 106,326 74,002 43,545 35,180 Income tax expense (benefit) 53,631 26,644 15,634 12,288 9,938 Net income $ 316,702 $ 79,682 $ 58,368 $ 31,257 $ 25,242 National Business Lines Balance Sheet: HOA Public & Nonprofit Finance Technology & Innovation Hotel Franchise Finance Other NBLs Corporate & Other At September 30, 2018 Assets: (in millions) Cash, cash equivalents, and investment securities $ — $ — $ — $ — $ — $ 4,319.8 Loans, net of deferred loan fees and costs 202.1 1,520.2 1,106.5 1,435.4 3,483.2 6.6 Less: allowance for credit losses (1.9 ) (14.4 ) (9.9 ) (7.3 ) (33.2 ) (0.1 ) Total loans 200.2 1,505.8 1,096.6 1,428.1 3,450.0 6.5 Other assets acquired through foreclosure, net — — — — — 4.2 Goodwill and other intangible assets, net — — 120.4 0.1 — — Other assets 1.0 19.2 5.4 6.8 23.8 745.2 Total assets $ 201.2 $ 1,525.0 $ 1,222.4 $ 1,435.0 $ 3,473.8 $ 5,075.7 Liabilities: Deposits $ 2,523.9 $ — $ 2,319.5 $ — $ — $ 384.0 Borrowings and qualifying debt — — — — — 359.1 Other liabilities 1.7 10.1 0.1 (0.1 ) 85.4 278.8 Total liabilities 2,525.6 10.1 2,319.6 (0.1 ) 85.4 1,021.9 Allocated equity: 68.5 121.4 256.5 119.1 286.0 375.3 Total liabilities and stockholders' equity $ 2,594.1 $ 131.5 $ 2,576.1 $ 119.0 $ 371.4 $ 1,397.2 Excess funds provided (used) 2,392.9 (1,393.5 ) 1,353.7 (1,316.0 ) (3,102.4 ) (3,678.5 ) Income Statement: Three Months Ended September 30, 2018 (in thousands) Net interest income $ 17,930 $ 3,683 $ 27,233 $ 13,557 $ 20,329 $ 3,275 Provision for (recovery of) credit losses 103 (553 ) 1,448 223 3,214 (49 ) Net interest income after provision for credit losses 17,827 4,236 25,785 13,334 17,115 3,324 Non-interest income 215 159 2,836 — 549 (7,387 ) Non-interest expense (8,254 ) (2,134 ) (9,933 ) (3,014 ) (7,280 ) (15,985 ) Income (loss) before income taxes 9,788 2,261 18,688 10,320 10,384 (20,048 ) Income tax expense (benefit) 2,251 521 4,298 2,374 2,388 (25,997 ) Net income $ 7,537 $ 1,740 $ 14,390 $ 7,946 $ 7,996 $ 5,949 Nine Months Ended September 30, 2018 (in thousands) Net interest income $ 49,335 $ 11,224 $ 74,615 $ 41,617 $ 58,813 $ 3,512 Provision for (recovery of) credit losses 285 (786 ) 5,355 2,006 6,573 (47 ) Net interest income after provision for credit losses 49,050 12,010 69,260 39,611 52,240 3,559 Non-interest income 543 159 9,518 12 1,182 (6,575 ) Non-interest expense (24,090 ) (6,386 ) (29,666 ) (7,419 ) (19,193 ) (32,535 ) Income (loss) before income taxes 25,503 5,783 49,112 32,204 34,229 (35,551 ) Income tax expense (benefit) 5,866 1,329 11,296 7,407 7,873 (44,644 ) Net income $ 19,637 $ 4,454 $ 37,816 $ 24,797 $ 26,356 $ 9,093 Regional Segments Consolidated Company Arizona Nevada Southern California Northern California At December 31, 2017 (in millions) Assets: Cash, cash equivalents, and investment securities $ 4,237.1 $ 2.1 $ 8.2 $ 2.1 $ 1.7 Loans, net of deferred loan fees and costs 15,093.9 3,323.7 1,844.8 1,934.7 1,275.5 Less: allowance for credit losses (140.0 ) (31.5 ) (18.1 ) (19.5 ) (13.2 ) Total loans 14,953.9 3,292.2 1,826.7 1,915.2 1,262.3 Other assets acquired through foreclosure, net 28.5 2.3 13.3 — 0.2 Goodwill and other intangible assets, net 300.7 — 23.2 — 156.5 Other assets 808.9 46.3 58.8 14.4 15.1 Total assets $ 20,329.1 $ 3,342.9 $ 1,930.2 $ 1,931.7 $ 1,435.8 Liabilities: Deposits $ 16,972.5 $ 4,841.3 $ 3,951.4 $ 2,461.1 $ 1,681.7 Borrowings and qualifying debt 766.9 — — — — Other liabilities 360.0 11.6 20.9 3.2 11.9 Total liabilities 18,099.4 4,852.9 3,972.3 2,464.3 1,693.6 Allocated equity: 2,229.7 396.5 263.7 221.8 303.1 Total liabilities and stockholders' equity $ 20,329.1 $ 5,249.4 $ 4,236.0 $ 2,686.1 $ 1,996.7 Excess funds provided (used) — 1,906.5 2,305.8 754.4 560.9 Income Statement: Three Months Ended September 30, 2017 (in thousands) Net interest income (expense) $ 201,583 $ 52,637 $ 36,310 $ 26,811 $ 21,932 Provision for (recovery of) credit losses 5,000 (289 ) (2,044 ) (58 ) 3,144 Net interest income (expense) after provision for credit losses 196,583 52,926 38,354 26,869 18,788 Non-interest income 10,456 1,265 2,354 971 1,796 Non-interest expense (89,296 ) (18,844 ) (14,748 ) (12,340 ) (11,317 ) Income (loss) before income taxes 117,743 35,347 25,960 15,500 9,267 Income tax expense (benefit) 34,899 13,857 9,086 6,517 3,897 Net income $ 82,844 $ 21,490 $ 16,874 $ 8,983 $ 5,370 Nine Months Ended September 30, 2017 (in thousands) Net interest income (expense) $ 573,635 $ 145,839 $ 108,028 $ 81,087 $ 63,686 Provision for (recovery of) credit losses 12,250 109 (5,378 ) (20 ) 4,238 Net interest income (expense) after provision for credit losses 561,385 145,730 113,406 81,107 59,448 Non-interest income 31,656 3,567 6,800 2,602 5,839 Non-interest expense (265,543 ) (55,388 ) (45,733 ) (38,063 ) (36,188 ) Income (loss) before income taxes 327,498 93,909 74,473 45,646 29,099 Income tax expense (benefit) 91,352 36,831 26,066 19,194 12,236 Net income $ 236,146 $ 57,078 $ 48,407 $ 26,452 $ 16,863 National Business Lines HOA Public & Nonprofit Finance Technology & Innovation Hotel Franchise Finance Other NBLs Corporate & Other At December 31, 2017 Assets: (in millions) Cash, cash equivalents, and investment securities $ — $ — $ — $ — $ — $ 4,223.0 Loans, net of deferred loan fees and costs 162.1 1,580.4 1,097.9 1,327.7 2,543.0 4.1 Less: allowance for credit losses (1.6 ) (15.6 ) (11.4 ) (4.0 ) (25.0 ) (0.1 ) Total loans 160.5 1,564.8 1,086.5 1,323.7 2,518.0 4.0 Other assets acquired through foreclosure, net — — — — — 12.7 Goodwill and other intangible assets, net — — 120.9 0.1 — — Other assets 0.9 17.9 6.0 5.9 15.5 628.1 Total assets $ 161.4 $ 1,582.7 $ 1,213.4 $ 1,329.7 $ 2,533.5 $ 4,867.8 Liabilities: Deposits $ 2,230.4 $ — $ 1,737.6 $ — $ — $ 69.0 Borrowings and qualifying debt — — — — — 766.9 Other liabilities 1.2 42.4 0.8 0.4 5.5 262.1 Total liabilities 2,231.6 42.4 1,738.4 0.4 5.5 1,098.0 Allocated equity: 59.4 126.5 244.1 108.3 206.0 300.3 Total liabilities and stockholders' equity $ 2,291.0 $ 168.9 $ 1,982.5 $ 108.7 $ 211.5 $ 1,398.3 Excess funds provided (used) 2,129.6 (1,413.8 ) 769.1 (1,221.0 ) (2,322.0 ) (3,469.5 ) Income Statement: Three Months Ended September 30, 2017 (in thousands) Net interest income (expense) $ 13,746 $ 7,269 $ 20,415 $ 15,346 $ 16,933 $ (9,816 ) Provision for (recovery of) credit losses 40 91 (83 ) 1,116 4,416 (1,333 ) Net interest income (expense) after provision for credit losses 13,706 7,178 20,498 14,230 12,517 (8,483 ) Non-interest income 136 183 1,855 — 379 1,517 Non-interest expense (7,011 ) (2,053 ) (8,824 ) (1,905 ) (5,286 ) (6,968 ) Income (loss) before income taxes 6,831 5,308 13,529 12,325 7,610 (13,934 ) Income tax expense (benefit) 2,562 1,028 5,075 4,622 2,853 (14,598 ) Net income $ 4,269 $ 4,280 $ 8,454 $ 7,703 $ 4,757 $ 664 Nine Months Ended September 30, 2017 (in thousands) Net interest income (expense) $ 40,275 $ 21,242 $ 59,610 $ 42,337 $ 46,380 $ (34,849 ) Provision for (recovery of) credit losses 332 796 816 2,924 10,265 (1,832 ) Net interest income (expense) after provision for credit losses 39,943 20,446 58,794 39,413 36,115 (33,017 ) Non-interest income 417 415 5,689 — 1,632 4,695 Non-interest expense (21,416 ) (6,522 ) (26,685 ) (7,949 ) (14,573 ) (13,026 ) Income (loss) before income taxes 18,944 14,339 37,798 31,464 23,174 (41,348 ) Income tax expense (benefit) 7,104 4,424 14,175 11,799 8,690 (49,167 ) Net income $ 11,840 $ 9,915 $ 23,623 $ 19,665 $ 14,484 $ 7,819

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Principal stockholders, directors, and executive officers of the Company, their immediate family members, and companies they control or own more than a 10% interest in, are considered to be related parties. In the ordinary course of business, the Company engages in various related party transactions, including extending credit and bank service transactions. All related party transactions are subject to review and approval pursuant to the Company's Related Party Transactions policy. On April 1, 2017, the Company hired an executive officer who was previously the Managing Partner of an external consulting firm that the Company actively uses for risk management services. Prior to joining the Company, the executive officer sold his interest in this external consulting firm and was paid with a combination of cash and a $1.0 million note, which as of September 30, 2018 , was paid in full. Donations and other services to related parties, including sponsorships and expenses to this external consulting firm, totaled $8.7 million and $2.1 million for the nine months ended September 30, 2018 and 2017 , respectively. For the nine months ended September 30, 2018 , total related party expenses of $8.7 million includes a donation to the Company's charitable foundation of $7.6 million, which consists of a non-cash donation of OREO property of $6.9 million and a cash donation of $0.7 million .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Nature of Operation	Nature of operation WAL is a bank holding company headquartered in Phoenix, Arizona, incorporated under the laws of the state of Delaware. WAL provides a full spectrum of deposit, lending, treasury management, international banking, and online banking products and services through its wholly-owned banking subsidiary, WAB. WAB operates the following full-service banking divisions: ABA, BON, FIB, Bridge, and TPB. The Company also serves business customers through a national platform of specialized financial services. In addition, the Company has two non-bank subsidiaries, LVSP, which holds and manages certain OREO properties and a captive insurance company formed and licensed under the laws of the State of Arizona, CSI. CSI was established as part of the Company's overall enterprise risk management strategy.
Basis of Presentation	Basis of presentation The accounting and reporting policies of the Company are in accordance with GAAP and conform to practices within the financial services industry. The accounts of the Company and its consolidated subsidiaries are included in the Consolidated Financial Statements.
Use of Estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management's estimates and judgments are ongoing and are based on experience, current and expected future conditions, third-party evaluations and various other assumptions that management believes are reasonable under the circumstances. The results of these estimates form the basis for making judgments about the carrying values of assets and liabilities, as well as identifying and assessing the accounting treatment with respect to commitments and contingencies. Actual results may differ from those estimates and assumptions used in the Consolidated Financial Statements and related notes. Material estimates that are particularly susceptible to significant changes in the near term relate to the determination of the allowance for credit losses; estimated cash flows related to PCI loans; fair value determinations related to acquisitions and certain assets and liabilities carried at fair value; and accounting for income taxes.
Principles of Consolidation	Principles of consolidation As of September 30, 2018 , WAL has the following significant wholly-owned subsidiaries: WAB, LVSP, and eight unconsolidated subsidiaries used as business trusts in connection with the issuance of trust-preferred securities. The Bank has the following significant wholly-owned subsidiaries: WABT, which holds certain investment securities, municipal and nonprofit loans, and leases; WA PWI, which holds certain limited partnerships invested primarily in low income housing tax credits and small business investment corporations; and BW Real Estate, Inc., which operates as a real estate investment trust and holds certain of WAB's real estate loans and related securities. The Company does not have any other significant entities that should be considered for consolidation. All significant intercompany balances and transactions have been eliminated in consolidation.
Reclassifications	Reclassifications Certain amounts reported in prior periods may have been reclassified in the Consolidated Financial Statements to conform to the current presentation. The reclassifications have no effect on net income or stockholders’ equity as previously reported.
Business Combinations	Business combinations Business combinations are accounted for under the acquisition method of accounting in accordance with ASC 805, Business Combinations. Under the acquisition method, the acquiring entity in a business combination recognizes all of the acquired assets and assumed liabilities at their estimated fair values as of the date of acquisition. Any excess of the purchase price over the fair value of net assets and other identifiable intangible assets acquired is recorded as goodwill. To the extent the fair value of net assets acquired, including identified intangible assets, exceeds the purchase price, a bargain purchase gain is recognized. Changes to estimated fair values from a business combination are recognized as an adjustment to goodwill during the measurement period and are recognized in the proper reporting period in which the adjustment amounts are determined. Results of operations of an acquired business are included in the Consolidated Income Statement from the date of acquisition. Acquisition-related costs, including conversion and restructuring charges, are expensed as incurred.
Investment Securities	Investment securities Investment securities include debt securities and equity securities. Debt securities may be classified as HTM, AFS, or measured at fair value. The appropriate classification is initially decided at the time of purchase. Securities classified as HTM are those debt securities that the Company has both the intent and ability to hold to maturity regardless of changes in market conditions, liquidity needs, or general economic conditions. These securities are carried at amortized cost. The sale of an HTM security within three months of its maturity date or after the majority of the principal outstanding has been collected is considered a maturity for purposes of classification and disclosure. Securities classified as AFS or trading securities are reported as an asset in the Consolidated Balance Sheet at their estimated fair value. As the fair value of AFS debt securities changes, the changes are reported net of income tax as an element of OCI, except for other-than-temporarily-impaired securities. When AFS debt securities are sold, the unrealized gain or loss is reclassified from OCI to non-interest income. The changes in the fair values of trading securities are reported in non-interest income. Securities classified as AFS are securities that the Company intends to hold for an indefinite period of time, but not necessarily to maturity. Any decision to sell a security classified as AFS would be based on various factors, including significant movements in interest rates, changes in the maturity mix of the Company’s assets and liabilities, liquidity needs, decline in credit quality, and regulatory capital considerations. For periods prior to January 1, 2018, equity securities were classified as AFS and reported at fair value with unrealized gains and losses included as a separate component of AOCI, net of tax. Upon adoption of ASU 2016-01, the fair value changes in equity securities are recognized as part of non-interest income, see "Recently adopted accounting guidance" below for further discussion. Interest income is recognized based on the coupon rate and increased by accretion of discounts earned or decreased by the amortization of premiums paid over the contractual life of the security, adjusted for prepayment estimates, using the interest method. In estimating whether there are any OTTI losses, management considers the 1) length of time and the extent to which the fair value has been less than amortized cost; 2) financial condition and near term prospects of the issuer; 3) impact of changes in market interest rates; and 4) intent and ability of the Company to retain its investment for a period of time sufficient to allow for any anticipated recovery in fair value and whether it is not more likely than not the Company would be required to sell the security. Declines in the fair value of individual AFS securities that are deemed to be other-than-temporary are reflected in earnings when identified. The fair value of the debt security then becomes the new cost basis. For individual debt securities where the Company does not intend to sell the security and it is not more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis, the other-than-temporary decline in fair value of the debt security related to 1) credit loss is recognized in earnings; and 2) interest rate, market, or other factors is recognized in other comprehensive income or loss. For individual debt securities where the Company either intends to sell the security or more likely than not will not recover all of its amortized cost, the OTTI is recognized in earnings equal to the entire difference between the security's cost basis and its fair value at the balance sheet date. For individual debt securities for which a credit loss has been recognized in earnings, interest accruals and amortization and accretion of premiums and discounts are suspended when the credit loss is recognized. Interest received after accruals have been suspended is recognized on a cash basis.
Restricted Stock	Restricted stock WAB is a member of the Federal Reserve System and, as part of its membership, is required to maintain stock in the FRB in a specified ratio to its capital. In addition, WAB is a member of the FHLB system and, accordingly, maintains an investment in capital stock of the FHLB based on the borrowing capacity used. The Bank also maintains an investment in its primary correspondent bank. All of these investments are considered equity securities with no actively traded market. Therefore, the shares are considered restricted investment securities. These investments are carried at cost, which is equal to the value at which they may be redeemed. The dividend income received from the stock is reported in interest income. The Company conducts a periodic review and evaluation of its restricted stock to determine if any impairment exists.
Loans, Interest and Fees from Loans	Loans, held for investment The Company generally holds loans for investment and has the intent and ability to hold loans until their maturity. Therefore, they are reported at book value. Net loans are stated at the amount of unpaid principal, adjusted for net deferred fees and costs, purchase accounting fair value adjustments, and an allowance for credit losses. In addition, the book values of loans subject to a fair value hedge are adjusted for changes in value attributable to the effective portion of the hedged benchmark interest rate risk. The Company may also acquire loans through a business combination. These acquired loans are recorded at estimated fair value on the date of purchase, which is comprised of unpaid principal adjusted for estimated credit losses and interest rate fair value adjustments. Loans are evaluated individually at the acquisition date to determine if there has been credit deterioration since origination. Such loans may then be aggregated and accounted for as a pool of loans based on common characteristics. When the Company acquires such loans, the yield that may be accreted (accretable yield) is limited to the excess of the Company’s estimate of undiscounted cash flows expected to be collected over the Company’s initial investment in the loan. The excess of contractual cash flows over the cash flows expected to be collected may not be recognized as an adjustment to yield, loss, or a valuation allowance. Subsequent increases in cash flows expected to be collected generally are recognized prospectively through adjustment of the loan’s yield over the remaining life. Subsequent decreases to cash flows expected to be collected are recognized as impairment. The Company may not carry over or create a valuation allowance in the initial accounting for loans acquired under these circumstances. For purchased loans that are not deemed impaired at the acquisition date, fair value adjustments attributable to both credit and interest rates are accreted (or amortized) over the contractual life of the individual loan. For additional information, see " Note 3. Loans, Leases and Allowance for Credit Losses " of these Notes to Unaudited Consolidated Financial Statements. Loan fees collected for the origination of loans less direct loan origination costs (net deferred loan fees) are amortized over the contractual life of the loan through interest income. If a loan has scheduled payments, the amortization of the net deferred loan fee is calculated using the interest method over the contractual life of the loan. If a loan does not have scheduled payments, such as a line of credit, the net deferred loan fee is recognized as interest income on a straight-line basis over the contractual life of the loan commitment. Commitment fees based on a percentage of a customer’s unused line of credit and fees related to standby letters of credit are recognized over the commitment period. When loans are repaid, any remaining unamortized balances of premiums, discounts, or net deferred fees are recognized as interest income. Non-accrual loans: When a borrower discontinues making payments as contractually required by the note, the Company must determine whether it is appropriate to continue to accrue interest. The Company ceases accruing interest income when the loan has become delinquent by more than 90 days or when management determines that the full repayment of principal and collection of interest according to contractual terms is no longer likely. The Company may decide to continue to accrue interest on certain loans more than 90 days delinquent if the loans are well secured by collateral and in the process of collection. For all loan types, when a loan is placed on non-accrual status, all interest accrued but uncollected is reversed against interest income in the period in which the status is changed, and the Company makes a loan-level decision to apply either the cash basis or cost recovery method. The Company recognizes income on a cash basis only for those non-accrual loans for which the collection of the remaining principal balance is not in doubt. Under the cost recovery method, subsequent payments received from the customer are applied to principal and generally no further interest income is recognized until the principal has been paid in full or until circumstances have changed such that payments are again consistently received as contractually required. Impaired loans: A loan is identified as impaired when it is no longer probable that interest and principal will be collected according to the contractual terms of the original loan agreement. Generally, impaired loans are classified as non-accrual. However, in certain instances, impaired loans may continue on an accrual basis, if full repayment of all principal and interest is expected and the loan is both well secured and in the process of collection. Impaired loans are measured for reserve requirements in accordance with ASC 310, Receivables, based on the present value of expected future cash flows discounted at the loan's effective interest rate or, as a practical expedient, at the loan's observable market price or the fair value of the collateral less applicable disposition costs if the loan is collateral dependent. The amount of an impairment reserve, if any, and any subsequent changes are recorded as a provision for credit losses. Losses are recorded as a charge-off when losses are confirmed. In addition to management's internal loan review process, regulators may from time to time direct the Company to modify loan grades, loan impairment calculations, or loan impairment methodology. Troubled Debt Restructured Loans : A TDR loan is a loan on which the Company, for reasons related to a borrower’s financial difficulties, grants a concession to the borrower that the Company would not otherwise consider. The loan terms that have been modified or restructured due to a borrower’s financial situation include, but are not limited to, a reduction in the stated interest rate, an extension of the maturity or renewal of the loan at an interest rate below current market, a reduction in the face amount of the debt, a reduction in the accrued interest, or deferral of interest payments. A TDR loan is also considered impaired. A TDR loan may be returned to accrual status when the loan is brought current, has performed in accordance with the contractual restructured terms for a reasonable period of time (generally six months) and the ultimate collectability of the total contractual restructured principal and interest is no longer in doubt. However, such loans continue to be considered impaired. Consistent with regulatory guidance, a TDR loan that is subsequently modified in another restructuring agreement but has shown sustained performance and classification as a TDR, will be removed from TDR status provided that the modified terms were market-based at the time of modification.
Allowance for Credit Losses	Allowance for credit losses Credit risk is inherent in the business of extending loans and leases to borrowers, for which the Company must maintain an adequate allowance for credit losses. The allowance for credit losses is established through a provision for credit losses recorded to expense. Loans are charged against the allowance for credit losses when management believes that the contractual principal or interest will not be collected. Subsequent recoveries, if any, are credited to the allowance. The allowance is an amount believed adequate to absorb estimated probable losses on existing loans that may become uncollectable, based on evaluation of the collectability of loans and prior credit loss experience, together with other factors. The Company formally re-evaluates and establishes the appropriate level of the allowance for credit losses on a quarterly basis. The allowance consists of specific and general components. The specific allowance applies to impaired loans. For impaired collateral dependent loans, the reserve is calculated based on the collateral value, net of estimated disposition costs. Generally, the Company obtains independent collateral valuation analysis for each loan every twelve months. Loans not collateral dependent are evaluated based on the expected future cash flows discounted at the original contractual interest rate. The general allowance covers all non-impaired loans and incorporates several quantitative and qualitative factors, which are used for all of the Company's portfolio segments. Quantitative factors include company-specific, ten-year historical net charge-offs stratified by loans with similar characteristics. Qualitative factors include: 1) levels of and trends in delinquencies and impaired loans; 2) levels of and trends in charge-offs and recoveries; 3) trends in volume and terms of loans; 4) changes in underwriting standards or lending policies; 5) experience, ability, depth of lending staff; 6) national and local economic trends and conditions; 7) changes in credit concentrations; 8) out-of-market exposures; 9) changes in quality of loan review system; and 10) changes in the value of underlying collateral. Due to the credit concentration of the Company's loan portfolio in real estate secured loans, the value of collateral is heavily dependent on real estate values in Arizona, Nevada, and California. While management uses the best information available to make its evaluation, future adjustments to the allowance may be necessary if there are significant changes in economic or other conditions. In addition, regulators, as an integral part of their examination processes, periodically review the Bank's allowance for credit losses, and may require the Bank to make additions to the allowance based on their judgment about information available to them at the time of their examination. Management regularly reviews the assumptions and formulae used in determining the allowance and makes adjustments if required to reflect the current risk profile of the portfolio.
Goodwill and Other Intangible Assets	Goodwill and other intangible assets The Company records as goodwill the excess of the purchase price over the fair value of the identifiable net assets acquired in accordance with applicable guidance. The Company performs its annual goodwill and intangibles impairment tests as of October 1 each year, or more often if events or circumstances indicate that the carrying value may not be recoverable. The Company can first elect to assess, through qualitative factors, whether it is more likely than not that goodwill is impaired. If the qualitative assessment indicates potential impairment, a quantitative impairment test is necessary. If, based on the quantitative test, a reporting unit's carrying amount exceeds its fair value, a goodwill impairment charge for this difference is recorded to current period earnings as non-interest expense. The Company’s intangible assets consist primarily of core deposit intangible assets that are amortized over periods ranging from 5 to 10 years. The Company considers the remaining useful lives of its core deposit intangible assets each reporting period, as required by ASC 350, Intangibles—Goodwill and Other, to determine whether events and circumstances warrant a revision to the remaining period of amortization. If the estimate of an intangible asset’s remaining useful life has changed, the remaining carrying amount of the intangible asset is amortized prospectively over the revised remaining useful life.
Other Assets Acquired Through Foreclosure	Other assets acquired through foreclosure Other assets acquired through foreclosure consist primarily of properties acquired as a result of, or in-lieu-of, foreclosure. Properties or other assets (primarily repossessed assets formerly leased) are classified as OREO and other repossessed property and are initially reported at fair value of the asset less estimated selling costs. Subsequent adjustments are based on the lower of carrying value or fair value less estimated costs to sell the property. Costs related to the development or improvement of the assets are capitalized and costs related to holding the assets are charged to non-interest expense. Property is evaluated regularly to ensure the recorded amount is supported by its current fair value and valuation allowances.
Treasury Shares	Treasury shares The Company separately presents treasury shares, which represent shares surrendered to the Company equal in value to the statutory payroll tax withholding obligations arising from the vesting of employee restricted stock awards. Treasury shares are carried at cost.
Derivative Financial Instruments	Derivative financial instruments The Company uses interest-rate swaps to mitigate interest-rate risk associated with changes to the fair value of certain fixed-rate financial instruments (fair value hedges). The Company recognizes derivatives as assets or liabilities in the Consolidated Balance Sheet at their fair value in accordance with ASC 815, Derivatives and Hedging . The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and further, on the type of hedging relationship. Derivative instruments designated in a hedge relationship to mitigate exposure to changes in the fair value of an asset or liability attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Changes in the fair value of a derivative that is designated and qualifies as a fair value hedge, along with changes in the fair value of the hedged asset or liability that are attributable to the hedged risk are recorded in current-period earnings. Changes in the fair value of derivatives not considered to be highly effective in hedging the change in fair value of the hedged item are recognized in earnings as non-interest income during the period of the change. The Company documents its hedge relationships, including identification of the hedging instruments and the hedged items, as well as its risk management objectives and strategies for undertaking the hedge transaction after the derivative contract is executed. At inception, the Company performs a quantitative assessment to determine whether the derivatives used in hedging transactions are highly effective (as defined in the guidance) in offsetting changes in the fair value of the hedged item. Retroactive effectiveness is assessed, as well as the continued expectation that the hedge will remain effective prospectively. After the initial quantitative assessment is performed, on a quarterly basis, the Company performs a qualitative hedge effectiveness assessment. This assessment takes into consideration any adverse developments related to the counterparty's risk of default and any negative events or circumstances that affect the factors that originally enabled the Company to assess that it could reasonably support, qualitatively, an expectation that the hedging relationship was and will continue to be highly effective. The Company discontinues hedge accounting prospectively when it is determined that a hedge is no longer highly effective. When hedge accounting is discontinued on a fair value hedge that no longer qualifies as an effective hedge, the derivative continues to be reported at fair value in the Consolidated Balance Sheet, but the carrying amount of the hedged item is no longer adjusted for future changes in fair value. The adjustment to the carrying amount of the hedged item that existed at the date hedge accounting is discontinued is amortized over the remaining life of the hedged item into earnings. Derivative instruments that are not designated as hedges, so called free-standing derivatives, are reported in the Consolidated Balance Sheet at fair value and the changes in fair value are recognized in earnings as non-interest income during the period of change. The Company may in the normal course of business purchase a financial instrument or originate a loan that contains an embedded derivative instrument. Upon purchasing the instrument or originating the loan, the Company assesses whether the economic characteristics of the embedded derivative are clearly and closely related to the economic characteristics of the remaining component of the financial instrument (i.e., the host contract) and whether a separate instrument with the same terms as the embedded instrument would meet the definition of a derivative instrument. When it is determined that the embedded derivative possesses economic characteristics that are not clearly and closely related to the economic characteristics of the host contract and a separate instrument with the same terms would qualify as a derivative instrument, the embedded derivative is separated from the host contract and carried at fair value. However, in cases where the host contract is measured at fair value, with changes in fair value reported in current earnings, or the Company is unable to reliably identify and measure an embedded derivative for separation from its host contract, the entire contract is carried in the Consolidated Balance Sheet at fair value and is not designated as a hedging instrument.
Income Taxes	Income taxes The Company is subject to income taxes in the United States and files a consolidated federal income tax return with all of its subsidiaries, with the exception of BW Real Estate, Inc. Deferred income taxes are recorded to reflect the effects of temporary differences between the financial reporting carrying amounts of assets and liabilities and their income tax bases using enacted tax rates that are expected to be in effect when the taxes are actually paid or recovered. As changes in tax laws or rates are enacted, deferred tax assets and liabilities are adjusted through the provision for income taxes. Net deferred tax assets are recorded to the extent that these assets will more-likely-than-not be realized. In making these determinations, all available positive and negative evidence is considered, including scheduled reversals of deferred tax liabilities, tax planning strategies, projected future taxable income, and recent operating results. If it is determined that deferred income tax assets to be realized in the future are in excess of their net recorded amount, an adjustment to the valuation allowance will be recorded, which will reduce the Company's provision for income taxes. A tax benefit from an unrecognized tax benefit may be recognized when it is more-likely-than-not that the position will be sustained upon examination, including related appeals or litigation, based on technical merits. Income tax benefits must meet a more-likely-than-not recognition threshold at the effective date to be recognized. Interest and penalties related to unrecognized tax benefits are recognized as part of the provision for income taxes in the Consolidated Income Statement. Accrued interest and penalties are included in the related tax liability line with other liabilities in the Consolidated Balance Sheet. See " Note 11. Income Taxes " of these Notes to Unaudited Consolidated Financial Statements for further discussion on income taxes.
Off-Balance Sheet Instruments	Off-balance sheet instruments In the ordinary course of business, the Company has entered into off-balance sheet financial instrument arrangements consisting of commitments to extend credit and standby letters of credit. Such financial instruments are recorded in the Consolidated Financial Statements when they are funded. They involve, to varying degrees, elements of credit risk in excess of amounts recognized in the Consolidated Balance Sheet. Losses would be experienced when the Company is contractually obligated to make a payment under these instruments and must seek repayment from the borrower, which may not be as financially sound in the current period as they were when the commitment was originally made. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. The Company enters into credit arrangements that generally provide for the termination of advances in the event of a covenant violation or other event of default. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer’s creditworthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the Company upon extension of credit, is based on management’s credit evaluation of the party. The commitments are collateralized by the same types of assets used as loan collateral. As with outstanding loans, the Company applies qualitative factors and utilization rates to its off-balance sheet obligations in determining an estimate of losses inherent in these contractual obligations. The estimate for credit losses on off-balance sheet instruments is included in other liabilities and the charge to income that establishes this liability is included in non-interest expense. The Company also has off-balance sheet arrangements related to its derivative instruments. Derivative instruments are recognized in the Consolidated Financial Statements at fair value and their notional values are carried off-balance sheet. See " Note 9. Derivatives and Hedging Activities " of these Notes to Unaudited Consolidated Financial Statements for further discussion.
Fair Values of Financial Instruments	Fair values of financial instruments The Company uses fair value measurements to record fair value adjustments to certain assets and liabilities. ASC 820, Fair Value Measurement , establishes a framework for measuring fair value and a three-level valuation hierarchy for disclosure of fair value measurement, as well as enhances disclosure requirements for fair value measurements. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. The Company uses various valuation approaches, including market, income, and/or cost approaches. ASC 820 establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability developed based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the factors market participants would consider in pricing the asset or liability developed based on the best information available in the circumstances. The hierarchy is broken down into three levels based on the reliability of inputs, as follows: • Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. • Level 2 - Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. These might include quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (such as interest rates, prepayment speeds, volatilities, etc.) or model-based valuation techniques where all significant assumptions are observable, either directly or indirectly, in the market. • Level 3 - Valuation is generated from model-based techniques where one or more significant inputs are not observable, either directly or indirectly, in the market. These unobservable assumptions reflect the Company’s own estimates of assumptions that market participants would use in pricing the asset or liability. Valuation techniques may include use of matrix pricing, discounted cash flow models, and similar techniques. The availability of observable inputs varies based on the nature of the specific financial instrument. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, for disclosure purposes, the level in the fair value hierarchy within which the fair value measurement in its entirety falls is determined based on the lowest level input that is significant to the fair value measurement in its entirety. Fair value is a market-based measure considered from the perspective of a market participant who may purchase the asset or assume the liability rather than an entity-specific measure. When market assumptions are available, ASC 820 requires the Company to make assumptions regarding the assumptions that market participants would use to estimate the fair value of the financial instrument at the measurement date. ASC 825, Financial Instruments , requires disclosure of fair value information about financial instruments, whether or not recognized in the balance sheet, for which it is practicable to estimate that value. Management uses its best judgment in estimating the fair value of the Company’s financial instruments; however, there are inherent limitations in any estimation technique. Therefore, for substantially all financial instruments, the fair value estimates presented herein are not necessarily indicative of the amounts the Company could have realized in a sales transaction at September 30, 2018 and 2017 . The estimated fair value amounts for September 30, 2018 and 2017 have been measured as of period-end, and have not been re-evaluated or updated for purposes of these Consolidated Financial Statements subsequent to those dates. As such, the estimated fair values of these financial instruments subsequent to the reporting date may be different than the amounts reported at period-end. The information in " Note 13. Fair Value Accounting " in these Notes to Unaudited Consolidated Financial Statements should not be interpreted as an estimate of the fair value of the entire Company since a fair value calculation is only required for a limited portion of the Company’s assets and liabilities. Due to the wide range of valuation techniques and the degree of subjectivity used in making the estimate, comparisons between the Company’s disclosures and those of other companies or banks may not be meaningful. The following methods and assumptions were used by the Company in estimating the fair value of its financial instruments: Cash, cash equivalents, and restricted cash The carrying amounts reported in the Consolidated Balance Sheets for cash and due from banks approximate their fair value. Money market investments The carrying amounts reported in the Consolidated Balance Sheets for money market investments approximate their fair value. Investment securities The fair values of CRA investments and exchange-listed preferred stock are based on quoted market prices and are categorized as Level 1 in the fair value hierarchy. The fair values of debt securities were determined based on matrix pricing. Matrix pricing is a mathematical technique that utilizes observable market inputs including, for example, yield curves, credit ratings, and prepayment speeds. Fair values determined using matrix pricing are generally categorized as Level 2 in the fair value hierarchy. Restricted stock WAB is a member of the Federal Reserve System and the FHLB and, accordingly, maintains investments in the capital stock of the FRB and the FHLB. WAB also maintains an investment in its primary correspondent bank. These investments are carried at cost since no ready market exists for them, and they have no quoted market value. The Company conducts a periodic review and evaluation of its restricted stock to determine if any impairment exists. The fair values of these investments have been categorized as Level 2 in the fair value hierarchy. Loans The fair value of loans is estimated based on discounted cash flows using interest rates currently being offered for loans with similar terms to borrowers with similar credit quality and adjustments that the Company believes a market participant would consider in determining fair value based on a third party independent valuation. As a result, the fair value for loans is categorized as Level 2 in the fair value hierarchy, excluding impaired loans which are categorized as Level 3. Accrued interest receivable and payable The carrying amounts reported in the Consolidated Balance Sheets for accrued interest receivable and payable approximate their fair value. Derivative financial instruments All derivatives are recognized in the Consolidated Balance Sheets at their fair value. The fair value for derivatives is determined based on market prices, broker-dealer quotations on similar products, or other related input parameters. As a result, the fair values have been categorized as Level 2 in the fair value hierarchy. Deposits The fair value disclosed for demand and savings deposits is by definition equal to the amount payable on demand at their reporting date (that is, their carrying amount), which the Company believes a market participant would consider in determining fair value. The carrying amount for variable-rate deposit accounts approximates their fair value. Fair values for fixed-rate certificates of deposit are estimated using a discounted cash flow calculation that applies interest rates currently being offered on certificates to a schedule of aggregated expected monthly maturities on these deposits. The fair value measurement of the deposit liabilities is categorized as Level 2 in the fair value hierarchy. FHLB advances and customer repurchase agreements The fair values of the Company’s borrowings are estimated using discounted cash flow analyses, based on the market rates for similar types of borrowing arrangements. The FHLB advances and customer repurchase agreements have been categorized as Level 2 in the fair value hierarchy due to their short durations. Subordinated debt The fair value of subordinated debt is based on the market rate for the respective subordinated debt security. Subordinated debt has been categorized as Level 3 in the fair value hierarchy. Junior subordinated debt Junior subordinated debt is valued based on a discounted cash flow model which uses as inputs Treasury Bond rates and the 'BB' rated financial index. Junior subordinated debt has been categorized as Level 3 in the fair value hierarchy. Off-balance sheet instruments The fair value of the Company’s off-balance sheet instruments (lending commitments and standby letters of credit) is based on quoted fees currently charged to enter into similar agreements, taking into account the remaining terms of the agreements, and the counterparties’ credit standing.
Recent Accounting Pronouncements	Recent accounting pronouncements In February 2016, the FASB issued guidance within ASU 2016-02, Leases. The amendments in ASU 2016-02 to Topic 842, Leases, require lessees to recognize the lease assets and lease liabilities arising from operating leases in the statement of financial position, which will result in a gross up of assets and liabilities on the balance sheet. The accounting applied by a lessor is largely unchanged from that applied under previous GAAP. In July 2018, the FASB issued guidance within ASU 2018-10, Codification Improvements to Topic 842, Leases and ASU 2018-11, Leases (Topic 842) Targeted Improvements . The amendments within ASU 2018-10 clarify how to apply certain aspects of the new leases standard. The amendments address the rate implicit in the lease, impairment of the net investment in the lease, lessee reassessment of lease classification, lessor reassessment of lease term and purchase options, variable payments that depend on an index or rate and certain transition adjustments, among other things. The amendments within ASU 2018-11 give entities another option for transition and provide lessors with a practical expedient. The transition option allows entities to continue to apply the legacy guidance in ASC 840, Leases, to prior periods, including disclosure requirements. Accordingly, under this transition approach, the modified retrospective transition method still applies; however, a cumulative-effect adjustment to the opening balance sheet of retained earnings is recognized in the period of adoption, rather than the earliest period presented. The practical expedient provides lessors with an option to not separate non-lease components from the associated lease components when certain criteria are met and requires them to account for the combined components in accordance with the new revenue standard if the associated non-lease components are the predominant components. The amendments in these ASUs are effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Management evaluated several lease software solutions and selected a software solution that it believes will be able to effectively facilitate the application of the new accounting requirements. The population of its leases that are within the scope of the new guidance has been finalized and largely relate to real estate leases. All key lease data has been gathered and input into the new application and management is in the process of validating this data. In June 2016, the FASB issued guidance within ASU 2016-13, Measurement of Credit Losses on Financial Instruments . The new standard significantly changes the impairment model for most financial assets that are measured at amortized cost, including off-balance sheet credit exposures, from an incurred loss model to an expected loss model. The amendments in ASU 2016-13 to Topic 326, Financial Instruments - Credit Losses, require that an organization measure all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. The ASU also requires enhanced disclosures, including qualitative and quantitative disclosures that provide additional information about the amounts recorded in the financial statements. Additionally, the ASU amends the accounting for credit losses on AFS debt securities and purchased financial assets with credit deterioration. The amendments in this ASU are effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Management has formed a Steering Committee and established an implementation team made up of subject matter experts across different functions within the Company, including Finance, Risk, Credit, and IT, that will facilitate all phases of planning and implementation of the new guidance. Under the direction of the Company's CECL Steering Committee and in partnership with its Enterprise Project Management Office, the implementation team is fully engaged with the implementation of its plan. The Company has identified its portfolio segments and made modeling choices that include both internally-developed models as well as vended solutions, with parallel testing of certain models expected to begin in early 2019. The team is also focused on updating its accounting policies and assessing its control framework to identify risks resulting from new processes, judgments and data. In March 2017, the FASB issued guidance within ASU 2017-08, Premium Amortization on Purchased Callable Debt Securities . The amendments in ASU 2017-08 to Subtopic 310-20, Receivables-Nonrefundable Fees and Other Costs, shorten the amortization period for certain purchased callable debt securities held at a premium to the earliest call date, which more closely align the amortization period of premiums and discounts to expectations incorporated in market pricing on the underlying securities. Under current GAAP, entities generally amortize the premium as an adjustment of yield over the contractual life of the instrument. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. The amendments in this ASU should be applied on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The amendments in this ASU are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted, including adoption in an interim period. The adoption of this guidance is not expected to have a significant impact on the Company's Consolidated Financial Statements. In June 2018, the FASB issued guidance within ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting . The amendments in ASU 2018-07 to Topic 718, Compensation-Stock Compensation, are intended to align the accounting for share-based payment awards issued to employees and nonemployees. Changes to the accounting for nonemployee awards include: 1) equity classified share-based payment awards issued to nonemployees will now be measured on the grant date, instead of the previous requirement to remeasure the awards through the performance completion date; 2) for performance conditions, compensation cost associated with the award will be recognized when achievement of the performance condition is probable, rather than upon achievement of the performance condition; and 3) the current requirement to reassess the classification (equity or liability) for nonemployee awards upon vesting will be eliminated, except for awards in the form of convertible instruments. The new guidance also clarifies that any share-based payment awards issued to customers should be evaluated under ASC 606, Revenue from Contracts with Customers . The amendments in this ASU are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Company's share-based payment awards to nonemployees consist only of grants made to the Company's BOD as compensation solely related to the individual's role as a Director. As such, in accordance with ASC 718, the Company accounts for these share-based payment awards to its Directors in the same manner as share-based payment awards for its employees. Accordingly, the amendments in this guidance will not have an effect on the accounting for the Company's share-based payment awards to its Directors. In July 2018, the FASB issued guidance within ASU 2018-09, Codification Improvements . The amendments in ASU 2018-09 are intended to clarify or correct unintended guidance in the FASB Codification and affect a wide variety of Topics in the Codification. The topics that are applicable to the Company include: 1) debt modifications and extinguishments; 2) stock compensation; and 3) derivatives and hedging. For debt modifications and extinguishments, the amendment clarifies that, in an early extinguishment of debt for which the fair value option has been elected, the net carrying amount of the extinguished debt is equal to its fair value at the reacquisition date, and upon extinguishment, the cumulative amount of the gain or loss on the extinguished debt that resulted from changes in instrument-specific credit risk should be presented in net income. The Company has junior subordinated debt that is recorded at fair value at each reporting period due to election of the FVO. Accordingly, if in the future, the Company chooses to repay this debt prior to its contractual maturity, this amendment would be applicable. For stock compensation, the amendment clarifies that excess tax benefits or tax deficiencies should be recognized in the period in which the amount of the tax deduction is determined, which is typically when an award is exercised (in the case of share options) or vests (in the case of non-vested stock awards). The Company already records excess tax benefits or tax deficiencies in the periods in which the tax deduction is determined. Therefore, this amendment will not have an effect on the Company's accounting for excess tax benefits or tax deficiencies. For derivatives and hedging, previous guidance permits derivatives to be offset only when all four conditions (including the intent to set off) are met. This amendment clarifies that the intent to set off is not required to offset fair value amounts recognized for derivative instruments that are executed with the same counterparty under a master netting agreement. This amendment will not have an effect on the offsetting of the Company's derivative assets and liabilities. In August 2018, the FASB issued guidance within ASU 2018-13, Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement . The amendments within ASU 2018-13 remove, modify, and supplement the disclosure requirements for fair value measurements. Disclosure requirements that were removed include: the amount and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, the policy for timing of transfers between levels, and the valuation processes for Level 3 fair value measurements. The amendments clarify that the measurement uncertainty disclosure is to communicate information about the uncertainty in measurement as of the reporting date. Additional disclosure requirements include: the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period, and the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. With the exception of the above additional disclosure requirements, which will be applied prospectively, all other amendments should be applied retrospectively to all periods presented upon their effective date. The amendments in this ASU are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. The adoption of this guidance is not expected to have a significant impact on the Company's Consolidated Financial Statements. In August 2018, the FASB issued guidance within ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40) . The amendments in this ASU align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). Accordingly, the amendments in this Update require an entity (customer) in a hosting arrangement that is a service contract to follow the guidance in Subtopic 350-40 to determine which implementation costs to capitalize as an asset related to the service contract and which costs to expense. The amendments in this Update also require that the capitalized implementation costs of a hosting arrangement that is a service contract be expensed over the term of the hosting arrangement. Presentation requirements include: expense related to the capitalized implementation costs should be presented in the same line item in the statement of income as the fees associated with the hosting element (service) of the arrangement, payments for capitalized implementation costs in the statement of cash flows should be classified in the same manner as payments made for fees associated with the hosting element, and capitalized implementation costs in the statement of financial position should be presented in the same line item that a prepayment for the fees of the associated hosting arrangement would be presented. The amendments in this ASU should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The amendments in this ASU are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. The adoption of this guidance is not expected to have a significant impact on the Company's Consolidated Financial Statements. Recently adopted accounting guidance In May 2014, the FASB issued guidance within ASU 2014-09, Revenue from Contracts with Customers . The amendments in ASU 2014-09 to ASC 606, Revenue from Contracts with Customers, creates a common revenue standard and clarifies the principles for recognizing revenue that can be applied consistently across various transactions, industries, and capital markets. The amendments in the ASU clarify that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. As part of that principle, the entity should identify the contract(s) with the customer, identify the performance obligation(s) of the contract, determine the transaction price, allocate that transaction price to the performance obligation(s) of the contract, and then recognize revenue when or as the entity satisfies the performance obligation(s). The Company adopted ASU 2014-09 on January 1, 2018 using the modified retrospective method. Substantially all of the Company's revenue is generated from interest income related to loans and investment securities, which are not within the scope of this guidance. The contracts that are within the scope of this guidance include service charges and fees on deposit accounts, certain types of card income, and success fees earned from equity investments. The Company completed its review of contracts and other agreements that are within the scope of this guidance and did not identify any material changes to the timing or amount of revenue recognition. Accordingly, the Company did not recognize an adjustment to retained earnings upon adoption of this guidance. The Company’s accounting policies did not change materially since the principles of revenue recognition in the ASU are largely consistent with current practices applied by the Company. The Company has expanded its qualitative disclosures of performance obligations and disaggregation of significant categories of revenue. See " Note 15. Revenue from Contracts with Customers " for further discussion. In January 2016, the FASB issued guidance within ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities . The amendments in ASU 2016-01 to Subtopic 825-10, Financial Instruments, contain the following elements: 1) requires equity investments to be measured at fair value with changes in fair value recognized in net income; 2) simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; 3) eliminates the requirement for public entities to disclose the methods and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; 4) requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; 5) requires an entity to present separately in OCI the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments; 6) requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or accompanying notes to the financial statements; 7) clarifies that the entity should evaluate the need for a valuation allowance on a deferred tax asset related to AFS securities in combination with the entity's other deferred tax assets. Effective on January 1, 2015, the Company adopted the amendment noted in item 5) above as discussed in the Company's Annual Report on Form 10-K for the year ended December 31, 2015. Effective on January 1, 2018, the Company adopted the other amendments in this guidance. The primary impact on the Company's Consolidated Financial Statements results from the amendments discussed in item 1) above as changes in the fair value of the Company's equity investments are now recognized in net income, rather than in AOCI. As of January 1, 2018, the Company recorded a cumulative-effect adjustment of $0.4 million to decrease accumulated other comprehensive income with a corresponding increase to opening retained earnings. During the nine months ended September 30, 2018 , the Company recognized a loss of $3.0 million related to fair value changes in equity securities, which was recorded in the Consolidated Income Statement. In August 2016, the FASB issued guidance within ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments. The amendments in ASU 2016-15 to Topic 230, Statement of Cash Flows, provide guidance on eight specific cash flow classification issues: 1) debt prepayment or debt extinguishment costs; 2) settlement of zero-coupon debt instruments; 3) contingent consideration payments made after a business combination; 4) proceeds from the settlement of insurance claims; 5) proceeds from the settlement of corporate-owned life insurance policies, including bank-owned life insurance policies; 6) distributions received from equity method investments; 7) beneficial interest in securitization transactions; and 8) separately identifiable cash flows and the application of the predominance principle. The adoption of this guidance did not have a significant impact on the Company's Consolidated Statement of Cash Flows. In January 2017, the FASB issued guidance within ASU 2017-01, Clarifying the Definition of a Business . The amendments in ASU 2017-01 to Topic 805, Business Combinations, clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The adoption of this guidance did not have a significant impact on the Company's Consolidated Financial Statements. In January 2017, the FASB issued guidance within ASU 2017-04, Simplifying the Test for Goodwill Impairment . The amendments in ASU 2017-04 to Topic 350, Intangibles - Goodwill and Other, modify the concept of impairment from the condition that exists when the carrying amount of goodwill exceeds its implied fair value to the condition that exists when the carrying amount of a reporting unit exceeds its fair value. Accordingly, the amendments eliminate Step 2 from the goodwill impairment test because goodwill impairment will no longer be determined by calculating the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities as if that reporting unit had been acquired in a business combination. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. The adoption of this guidance did not have a significant impact on the Company's Consolidated Financial Statements. In February 2017, the FASB issued guidance within ASU 2017-05, Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets . The amendments in ASU 2017-05 to Subtopic 610-20, Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets, clarify the scope of Subtopic 610-20 and add guidance for partial sales of nonfinancial assets, including partial sales of real estate. Under current GAAP, there are several different accounting models to evaluate whether the transfer of certain assets qualify for sale treatment. The new standard reduces the number of potential accounting models that might apply and clarifies which model does apply in various circumstances. The adoption of this guidance did not have a significant impact on the Company's Consolidated Financial Statements. In May 2017, the FASB issued guidance within ASU 2017-09, Scope of Modification Accounting . The amendments in ASU 2017-09 to Topic 718, Compensation - Stock Compensation, provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. An entity should account for the effects of a modification unless all of the following conditions are met: the fair value of the modified award is the same as the fair value of the original award immediately before the original award is modified; the vesting conditions of the modified award are the same as the vesting conditions of the original award immediately before the original award is modified; and the classification of the modified award as an equity instrument or a liability instrument is the same as the classification of the original award immediately before the original award is modified. The adoption of this guidance did not have a significant impact on the Company's Consolidated Financial Statements. In February 2018, the FASB issued guidance within ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . Under current GAAP, the effect of a change in tax laws or rates on deferred tax liabilities and assets are included in income from continuing operations even in situations in which the related income tax effects of items in AOCI were originally recognized in comprehensive income. Accordingly, as the adjustment of deferred taxes due to the reduction of the historical corporate income tax rate to the newly enacted corporate income tax rate is required to be included in income from continuing operations, the tax effects of items within AOCI do not reflect the current tax rate. The amendments in ASU 2018-02 to Topic 220, Income Statement - Reporting Comprehensive Income, allow a reclassification from AOCI to retained earnings from tax effects resulting from the TCJA. The Company elected to adopt this guidance effective January 1, 2018 and recorded a cumulative-effect adjustment of $0.7 million to decrease accumulated other comprehensive income with a corresponding increase to opening retained earnings.

Investment Securities (Tables)

Investment Securities (Tables)	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Carrying Amounts and Fair Values of Investment Securities	The carrying amounts and fair values of investment securities at September 30, 2018 and December 31, 2017 are summarized as follows: September 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (in thousands) Held-to-maturity debt securities Tax-exempt $ 288,290 $ 773 $ (10,030 ) $ 279,033 Available-for-sale debt securities CDO $ 50 $ 19,098 $ — $ 19,148 Commercial MBS issued by GSEs 107,915 42 (7,014 ) 100,943 Corporate debt securities 105,033 119 (5,768 ) 99,384 Private label residential MBS 887,581 42 (31,681 ) 855,942 Residential MBS issued by GSEs 1,515,408 167 (65,516 ) 1,450,059 Tax-exempt 511,957 4,015 (11,065 ) 504,907 Trust preferred securities 32,000 — (3,383 ) 28,617 U.S. government sponsored agency securities 49,000 — (3,399 ) 45,601 U.S. treasury securities 2,496 — (21 ) 2,475 Total AFS debt securities $ 3,211,440 $ 23,483 $ (127,847 ) $ 3,107,076 Equity securities (1) CRA investments $ 52,058 $ — $ (1,314 ) $ 50,744 Preferred stock 122,699 880 (2,029 ) 121,550 Total equity securities $ 174,757 $ 880 $ (3,343 ) $ 172,294 December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (in thousands) Held-to-maturity debt securities Tax-exempt $ 255,050 $ 4,514 $ (3,250 ) $ 256,314 Available-for-sale debt securities CDO $ 50 $ 21,807 $ — $ 21,857 Commercial MBS issued by GSEs 113,069 46 (4,038 ) 109,077 Corporate debt securities 105,044 261 (1,822 ) 103,483 Private label residential MBS 874,261 756 (6,493 ) 868,524 Residential MBS issued by GSEs 1,719,188 810 (30,703 ) 1,689,295 Tax-exempt 501,988 10,893 (1,971 ) 510,910 Trust preferred securities 32,000 — (3,383 ) 28,617 U.S. government sponsored agency securities 64,000 — (2,538 ) 61,462 U.S. treasury securities 2,496 — (14 ) 2,482 Available-for-sale equity securities (1) CRA investments 51,133 — (517 ) 50,616 Preferred stock 52,172 1,160 (136 ) 53,196 Total AFS securities $ 3,515,401 $ 35,733 $ (51,615 ) $ 3,499,519
Unrealized Losses and Fair Value of Investment Securities in Continuous Unrealized Loss Position	Information pertaining to securities with gross unrealized losses at September 30, 2018 and December 31, 2017 , aggregated by investment category and length of time that individual securities have been in a continuous loss position follows: September 30, 2018 Less Than Twelve Months More Than Twelve Months Total Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (in thousands) Held-to-maturity debt securities Tax-exempt $ 10,030 $ 215,827 $ — $ — $ 10,030 $ 215,827 Available-for-sale debt securities Commercial MBS issued by GSEs $ — $ — $ 7,014 $ 99,134 $ 7,014 $ 99,134 Corporate debt securities 766 19,234 5,002 74,998 5,768 94,232 Private label residential MBS 13,004 463,026 18,677 374,504 31,681 837,530 Residential MBS issued by GSEs 16,624 563,642 48,892 878,925 65,516 1,442,567 Tax-exempt 6,337 227,531 4,728 66,047 11,065 293,578 Trust preferred securities — — 3,383 28,617 3,383 28,617 U.S. government sponsored agency securities 151 4,849 3,248 40,752 3,399 45,601 U.S. treasury securities 16 978 5 1,497 21 2,475 Total AFS securities $ 36,898 $ 1,279,260 $ 90,949 $ 1,564,474 $ 127,847 $ 2,843,734 December 31, 2017 Less Than Twelve Months More Than Twelve Months Total Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (in thousands) Held-to-maturity debt securities Tax-exempt $ 3,250 $ 107,921 $ — $ — $ 3,250 $ 107,921 Available-for-sale debt securities Commercial MBS issued by GSEs $ 161 $ 13,565 $ 3,877 $ 93,641 $ 4,038 $ 107,206 Corporate debt securities 1,398 78,602 424 19,576 1,822 98,178 Private label residential MBS 3,115 480,885 3,378 188,710 6,493 669,595 Residential MBS issued by GSEs 13,875 999,478 16,828 523,270 30,703 1,522,748 Tax-exempt 17 6,159 1,954 69,674 1,971 75,833 Trust preferred securities — — 3,383 28,617 3,383 28,617 U.S. government sponsored agency securities 14 4,986 2,524 56,476 2,538 61,462 U.S. treasury securities 14 2,482 — — 14 2,482 Available-for-sale equity securities CRA investments — — 517 50,616 517 50,616 Preferred stock 136 7,357 — — 136 7,357 Total AFS securities $ 18,730 $ 1,593,514 $ 32,885 $ 1,030,580 $ 51,615 $ 2,624,094
Amortized Cost and Fair Value of Investment Securities by Contractual Maturities	The amortized cost and fair value of securities as of September 30, 2018 , by contractual maturities, are shown below. MBS are shown separately as individual MBS are comprised of pools of loans with varying maturities. Therefore, these securities are listed separately in the maturity summary. September 30, 2018 Amortized Cost Estimated Fair Value (in thousands) Held-to-maturity Due in one year or less $ 1,200 $ 1,236 After one year through five years 10,100 10,122 After five years through ten years 14,602 14,351 After ten years 262,388 253,324 Total HTM securities $ 288,290 $ 279,033 Available-for-sale Due in one year or less $ 4,001 $ 3,996 After one year through five years 17,355 17,571 After five years through ten years 223,060 215,580 After ten years 456,120 462,985 Mortgage-backed securities 2,510,904 2,406,944 Total AFS securities $ 3,211,440 $ 3,107,076
Investment Securities by Credit Rating Type	The following tables summarize the carrying amount of the Company’s investment ratings position as of September 30, 2018 and December 31, 2017 : September 30, 2018 AAA Split-rated AAA/AA+ AA+ to AA- A+ to A- BBB+ to BBB- BB+ and below Unrated Totals (in thousands) Held-to-maturity debt securities Tax-exempt $ — $ — $ — $ — $ — $ — $ 288,290 $ 288,290 Available-for-sale debt securities CDO $ — $ — $ — $ — $ — $ 19,148 $ — $ 19,148 Commercial MBS issued by GSEs — 100,943 — — — — — 100,943 Corporate debt securities — — — 71,685 27,699 — — 99,384 Private label residential MBS 818,046 — 34,957 395 1,019 1,525 — 855,942 Residential MBS issued by GSEs — 1,450,059 — — — — — 1,450,059 Tax-exempt 61,443 20,636 244,696 170,409 — — 7,723 504,907 Trust preferred securities — — — — 28,617 — — 28,617 U.S. government sponsored agency securities — 45,601 — — — — — 45,601 U.S. treasury securities — 2,475 — — — — — 2,475 Total AFS securities (1) $ 879,489 $ 1,619,714 $ 279,653 $ 242,489 $ 57,335 $ 20,673 $ 7,723 $ 3,107,076 Equity securities CRA investments $ — $ 26,291 $ — $ — $ — $ — $ 24,453 $ 50,744 Preferred stock — — — — 72,991 39,032 9,527 121,550 Total equity securities (1) $ — $ 26,291 $ — $ — $ 72,991 $ 39,032 $ 33,980 $ 172,294 (1) Where ratings differ, the Company uses an average of the available ratings by major credit agencies. December 31, 2017 AAA Split-rated AAA/AA+ AA+ to AA- A+ to A- BBB+ to BBB- BB+ and below Unrated Totals (in thousands) Held-to-maturity debt securities Tax-exempt $ — $ — $ — $ — $ — $ — $ 255,050 $ 255,050 Available-for-sale debt securities CDO $ — $ — $ — $ — $ — $ 21,857 $ — $ 21,857 Commercial MBS issued by GSEs — 109,077 — — — — — 109,077 Corporate debt securities — — — 74,293 29,190 — — 103,483 Private label residential MBS 809,242 — 55,161 1,350 931 1,840 — 868,524 Residential MBS issued by GSEs — 1,689,295 — — — — — 1,689,295 Tax-exempt 64,893 25,280 249,200 167,994 — — 3,543 510,910 Trust preferred securities — — — — 28,617 — — 28,617 U.S. government sponsored agency securities — 61,462 — — — — — 61,462 U.S. treasury securities — 2,482 — — — — — 2,482 Available-for-sale equity securities CRA investments — 25,349 — — — — 25,267 50,616 Preferred stock — — — 10,388 23,822 4,104 14,882 53,196 Total AFS securities (1) $ 874,135 $ 1,912,945 $ 304,361 $ 254,025 $ 82,560 $ 27,801 $ 43,692 $ 3,499,519 (1) Where ratings differ, the Company uses an average of the available ratings by major credit agencies.
Gross Gains and (Losses) on Sales of Investment Securities	The following table presents gross gains and losses on sales of investment securities: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Gross gains $ — $ 468 $ — $ 1,181 Gross losses (7,232 ) (149 ) (7,232 ) (274 ) Net (losses) gains on sales of investment securities $ (7,232 ) $ 319 $ (7,232 ) $ 907

Loans, Leases and Allowance f_2

Loans, Leases and Allowance for Credit Losses (Tables)	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Schedule of Held for Investment Loan Portfolio Composition of Loans, Leases and Allowance for Credit Losses	The composition of the Company’s held for investment loan portfolio is as follows: September 30, 2018 December 31, 2017 (in thousands) Commercial and industrial $ 7,487,725 $ 6,841,381 Commercial real estate - non-owner occupied 3,952,966 3,904,011 Commercial real estate - owner occupied 2,288,156 2,241,613 Construction and land development 2,107,631 1,632,204 Residential real estate 827,073 425,940 Consumer 69,214 48,786 Loans, net of deferred loan fees and costs 16,732,765 15,093,935 Allowance for credit losses (150,011 ) (140,050 ) Total loans HFI $ 16,582,754 $ 14,953,885
Contractual Aging of Loan Portfolio by Class of Loans Including Loans Held for Sale and Excluding Deferred Fees/Costs	The following table presents the contractual aging of the recorded investment in past due loans held for investment by class of loans: September 30, 2018 Current 30-59 Days 60-89 Days Over 90 Days Past Due Total Total (in thousands) Commercial and industrial $ 7,477,017 $ 8,870 $ 254 $ 1,584 $ 10,708 $ 7,487,725 Commercial real estate Owner occupied 2,287,826 — 330 — 330 2,288,156 Non-owner occupied 3,787,571 — 531 — 531 3,788,102 Multi-family 164,864 — — — — 164,864 Construction and land development Construction 1,412,161 — — — — 1,412,161 Land 695,470 — — — — 695,470 Residential real estate 811,516 5,865 1,338 8,354 15,557 827,073 Consumer 68,881 — — 333 333 69,214 Total loans $ 16,705,306 $ 14,735 $ 2,453 $ 10,271 $ 27,459 $ 16,732,765 December 31, 2017 Current 30-59 Days 60-89 Days Over 90 days Total Total (in thousands) Commercial and industrial $ 6,835,385 $ 2,245 $ 669 $ 3,082 $ 5,996 $ 6,841,381 Commercial real estate Owner occupied 2,240,457 1,026 — 130 1,156 2,241,613 Non-owner occupied 3,696,729 2,993 — 2,847 5,840 3,702,569 Multi-family 201,442 — — — — 201,442 Construction and land development Construction 1,090,176 — — — — 1,090,176 Land 536,917 — — 5,111 5,111 542,028 Residential real estate 411,857 6,874 1,487 5,722 14,083 425,940 Consumer 48,408 83 213 82 378 48,786 Total loans $ 15,061,371 $ 13,221 $ 2,369 $ 16,974 $ 32,564 $ 15,093,935
Summary of Recorded Investment in Nonaccrual Loans and Loans Past Due 90 Days Still Accruing Interest by Loan Class	The following table presents the recorded investment in non-accrual loans and loans past due ninety days or more and still accruing interest by class of loans: September 30, 2018 December 31, 2017 Non-accrual loans Loans past due 90 days or more and still accruing Non-accrual loans Loans past due 90 days or more and still accruing Current Past Due/ Total Current Past Due/ Total (in thousands) Commercial and industrial $ 14,894 $ 9,083 $ 23,977 $ — $ 17,913 $ 4,113 $ 22,026 $ 43 Commercial real estate Owner occupied — — — — 1,089 792 1,881 — Non-owner occupied — — — — — 5,840 5,840 — Multi-family — — — — — — — — Construction and land development Construction — — — — — — — — Land — — — — 868 5,111 5,979 — Residential real estate 4,204 8,354 12,558 — 2,039 6,078 8,117 — Consumer — 333 333 — — 82 82 — Total $ 19,098 $ 17,770 $ 36,868 $ — $ 21,909 $ 22,016 $ 43,925 $ 43
Loans by Risk Rating	The following tables present gross loans by risk rating: September 30, 2018 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Commercial and industrial $ 7,273,634 $ 83,886 $ 129,183 $ 1,022 $ — $ 7,487,725 Commercial real estate Owner occupied 2,214,765 18,713 54,678 — — 2,288,156 Non-owner occupied 3,765,340 14,666 8,096 — — 3,788,102 Multi-family 164,864 — — — — 164,864 Construction and land development Construction 1,404,619 1,233 6,309 — — 1,412,161 Land 694,596 266 608 — — 695,470 Residential real estate 808,065 5,884 13,124 — — 827,073 Consumer 68,599 41 574 — — 69,214 Total $ 16,394,482 $ 124,689 $ 212,572 $ 1,022 $ — $ 16,732,765 September 30, 2018 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Current (up to 29 days past due) $ 16,386,286 $ 124,056 $ 194,118 $ 846 $ — $ 16,705,306 Past due 30 - 59 days 5,991 393 8,351 — — 14,735 Past due 60 - 89 days 1,870 240 343 — — 2,453 Past due 90 days or more 335 — 9,760 176 — 10,271 Total $ 16,394,482 $ 124,689 $ 212,572 $ 1,022 $ — $ 16,732,765 December 31, 2017 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Commercial and industrial $ 6,675,574 $ 85,781 $ 76,328 $ 3,698 $ — $ 6,841,381 Commercial real estate Owner occupied 2,149,465 43,122 48,397 629 — 2,241,613 Non-owner occupied 3,676,711 11,166 14,692 — — 3,702,569 Multi-family 201,442 — — — — 201,442 Construction and land development Construction 1,072,342 4,477 13,357 — — 1,090,176 Land 535,412 637 5,979 — — 542,028 Residential real estate 408,527 8,971 8,442 — — 425,940 Consumer 47,824 878 84 — — 48,786 Total $ 14,767,297 $ 155,032 $ 167,279 $ 4,327 $ — $ 15,093,935 December 31, 2017 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Current (up to 29 days past due) $ 14,758,149 $ 154,295 $ 145,934 $ 2,993 $ — $ 15,061,371 Past due 30 - 59 days 7,966 518 4,737 — — 13,221 Past due 60 - 89 days 1,182 219 968 — — 2,369 Past due 90 days or more — — 15,640 1,334 — 16,974 Total $ 14,767,297 $ 155,032 $ 167,279 $ 4,327 $ — $ 15,093,935
Impaired Loans by Loan Class	The following table presents impaired loans by class: September 30, 2018 December 31, 2017 (in thousands) Commercial and industrial $ 76,185 $ 34,156 Commercial real estate Owner occupied 6,660 10,430 Non-owner occupied 12,544 21,251 Multi-family — — Construction and land development Construction — — Land 9,128 15,426 Residential real estate 20,686 17,170 Consumer 366 121 Total $ 125,569 $ 98,554
Recorded Investment in Loans Classified as Impaired	The following table presents the average investment in impaired loans and income recognized on impaired loans: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Average balance on impaired loans $ 104,652 $ 108,033 $ 100,712 $ 106,456 Interest income recognized on impaired loans 1,114 1,040 3,109 3,075 Interest recognized on non-accrual loans, cash basis 569 694 1,443 1,372 The table below reflects the recorded investment in loans classified as impaired: September 30, 2018 December 31, 2017 (in thousands) Impaired loans with a specific valuation allowance under ASC 310 (1) $ 3,601 $ 19,315 Impaired loans without a specific valuation allowance under ASC 310 (2) 121,968 79,239 Total impaired loans $ 125,569 $ 98,554 Valuation allowance related to impaired loans (3) $ (1,171 ) $ (5,606 ) (1) Includes TDR loans of $2.6 million and $3.7 million at September 30, 2018 and December 31, 2017 , respectively. (2) Includes TDR loans of $49.5 million and $48.8 million at September 30, 2018 and December 31, 2017 , respectively. (3) Includes valuation allowance related to TDR loans of $0.7 million and $1.2 million at September 30, 2018 and December 31, 2017 , respectively.
Average Investment in Impaired Loans by Loan Class	The following table presents the average investment in impaired loans by loan class: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Commercial and industrial $ 55,026 $ 40,074 $ 47,083 $ 33,358 Commercial real estate Owner occupied 6,698 17,779 8,053 20,136 Non-owner occupied 12,597 20,789 16,349 22,446 Multi-family — — — — Construction and land development Construction — — — — Land 9,218 12,503 9,701 13,297 Residential real estate 20,746 16,692 19,217 17,011 Consumer 367 196 309 208 Total $ 104,652 $ 108,033 $ 100,712 $ 106,456
Interest Income on Impaired Loans by Loan Class	The following table presents interest income on impaired loans by class: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Commercial and industrial $ 537 $ 307 $ 1,276 $ 788 Commercial real estate Owner occupied 118 166 376 530 Non-owner occupied 218 279 744 798 Multi-family — — — — Construction and land development Construction — — — — Land 146 163 425 551 Residential real estate 95 124 287 406 Consumer — 1 1 2 Total $ 1,114 $ 1,040 $ 3,109 $ 3,075
Tabular Disclosure of Nonperforming Assets	The following table summarizes nonperforming assets: September 30, 2018 December 31, 2017 (in thousands) Non-accrual loans (1) $ 36,868 $ 43,925 Loans past due 90 days or more on accrual status (2) — 43 Accruing troubled debt restructured loans 42,567 42,431 Total nonperforming loans 79,435 86,399 Other assets acquired through foreclosure, net 20,028 28,540 Total nonperforming assets $ 99,463 $ 114,939 (1) Includes non-accrual TDR loans of $9.6 million and $10.1 million at September 30, 2018 and December 31, 2017 , respectively. (2)
Accretable Yield Table	Changes in the accretable yield for loans acquired with deteriorated credit quality are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Balance, at beginning of period $ 4,828 $ 14,247 $ 9,324 $ 15,177 Reclassifications from non-accretable to accretable yield (1) — — 683 2,086 Accretion to interest income (224 ) (690 ) (801 ) (2,374 ) Reversal of fair value adjustments upon disposition of loans (563 ) (2,199 ) (5,165 ) (3,531 ) Balance, at end of period $ 4,041 $ 11,358 $ 4,041 $ 11,358 (1) The primary drivers of reclassification from non-accretable to accretable yield resulted from changes in estimated cash flows.
Allowances for Credit Losses	The following table presents impairment method information related to loans and allowance for credit losses by loan portfolio segment: Commercial Real Estate-Owner Occupied Commercial Real Estate-Non-Owner Occupied Commercial and Industrial Residential Real Estate Construction and Land Development Consumer Total Loans (in thousands) Loans as of September 30, 2018; Recorded Investment Impaired loans with an allowance recorded $ — $ — $ 3,238 $ 363 $ — $ — $ 3,601 Impaired loans with no allowance recorded 6,660 12,544 72,947 20,323 9,128 366 121,968 Total loans individually evaluated for impairment 6,660 12,544 76,185 20,686 9,128 366 125,569 Loans collectively evaluated for impairment 2,276,847 3,859,914 7,411,540 805,800 2,098,503 68,848 16,521,452 Loans acquired with deteriorated credit quality 4,649 80,508 — 587 — — 85,744 Total recorded investment $ 2,288,156 $ 3,952,966 $ 7,487,725 $ 827,073 $ 2,107,631 $ 69,214 $ 16,732,765 Unpaid Principal Balance Impaired loans with an allowance recorded $ — $ — $ 5,520 $ 363 $ — $ — $ 5,883 Impaired loans with no allowance recorded 13,164 18,292 108,469 29,312 25,756 10,726 205,719 Total loans individually evaluated for impairment 13,164 18,292 113,989 29,675 25,756 10,726 211,602 Loans collectively evaluated for impairment 2,276,847 3,859,914 7,411,540 805,800 2,098,503 68,848 16,521,452 Loans acquired with deteriorated credit quality 6,351 96,840 4,357 706 — — 108,254 Total unpaid principal balance $ 2,296,362 $ 3,975,046 $ 7,529,886 $ 836,181 $ 2,124,259 $ 79,574 $ 16,841,308 Related Allowance for Credit Losses Impaired loans with an allowance recorded $ — $ — $ 1,111 $ 60 $ — $ — $ 1,171 Impaired loans with no allowance recorded — — — — — — — Total loans individually evaluated for impairment — — 1,111 60 — — 1,171 Loans collectively evaluated for impairment 13,946 17,497 85,528 8,015 22,656 1,047 148,689 Loans acquired with deteriorated credit quality — 142 9 — — — 151 Total allowance for credit losses $ 13,946 $ 17,639 $ 86,648 $ 8,075 $ 22,656 $ 1,047 $ 150,011 Commercial Real Estate-Owner Occupied Commercial Real Estate-Non-Owner Occupied Commercial and Industrial Residential Real Estate Construction and Land Development Consumer Total Loans (in thousands) Loans as of December 31, 2017; Recorded Investment Impaired loans with an allowance recorded $ — $ — $ 19,315 $ — $ — $ — $ 19,315 Impaired loans with no allowance recorded 10,430 21,250 14,842 17,170 15,426 121 79,239 Total loans individually evaluated for impairment 10,430 21,250 34,157 17,170 15,426 121 98,554 Loans collectively evaluated for impairment 2,221,614 3,777,219 6,807,181 408,169 1,616,778 48,665 14,879,626 Loans acquired with deteriorated credit quality 9,569 105,542 43 601 — — 115,755 Total recorded investment $ 2,241,613 $ 3,904,011 $ 6,841,381 $ 425,940 $ 1,632,204 $ 48,786 $ 15,093,935 Unpaid Principal Balance Impaired loans with an allowance recorded $ — $ — $ 20,795 $ — $ — $ — $ 20,795 Impaired loans with no allowance recorded 17,459 28,028 42,261 26,057 32,289 10,695 156,789 Total loans individually evaluated for impairment 17,459 28,028 63,056 26,057 32,289 10,695 177,584 Loans collectively evaluated for impairment 2,221,614 3,777,219 6,807,181 408,169 1,616,778 48,665 14,879,626 Loans acquired with deteriorated credit quality 12,619 128,440 3,146 720 — — 144,925 Total unpaid principal balance $ 2,251,692 $ 3,933,687 $ 6,873,383 $ 434,946 $ 1,649,067 $ 59,360 $ 15,202,135 Related Allowance for Credit Losses Impaired loans with an allowance recorded $ — $ — $ 5,606 $ — $ — $ — $ 5,606 Impaired loans with no allowance recorded — — — — — — — Total loans individually evaluated for impairment — — 5,606 — — — 5,606 Loans collectively evaluated for impairment 13,884 16,135 76,919 5,500 19,599 776 132,813 Loans acquired with deteriorated credit quality — 1,629 2 — — — 1,631 Total allowance for credit losses $ 13,884 $ 17,764 $ 82,527 $ 5,500 $ 19,599 $ 776 $ 140,050 The following table summarizes the changes in the allowance for credit losses by portfolio type: Three Months Ended September 30, Construction and Land Development Commercial Real Estate Residential Real Estate Commercial and Industrial Consumer Total (in thousands) 2018 Beginning Balance $ 22,159 $ 31,979 $ 6,849 $ 85,244 $ 852 $ 147,083 Charge-offs — — 46 4,610 109 4,765 Recoveries (24 ) (856 ) (440 ) (362 ) (11 ) (1,693 ) Provision 473 (1,250 ) 832 5,652 293 6,000 Ending balance $ 22,656 $ 31,585 $ 8,075 $ 86,648 $ 1,047 $ 150,011 2017 Beginning Balance $ 20,852 $ 28,593 $ 4,838 $ 76,734 $ 794 $ 131,811 Charge-offs — 175 — 2,921 61 3,157 Recoveries (226 ) (1,781 ) (108 ) (619 ) (33 ) (2,767 ) Provision (619 ) (1,474 ) (141 ) 7,192 42 5,000 Ending balance $ 20,459 $ 28,725 $ 4,805 $ 81,624 $ 808 $ 136,421 Nine Months Ended September 30, Construction and Land Development Commercial Real Estate Residential Real Estate Commercial and Industrial Consumer Total (in thousands) 2018 Beginning Balance $ 19,511 $ 31,495 $ 5,478 $ 82,793 $ 773 $ 140,050 Charge-offs 1 233 1,038 10,904 114 12,290 Recoveries (1,420 ) (1,228 ) (831 ) (1,737 ) (35 ) (5,251 ) Provision 1,726 (905 ) 2,804 13,022 353 17,000 Ending balance $ 22,656 $ 31,585 $ 8,075 $ 86,648 $ 1,047 $ 150,011 2017 Beginning Balance $ 21,175 $ 25,673 $ 3,851 $ 73,333 $ 672 $ 124,704 Charge-offs — 1,994 447 6,166 103 8,710 Recoveries (1,011 ) (2,719 ) (1,659 ) (2,705 ) (83 ) (8,177 ) Provision (1,727 ) 2,327 (258 ) 11,752 156 12,250 Ending balance $ 20,459 $ 28,725 $ 4,805 $ 81,624 $ 808 $ 136,421

Other Assets Acquired Through_2

Other Assets Acquired Through Foreclosure (Tables)	9 Months Ended
	Sep. 30, 2018
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Changes in Other Assets Acquired Through Foreclosure	The following table represents the changes in other assets acquired through foreclosure: Three Months Ended September 30, 2018 Gross Balance Valuation Allowance Net Balance (in thousands) Balance, beginning of period $ 31,145 $ (3,604 ) $ 27,541 Proceeds from sale of other real estate owned and repossessed assets, net (1,093 ) 401 (692 ) Charitable contribution (1) (6,895 ) — (6,895 ) Valuation adjustments, net — — — Gains (losses), net (2) 74 — 74 Balance, end of period $ 23,231 $ (3,203 ) $ 20,028 2017 Balance, beginning of period $ 35,037 $ (4,049 ) $ 30,988 Transfers to other assets acquired through foreclosure, net 430 — 430 Proceeds from sale of other real estate owned and repossessed assets, net (2,491 ) 330 (2,161 ) Valuation adjustments, net — (343 ) (343 ) Gains (losses), net (2) 78 — 78 Balance, end of period $ 33,054 $ (4,062 ) $ 28,992 Nine Months Ended September 30, 2018 Gross Balance Valuation Allowance Net Balance (in thousands) Balance, beginning of period $ 32,552 $ (4,012 ) $ 28,540 Transfers to other assets acquired through foreclosure, net 5,744 — 5,744 Proceeds from sale of other real estate owned and repossessed assets, net (9,634 ) 841 (8,793 ) Charitable contribution (1) (6,895 ) — (6,895 ) Valuation adjustments, net — (32 ) (32 ) Gains (losses), net (3) 1,464 — 1,464 Balance, end of period $ 23,231 $ (3,203 ) $ 20,028 2017 Balance, beginning of period $ 54,138 $ (6,323 ) $ 47,815 Transfers to other assets acquired through foreclosure, net 1,812 — 1,812 Proceeds from sale of other real estate owned and repossessed assets, net (23,129 ) 2,381 (20,748 ) Valuation adjustments, net — (120 ) (120 ) Gains (losses), net (3) 233 — 233 Balance, end of period $ 33,054 $ (4,062 ) $ 28,992 (1) Represents a contribution of OREO property to the Company's charitable foundation. See Note 16. Related Party Transactions for further discussion. (2) There were no net gains related to initial transfers to other assets during the three months ended September 30, 2018 and 2017

Other Borrowings (Tables)

Other Borrowings (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Company's Borrowings	The following table summarizes the Company’s borrowings as of September 30, 2018 and December 31, 2017 : September 30, 2018 December 31, 2017 (in thousands) Short-Term: FHLB advances $ — $ 390,000 Total short-term borrowings $ — $ 390,000

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Summary of Changes in Accumulated Other Comprehensive Income	The following table summarizes the changes in accumulated other comprehensive income (loss) by component, net of tax, for the periods indicated: Three Months Ended September 30, Unrealized holding (losses) gains on AFS Unrealized holding gains (losses) on SERP Unrealized holding gains (losses) on junior subordinated debt Impairment loss on securities Total (in thousands) Balance, June 30, 2018 $ (61,859 ) $ 446 $ 9,954 $ 144 $ (51,315 ) Other comprehensive (loss) income before reclassifications (22,462 ) (12 ) (2,028 ) — (24,502 ) Amounts reclassified from AOCI 5,454 — — — 5,454 Net current-period other comprehensive (loss) income (17,008 ) (12 ) (2,028 ) — (19,048 ) Balance, September 30, 2018 $ (78,867 ) $ 434 $ 7,926 $ 144 $ (70,363 ) Balance, June 30, 2017 $ (449 ) $ 157 $ 6,638 $ 144 $ 6,490 Other comprehensive income (loss) before reclassifications 1,116 114 641 — 1,871 Amounts reclassified from AOCI (197 ) — — — (197 ) Net current-period other comprehensive income (loss) 919 114 641 — 1,674 Balance, September 30, 2017 $ 470 $ 271 $ 7,279 $ 144 $ 8,164 Nine Months Ended September 30, Unrealized holding (losses) gains on AFS Unrealized holding gains (losses) on SERP Unrealized holding gains (losses) on junior subordinated debt Impairment loss on securities Total (in thousands) Balance, December 31, 2017 $ (10,026 ) $ 385 $ 6,352 $ 144 $ (3,145 ) Balance, January 1, 2018 (1) (12,556 ) 469 7,740 144 (4,203 ) Other comprehensive (loss) income before reclassifications (71,765 ) (35 ) 186 — (71,614 ) Amounts reclassified from AOCI 5,454 — — — 5,454 Net current-period other comprehensive (loss) income (66,311 ) (35 ) 186 — (66,160 ) Balance, September 30, 2018 $ (78,867 ) $ 434 $ 7,926 $ 144 $ (70,363 ) Balance, December 31, 2016 $ (14,916 ) $ 121 $ 9,956 $ 144 $ (4,695 ) Other comprehensive income (loss) before reclassifications 15,947 150 (2,677 ) — 13,420 Amounts reclassified from AOCI (561 ) — — — (561 ) Net current-period other comprehensive income (loss) 15,386 150 (2,677 ) — 12,859 Balance, September 30, 2017 $ 470 $ 271 $ 7,279 $ 144 $ 8,164 (1) As adjusted for adoption of ASU 2016-01 and ASU 2018-02, see " Note 1. Summary of Significant Accounting Policies " for further discussion.
Schedule of Reclassifications Out of Accumulated Other Comprehensive Income	The following table presents reclassifications out of accumulated other comprehensive income (loss): Three Months Ended September 30, Nine Months Ended September 30, Income Statement Classification 2018 2017 2018 2017 (in thousands) (Loss) gain on sales of investment securities, net $ (7,232 ) $ 319 $ (7,232 ) $ 907 Income tax expense (benefit) 1,778 (122 ) 1,778 (346 ) Net of tax $ (5,454 ) $ 197 $ (5,454 ) $ 561

Derivatives and Hedging (Tables

Derivatives and Hedging (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position	The fair value of derivative contracts, after taking into account the effects of master netting agreements, is included in other assets or other liabilities in the Consolidated Balance Sheets, as indicated in the following table: September 30, 2018 December 31, 2017 September 30, 2017 Fair Value Fair Value Fair Value Notional Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities (in thousands) Derivatives designated as hedging instruments: Fair value hedges Interest rate swaps $ 971,408 $ 7,883 $ 38,040 $ 993,432 $ 1,703 $ 53,581 $ 1,016,694 $ 1,656 $ 59,346 Total 971,408 7,883 38,040 993,432 1,703 53,581 1,016,694 1,656 59,346 Netting adjustments (1) — 6,119 6,119 — 896 896 — 1,588 1,588 Net derivatives in the balance sheet $ 971,408 $ 1,764 $ 31,921 $ 993,432 $ 807 $ 52,685 $ 1,016,694 $ 68 $ 57,758 Derivatives not designated as hedging instruments: Foreign currency contracts (2) $ 47,349 $ 1,003 $ 841 $ 85,335 $ 1,232 $ 983 $ 68,122 $ 494 $ 291 Interest rate swaps 2,348 92 92 36,969 776 776 35,578 641 641 Total $ 49,697 $ 1,095 $ 933 $ 122,304 $ 2,008 $ 1,759 $ 103,700 $ 1,135 $ 932 (1) Netting adjustments represent the amounts recorded to convert the Company's derivative balances from a gross basis to a net basis in accordance with the applicable accounting guidance.
Largest Exposure To Individual Counterparty	The following table summarizes the Company's largest exposure to an individual counterparty at the dates indicated: September 30, 2018 December 31, 2017 September 30, 2017 (in thousands) Largest gross exposure (derivative asset) to an individual counterparty $ 5,802 $ 893 $ 945 Collateral posted by this counterparty — — — Derivative liability with this counterparty 9,567 40,340 44,053 Collateral pledged to this counterparty 22,179 60,476 65,051 Net exposure after netting adjustments and collateral $ — $ — $ —

Earnings per Share (Tables)

Earnings per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table presents the calculation of basic and diluted EPS: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands, except per share amounts) Weighted average shares - basic 104,768 104,221 104,664 104,124 Dilutive effect of stock awards 680 721 734 817 Weighted average shares - diluted 105,448 104,942 105,398 104,941 Net income $ 111,123 $ 82,844 $ 316,702 $ 236,146 Earnings per share - basic 1.06 0.79 3.03 2.27 Earnings per share - diluted 1.05 0.79 3.00 2.25

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Summary of Contractual Amounts for Unfunded Commitments and Letters of Credit	A summary of the contractual amounts for unfunded commitments and letters of credit are as follows: September 30, 2018 December 31, 2017 (in thousands) Commitments to extend credit, including unsecured loan commitments of $594,074 at September 30, 2018 and $364,638 at December 31, 2017 $ 6,798,062 $ 5,851,158 Credit card commitments and financial guarantees 218,993 153,752 Standby letters of credit, including unsecured letters of credit of $16,940 at September 30, 2018 and $11,664 at December 31, 2017 216,636 161,966 Total $ 7,233,691 $ 6,166,876

Fair Value Accounting (Tables)

Fair Value Accounting (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Gains and Losses from Fair Value Changes Included in Consolidated Statement of Operations	For the three and nine months ended September 30, 2018 and 2017 , gains and losses from fair value changes on junior subordinated debt and trading securities were as follows: Changes in Fair Values for Items Measured at Fair Value Unrealized Gain/(Loss) on Assets and Liabilities Measured at Fair Value, Net Interest Income on Securities Interest Expense on Junior Subordinated Debt Total Changes Included in Current-Period Earnings Changes Included in OCI (in thousands) Three Months Ended September 30, 2018 Junior subordinated debt $ (2,689 ) $ — $ 1,056 $ 1,056 $ (2,028 ) Nine Months Ended September 30, 2018 Junior subordinated debt $ 247 $ — $ 2,979 $ 2,979 $ 186 Three Months Ended September 30, 2017 Junior subordinated debt $ 1,035 $ — $ (835 ) $ (835 ) $ 641 Nine Months Ended September 30, 2017 Trading securities $ — $ 9 $ — $ 9 $ — Junior subordinated debt (4,327 ) — (2,376 ) (2,376 ) (2,677 ) Total $ (4,327 ) $ 9 $ (2,376 ) $ (2,367 ) $ (2,677 )
Fair Value of Assets and Liabilities	The fair value of assets and liabilities measured at fair value on a recurring basis was determined using the following inputs as of the periods presented: Fair Value Measurements at the End of the Reporting Period Using: Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Fair Value (in thousands) September 30, 2018 Assets: Available-for-sale debt securities CDO $ — $ 19,148 $ — $ 19,148 Commercial MBS issued by GSEs — 100,943 — 100,943 Corporate debt securities — 99,384 — 99,384 Private label residential MBS — 855,942 — 855,942 Residential MBS issued by GSEs — 1,450,059 — 1,450,059 Tax-exempt — 504,907 — 504,907 Trust preferred securities — 28,617 — 28,617 U.S. government sponsored agency securities — 45,601 — 45,601 U.S. treasury securities — 2,475 — 2,475 Total AFS debt securities $ — $ 3,107,076 $ — $ 3,107,076 Equity securities CRA investments 50,744 — — 50,744 Preferred stock 121,550 — — 121,550 Total equity securities $ 172,294 $ — $ — $ 172,294 Derivative assets (1) $ — $ 8,978 $ — $ 8,978 Liabilities: Junior subordinated debt (2) $ — $ — $ 55,987 $ 55,987 Derivative liabilities (1) — 38,973 — 38,973 (1) Derivative assets and liabilities relate to interest rate swaps, see " Note 9. Derivatives and Hedging Activities ." In addition, the carrying value of loans is decreased by $1,997 and the net carrying value of subordinated debt is increased by $28,160 as of September 30, 2018 for the effective portion of the hedge, which relates to the fair value of the hedges put in place to mitigate against fluctuations in interest rates. (2) Includes only the portion of junior subordinated debt that is recorded at fair value at each reporting period pursuant to the election of FVO treatment. Fair Value Measurements at the End of the Reporting Period Using: Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Fair Value (in thousands) December 31, 2017 Assets: Available-for-sale debt securities CDO $ — $ 21,857 $ — $ 21,857 Commercial MBS issued by GSEs — 109,077 — 109,077 Corporate debt securities — 103,483 — 103,483 Private label residential MBS — 868,524 — 868,524 Residential MBS issued by GSEs — 1,689,295 — 1,689,295 Tax-exempt — 510,910 — 510,910 Trust preferred securities — 28,617 — 28,617 U.S. government sponsored agency securities — 61,462 — 61,462 U.S. treasury securities — 2,482 — 2,482 Available-for-sale equity securities CRA investments 50,616 — — 50,616 Preferred stock 53,196 — — 53,196 Total AFS securities $ 103,812 $ 3,395,707 $ — $ 3,499,519 Derivative assets (1) $ — $ 3,711 $ — $ 3,711 Liabilities: Junior subordinated debt (2) $ — $ — $ 56,234 $ 56,234 Derivative liabilities (1) — 55,340 — 55,340 (1) Derivative assets and liabilities relate to interest rate swaps, see " Note 9. Derivatives and Hedging Activities ." In addition, the carrying value of loans is increased by $41,919 and the net carrying value of subordinated debt is decreased by $9,959 as of December 31, 2017 for the effective portion of the hedge, which relates to the fair value of the hedges put in place to mitigate against fluctuations in interest rates. (2) Includes only the portion of junior subordinated debt that is recorded at fair value at each reporting period pursuant to the election of FVO treatment.
Change in Level 3 Liabilities Measured at Fair Value on Recurring Basis	For the three and nine months ended September 30, 2018 and 2017 , the change in Level 3 liabilities measured at fair value on a recurring basis was as follows: Junior Subordinated Debt Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Beginning balance $ (53,298 ) $ (55,772 ) $ (56,234 ) $ (50,410 ) Change in fair value (2,689 ) 1,035 247 (4,327 ) Ending balance $ (55,987 ) $ (54,737 ) $ (55,987 ) $ (54,737 )
Assets Measured at Fair Value on Nonrecurring Basis	The following table presents such assets carried on the Balance Sheet by caption and by level within the ASC 825 hierarchy: Fair Value Measurements at the End of the Reporting Period Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Active Markets for Similar Assets (Level 2) Unobservable Inputs (Level 3) (in thousands) As of September 30, 2018; Impaired loans with specific valuation allowance $ 2,430 $ — $ — $ 2,430 Impaired loans without specific valuation allowance (1) 81,445 — — 81,445 Other assets acquired through foreclosure 20,028 — — 20,028 As of December 31, 2017: Impaired loans with specific valuation allowance $ 13,709 $ — $ — $ 13,709 Impaired loans without specific valuation allowance (1) 63,607 — — 63,607 Other assets acquired through foreclosure 28,540 — — 28,540 (1) Net of loan balances with charge-offs of $40.5 million and $15.6 million as of September 30, 2018 and December 31, 2017 , respectively.
Estimated Fair Value of Financial Instruments	The estimated fair value of the Company’s financial instruments is as follows: September 30, 2018 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (in thousands) Financial assets: Federal funds sold $ 70,000 $ — $ 70,000 $ — $ 70,000 Investment securities: HTM 288,290 — 279,033 — 279,033 AFS 3,107,076 — 3,107,076 — 3,107,076 Equity 172,294 172,294 — — 172,294 Derivative assets 8,978 — 8,978 — 8,978 Loans, net 16,582,754 — 15,964,980 83,875 16,048,855 Accrued interest receivable 88,847 — 88,847 — 88,847 Financial liabilities: Deposits $ 18,908,580 $ — $ 18,918,956 $ — $ 18,918,956 Customer repurchase agreements 20,969 — 20,969 — 20,969 Qualifying debt 359,082 — 328,448 67,013 395,461 Derivative liabilities 38,973 — 38,973 — 38,973 Accrued interest payable 14,268 — 14,268 — 14,268 December 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (in thousands) Financial assets: Investment securities: HTM $ 255,050 $ — $ 256,314 $ — $ 256,314 AFS 3,499,519 103,812 3,395,707 — 3,499,519 Derivative assets 3,711 — 3,711 — 3,711 Loans, net 14,953,885 — 14,577,010 77,316 14,654,326 Accrued interest receivable 85,517 — 85,517 — 85,517 Financial liabilities: Deposits $ 16,972,532 $ — $ 16,980,066 $ — $ 16,980,066 Customer repurchase agreements 26,017 — 26,017 — 26,017 FHLB advances 390,000 — 390,000 — 390,000 Qualifying debt 376,905 — 336,803 67,210 404,013 Derivative liabilities 55,340 — 55,340 — 55,340 Accrued interest payable 16,366 — 16,366 — 16,366

Segments (Tables)

Segments (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Operating Segment Information	The following is a summary of operating segment information for the periods indicated: Regional Segments Balance Sheet: Consolidated Company Arizona Nevada Southern California Northern California At September 30, 2018 (in millions) Assets: Cash, cash equivalents, and investment securities $ 4,334.2 $ 2.0 $ 8.5 $ 2.1 $ 1.8 Loans, net of deferred loan fees and costs 16,732.8 3,593.5 1,936.7 2,116.3 1,332.3 Less: allowance for credit losses (150.0 ) (33.1 ) (18.6 ) (20.2 ) (11.3 ) Total loans 16,582.8 3,560.4 1,918.1 2,096.1 1,321.0 Other assets acquired through foreclosure, net 20.0 1.7 14.1 — — Goodwill and other intangible assets, net 299.5 — 23.2 — 155.8 Other assets 939.6 46.3 58.0 15.1 18.8 Total assets $ 22,176.1 $ 3,610.4 $ 2,021.9 $ 2,113.3 $ 1,497.4 Liabilities: Deposits $ 18,908.6 $ 5,331.7 $ 3,847.3 $ 2,550.7 $ 1,951.5 Borrowings and qualifying debt 359.1 — — — — Other liabilities 420.0 13.5 16.3 1.9 12.3 Total liabilities 19,687.7 5,345.2 3,863.6 2,552.6 1,963.8 Allocated equity: 2,488.4 439.8 270.7 242.4 308.7 Total liabilities and stockholders' equity $ 22,176.1 $ 5,785.0 $ 4,134.3 $ 2,795.0 $ 2,272.5 Excess funds provided (used) — 2,174.6 2,112.4 681.7 775.1 Income Statement: Three Months Ended September 30, 2018 (in thousands) Net interest income $ 234,038 $ 56,701 $ 37,933 $ 29,572 $ 23,825 Provision for (recovery of) credit losses 6,000 (297 ) (38 ) 1,467 482 Net interest income after provision for credit losses 228,038 56,998 37,971 28,105 23,343 Non-interest income 4,418 2,230 2,573 931 2,312 Non-interest expense (113,841 ) (23,231 ) (16,471 ) (14,332 ) (13,207 ) Income (loss) before income taxes 118,615 35,997 24,073 14,704 12,448 Income tax expense (benefit) 7,492 8,999 5,055 4,117 3,486 Net income $ 111,123 $ 26,998 $ 19,018 $ 10,587 $ 8,962 Nine Months Ended September 30, 2018 (in thousands) Net interest income $ 672,366 $ 169,233 $ 109,898 $ 85,038 $ 69,081 Provision for (recovery of) credit losses 17,000 1,655 (2,005 ) 1,921 2,043 Net interest income after provision for credit losses 655,366 167,578 111,903 83,117 67,038 Non-interest income 29,505 5,902 8,585 2,898 7,281 Non-interest expense (314,538 ) (67,154 ) (46,486 ) (42,470 ) (39,139 ) Income (loss) before income taxes 370,333 106,326 74,002 43,545 35,180 Income tax expense (benefit) 53,631 26,644 15,634 12,288 9,938 Net income $ 316,702 $ 79,682 $ 58,368 $ 31,257 $ 25,242 National Business Lines Balance Sheet: HOA Public & Nonprofit Finance Technology & Innovation Hotel Franchise Finance Other NBLs Corporate & Other At September 30, 2018 Assets: (in millions) Cash, cash equivalents, and investment securities $ — $ — $ — $ — $ — $ 4,319.8 Loans, net of deferred loan fees and costs 202.1 1,520.2 1,106.5 1,435.4 3,483.2 6.6 Less: allowance for credit losses (1.9 ) (14.4 ) (9.9 ) (7.3 ) (33.2 ) (0.1 ) Total loans 200.2 1,505.8 1,096.6 1,428.1 3,450.0 6.5 Other assets acquired through foreclosure, net — — — — — 4.2 Goodwill and other intangible assets, net — — 120.4 0.1 — — Other assets 1.0 19.2 5.4 6.8 23.8 745.2 Total assets $ 201.2 $ 1,525.0 $ 1,222.4 $ 1,435.0 $ 3,473.8 $ 5,075.7 Liabilities: Deposits $ 2,523.9 $ — $ 2,319.5 $ — $ — $ 384.0 Borrowings and qualifying debt — — — — — 359.1 Other liabilities 1.7 10.1 0.1 (0.1 ) 85.4 278.8 Total liabilities 2,525.6 10.1 2,319.6 (0.1 ) 85.4 1,021.9 Allocated equity: 68.5 121.4 256.5 119.1 286.0 375.3 Total liabilities and stockholders' equity $ 2,594.1 $ 131.5 $ 2,576.1 $ 119.0 $ 371.4 $ 1,397.2 Excess funds provided (used) 2,392.9 (1,393.5 ) 1,353.7 (1,316.0 ) (3,102.4 ) (3,678.5 ) Income Statement: Three Months Ended September 30, 2018 (in thousands) Net interest income $ 17,930 $ 3,683 $ 27,233 $ 13,557 $ 20,329 $ 3,275 Provision for (recovery of) credit losses 103 (553 ) 1,448 223 3,214 (49 ) Net interest income after provision for credit losses 17,827 4,236 25,785 13,334 17,115 3,324 Non-interest income 215 159 2,836 — 549 (7,387 ) Non-interest expense (8,254 ) (2,134 ) (9,933 ) (3,014 ) (7,280 ) (15,985 ) Income (loss) before income taxes 9,788 2,261 18,688 10,320 10,384 (20,048 ) Income tax expense (benefit) 2,251 521 4,298 2,374 2,388 (25,997 ) Net income $ 7,537 $ 1,740 $ 14,390 $ 7,946 $ 7,996 $ 5,949 Nine Months Ended September 30, 2018 (in thousands) Net interest income $ 49,335 $ 11,224 $ 74,615 $ 41,617 $ 58,813 $ 3,512 Provision for (recovery of) credit losses 285 (786 ) 5,355 2,006 6,573 (47 ) Net interest income after provision for credit losses 49,050 12,010 69,260 39,611 52,240 3,559 Non-interest income 543 159 9,518 12 1,182 (6,575 ) Non-interest expense (24,090 ) (6,386 ) (29,666 ) (7,419 ) (19,193 ) (32,535 ) Income (loss) before income taxes 25,503 5,783 49,112 32,204 34,229 (35,551 ) Income tax expense (benefit) 5,866 1,329 11,296 7,407 7,873 (44,644 ) Net income $ 19,637 $ 4,454 $ 37,816 $ 24,797 $ 26,356 $ 9,093 Regional Segments Consolidated Company Arizona Nevada Southern California Northern California At December 31, 2017 (in millions) Assets: Cash, cash equivalents, and investment securities $ 4,237.1 $ 2.1 $ 8.2 $ 2.1 $ 1.7 Loans, net of deferred loan fees and costs 15,093.9 3,323.7 1,844.8 1,934.7 1,275.5 Less: allowance for credit losses (140.0 ) (31.5 ) (18.1 ) (19.5 ) (13.2 ) Total loans 14,953.9 3,292.2 1,826.7 1,915.2 1,262.3 Other assets acquired through foreclosure, net 28.5 2.3 13.3 — 0.2 Goodwill and other intangible assets, net 300.7 — 23.2 — 156.5 Other assets 808.9 46.3 58.8 14.4 15.1 Total assets $ 20,329.1 $ 3,342.9 $ 1,930.2 $ 1,931.7 $ 1,435.8 Liabilities: Deposits $ 16,972.5 $ 4,841.3 $ 3,951.4 $ 2,461.1 $ 1,681.7 Borrowings and qualifying debt 766.9 — — — — Other liabilities 360.0 11.6 20.9 3.2 11.9 Total liabilities 18,099.4 4,852.9 3,972.3 2,464.3 1,693.6 Allocated equity: 2,229.7 396.5 263.7 221.8 303.1 Total liabilities and stockholders' equity $ 20,329.1 $ 5,249.4 $ 4,236.0 $ 2,686.1 $ 1,996.7 Excess funds provided (used) — 1,906.5 2,305.8 754.4 560.9 Income Statement: Three Months Ended September 30, 2017 (in thousands) Net interest income (expense) $ 201,583 $ 52,637 $ 36,310 $ 26,811 $ 21,932 Provision for (recovery of) credit losses 5,000 (289 ) (2,044 ) (58 ) 3,144 Net interest income (expense) after provision for credit losses 196,583 52,926 38,354 26,869 18,788 Non-interest income 10,456 1,265 2,354 971 1,796 Non-interest expense (89,296 ) (18,844 ) (14,748 ) (12,340 ) (11,317 ) Income (loss) before income taxes 117,743 35,347 25,960 15,500 9,267 Income tax expense (benefit) 34,899 13,857 9,086 6,517 3,897 Net income $ 82,844 $ 21,490 $ 16,874 $ 8,983 $ 5,370 Nine Months Ended September 30, 2017 (in thousands) Net interest income (expense) $ 573,635 $ 145,839 $ 108,028 $ 81,087 $ 63,686 Provision for (recovery of) credit losses 12,250 109 (5,378 ) (20 ) 4,238 Net interest income (expense) after provision for credit losses 561,385 145,730 113,406 81,107 59,448 Non-interest income 31,656 3,567 6,800 2,602 5,839 Non-interest expense (265,543 ) (55,388 ) (45,733 ) (38,063 ) (36,188 ) Income (loss) before income taxes 327,498 93,909 74,473 45,646 29,099 Income tax expense (benefit) 91,352 36,831 26,066 19,194 12,236 Net income $ 236,146 $ 57,078 $ 48,407 $ 26,452 $ 16,863 National Business Lines HOA Public & Nonprofit Finance Technology & Innovation Hotel Franchise Finance Other NBLs Corporate & Other At December 31, 2017 Assets: (in millions) Cash, cash equivalents, and investment securities $ — $ — $ — $ — $ — $ 4,223.0 Loans, net of deferred loan fees and costs 162.1 1,580.4 1,097.9 1,327.7 2,543.0 4.1 Less: allowance for credit losses (1.6 ) (15.6 ) (11.4 ) (4.0 ) (25.0 ) (0.1 ) Total loans 160.5 1,564.8 1,086.5 1,323.7 2,518.0 4.0 Other assets acquired through foreclosure, net — — — — — 12.7 Goodwill and other intangible assets, net — — 120.9 0.1 — — Other assets 0.9 17.9 6.0 5.9 15.5 628.1 Total assets $ 161.4 $ 1,582.7 $ 1,213.4 $ 1,329.7 $ 2,533.5 $ 4,867.8 Liabilities: Deposits $ 2,230.4 $ — $ 1,737.6 $ — $ — $ 69.0 Borrowings and qualifying debt — — — — — 766.9 Other liabilities 1.2 42.4 0.8 0.4 5.5 262.1 Total liabilities 2,231.6 42.4 1,738.4 0.4 5.5 1,098.0 Allocated equity: 59.4 126.5 244.1 108.3 206.0 300.3 Total liabilities and stockholders' equity $ 2,291.0 $ 168.9 $ 1,982.5 $ 108.7 $ 211.5 $ 1,398.3 Excess funds provided (used) 2,129.6 (1,413.8 ) 769.1 (1,221.0 ) (2,322.0 ) (3,469.5 ) Income Statement: Three Months Ended September 30, 2017 (in thousands) Net interest income (expense) $ 13,746 $ 7,269 $ 20,415 $ 15,346 $ 16,933 $ (9,816 ) Provision for (recovery of) credit losses 40 91 (83 ) 1,116 4,416 (1,333 ) Net interest income (expense) after provision for credit losses 13,706 7,178 20,498 14,230 12,517 (8,483 ) Non-interest income 136 183 1,855 — 379 1,517 Non-interest expense (7,011 ) (2,053 ) (8,824 ) (1,905 ) (5,286 ) (6,968 ) Income (loss) before income taxes 6,831 5,308 13,529 12,325 7,610 (13,934 ) Income tax expense (benefit) 2,562 1,028 5,075 4,622 2,853 (14,598 ) Net income $ 4,269 $ 4,280 $ 8,454 $ 7,703 $ 4,757 $ 664 Nine Months Ended September 30, 2017 (in thousands) Net interest income (expense) $ 40,275 $ 21,242 $ 59,610 $ 42,337 $ 46,380 $ (34,849 ) Provision for (recovery of) credit losses 332 796 816 2,924 10,265 (1,832 ) Net interest income (expense) after provision for credit losses 39,943 20,446 58,794 39,413 36,115 (33,017 ) Non-interest income 417 415 5,689 — 1,632 4,695 Non-interest expense (21,416 ) (6,522 ) (26,685 ) (7,949 ) (14,573 ) (13,026 ) Income (loss) before income taxes 18,944 14,339 37,798 31,464 23,174 (41,348 ) Income tax expense (benefit) 7,104 4,424 14,175 11,799 8,690 (49,167 ) Net income $ 11,840 $ 9,915 $ 23,623 $ 19,665 $ 14,484 $ 7,819

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)Subsidiary	Dec. 31, 2017USD ($)
Significant Of Accounting Policies [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017 | $	$ 3,107,076	$ 3,499,519
Number Of Wholly Owned Subsidiaries Non Bank Subsidiaries | Subsidiary	2
Number Of Unconsolidated Subsidiaries | Subsidiary	8
Preferred Stock [Member]
Significant Of Accounting Policies [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017 | $		$ 53,196

Investment Securities - Carryin

Investment Securities - Carrying Amounts and Fair Values of Investment Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	$ 172,294	$ 0
Debt Securities, Held-to-maturity	288,290	255,050
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	773	4,514
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(10,030)	(3,250)
Debt Securities, Held-to-maturity, Fair Value	279,033	256,314
Securities available for sale Total, Amortized Cost	3,211,440	3,515,401
Securities available-for-sale, Gross Unrealized Gains	23,483	35,733
Securities available-for-sale, Gross Unrealized (Losses)	(127,847)	(51,615)
Securities available for sale Total, Estimated Fair Value	3,107,076	3,499,519
Equity Securities, FV-NI, Cost	174,757
Equity Securities, FV-NI, Unrealized Gain	880
Equity Securities, FV-NI, Unrealized Loss	3,343
Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Amortized Cost	50	50
Securities available-for-sale, Gross Unrealized Gains	19,098	21,807
Securities available-for-sale, Gross Unrealized (Losses)	0	0
Securities available for sale Total, Estimated Fair Value	19,148	21,857
Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Amortized Cost	107,915	113,069
Securities available-for-sale, Gross Unrealized Gains	42	46
Securities available-for-sale, Gross Unrealized (Losses)	(7,014)	(4,038)
Securities available for sale Total, Estimated Fair Value	100,943	109,077
Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Amortized Cost	105,033	105,044
Securities available-for-sale, Gross Unrealized Gains	119	261
Securities available-for-sale, Gross Unrealized (Losses)	(5,768)	(1,822)
Securities available for sale Total, Estimated Fair Value	99,384	103,483
Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Amortized Cost	887,581	874,261
Securities available-for-sale, Gross Unrealized Gains	42	756
Securities available-for-sale, Gross Unrealized (Losses)	(31,681)	(6,493)
Securities available for sale Total, Estimated Fair Value	855,942	868,524
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Amortized Cost	1,515,408	1,719,188
Securities available-for-sale, Gross Unrealized Gains	167	810
Securities available-for-sale, Gross Unrealized (Losses)	(65,516)	(30,703)
Securities available for sale Total, Estimated Fair Value	1,450,059	1,689,295
Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Held-to-maturity	288,290	255,050
Securities available for sale Total, Amortized Cost	511,957	501,988
Securities available-for-sale, Gross Unrealized Gains	4,015	10,893
Securities available-for-sale, Gross Unrealized (Losses)	(11,065)	(1,971)
Securities available for sale Total, Estimated Fair Value	504,907	510,910
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Amortized Cost	32,000	32,000
Securities available-for-sale, Gross Unrealized Gains	0	0
Securities available-for-sale, Gross Unrealized (Losses)	(3,383)	(3,383)
Securities available for sale Total, Estimated Fair Value	28,617	28,617
US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Amortized Cost	49,000	64,000
Securities available-for-sale, Gross Unrealized Gains	0	0
Securities available-for-sale, Gross Unrealized (Losses)	(3,399)	(2,538)
Securities available for sale Total, Estimated Fair Value	45,601	61,462
US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Amortized Cost	2,496	2,496
Securities available-for-sale, Gross Unrealized Gains	0	0
Securities available-for-sale, Gross Unrealized (Losses)	(21)	(14)
Securities available for sale Total, Estimated Fair Value	2,475	2,482
CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	50,744
Securities available for sale Total, Amortized Cost		51,133
Securities available-for-sale, Gross Unrealized Gains		0
Securities available-for-sale, Gross Unrealized (Losses)		(517)
Securities available for sale Total, Estimated Fair Value		50,616
Equity Securities, FV-NI, Cost	52,058
Equity Securities, FV-NI, Unrealized Gain	0
Equity Securities, FV-NI, Unrealized Loss	1,314
Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	121,550
Securities available for sale Total, Amortized Cost		52,172
Securities available-for-sale, Gross Unrealized Gains		1,160
Securities available-for-sale, Gross Unrealized (Losses)		(136)
Securities available for sale Total, Estimated Fair Value		53,196
Equity Securities, FV-NI, Cost	122,699
Equity Securities, FV-NI, Unrealized Gain	880
Equity Securities, FV-NI, Unrealized Loss	2,029
AAA [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	0
Securities available for sale Total, Estimated Fair Value	879,489	874,135
AAA [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	818,046	809,242
AAA [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Held-to-maturity	0	0
Securities available for sale Total, Estimated Fair Value	61,443	64,893
AAA [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	0
Securities available for sale Total, Estimated Fair Value		0
AAA [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	0
Securities available for sale Total, Estimated Fair Value		0
Split-rated AAA/AA Plus [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	26,291
Securities available for sale Total, Estimated Fair Value	1,619,714	1,912,945
Split-rated AAA/AA Plus [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Split-rated AAA/AA Plus [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	100,943	109,077
Split-rated AAA/AA Plus [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Split-rated AAA/AA Plus [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Split-rated AAA/AA Plus [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	1,450,059	1,689,295
Split-rated AAA/AA Plus [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Held-to-maturity	0	0
Securities available for sale Total, Estimated Fair Value	20,636	25,280
Split-rated AAA/AA Plus [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Split-rated AAA/AA Plus [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	45,601	61,462
Split-rated AAA/AA Plus [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	2,475	2,482
Split-rated AAA/AA Plus [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	26,291
Securities available for sale Total, Estimated Fair Value		25,349
Split-rated AAA/AA Plus [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	0
Securities available for sale Total, Estimated Fair Value		0
AA Plus to AA- [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	0
Securities available for sale Total, Estimated Fair Value	279,653	304,361
AA Plus to AA- [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	34,957	55,161
AA Plus to AA- [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Held-to-maturity	0	0
Securities available for sale Total, Estimated Fair Value	244,696	249,200
AA Plus to AA- [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	0
Securities available for sale Total, Estimated Fair Value		0
AA Plus to AA- [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	0
Securities available for sale Total, Estimated Fair Value		0
A Plus to A- [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	0
Securities available for sale Total, Estimated Fair Value	242,489	254,025
A Plus to A- [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	71,685	74,293
A Plus to A- [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	395	1,350
A Plus to A- [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Held-to-maturity	0	0
Securities available for sale Total, Estimated Fair Value	170,409	167,994
A Plus to A- [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	0
Securities available for sale Total, Estimated Fair Value		0
A Plus to A- [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	0
Securities available for sale Total, Estimated Fair Value		10,388
BBB Plus to BBB- [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	72,991
Securities available for sale Total, Estimated Fair Value	57,335	82,560
BBB Plus to BBB- [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	27,699	29,190
BBB Plus to BBB- [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	1,019	931
BBB Plus to BBB- [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Held-to-maturity	0	0
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	28,617	28,617
BBB Plus to BBB- [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	0
Securities available for sale Total, Estimated Fair Value		0
BBB Plus to BBB- [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	72,991
Securities available for sale Total, Estimated Fair Value		23,822
BB Plus and below [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	39,032
Securities available for sale Total, Estimated Fair Value	20,673	27,801
BB Plus and below [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	19,148	21,857
BB Plus and below [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	1,525	1,840
BB Plus and below [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Held-to-maturity	0	0
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	0
Securities available for sale Total, Estimated Fair Value		0
BB Plus and below [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	39,032
Securities available for sale Total, Estimated Fair Value		4,104
Corporate Credit Quality Indicator Unrated [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	33,980
Securities available for sale Total, Estimated Fair Value	7,723	43,692
Corporate Credit Quality Indicator Unrated [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Held-to-maturity	288,290	255,050
Securities available for sale Total, Estimated Fair Value	7,723	3,543
Corporate Credit Quality Indicator Unrated [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	24,453
Securities available for sale Total, Estimated Fair Value		25,267
Corporate Credit Quality Indicator Unrated [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - equity	$ 9,527
Securities available for sale Total, Estimated Fair Value		$ 14,882

Investment Securities - Additio

Investment Securities - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018USD ($)positions	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)positions
Investment Identifier [Line Items]
Number Of Securities In Unrealized Position | positions	409		302
Amount of impairment losses reclassified out of accumulated other comprehensive income into earnings	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	127,847,000		$ 51,615,000
Securities with carrying amounts were pledged	$ 814,100,000		$ 913,700,000

Investment Securities - Unreali

Investment Securities - Unrealized Losses and Fair Value of Investment Securities in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Net (losses) gains on equity securities	$ (1,212)		$ (2,971)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	10,030		10,030		$ 3,250
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	215,827		215,827		107,921
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0		0		0
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	0		0		0
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	10,030		10,030		3,250
Held-to-maturity Securities, Fair Value	215,827		215,827		107,921
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	36,898		36,898		18,730
Available-for-sale securities, Less Than Twelve Months, Fair Value	1,279,260		1,279,260		1,593,514
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	90,949		90,949		32,885
Available-for-sale securities, Twelve Months or Longer, Fair Value	1,564,474		1,564,474		1,030,580
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	127,847		127,847		51,615
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	2,843,734		2,843,734		2,624,094
Less: Net gains (losses) recognized on equity securities sold	0		0
Equity Securities, FV-NI, Unrealized Gain (Loss)	(1,212)	$ 0	(2,971)	$ (1)
US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	151		151		14
Available-for-sale securities, Less Than Twelve Months, Fair Value	4,849		4,849		4,986
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	3,248		3,248		2,524
Available-for-sale securities, Twelve Months or Longer, Fair Value	40,752		40,752		56,476
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	3,399		3,399		2,538
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	45,601		45,601		61,462
Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	766		766		1,398
Available-for-sale securities, Less Than Twelve Months, Fair Value	19,234		19,234		78,602
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	5,002		5,002		424
Available-for-sale securities, Twelve Months or Longer, Fair Value	74,998		74,998		19,576
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	5,768		5,768		1,822
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	94,232		94,232		98,178
Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses					136
Available-for-sale securities, Less Than Twelve Months, Fair Value					7,357
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses					0
Available-for-sale securities, Twelve Months or Longer, Fair Value					0
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total					136
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total					7,357
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	16,624		16,624		13,875
Available-for-sale securities, Less Than Twelve Months, Fair Value	563,642		563,642		999,478
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	48,892		48,892		16,828
Available-for-sale securities, Twelve Months or Longer, Fair Value	878,925		878,925		523,270
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	65,516		65,516		30,703
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	1,442,567		1,442,567		1,522,748
Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	6,337		6,337		17
Available-for-sale securities, Less Than Twelve Months, Fair Value	227,531		227,531		6,159
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	4,728		4,728		1,954
Available-for-sale securities, Twelve Months or Longer, Fair Value	66,047		66,047		69,674
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	11,065		11,065		1,971
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	293,578		293,578		75,833
Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	13,004		13,004		3,115
Available-for-sale securities, Less Than Twelve Months, Fair Value	463,026		463,026		480,885
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	18,677		18,677		3,378
Available-for-sale securities, Twelve Months or Longer, Fair Value	374,504		374,504		188,710
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	31,681		31,681		6,493
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	837,530		837,530		669,595
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	0		0		0
Available-for-sale securities, Less Than Twelve Months, Fair Value	0		0		0
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	3,383		3,383		3,383
Available-for-sale securities, Twelve Months or Longer, Fair Value	28,617		28,617		28,617
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	3,383		3,383		3,383
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	28,617		28,617		28,617
CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses					0
Available-for-sale securities, Less Than Twelve Months, Fair Value					0
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses					517
Available-for-sale securities, Twelve Months or Longer, Fair Value					50,616
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total					517
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total					50,616
Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	0		0		161
Available-for-sale securities, Less Than Twelve Months, Fair Value	0		0		13,565
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	7,014		7,014		3,877
Available-for-sale securities, Twelve Months or Longer, Fair Value	99,134		99,134		93,641
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	7,014		7,014		4,038
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	99,134		99,134		107,206
US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	16		16		14
Available-for-sale securities, Less Than Twelve Months, Fair Value	978		978		2,482
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	5		5		0
Available-for-sale securities, Twelve Months or Longer, Fair Value	1,497		1,497		0
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	21		21		14
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 2,475		$ 2,475		$ 2,482

Investment Securities - Amortiz

Investment Securities - Amortized Cost and Fair Value of Investment Securities by Contractual Maturities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost	$ 1,200
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	1,236
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost	10,100
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	10,122
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost	14,602
Held-to-maturity Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value	14,351
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Amortized Cost	262,388
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	253,324
Debt Securities, Held-to-maturity	288,290	$ 255,050
Debt Securities, Held-to-maturity, Fair Value	279,033	256,314
Securities available for sale, Due in one year or less, Amortized Cost	4,001
Securities available for sale, After one year through five years, Amortized Cost	17,355
Securities available for sale, After five years through ten years, Amortized Cost	223,060
Securities available for sale, After ten years, Amortized Cost	456,120
Securities available for sale, Mortgage backed securities, Amortized Cost	2,510,904
Securities available for sale Total, Amortized Cost	3,211,440	3,515,401
Securities available for sale, Due in one year or less, Estimated Fair Value	3,996
Securities available for sale, After one year through five years, Estimated Fair Value	17,571
Securities available for sale, After five years through ten years, Estimated Fair Value	215,580
Securities available for sale, After ten years, Estimated Fair Value	462,985
Securities available for sale, Mortgage backed securities, Estimated Fair Value	2,406,944
Securities available for sale Total, Estimated Fair Value	$ 3,107,076	$ 3,499,519

Investment Securities - Investm

Investment Securities - Investment Securities by Credit Rating Type (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	$ 288,290	$ 255,050
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	3,107,076	3,499,519
Investment securities - equity	172,294	0
Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	288,290	255,050
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	504,907	510,910
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	1,450,059	1,689,295
Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	100,943	109,077
Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	855,942	868,524
US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	45,601	61,462
US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	2,475	2,482
Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		53,196
Investment securities - equity	121,550
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	28,617	28,617
Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	19,148	21,857
Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	99,384	103,483
CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		50,616
Investment securities - equity	50,744
AAA [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	879,489	874,135
Investment securities - equity	0
AAA [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	0	0
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	61,443	64,893
AAA [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	818,046	809,242
AAA [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		0
Investment securities - equity	0
AAA [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		0
Investment securities - equity	0
Split-rated AAA/AA Plus [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	1,619,714	1,912,945
Investment securities - equity	26,291
Split-rated AAA/AA Plus [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	0	0
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	20,636	25,280
Split-rated AAA/AA Plus [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	1,450,059	1,689,295
Split-rated AAA/AA Plus [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	100,943	109,077
Split-rated AAA/AA Plus [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Split-rated AAA/AA Plus [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	45,601	61,462
Split-rated AAA/AA Plus [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	2,475	2,482
Split-rated AAA/AA Plus [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		0
Investment securities - equity	0
Split-rated AAA/AA Plus [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Split-rated AAA/AA Plus [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Split-rated AAA/AA Plus [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Split-rated AAA/AA Plus [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		25,349
Investment securities - equity	26,291
AA Plus to AA- [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	279,653	304,361
Investment securities - equity	0
AA Plus to AA- [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	0	0
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	244,696	249,200
AA Plus to AA- [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	34,957	55,161
AA Plus to AA- [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		0
Investment securities - equity	0
AA Plus to AA- [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		0
Investment securities - equity	0
A Plus to A- [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	242,489	254,025
Investment securities - equity	0
A Plus to A- [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	0	0
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	170,409	167,994
A Plus to A- [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	395	1,350
A Plus to A- [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		10,388
Investment securities - equity	0
A Plus to A- [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	71,685	74,293
A Plus to A- [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		0
Investment securities - equity	0
BBB Plus to BBB- [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	57,335	82,560
Investment securities - equity	72,991
BBB Plus to BBB- [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	0	0
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	1,019	931
BBB Plus to BBB- [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		23,822
Investment securities - equity	72,991
BBB Plus to BBB- [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	28,617	28,617
BBB Plus to BBB- [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	27,699	29,190
BBB Plus to BBB- [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		0
Investment securities - equity	0
BB Plus and below [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	20,673	27,801
Investment securities - equity	39,032
BB Plus and below [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	0	0
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	1,525	1,840
BB Plus and below [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		4,104
Investment securities - equity	39,032
BB Plus and below [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	19,148	21,857
BB Plus and below [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		0
Investment securities - equity	0
Corporate Credit Quality Indicator Unrated [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	7,723	43,692
Investment securities - equity	33,980
Corporate Credit Quality Indicator Unrated [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	288,290	255,050
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	7,723	3,543
Corporate Credit Quality Indicator Unrated [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] | US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] | Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		14,882
Investment securities - equity	9,527
Corporate Credit Quality Indicator Unrated [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] | Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] | CRA investments [Member]
Debt Securities, Available-for-sale [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017		$ 25,267
Investment securities - equity	$ 24,453

Investment Securities - Gross G

Investment Securities - Gross Gains and (Losses) on Sales of Investments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Gross gains	$ 0	$ 468	$ 0	$ 1,181
Gross (losses)	(7,232)	(149)	(7,232)	(274)
Net (losses) gains	$ (7,232)	$ 319	$ (7,232)	$ 907

Loans, Leases and Allowance f_3

Loans, Leases and Allowance for Credit Losses - Schedule of Held for Investment Loan Portfolio Composition of Loans, Leases and Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit Mark on Acquired Loans	$ 17,200	$ 27,000
Net deferred loan fees and costs	(31,000)	(25,300)
Receivable with Imputed Interest, Discount	3,300	8,500
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield		9,324	$ 15,177
Loans, net of deferred loan fees and costs	16,732,765	15,093,935
Allowance for credit losses	(150,011)	(140,050)
Loans, net	16,582,754	14,953,885
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	7,487,725	6,841,381
Commercial Real Estate Non Owner Occupied Multi Family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	3,952,966	3,904,011
Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	2,288,156	2,241,613
Allowance for credit losses	(13,946)	(13,884)
Construction and land development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	2,107,631	1,632,204
Allowance for credit losses	(22,656)	(19,599)
Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	827,073	425,940
Allowance for credit losses	(8,075)	(5,500)
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	69,214	48,786
Allowance for credit losses	$ (1,047)	$ (776)

Loans, Leases and Allowance f_4

Loans, Leases and Allowance for Credit Losses - Contractual Aging of Loan Portfolio by Class of Loans Including Loans Held for Sale and Excluding Deferred Fees/Costs (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 16,705,306	$ 15,061,371
Past Due	27,459	32,564
Total	16,732,765	15,093,935
Financing Receivable, Recorded Investment, Nonaccrual Status	36,868	43,925
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	43
Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,287,826	2,240,457
Past Due	330	1,156
Total	2,288,156	2,241,613
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	3,787,571	3,696,729
Past Due	531	5,840
Total	3,788,102	3,702,569
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	164,864	201,442
Past Due	0	0
Total	164,864	201,442
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	7,477,017	6,835,385
Past Due	10,708	5,996
Total	7,487,725	6,841,381
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	43
Construction and land development [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,412,161	1,090,176
Past Due	0	0
Total	1,412,161	1,090,176
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Construction and land development [Member] | Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	695,470	536,917
Past Due	0	5,111
Total	695,470	542,028
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	811,516	411,857
Past Due	15,557	14,083
Total	827,073	425,940
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	68,881	48,408
Past Due	333	378
Total	69,214	48,786
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	19,098	21,909
Past Due	17,770	22,016
Financing Receivable, Recorded Investment, Nonaccrual Status	36,868	43,925
Non-accrual loans [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	1,089
Past Due	0	792
Financing Receivable, Recorded Investment, Nonaccrual Status	0	1,881
Non-accrual loans [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Past Due	0	5,840
Financing Receivable, Recorded Investment, Nonaccrual Status	0	5,840
Non-accrual loans [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Past Due	0	0
Financing Receivable, Recorded Investment, Nonaccrual Status	0	0
Non-accrual loans [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	14,894	17,913
Past Due	9,083	4,113
Financing Receivable, Recorded Investment, Nonaccrual Status	23,977	22,026
Non-accrual loans [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Past Due	0	0
Financing Receivable, Recorded Investment, Nonaccrual Status	0	0
Non-accrual loans [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	868
Past Due	0	5,111
Financing Receivable, Recorded Investment, Nonaccrual Status	0	5,979
Non-accrual loans [Member] | Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	4,204	2,039
Past Due	8,354	6,078
Financing Receivable, Recorded Investment, Nonaccrual Status	12,558	8,117
Non-accrual loans [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Past Due	333	82
Financing Receivable, Recorded Investment, Nonaccrual Status	333	82
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	14,735	13,221
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	1,026
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	2,993
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	8,870	2,245
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	5,865	6,874
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	83
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2,453	2,369
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	330	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	531	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	254	669
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,338	1,487
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	213
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	10,271	16,974
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	130
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	2,847
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,584	3,082
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	5,111
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	8,354	5,722
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	$ 333	$ 82

Loans, Leases and Allowance f_5

Loans, Leases and Allowance for Credit Losses - Summary of Recorded Investment in Nonaccrual Loans and Loans Past Due 90 Days Still Accruing Interest by Loan Class (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 27,459	$ 32,564
Total Non-accrual	36,868	43,925
Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	10,708	5,996
Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	330	1,156
Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	531	5,840
Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Construction and land development [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Construction and land development [Member] | Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	5,111
Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	15,557	14,083
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	333	378
Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	17,770	22,016
Total Non-accrual	36,868	43,925
Non-accrual loans [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	9,083	4,113
Total Non-accrual	23,977	22,026
Non-accrual loans [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	792
Total Non-accrual	0	1,881
Non-accrual loans [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	5,840
Total Non-accrual	0	5,840
Non-accrual loans [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Total Non-accrual	0	0
Non-accrual loans [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Total Non-accrual	0	0
Non-accrual loans [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	5,111
Total Non-accrual	0	5,979
Non-accrual loans [Member] | Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	8,354	6,078
Total Non-accrual	12,558	8,117
Non-accrual loans [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	333	82
Total Non-accrual	$ 333	$ 82

Loans, Leases and Allowance f_6

Loans, Leases and Allowance for Credit Losses - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)SecurityLoan	Sep. 30, 2017USD ($)TDRsSecurityLoan	Sep. 30, 2018USD ($)SecurityLoan	Sep. 30, 2017USD ($)TDRsSecurityLoan	Dec. 31, 2017USD ($)
Leases [Line Items]
Loans and Leases Receivable, Deferred Income	$ 31,000,000		$ 31,000,000		$ 25,300,000
Receivable with Imputed Interest, Discount	(3,300,000)		(3,300,000)		(8,500,000)
Interest Rate and Credit Marks on Acquired Loans	8,700,000		8,700,000		14,100,000
Credit Mark on Acquired Loans	17,200,000		17,200,000		27,000,000
Reduction in interest income due to nonaccrual loans	600,000	$ 700,000	1,800,000
Aggregate carrying amount of impaired loans	3,601,000		3,601,000		19,315,000
Impaired loans with no allowance recorded	121,968,000		121,968,000		79,239,000
Impaired loans with an allowance recorded	1,171,000		1,171,000		5,606,000
Impaired Financing Receivable, Average Recorded Investment	104,652,000	$ 108,033,000	100,712,000	$ 106,456,000
Financing Receivable, Recorded Investment, Nonaccrual Status	36,868,000		36,868,000		43,925,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0		0		43,000
Financing Receivable, Net	$ 16,732,765,000		$ 16,732,765,000		15,093,935,000
Financing Receivable, Modifications, Number of Contracts | SecurityLoan	4	2	11	3
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 2,800,000	$ 1,900,000	$ 34,400,000	$ 6,800,000
Financing Receivable, Modifications, Subsequent Default, Recorded Investment		$ 100,000		$ 500,000
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	1		3
Loans And Loans Receivable Purchases	$ 482,800,000	$ 216,800,000	1,010,000,000	$ 666,800,000
Financing Receivable, Significant Sales	12,400,000	41,300,000	46,500,000	50,500,000
Loans and Leases Receivable, Gain (Loss) on Sales, Net	1,000,000		2,400,000	100,000
Troubled Debt Restructured Loans [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans	2,600,000		2,600,000		3,700,000
Impaired loans with no allowance recorded	49,500,000		49,500,000		48,800,000
Impaired loans with an allowance recorded	700,000		700,000		1,200,000
Impaired Financing Receivable, Average Recorded Investment	52,200,000	52,000,000	51,900,000	56,600,000
Financing Receivable, Recorded Investment, Nonaccrual Status	9,600,000		9,600,000		10,100,000
Loan commitments outstanding	300,000		300,000		0
Non-owner occupied [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans	0		0		0
Impaired loans with no allowance recorded	12,544,000		12,544,000		21,250,000
Impaired loans with an allowance recorded	0		0		0
Construction and land development [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans	0		0		0
Impaired loans with no allowance recorded	9,128,000		9,128,000		15,426,000
Impaired loans with an allowance recorded	0		0		0
Residential real estate [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans	363,000		363,000		0
Impaired loans with no allowance recorded	20,323,000		20,323,000		17,170,000
Impaired loans with an allowance recorded	60,000		60,000		0
Loans And Loans Receivable Purchases			471,700,000	146,400,000
Construction Loans [Member]
Leases [Line Items]
Loans And Loans Receivable Purchases			27,100,000
Commercial and industrial [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans	3,238,000		3,238,000		19,315,000
Impaired loans with no allowance recorded	72,947,000		72,947,000		14,842,000
Impaired loans with an allowance recorded	1,111,000		1,111,000		5,606,000
Loans And Loans Receivable Purchases			511,500,000	520,400,000
Consumer [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans	0		0		0
Impaired loans with no allowance recorded	366,000		366,000		121,000
Impaired loans with an allowance recorded	0		0		0
Non-owner occupied [Member] | Commercial real estate [Member]
Leases [Line Items]
Impaired Financing Receivable, Average Recorded Investment	12,597,000	$ 20,789,000	16,349,000	$ 22,446,000
Financing Receivable, Net	3,788,102,000		3,788,102,000		3,702,569,000
Financial Asset Acquired with Credit Deterioration [Member]
Leases [Line Items]
Impaired loans with an allowance recorded	151,000		151,000		1,631,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing					100,000
Financial Asset Acquired with Credit Deterioration [Member] | Non-owner occupied [Member]
Leases [Line Items]
Impaired loans with an allowance recorded	142,000		142,000		1,629,000
Financial Asset Acquired with Credit Deterioration [Member] | Construction and land development [Member]
Leases [Line Items]
Impaired loans with an allowance recorded	0		0		0
Financial Asset Acquired with Credit Deterioration [Member] | Residential real estate [Member]
Leases [Line Items]
Impaired loans with an allowance recorded	0		0		0
Financial Asset Acquired with Credit Deterioration [Member] | Commercial and industrial [Member]
Leases [Line Items]
Impaired loans with an allowance recorded	9,000		9,000		2,000
Financial Asset Acquired with Credit Deterioration [Member] | Consumer [Member]
Leases [Line Items]
Impaired loans with an allowance recorded	$ 0		$ 0		$ 0

Loans, Leases and Allowance f_7

Loans, Leases and Allowance for Credit Losses - Loans by Risk Rating (Detail) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	$ 16,732,765,000	$ 15,093,935,000
Current	16,705,306,000	15,061,371,000
Past Due	27,459,000	32,564,000
Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	7,487,725,000	6,841,381,000
Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	827,073,000	425,940,000
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	69,214,000	48,786,000
Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	2,288,156,000	2,241,613,000
Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	3,788,102,000	3,702,569,000
Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	164,864,000	201,442,000
Construction and land development [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	1,412,161,000	1,090,176,000
Construction and land development [Member] | Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	695,470,000	542,028,000
Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	16,394,482,000	14,767,297,000
Current	16,386,286,000	14,758,149,000
Pass [Member] | Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	7,273,634,000	6,675,574,000
Pass [Member] | Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	808,065,000	408,527,000
Pass [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	68,599,000	47,824,000
Pass [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	2,214,765,000	2,149,465,000
Pass [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	3,765,340,000	3,676,711,000
Pass [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	164,864,000	201,442,000
Pass [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	1,404,619,000	1,072,342,000
Pass [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	694,596,000	535,412,000
Watch [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	124,689,000	155,032,000
Current	124,056,000	154,295,000
Watch [Member] | Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	83,886,000	85,781,000
Watch [Member] | Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	5,884,000	8,971,000
Watch [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	41,000	878,000
Watch [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	18,713,000	43,122,000
Watch [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	14,666,000	11,166,000
Watch [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Watch [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	1,233,000	4,477,000
Watch [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	266,000	637,000
Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	212,572,000	167,279,000
Current	194,118,000	145,934,000
Substandard [Member] | Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	129,183,000	76,328,000
Substandard [Member] | Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	13,124,000	8,442,000
Substandard [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	574,000	84,000
Substandard [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	54,678,000	48,397,000
Substandard [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	8,096,000	14,692,000
Substandard [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Substandard [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	6,309,000	13,357,000
Substandard [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	608,000	5,979,000
Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	1,022,000	4,327,000
Current	846,000	2,993,000
Doubtful [Member] | Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	1,022,000	3,698,000
Doubtful [Member] | Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Doubtful [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Doubtful [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	629,000
Doubtful [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Doubtful [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Doubtful [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Doubtful [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Current	0	0
Loss [Member] | Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] | Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	14,735,000	13,221,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	5,991,000	7,966,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Watch [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	393,000	518,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	8,351,000	4,737,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Loss [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	2,453,000	2,369,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	1,870,000	1,182,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Watch [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	240,000	219,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	343,000	968,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Loss [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	10,271,000	16,974,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	335,000	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Watch [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	9,760,000	15,640,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	176,000	1,334,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Loss [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	$ 0	$ 0

Loans, Leases and Allowance f_8

Loans, Leases and Allowance for Credit Losses - Impaired Loans by Loan Class (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	$ 125,569	$ 98,554
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	76,185	34,156
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	20,686	17,170
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	366	121
Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	6,660	10,430
Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	12,544	21,251
Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	0	0
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	76,185	34,157
Construction and land development [Member] | Construction [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	0	0
Construction and land development [Member] | Land [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	$ 9,128	$ 15,426

Loans, Leases and Allowance f_9

Loans, Leases and Allowance for Credit Losses - Recorded Investment in Loans Classified as Impaired (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Receivables [Abstract]
Impaired loans with an allowance recorded	$ 3,601	$ 19,315
Impaired loans with no allowance recorded	121,968	79,239
Total impaired loans	125,569	98,554
Valuation allowance related to impaired loans	$ (1,171)	$ (5,606)

Loans, Leases and Allowance _10

Loans, Leases and Allowance for Credit Losses - Schedule of Average Investment in Impaired Loans and Income Recognized on Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Receivables [Abstract]
Impaired Financing Receivable, Average Recorded Investment	$ 104,652	$ 108,033	$ 100,712	$ 106,456
Interest income recognized on impaired loans	1,114	1,040	3,109	3,075
Interest recognized on nonaccrual loans, cash basis	$ 569	$ 694	$ 1,443	$ 1,372

Loans, Leases and Allowance _11

Loans, Leases and Allowance for Credit Losses - Average Investment in Impaired Loans by Loan Class (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	$ 104,652	$ 108,033	$ 100,712	$ 106,456
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	55,026	40,074	47,083	33,358
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	20,746	16,692	19,217	17,011
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	367	196	309	208
Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	6,698	17,779	8,053	20,136
Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	12,597	20,789	16,349	22,446
Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	0	0	0	0
Construction and land development [Member] | Construction [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	0	0	0	0
Construction and land development [Member] | Land [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	9,218	12,503	9,701	13,297
Troubled Debt Restructured Loans [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	$ 52,200	$ 52,000	$ 51,900	$ 56,600

Loans, Leases and Allowance _12

Loans, Leases and Allowance for Credit Losses - Interest Income on Impaired Loans by Loan Class (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	$ 1,114	$ 1,040	$ 3,109	$ 3,075
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	537	307	1,276	788
Owner occupied [Member] | Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	118	166	376	530
Non-owner occupied [Member] | Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	218	279	744	798
Multi-family [Member] | Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	0	0	0	0
Construction [Member] | Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	0	0	0	0
Land [Member] | Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	146	163	425	551
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	95	124	287	406
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	$ 0	$ 1	$ 1	$ 2

Loans, Leases and Allowance _13

Loans, Leases and Allowance for Credit Losses - Tabular Disclosure of Nonperforming Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 36,868		$ 43,925
Loans past due 90 days or more on accrual status	0		43
Troubled debt restructured loans	42,567		42,431
Total nonperforming loans	79,435		86,399
Other assets acquired through foreclosure, net	20,028	$ 27,541	28,540	$ 28,992	$ 30,988	$ 47,815
Total nonperforming assets	99,463		114,939
Troubled Debt Restructured Loans [Member]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 9,600		10,100
Financial Asset Acquired with Credit Deterioration [Member]
Loans past due 90 days or more on accrual status			$ 100

Loans, Leases and Allowance _14

Loans, Leases and Allowance for Credit Losses - Changes in Accretable Discount for Loans Purchased with Credit Quality Deterioration (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period			$ 9,324	$ 15,177
Reclassifications from non-accretable to accretable yield (1)	$ 0
Accretion to interest income	(224)	$ (690)
Financial Asset Acquired with Credit Deterioration [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,828	14,247
Reclassifications from non-accretable to accretable yield (1)		0	683	2,086
Accretion to interest income			(801)	(2,374)
Reversal of fair value adjustments upon disposition of loans	(563)	(2,199)	(5,165)	(3,531)
Balance at end of period	$ 4,041	$ 11,358	$ 4,041	$ 11,358

Loans, Leases and Allowance _15

Loans, Leases and Allowance for Credit Losses - Allowances for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Valuation Allowance [Line Items]
Beginning Balance	$ 147,083	$ 131,811	$ 140,050	$ 124,704
Charge-offs	4,765	3,157	12,290	8,710
Recoveries	(1,693)	(2,767)	(5,251)	(8,177)
Provision for credit losses	6,000	5,000	17,000	12,250
Ending balance	150,011	136,421	150,011	136,421
Construction and land development [Member]
Valuation Allowance [Line Items]
Beginning Balance	22,159	20,852	19,511	21,175
Charge-offs	0	0	1	0
Recoveries	(24)	(226)	(1,420)	(1,011)
Provision for credit losses	473	(619)	1,726	(1,727)
Ending balance	22,656	20,459	22,656	20,459
Commercial real estate [Member]
Valuation Allowance [Line Items]
Beginning Balance	31,979	28,593	31,495	25,673
Charge-offs	0	175	233	1,994
Recoveries	(856)	(1,781)	(1,228)	(2,719)
Provision for credit losses	(1,250)	(1,474)	(905)	2,327
Ending balance	31,585	28,725	31,585	28,725
Residential real estate [Member]
Valuation Allowance [Line Items]
Beginning Balance	6,849	4,838	5,478	3,851
Charge-offs	46	0	1,038	447
Recoveries	(440)	(108)	(831)	(1,659)
Provision for credit losses	832	(141)	2,804	(258)
Ending balance	8,075	4,805	8,075	4,805
Commercial and industrial [Member]
Valuation Allowance [Line Items]
Beginning Balance	85,244	76,734	82,793	73,333
Charge-offs	4,610	2,921	10,904	6,166
Recoveries	(362)	(619)	(1,737)	(2,705)
Provision for credit losses	5,652	7,192	13,022	11,752
Ending balance	86,648	81,624	86,648	81,624
Consumer [Member]
Valuation Allowance [Line Items]
Beginning Balance	852	794	773	672
Charge-offs	109	61	114	103
Recoveries	(11)	(33)	(35)	(83)
Provision for credit losses	293	42	353	156
Ending balance	$ 1,047	$ 808	$ 1,047	$ 808

Loans, Leases and Allowance _16

Loans, Leases and Allowance for Credit Losses - Summary of Impairment Method Information Related to Loans and Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	$ 3,601	$ 19,315
Impaired loans with no allowance recorded	121,968	79,239
Total loans individually evaluated for impairment	125,569	98,554
Loans collectively evaluated for impairment	16,521,452	14,879,626
Impaired Financing Receivable, Recorded Investment	125,569	98,554
Total recorded investment	16,732,765	15,093,935
Impaired loans with an allowance recorded	5,883	20,795
Impaired loans with no allowance recorded	205,719	156,789
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	211,602	177,584
Loans collectively evaluated for impairment	16,521,452	14,879,626
Financing Receivable Unpaid Principal Balance	16,841,308	15,202,135
Impaired loans with an allowance recorded	1,171	5,606
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	1,171	5,606
Loans collectively evaluated for impairment	148,689	132,813
Total loans held for investment	150,011	140,050
Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	6,660	10,430
Total loans individually evaluated for impairment	6,660	10,430
Loans collectively evaluated for impairment	2,276,847	2,221,614
Total recorded investment	2,288,156	2,241,613
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	13,164	17,459
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	13,164	17,459
Loans collectively evaluated for impairment	2,276,847	2,221,614
Financing Receivable Unpaid Principal Balance	2,296,362	2,251,692
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	13,946	13,884
Total loans held for investment	13,946	13,884
Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	12,544	21,250
Total loans individually evaluated for impairment	12,544	21,250
Loans collectively evaluated for impairment	3,859,914	3,777,219
Total recorded investment	3,952,966	3,904,011
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	18,292	28,028
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	18,292	28,028
Loans collectively evaluated for impairment	3,859,914	3,777,219
Financing Receivable Unpaid Principal Balance	3,975,046	3,933,687
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	17,497	16,135
Total loans held for investment	17,639	17,764
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	3,238	19,315
Impaired loans with no allowance recorded	72,947	14,842
Total loans individually evaluated for impairment	76,185	34,157
Loans collectively evaluated for impairment	7,411,540	6,807,181
Total recorded investment	7,487,725	6,841,381
Impaired loans with an allowance recorded	5,520	20,795
Impaired loans with no allowance recorded	108,469	42,261
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	113,989	63,056
Loans collectively evaluated for impairment	7,411,540	6,807,181
Financing Receivable Unpaid Principal Balance	7,529,886	6,873,383
Impaired loans with an allowance recorded	1,111	5,606
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	1,111	5,606
Loans collectively evaluated for impairment	85,528	76,919
Total loans held for investment	86,648	82,527
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	363	0
Impaired loans with no allowance recorded	20,323	17,170
Total loans individually evaluated for impairment	20,686	17,170
Loans collectively evaluated for impairment	805,800	408,169
Total recorded investment	827,073	425,940
Impaired loans with an allowance recorded	363	0
Impaired loans with no allowance recorded	29,312	26,057
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	29,675	26,057
Loans collectively evaluated for impairment	805,800	408,169
Financing Receivable Unpaid Principal Balance	836,181	434,946
Impaired loans with an allowance recorded	60	0
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	60	0
Loans collectively evaluated for impairment	8,015	5,500
Total loans held for investment	8,075	5,500
Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	9,128	15,426
Total loans individually evaluated for impairment	9,128	15,426
Loans collectively evaluated for impairment	2,098,503	1,616,778
Total recorded investment	2,107,631	1,632,204
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	25,756	32,289
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	25,756	32,289
Loans collectively evaluated for impairment	2,098,503	1,616,778
Financing Receivable Unpaid Principal Balance	2,124,259	1,649,067
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	22,656	19,599
Total loans held for investment	22,656	19,599
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	366	121
Total loans individually evaluated for impairment	366	121
Loans collectively evaluated for impairment	68,848	48,665
Total recorded investment	69,214	48,786
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	10,726	10,695
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	10,726	10,695
Loans collectively evaluated for impairment	68,848	48,665
Financing Receivable Unpaid Principal Balance	79,574	59,360
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	1,047	776
Total loans held for investment	1,047	776
Financial Asset Acquired with Credit Deterioration [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	85,744	115,755
Loans acquired with deteriorated credit quality	108,254	144,925
Impaired loans with an allowance recorded	151	1,631
Financial Asset Acquired with Credit Deterioration [Member] | Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	4,649	9,569
Loans acquired with deteriorated credit quality	6,351	12,619
Impaired loans with an allowance recorded	0	0
Financial Asset Acquired with Credit Deterioration [Member] | Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	80,508	105,542
Loans acquired with deteriorated credit quality	96,840	128,440
Impaired loans with an allowance recorded	142	1,629
Financial Asset Acquired with Credit Deterioration [Member] | Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	43
Loans acquired with deteriorated credit quality	4,357	3,146
Impaired loans with an allowance recorded	9	2
Financial Asset Acquired with Credit Deterioration [Member] | Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	587	601
Loans acquired with deteriorated credit quality	706	720
Impaired loans with an allowance recorded	0	0
Financial Asset Acquired with Credit Deterioration [Member] | Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
Loans acquired with deteriorated credit quality	0	0
Impaired loans with an allowance recorded	0	0
Financial Asset Acquired with Credit Deterioration [Member] | Consumer [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
Loans acquired with deteriorated credit quality	0	0
Impaired loans with an allowance recorded	$ 0	$ 0

Other Assets Acquired through_3

Other Assets Acquired through Foreclosure - Changes in Other Assets Acquired through Foreclosure (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)Property	Sep. 30, 2017USD ($)Property	Sep. 30, 2018USD ($)Property	Sep. 30, 2017USD ($)Property	Dec. 31, 2017Property
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Balance, beginning of the period, Gross Balance	$ 31,145	$ 35,037	$ 32,552	$ 54,138
Transfers to other assets acquired through foreclosure, net, Gross Balance		430	5,744	1,812
Proceeds from sale of other real estate owned and repossessed assets, net, Gross Balance	(1,093)	(2,491)	(9,634)	(23,129)
Gains (losses), net, Gross Balance	74	78	1,464	233
Balance, end of period, Gross Balance	23,231	33,054	23,231	33,054
Balance, beginning of the period, Valuation Allowance	(3,604)	(4,049)	(4,012)	(6,323)
Proceeds from sale of other real estate owned and repossessed assets, net, Valuation Allowance	401	330	841	2,381
Valuation adjustments, net, Valuation Allowance	0	(343)	(32)	(120)
Balance, end of period, Valuation Allowance	(3,203)	(4,062)	(3,203)	(4,062)
Balance, beginning of the period, Net Balance	27,541	30,988	28,540	47,815
Transfers to other assets acquired through foreclosure, net, Net Balance		430	5,744	1,812
Proceeds from sale of other real estate owned and repossessed assets, net, Net Balance	(692)	(2,161)	(8,793)	(20,748)
Noncash Contribution Expense	(6,895)		(6,895)	0
Valuation adjustments of other repossessed assets, net	0	(343)	(32)	(120)
Gains (losses), net, Net Balance	74	78	1,464	233
Balance, end of period, Net Balance	20,028	$ 28,992	20,028	28,992
Gains Losses On Transfers To Other Real Estate And Foreclosed Assets	$ 0		$ 1,000	$ 100
Number of Real Estate Properties | Property	12	20	12	20	19

Other Borrowings - Additional I

Other Borrowings - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2018
Debt [Line Items]
FHLB advances	$ 390,000,000	$ 0
Short-term Debt	390,000,000	0
Revolving line of credit	$ 0	0
Weighted average interest rate of FHLB and FRB Short-term advances	1.41%
Customer repurchase agreements	$ 26,017,000	20,969,000
Federal Funds Purchased	0	0
FRB [Member]
Debt [Line Items]
Additional available credit with the entity	1,110,000,000	1,400,000,000
Unsecured Credit Facility [Member]
Debt [Line Items]
Secured borrowing credit line		306,000,000
FHLB [Member]
Debt [Line Items]
Additional available credit with the entity	$ 1,910,000,000	$ 2,840,000,000

Qualifying Debt (Details)

Qualifying Debt (Details)	3 Months Ended
	Sep. 30, 2018USD ($)Trust	Dec. 31, 2017USD ($)	Jun. 16, 2016USD ($)	Jun. 29, 2015USD ($)
Debt Instrument [Line Items]
Subordinated Debt	$ 290,800,000	$ 308,600,000
Number of Statutory Business Trusts Formed or Acquired | Trust	8
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	$ 68,300,000
Subordinated Debt [Member] | Subordinated Debentures Maturing July 2056 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 175,000,000
Debt Issuance Cost			$ 5,500,000
Debt Instrument, Interest Rate, Stated Percentage			6.25%
Subordinated Debt [Member] | Subordinated Debentures Maturing July 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 150,000,000
Debt Issuance Cost				$ 1,800,000
Debt Instrument, Interest Rate, Stated Percentage				0.00%
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate, at Point in Time	4.74%	4.03%

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury Stock, Shares, Acquired	18,402	64,705	201,354	266,883
Treasury Stock Acquired, Average Cost Per Share	$ 57.81	$ 51.82	$ 58.91	$ 51.10
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 1.5	$ 1.9	$ 4.8	$ 4.5
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Granted, Value, Share-based Compensation, Gross	0.7		23.7
Allocated Share-based Compensation Expense	3.4	2.7	12.4	11.3
Executive Officer [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 0.6	$ 0.8	$ 1.9	$ 1.6

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income - Summary of Changes in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (51,315)	$ 6,490	$ (3,145)	$ (4,695)
Other comprehensive income before reclassifications	(24,502)	1,871	(71,614)	13,420
Amounts reclassified from accumulated other comprehensive income	5,454	(197)	5,454	(561)
Net other comprehensive (loss) income	(19,048)	1,674	(66,160)	12,859
Ending balance	(70,363)	8,164	(70,363)	8,164
Unrealized holding gains (losses) on AFS
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(61,859)	(449)	(10,026)	(14,916)
Other comprehensive income before reclassifications	(22,462)	1,116	(71,765)	15,947
Amounts reclassified from accumulated other comprehensive income	5,454	(197)	5,454	(561)
Net other comprehensive (loss) income	(17,008)	919	(66,311)	15,386
Ending balance	(78,867)	470	(78,867)	470
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	9,954	6,638	6,352	9,956
Other comprehensive income before reclassifications	(2,028)	641	186	(2,677)
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Net other comprehensive (loss) income	(2,028)	641	186	(2,677)
Ending balance	7,926	7,279	7,926	7,279
Impairment loss on securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	144	144	144	144
Other comprehensive income before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Net other comprehensive (loss) income	0	0	0	0
Ending balance	144	144	144	144
Supplemental Employee Retirement Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	446	157	385	121
Other comprehensive income before reclassifications	(12)	114	(35)	150
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Net other comprehensive (loss) income	(12)	114	(35)	150
Ending balance	$ 434	$ 271	$ 434	$ 271

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income	$ 1,778	$ (122)	$ 1,778	$ (346)
Amount reclassified from accumulated other comprehensive income	(5,454)	197	(5,454)	561
Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized gains on sales of investment securities	(7,232)	319	(7,232)	907
Amount reclassified from accumulated other comprehensive income	(1,778)	122	(1,778)	346
Amount reclassified from accumulated other comprehensive income	$ (5,454)	$ 197	$ (5,454)	$ 561

Derivatives and Hedging Fair Va

Derivatives and Hedging Fair Value of Derivative Contracts (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	$ 49,697	$ 122,304	$ 103,700
Derivative Liability, Fair Value	933	1,759	932
Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	1,095	2,008	1,135
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	2,348	36,969	35,578
Derivative Liability, Fair Value	92	776	641
Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	92	776	641
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	47,349	85,335	68,122
Derivative Liability, Fair Value	841	983	291
Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	1,003	1,232	494
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	971,408	993,432	1,016,694
Derivative Asset, Fair Value	7,883	1,703	1,656
Derivative Liability, Fair Value	38,040	53,581	59,346
Notional Amount, Netting Adjustments	0	0	0
Derivative Netting Adjustments	6,119	896	1,588
Positive NPVs	1,764	807	68
Negative NPVs	31,921	52,685	57,758
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	971,408	993,432	1,016,694
Derivative Asset, Fair Value	7,883	1,703	1,656
Derivative Liability, Fair Value	$ 38,040	$ 53,581	$ 59,346

Derivatives and Hedging Largest

Derivatives and Hedging Largest Exposure to Individual Counterparty (Detail) - Largest individual counterparty [Member] - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Largest gross exposure (positive derivative NPV) to an individual counterparty	$ 5,802	$ 893	$ 945
Collateral posted by this counterparty	0	0	0
Negative derivative NPV with this counterparty	9,567	40,340	44,053
Collateral pledged to this counterparty	22,179	60,476	65,051
Net exposure after netting adjustments and collateral	$ 0	$ 0	$ 0

Derivatives and Hedging Additio

Derivatives and Hedging Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Jun. 16, 2016	Jun. 29, 2015
Derivative [Line Items]
Derivative, Amount of Hedged Item, Loans	$ 635,184,000		$ 635,184,000		$ 699,452,000
Collateral netted against derivative liabilities	34,700,000	$ 59,300,000	34,700,000	$ 59,300,000	53,600,000
Over collateralization net position	17,700,000	25,100,000	17,700,000	25,100,000	25,000,000
Additional collateral held in securities	52,400,000		52,400,000
Fair Value Hedge Assets, Loans	1,997,000		1,997,000		41,919,000
Derivative, Amount of Hedged Item	(290,801,000)		(290,801,000)		(308,608,000)
Fair Value Hedge Assets	28,160,000		28,160,000		$ 9,959,000
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	$ 1,100,000	$ 800,000	$ 3,500,000	$ 2,600,000
Subordinated Debentures Maturing July 2025 [Member] | Subordinated Debt [Member]
Derivative [Line Items]
Debt Instrument, Face Amount							$ 150,000,000
Subordinated Debentures Maturing July 2056 [Member] | Subordinated Debt [Member]
Derivative [Line Items]
Debt Instrument, Face Amount						$ 175,000,000

Earnings per Share (Details)

Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Basic	104,768	104,221	104,664	104,124
Dilutive Effect Of Stock Options Restricted Stock And Equity Settled Awards	680	721	734	817
Diluted	105,448	104,942	105,398	104,941
Net income available to common shareholders	$ 111,123	$ 82,844	$ 316,702	$ 236,146
Earnings (loss) per share - basic	$ 1.06	$ 0.79	$ 3.03	$ 2.27
Earnings (loss) per share - diluted	$ 1.05	$ 0.79	$ 3	$ 2.25
Anti-dilutive stock options outstanding that were not included in computation of diluted earnings per common share			0

Income Taxes Additional Informa

Income Taxes Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Jun. 30, 2017
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation, Percent	6.32%	29.64%	14.48%	27.89%
Deferred tax assets, net	$ 43,483		$ 43,483		$ 5,780	$ 43,500
Increase (Decrease) in Deferred Income Taxes			37,700
Operating Loss Carryforwards, Valuation Allowance	0		0		0
Amortization Method Qualified Affordable Housing Project Investments	295,116		295,116		267,023
Affordable Housing Program Obligation	139,400		139,400		$ 151,300
Amortization of tax credit investments	9,000	$ 6,800	26,546	$ 19,524
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	49,800		49,800
Deferred Tax Assets, Operating Loss Carryforwards	6,300		6,300
CALIFORNIA
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward, Amount	7,300		7,300
ARIZONA
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward, Amount	5,000		5,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	$ 1,100		$ 1,100

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Loss Contingencies [Line Items]
Letters of credit expiration period			1 year
Percentage of first liens initial loan to value ratio			75.00%
Percentage Of Commercial Real Estate Loans Occupied By Owners	37.00%		37.00%		36.00%
Operating Leases, Rent Expense, Net	$ 2.8	$ 2.8	$ 8.1	$ 8.2
Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Credit Concentration Risk [Member]
Loss Contingencies [Line Items]
Percent of commercial real estate related loans			50.00%		52.00%
Unfunded Loan Commitment [Member]
Loss Contingencies [Line Items]
Loss Contingency Accrual	$ 7.6		$ 7.6		$ 6.2

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Contractual Amounts for Unfunded Commitments and Letters of Credit (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Other Commitments [Line Items]
Total amount	$ 7,233,691		$ 7,233,691		$ 6,166,876
Percentage Of Commercial Real Estate Loans Occupied By Owners	37.00%		37.00%		36.00%
Operating Leases, Rent Expense, Net	$ 2,800	$ 2,800	$ 8,100	$ 8,200
Commitments to extend credit [Member]
Other Commitments [Line Items]
Unsecured Loan Commitments	594,074		594,074		$ 364,638
Total amount	6,798,062		6,798,062		5,851,158
Credit card guarantees [Member]
Other Commitments [Line Items]
Total amount	218,993		218,993		153,752
Standby letters of credit [Member]
Other Commitments [Line Items]
Total amount	216,636		216,636		161,966
Unsecured Letters Of Credit	$ 16,940		$ 16,940		$ 11,664
Commercial Real Estate Portfolio Segment [Member] | Credit Concentration Risk [Member] | Loans Receivable [Member]
Other Commitments [Line Items]
Concentration Risk, Percentage			50.00%		52.00%

Fair Value Accounting - Gains a

Fair Value Accounting - Gains and Losses from Fair Value Changes Included in Consolidated Statement of Operations (Detail) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Subordinated Debt Obligations, Fair Value Disclosure	$ 55,987		$ 55,987		$ 56,234
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)				$ (4,327)
Interest and Dividend Income, Securities, Operating				9
Interest Expense on Junior Subordinated Debt				2,376
Total Changes Included in Current-Period Earnings				(2,367)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)				(2,677)
Junior Subordinated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Measurement Input	0.06199		0.06199		0.0561
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ (2,689)	$ 1,035	$ 247	(4,327)
Interest and Dividend Income, Securities, Operating	0	0	0	0
Interest Expense on Junior Subordinated Debt	1,056	835	2,979	2,376
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	$ (2,028)	$ 641	$ 186	$ (2,677)
Period of basis point spread			3.80%		3.92%
Percentage of LIBOR			2.40%	1.69%
Debt Securities, Trading [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)				$ 0
Interest and Dividend Income, Securities, Operating				9
Interest Expense on Junior Subordinated Debt				0
Total Changes Included in Current-Period Earnings				9
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)				$ 0

Fair Value Accounting - Fair Va

Fair Value Accounting - Fair Value of Assets and Liabilities (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)				$ (4,327)
Interest and Dividend Income, Securities, Operating				9
Securities available for sale	$ 3,107,076		$ 3,107,076		$ 3,499,519
Investment securities - equity	172,294		172,294		0
Subordinated Debt Obligations, Fair Value Disclosure	55,987		55,987		56,234
Fair Value Hedge Assets, Loans	1,997		1,997		41,919
Fair Value Hedge Assets	28,160		28,160		9,959
Interest Expense on Junior Subordinated Debt				(2,376)
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings				(2,367)
Change in unrealized gain (loss) on junior subordinated debt, net of tax				(2,677)
Debt Securities, Trading [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest and Dividend Income, Securities, Operating				9
Interest Expense on Junior Subordinated Debt				0
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings				9
Change in unrealized gain (loss) on junior subordinated debt, net of tax				0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)				0
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	3,107,076		3,107,076		3,499,519
Investment securities - equity	172,294		172,294
Derivative Liability	38,973		38,973		55,340
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		103,812
Investment securities - equity	172,294		172,294
Subordinated Debt Obligations, Fair Value Disclosure	0		0		0
Derivative Liability	0		0		0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	3,107,076		3,107,076		3,395,707
Investment securities - equity	0		0
Subordinated Debt Obligations, Fair Value Disclosure	0		0		0
Derivative Liability	38,973		38,973		55,340
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Investment securities - equity	0		0
Subordinated Debt Obligations, Fair Value Disclosure	55,987		55,987		56,234
Derivative Liability	0		0		0
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,450,059		1,450,059		1,689,295
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,450,059		1,450,059		1,689,295
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	855,942		855,942		868,524
Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	855,942		855,942		868,524
Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	100,943		100,943		109,077
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	100,943		100,943		109,077
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Corporate Bond Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	99,384		99,384		103,483
Fair Value, Measurements, Recurring [Member] | Corporate Bond Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Corporate Bond Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	99,384		99,384		103,483
Fair Value, Measurements, Recurring [Member] | Corporate Bond Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	504,907		504,907		510,910
Fair Value, Measurements, Recurring [Member] | Municipal Bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Municipal Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	504,907		504,907		510,910
Fair Value, Measurements, Recurring [Member] | Municipal Bonds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale					53,196
Investment securities - equity	121,550		121,550
Fair Value, Measurements, Recurring [Member] | Preferred Stock [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale					53,196
Investment securities - equity	121,550		121,550
Fair Value, Measurements, Recurring [Member] | Preferred Stock [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale					0
Investment securities - equity	0		0
Fair Value, Measurements, Recurring [Member] | Preferred Stock [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale					0
Investment securities - equity	0		0
Fair Value, Measurements, Recurring [Member] | CRA investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale					50,616
Investment securities - equity	50,744		50,744
Fair Value, Measurements, Recurring [Member] | CRA investments [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale					50,616
Investment securities - equity	50,744		50,744
Fair Value, Measurements, Recurring [Member] | CRA investments [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale					0
Investment securities - equity	0		0
Fair Value, Measurements, Recurring [Member] | CRA investments [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale					0
Investment securities - equity	0		0
Fair Value, Measurements, Recurring [Member] | Collateralized Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	19,148		19,148		21,857
Fair Value, Measurements, Recurring [Member] | Collateralized Debt Obligations [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Collateralized Debt Obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	19,148		19,148		21,857
Fair Value, Measurements, Recurring [Member] | Collateralized Debt Obligations [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	28,617		28,617		28,617
Fair Value, Measurements, Recurring [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	28,617		28,617		28,617
Fair Value, Measurements, Recurring [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	45,601		45,601		61,462
Fair Value, Measurements, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	45,601		45,601		61,462
Fair Value, Measurements, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,475		2,475		2,482
Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,475		2,475		2,482
Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0		0
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	3,107,076		3,107,076		3,499,519
Investment securities - equity	172,294		172,294
Derivative Liability	38,973		38,973		55,340
Junior Subordinated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(2,689)	$ 1,035	247	(4,327)
Interest and Dividend Income, Securities, Operating	0	0	0	0
Interest Expense on Junior Subordinated Debt	(1,056)	(835)	(2,979)	(2,376)
Change in unrealized gain (loss) on junior subordinated debt, net of tax	(2,028)	$ 641	186	$ (2,677)
Junior Subordinated Debt [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Subordinated Debt Obligations, Fair Value Disclosure	$ 55,987		$ 55,987		$ 56,234

Fair Value Accounting - Change

Fair Value Accounting - Change in Level 3 Liabilities Measured at Fair Value on Recurring Basis (Detail) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt	$ 55,987		$ 55,987		$ 56,234
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt	55,987		$ 55,987		$ 56,234
Loans and Finance Receivables [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description			Discounted cash flow method		Discounted cash flow method
Other Assets [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description			Collateral method		Collateral method
Junior Subordinated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	$ (2,689)	$ 1,035	$ 247	$ (4,327)
Debt Instrument, Measurement Input	0.06199		0.06199		0.0561
Junior Subordinated Debt [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt	$ 55,987		$ 55,987		$ 56,234
Fair Value Measurements, Valuation Processes, Description			Implied credit rating of the Company		Implied credit rating of the Company
Junior Subordinated Debt [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance	(53,298)	55,772	$ (56,234)	50,410	$ 50,410
Closing balance	$ (55,987)	$ (54,737)	$ (55,987)	$ (54,737)	$ (56,234)
Valuation Technique, Discounted Cash Flow [Member] | Junior Subordinated Debt [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description			Discounted cash flow	Discounted cash flow
Collateral Method [Member] | Loans and Finance Receivables [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description			Collateral method		Collateral method
Third Party Appraisal [Member] | Loans and Finance Receivables [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description			Third party appraisal		Third party appraisal
Third Party Appraisal [Member] | Other Assets [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description			Third party appraisal		Third party appraisal
Discount Rate [Member] | Loans and Finance Receivables [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description			Discount rate		Discount rate
Scheduled Cash Collections [Member] | Loans and Finance Receivables [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description			Scheduled cash collections		Scheduled cash collections
Proceeds from Non-Real Estate Collateral [Member] | Loans and Finance Receivables [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description			Proceeds from non-real estate collateral		Proceeds from non-real estate collateral

Fair Value Accounting - Assets

Fair Value Accounting - Assets Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans without specific valuation allowance	$ 121,968	$ 79,239
Other assets acquired through foreclosure	20,028	28,540	$ 27,541	$ 28,992	$ 30,988	$ 47,815
Impaired Financing Receivables, With No related Allowance, Balances with Charge-offs	40,500	15,600
Impaired Financing Receivable, Recorded Investment	125,569	98,554
Impaired loans with an allowance recorded	3,601	19,315
Impaired loans with an allowance recorded	1,171	5,606
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded	1,200	5,600
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans without specific valuation allowance	81,445	63,607
Other assets acquired through foreclosure	20,028	28,540
Impaired loans with an allowance recorded	2,430	13,709
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans without specific valuation allowance	0	0
Other assets acquired through foreclosure	0	0
Impaired loans with an allowance recorded	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans without specific valuation allowance	0	0
Other assets acquired through foreclosure	0	0
Impaired loans with an allowance recorded	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans without specific valuation allowance	81,445	63,607
Other assets acquired through foreclosure	20,028	28,540
Impaired Financing Receivable, Recorded Investment	83,875	77,316
Impaired loans with an allowance recorded	$ 2,430	$ 13,709
Loans and Finance Receivables [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description	Discounted cash flow method	Discounted cash flow method
Other Assets [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description	Collateral method	Collateral method
Collateral Method [Member] | Loans and Finance Receivables [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description	Collateral method	Collateral method
Third Party Appraisal [Member] | Loans and Finance Receivables [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description	Third party appraisal	Third party appraisal
Level 3 Fair Value Measurement Inputs	Costs to sell	Costs to sell
Third Party Appraisal [Member] | Other Assets [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description	Third party appraisal	Third party appraisal
Level 3 Fair Value Measurement Inputs	Costs to sell	Costs to sell
Discount Rate [Member] | Loans and Finance Receivables [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description	Discount rate	Discount rate
Level 3 Fair Value Measurement Inputs	Contractual loan rate	Contractual loan rate
Scheduled Cash Collections [Member] | Loans and Finance Receivables [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description	Scheduled cash collections	Scheduled cash collections
Level 3 Fair Value Measurement Inputs	Probability of default	Probability of default
Proceeds from Non-Real Estate Collateral [Member] | Loans and Finance Receivables [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description	Proceeds from non-real estate collateral	Proceeds from non-real estate collateral
Level 3 Fair Value Measurement Inputs	Loss given default	Loss given default

Fair Value Accounting - Estimat

Fair Value Accounting - Estimated Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Federal Funds Sold	$ 70,000	$ 0
Impaired Financing Receivable, Recorded Investment	125,569	98,554
Other Repossessed Assets	20,000	28,500
Financial assets
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	288,290	255,050
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	3,107,076	3,499,519
Investment securities - equity	172,294	0
Loans, net	16,582,754	14,953,885
Financial liabilities
Deposits	18,908,580	16,972,532
Customer repurchase agreements	20,969	26,017
Junior subordinated debt	55,987	56,234
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Financing Receivable, Recorded Investment	83,875	77,316
Fair Value, Measurements, Nonrecurring [Member] | Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Federal Funds Sold	70,000
Financial assets
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	288,290	255,050
Loans, net	16,582,754	14,953,885
Financial liabilities
Deposits	18,908,580	16,972,532
Junior subordinated debt	359,082	376,905
Fair Value, Measurements, Nonrecurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Federal Funds Sold	70,000
Financial assets
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	279,033	256,314
Loans, net	16,048,855	14,654,326
Financial liabilities
Deposits	18,918,956	16,980,066
Junior subordinated debt	395,461	404,013
Fair Value, Measurements, Nonrecurring [Member] | Fair Value [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Federal Funds Sold	0
Financial assets
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	0	0
Loans, net	0	0
Financial liabilities
Deposits	0	0
Junior subordinated debt	0	0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Federal Funds Sold	70,000
Financial assets
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	279,033	256,314
Loans, net	15,964,980	14,577,010
Financial liabilities
Deposits	18,918,956	16,980,066
Junior subordinated debt	328,448	336,803
Fair Value, Measurements, Nonrecurring [Member] | Fair Value [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Federal Funds Sold	0
Financial assets
Investment securities - HTM, at amortized cost; fair value of $279,033 at September 30, 2018 and $256,314 at December 31, 2017	0	0
Loans, net	83,875	77,316
Financial liabilities
Deposits	0	0
Junior subordinated debt	67,013	67,210
Fair Value, Measurements, Recurring [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	3,107,076	3,499,519
Investment securities - equity	172,294
Derivative Asset	8,978	3,711
Financial liabilities
Derivative Liability	38,973	55,340
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	103,812
Investment securities - equity	172,294
Derivative Asset	0	0
Financial liabilities
Junior subordinated debt	0	0
Derivative Liability	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	3,107,076	3,395,707
Investment securities - equity	0
Derivative Asset	8,978	3,711
Financial liabilities
Junior subordinated debt	0	0
Derivative Liability	38,973	55,340
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Investment securities - equity	0
Derivative Asset	0	0
Financial liabilities
Junior subordinated debt	55,987	56,234
Derivative Liability	0	0
Fair Value, Measurements, Recurring [Member] | Reported Value Measurement [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	3,107,076	3,499,519
Investment securities - equity	172,294
Derivative Asset	8,978	3,711
Accrued Investment Income Receivable	88,847	85,517
Financial liabilities
Customer repurchase agreements	20,969	26,017
Federal Home Loan Bank Borrowings, Fair Value Disclosure		390,000
Derivative Liability	38,973	55,340
Interest Payable, Current	14,268	16,366
Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	3,107,076	3,499,519
Investment securities - equity	172,294
Derivative Asset	8,978	3,711
Accrued Investment Income Receivable	88,847	85,517
Financial liabilities
Customer repurchase agreements	20,969	26,017
Federal Home Loan Bank Borrowings, Fair Value Disclosure		390,000
Derivative Liability	38,973	55,340
Interest Payable, Current	14,268	16,366
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Level 1 [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	103,812
Investment securities - equity	172,294
Derivative Asset	0	0
Accrued Investment Income Receivable	0	0
Financial liabilities
Customer repurchase agreements	0	0
Federal Home Loan Bank Borrowings, Fair Value Disclosure		0
Derivative Liability	0	0
Interest Payable, Current	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Level 2 [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	3,107,076	3,395,707
Investment securities - equity	0
Derivative Asset	8,978	3,711
Accrued Investment Income Receivable	88,847	85,517
Financial liabilities
Customer repurchase agreements	20,969	26,017
Federal Home Loan Bank Borrowings, Fair Value Disclosure		390,000
Derivative Liability	38,973	55,340
Interest Payable, Current	14,268	16,366
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Level 3 [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,211,440 at September 30, 2018 and $3,515,401 at December 31, 2017	0	0
Investment securities - equity	0
Derivative Asset	0	0
Accrued Investment Income Receivable	0	0
Financial liabilities
Customer repurchase agreements	0	0
Federal Home Loan Bank Borrowings, Fair Value Disclosure		0
Derivative Liability	0	0
Interest Payable, Current	$ 0	$ 0

Fair Value Accounting - Additio

Fair Value Accounting - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Financing Receivable, Recorded Investment	$ 125,569		$ 98,554
Aggregate carrying amount of impaired loans	3,601		19,315
Impaired loans with an allowance recorded	(1,171)		(5,606)
Other assets acquired through foreclosure	20,000		28,500
Goodwill	$ 289,895		$ 289,895
Common Stock, Shares, Issued	107,633,006		107,057,520
Collateralized Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities contained credit losses	0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded	$ (1,200)		$ (5,600)
Junior Subordinated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Period of basis point spread	3.80%		3.92%
Percentage of LIBOR	2.40%	1.69%
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate carrying amount of impaired loans	$ 2,430		$ 13,709
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Financing Receivable, Recorded Investment	83,875		77,316
Aggregate carrying amount of impaired loans	$ 2,430		$ 13,709

Segments - Operating Segment In

Segments - Operating Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017	Jan. 01, 2017	Dec. 31, 2016
Operating Statistics [Line Items]
Service charges and fees	$ 5,267	$ 5,248	$ 16,684	$ 15,189
Cash, Cash Equivalents and Investment Securities	4,334,200		4,334,200			$ 4,237,100
Loans, net of deferred loan fees and costs	16,732,800		16,732,800			15,093,900
Less: Allowance for credit losses	(150,011)		(150,011)			(140,050)
Total loans held for investment	16,582,800		16,582,800			14,953,900
Other Repossessed Assets	20,000		20,000			28,500
Intangible Assets, Net (Including Goodwill)	299,500		299,500			300,700
Other Assets Segment	939,600		939,600			808,900
Assets	22,176,147		22,176,147			20,329,085
Deposits	18,908,580		18,908,580			16,972,532
Other borrowings	359,100		359,100			766,900
Other Liabilities Segment	420,000		420,000			360,000
Total liabilities	19,687,754		19,687,754			18,099,387
Stockholders' equity	2,488,393	2,146,125	2,488,393	2,146,125	$ 2,229,698	2,229,698	$ 1,892,067	$ 1,891,529
Liabilities and Equity	22,176,147		22,176,147			20,329,085
Excess Funds Provided by (Used in) Segment Basis	0		0			0
Net interest income	234,038	201,583	672,366	573,635
Provision for Loan, Lease, and Other Losses	6,000	5,000	17,000	12,250
Net interest income (loss) after provision for credit losses	228,038	196,583	655,366	561,385
Total non-interest income	4,418	10,456	29,505	31,656
Non-interest expense	(113,841)	(89,296)	(314,538)	(265,543)
Income from continuing operations before income taxes	118,615	117,743	370,333	327,498
Income tax expense (benefit)	7,492	34,899	53,631	91,352
Net income	111,123	82,844	316,702	236,146
Debit and credit card interchange fees	1,834	1,250	4,990	3,714
Success fees (2)	675	701	2,370	1,162
Other income	84	127	497	373
Total revenue from contracts with customers	7,860	7,326	24,541	20,438
Revenues outside the scope of ASC 606 (3)	(3,442)	3,130	4,964	11,218
Operating Segments [Member] | HOA Services [Member]
Operating Statistics [Line Items]
Service charges and fees	208	136	525	416
Cash, Cash Equivalents and Investment Securities	0		0			0
Loans, net of deferred loan fees and costs	202,100		202,100			162,100
Less: Allowance for credit losses	(1,900)		(1,900)			(1,600)
Total loans held for investment	200,200		200,200			160,500
Other Repossessed Assets	0		0			0
Intangible Assets, Net (Including Goodwill)	0		0			0
Other Assets Segment	1,000		1,000			900
Assets	201,200		201,200			161,400
Deposits	2,523,900		2,523,900			2,230,400
Other borrowings	0		0			0
Other Liabilities Segment	1,700		1,700			1,200
Total liabilities	2,525,600		2,525,600			2,231,600
Stockholders' equity	68,500		68,500			59,400
Liabilities and Equity	2,594,100		2,594,100			2,291,000
Excess Funds Provided by (Used in) Segment Basis	2,392,900		2,392,900			2,129,600
Net interest income	17,930	13,746	49,335	40,275
Provision for Loan, Lease, and Other Losses	103	40	285	332
Net interest income (loss) after provision for credit losses	17,827	13,706	49,050	39,943
Total non-interest income	215	136	543	417
Non-interest expense	(8,254)	(7,011)	(24,090)	(21,416)
Income from continuing operations before income taxes	9,788	6,831	25,503	18,944
Income tax expense (benefit)	2,251	2,562	5,866	7,104
Net income	7,537	4,269	19,637	11,840
Debit and credit card interchange fees	6	0	15	0
Success fees (2)	0	0	0	0
Other income	1	0	3	1
Total revenue from contracts with customers	215	136	543	417
Revenues outside the scope of ASC 606 (3)	0	0	0	0
Operating Segments [Member] | Public and Non-Profit Finance [Member]
Operating Statistics [Line Items]
Service charges and fees	0	0	0	0
Cash, Cash Equivalents and Investment Securities	0		0			0
Loans, net of deferred loan fees and costs	1,520,200		1,520,200			1,580,400
Less: Allowance for credit losses	(14,400)		(14,400)			(15,600)
Total loans held for investment	1,505,800		1,505,800			1,564,800
Other Repossessed Assets	0		0			0
Intangible Assets, Net (Including Goodwill)	0		0			0
Other Assets Segment	19,200		19,200			17,900
Assets	1,525,000		1,525,000			1,582,700
Deposits	0		0			0
Other borrowings	0		0			0
Other Liabilities Segment	10,100		10,100			42,400
Total liabilities	10,100		10,100			42,400
Stockholders' equity	121,400		121,400			126,500
Liabilities and Equity	131,500		131,500			168,900
Excess Funds Provided by (Used in) Segment Basis	(1,393,500)		(1,393,500)			(1,413,800)
Net interest income	3,683	7,269	11,224	21,242
Provision for Loan, Lease, and Other Losses	(553)	91	(786)	796
Net interest income (loss) after provision for credit losses	4,236	7,178	12,010	20,446
Total non-interest income	159	183	159	415
Non-interest expense	(2,134)	(2,053)	(6,386)	(6,522)
Income from continuing operations before income taxes	2,261	5,308	5,783	14,339
Income tax expense (benefit)	521	1,028	1,329	4,424
Net income	1,740	4,280	4,454	9,915
Debit and credit card interchange fees	0	0	0	0
Success fees (2)	0	0	0	0
Other income	0	0	0	0
Total revenue from contracts with customers	0	0	0	0
Revenues outside the scope of ASC 606 (3)	159	183	159	415
Operating Segments [Member] | Technology and Innovation [Member]
Operating Statistics [Line Items]
Service charges and fees	643	762	2,197	2,319
Cash, Cash Equivalents and Investment Securities	0		0			0
Loans, net of deferred loan fees and costs	1,106,500		1,106,500			1,097,900
Less: Allowance for credit losses	(9,900)		(9,900)			(11,400)
Total loans held for investment	1,096,600		1,096,600			1,086,500
Other Repossessed Assets	0		0			0
Intangible Assets, Net (Including Goodwill)	120,400		120,400			120,900
Other Assets Segment	5,400		5,400			6,000
Assets	1,222,400		1,222,400			1,213,400
Deposits	2,319,500		2,319,500			1,737,600
Other borrowings	0		0			0
Other Liabilities Segment	100		100			800
Total liabilities	2,319,600		2,319,600			1,738,400
Stockholders' equity	256,500		256,500			244,100
Liabilities and Equity	2,576,100		2,576,100			1,982,500
Excess Funds Provided by (Used in) Segment Basis	1,353,700		1,353,700			769,100
Net interest income	27,233	20,415	74,615	59,610
Provision for Loan, Lease, and Other Losses	1,448	(83)	5,355	816
Net interest income (loss) after provision for credit losses	25,785	20,498	69,260	58,794
Total non-interest income	2,836	1,855	9,518	5,689
Non-interest expense	(9,933)	(8,824)	(29,666)	(26,685)
Income from continuing operations before income taxes	18,688	13,529	49,112	37,798
Income tax expense (benefit)	4,298	5,075	11,296	14,175
Net income	14,390	8,454	37,816	23,623
Debit and credit card interchange fees	0	0	0	0
Success fees (2)	675	599	2,349	915
Other income	0	0	0	3
Total revenue from contracts with customers	1,318	1,361	4,546	3,237
Revenues outside the scope of ASC 606 (3)	1,518	494	4,972	2,452
Operating Segments [Member] | HFF Loan Portfolio [Member]
Operating Statistics [Line Items]
Service charges and fees	0	0	0	0
Cash, Cash Equivalents and Investment Securities	0		0			0
Loans, net of deferred loan fees and costs	1,435,400		1,435,400			1,327,700
Less: Allowance for credit losses	(7,300)		(7,300)			(4,000)
Total loans held for investment	1,428,100		1,428,100			1,323,700
Other Repossessed Assets	0		0			0
Intangible Assets, Net (Including Goodwill)	100		100			100
Other Assets Segment	6,800		6,800			5,900
Assets	1,435,000		1,435,000			1,329,700
Deposits	0		0			0
Other borrowings	0		0			0
Other Liabilities Segment	(100)		(100)			400
Total liabilities	(100)		(100)			400
Stockholders' equity	119,100		119,100			108,300
Liabilities and Equity	119,000		119,000			108,700
Excess Funds Provided by (Used in) Segment Basis	(1,316,000)		(1,316,000)			(1,221,000)
Net interest income	13,557	15,346	41,617	42,337
Provision for Loan, Lease, and Other Losses	223	1,116	2,006	2,924
Net interest income (loss) after provision for credit losses	13,334	14,230	39,611	39,413
Total non-interest income	0	0	12	0
Non-interest expense	(3,014)	(1,905)	(7,419)	(7,949)
Income from continuing operations before income taxes	10,320	12,325	32,204	31,464
Income tax expense (benefit)	2,374	4,622	7,407	11,799
Net income	7,946	7,703	24,797	19,665
Debit and credit card interchange fees	0	0	0	0
Success fees (2)	0	0	0	0
Other income	0	0	0	0
Total revenue from contracts with customers	0	0	0	0
Revenues outside the scope of ASC 606 (3)	0	0	12	0
Operating Segments [Member] | Other National Business Lines [Member]
Operating Statistics [Line Items]
Service charges and fees	0	0	0	0
Cash, Cash Equivalents and Investment Securities	0		0			0
Loans, net of deferred loan fees and costs	3,483,200		3,483,200			2,543,000
Less: Allowance for credit losses	(33,200)		(33,200)			(25,000)
Total loans held for investment	3,450,000		3,450,000			2,518,000
Other Repossessed Assets	0		0			0
Intangible Assets, Net (Including Goodwill)	0		0			0
Other Assets Segment	23,800		23,800			15,500
Assets	3,473,800		3,473,800			2,533,500
Deposits	0		0			0
Other borrowings	0		0			0
Other Liabilities Segment	85,400		85,400			5,500
Total liabilities	85,400		85,400			5,500
Stockholders' equity	286,000		286,000			206,000
Liabilities and Equity	371,400		371,400			211,500
Excess Funds Provided by (Used in) Segment Basis	(3,102,400)		(3,102,400)			(2,322,000)
Net interest income	20,329	16,933	58,813	46,380
Provision for Loan, Lease, and Other Losses	3,214	4,416	6,573	10,265
Net interest income (loss) after provision for credit losses	17,115	12,517	52,240	36,115
Total non-interest income	549	379	1,182	1,632
Non-interest expense	(7,280)	(5,286)	(19,193)	(14,573)
Income from continuing operations before income taxes	10,384	7,610	34,229	23,174
Income tax expense (benefit)	2,388	2,853	7,873	8,690
Net income	7,996	4,757	26,356	14,484
Debit and credit card interchange fees	0	0	0	0
Success fees (2)	0	0	0	0
Other income	0	0	1	113
Total revenue from contracts with customers	0	0	1	113
Revenues outside the scope of ASC 606 (3)	549	379	1,181	1,519
Corporate & Other
Operating Statistics [Line Items]
Service charges and fees	(7)	(6)	(5)	(3)
Cash, Cash Equivalents and Investment Securities	4,319,800		4,319,800			4,223,000
Loans, net of deferred loan fees and costs	6,600		6,600			4,100
Less: Allowance for credit losses	(100)		(100)			(100)
Total loans held for investment	6,500		6,500			4,000
Other Repossessed Assets	4,200		4,200			12,700
Intangible Assets, Net (Including Goodwill)	0		0			0
Other Assets Segment	745,200		745,200			628,100
Assets	5,075,700		5,075,700			4,867,800
Deposits	384,000		384,000			69,000
Other borrowings	359,100		359,100			766,900
Other Liabilities Segment	278,800		278,800			262,100
Total liabilities	1,021,900		1,021,900			1,098,000
Stockholders' equity	375,300		375,300			300,300
Liabilities and Equity	1,397,200		1,397,200			1,398,300
Excess Funds Provided by (Used in) Segment Basis	(3,678,500)		(3,678,500)			(3,469,500)
Net interest income	3,275	(9,816)	3,512	(34,849)
Provision for Loan, Lease, and Other Losses	(49)	(1,333)	(47)	(1,832)
Net interest income (loss) after provision for credit losses	3,324	(8,483)	3,559	(33,017)
Total non-interest income	(7,387)	1,517	(6,575)	4,695
Non-interest expense	(15,985)	(6,968)	(32,535)	(13,026)
Income from continuing operations before income taxes	(20,048)	(13,934)	(35,551)	(41,348)
Income tax expense (benefit)	(25,997)	(14,598)	(44,644)	(49,167)
Net income	5,949	664	9,093	7,819
Debit and credit card interchange fees	0	0	0	0
Success fees (2)	0	0	0	0
Other income	(5)	4	16	11
Total revenue from contracts with customers	(12)	(2)	11	8
Revenues outside the scope of ASC 606 (3)	(7,375)	1,519	(6,586)	4,687
Reportable Geographical Components [Member] | ARIZONA
Operating Statistics [Line Items]
Service charges and fees	917	765	2,826	2,095
Cash, Cash Equivalents and Investment Securities	2,000		2,000			2,100
Loans, net of deferred loan fees and costs	3,593,500		3,593,500			3,323,700
Less: Allowance for credit losses	(33,100)		(33,100)			(31,500)
Total loans held for investment	3,560,400		3,560,400			3,292,200
Other Repossessed Assets	1,700		1,700			2,300
Intangible Assets, Net (Including Goodwill)	0		0			0
Other Assets Segment	46,300		46,300			46,300
Assets	3,610,400		3,610,400			3,342,900
Deposits	5,331,700		5,331,700			4,841,300
Other borrowings	0		0			0
Other Liabilities Segment	13,500		13,500			11,600
Total liabilities	5,345,200		5,345,200			4,852,900
Stockholders' equity	439,800		439,800			396,500
Liabilities and Equity	5,785,000		5,785,000			5,249,400
Excess Funds Provided by (Used in) Segment Basis	2,174,600		2,174,600			1,906,500
Net interest income	56,701	52,637	169,233	145,839
Provision for Loan, Lease, and Other Losses	(297)	(289)	1,655	109
Net interest income (loss) after provision for credit losses	56,998	52,926	167,578	145,730
Total non-interest income	2,230	1,265	5,902	3,567
Non-interest expense	(23,231)	(18,844)	(67,154)	(55,388)
Income from continuing operations before income taxes	35,997	35,347	106,326	93,909
Income tax expense (benefit)	8,999	13,857	26,644	36,831
Net income	26,998	21,490	79,682	57,078
Debit and credit card interchange fees	284	232	822	661
Success fees (2)	0	0	0	0
Other income	29	61	139	99
Total revenue from contracts with customers	1,230	1,058	3,787	2,855
Revenues outside the scope of ASC 606 (3)	1,000	207	2,115	712
Reportable Geographical Components [Member] | NEVADA
Operating Statistics [Line Items]
Service charges and fees	1,967	1,952	6,143	5,544
Cash, Cash Equivalents and Investment Securities	8,500		8,500			8,200
Loans, net of deferred loan fees and costs	1,936,700		1,936,700			1,844,800
Less: Allowance for credit losses	(18,600)		(18,600)			(18,100)
Total loans held for investment	1,918,100		1,918,100			1,826,700
Other Repossessed Assets	14,100		14,100			13,300
Intangible Assets, Net (Including Goodwill)	23,200		23,200			23,200
Other Assets Segment	58,000		58,000			58,800
Assets	2,021,900		2,021,900			1,930,200
Deposits	3,847,300		3,847,300			3,951,400
Other borrowings	0		0			0
Other Liabilities Segment	16,300		16,300			20,900
Total liabilities	3,863,600		3,863,600			3,972,300
Stockholders' equity	270,700		270,700			263,700
Liabilities and Equity	4,134,300		4,134,300			4,236,000
Excess Funds Provided by (Used in) Segment Basis	2,112,400		2,112,400			2,305,800
Net interest income	37,933	36,310	109,898	108,028
Provision for Loan, Lease, and Other Losses	(38)	(2,044)	(2,005)	(5,378)
Net interest income (loss) after provision for credit losses	37,971	38,354	111,903	113,406
Total non-interest income	2,573	2,354	8,585	6,800
Non-interest expense	(16,471)	(14,748)	(46,486)	(45,733)
Income from continuing operations before income taxes	24,073	25,960	74,002	74,473
Income tax expense (benefit)	5,055	9,086	15,634	26,066
Net income	19,018	16,874	58,368	48,407
Debit and credit card interchange fees	381	246	995	723
Success fees (2)	0	0	0	0
Other income	34	(4)	153	(4)
Total revenue from contracts with customers	2,382	2,194	7,291	6,263
Revenues outside the scope of ASC 606 (3)	191	160	1,294	537
Reportable Geographical Components [Member] | Southern California [Member]
Operating Statistics [Line Items]
Service charges and fees	634	628	2,053	1,749
Cash, Cash Equivalents and Investment Securities	2,100		2,100			2,100
Loans, net of deferred loan fees and costs	2,116,300		2,116,300			1,934,700
Less: Allowance for credit losses	(20,200)		(20,200)			(19,500)
Total loans held for investment	2,096,100		2,096,100			1,915,200
Other Repossessed Assets	0		0			0
Intangible Assets, Net (Including Goodwill)	0		0			0
Other Assets Segment	15,100		15,100			14,400
Assets	2,113,300		2,113,300			1,931,700
Deposits	2,550,700		2,550,700			2,461,100
Other borrowings	0		0			0
Other Liabilities Segment	1,900		1,900			3,200
Total liabilities	2,552,600		2,552,600			2,464,300
Stockholders' equity	242,400		242,400			221,800
Liabilities and Equity	2,795,000		2,795,000			2,686,100
Excess Funds Provided by (Used in) Segment Basis	681,700		681,700			754,400
Net interest income	29,572	26,811	85,038	81,087
Provision for Loan, Lease, and Other Losses	1,467	(58)	1,921	(20)
Net interest income (loss) after provision for credit losses	28,105	26,869	83,117	81,107
Total non-interest income	931	971	2,898	2,602
Non-interest expense	(14,332)	(12,340)	(42,470)	(38,063)
Income from continuing operations before income taxes	14,704	15,500	43,545	45,646
Income tax expense (benefit)	4,117	6,517	12,288	19,194
Net income	10,587	8,983	31,257	26,452
Debit and credit card interchange fees	171	138	471	400
Success fees (2)	0	0	0	0
Other income	7	32	51	43
Total revenue from contracts with customers	812	798	2,575	2,192
Revenues outside the scope of ASC 606 (3)	119	173	323	410
Reportable Geographical Components [Member] | Northern California [Member]
Operating Statistics [Line Items]
Service charges and fees	905	1,011	2,945	3,069
Cash, Cash Equivalents and Investment Securities	1,800		1,800			1,700
Loans, net of deferred loan fees and costs	1,332,300		1,332,300			1,275,500
Less: Allowance for credit losses	(11,300)		(11,300)			(13,200)
Total loans held for investment	1,321,000		1,321,000			1,262,300
Other Repossessed Assets	0		0			200
Intangible Assets, Net (Including Goodwill)	155,800		155,800			156,500
Other Assets Segment	18,800		18,800			15,100
Assets	1,497,400		1,497,400			1,435,800
Deposits	1,951,500		1,951,500			1,681,700
Other borrowings	0		0			0
Other Liabilities Segment	12,300		12,300			11,900
Total liabilities	1,963,800		1,963,800			1,693,600
Stockholders' equity	308,700		308,700			303,100
Liabilities and Equity	2,272,500		2,272,500			1,996,700
Excess Funds Provided by (Used in) Segment Basis	775,100		775,100			$ 560,900
Net interest income	23,825	21,932	69,081	63,686
Provision for Loan, Lease, and Other Losses	482	3,144	2,043	4,238
Net interest income (loss) after provision for credit losses	23,343	18,788	67,038	59,448
Total non-interest income	2,312	1,796	7,281	5,839
Non-interest expense	(13,207)	(11,317)	(39,139)	(36,188)
Income from continuing operations before income taxes	12,448	9,267	35,180	29,099
Income tax expense (benefit)	3,486	3,897	9,938	12,236
Net income	8,962	5,370	25,242	16,863
Debit and credit card interchange fees	992	634	2,687	1,930
Success fees (2)	0	102	21	247
Other income	18	34	134	107
Total revenue from contracts with customers	1,915	1,781	5,787	5,353
Revenues outside the scope of ASC 606 (3)	$ 397	$ 15	$ 1,494	$ 486

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Related Party Transactions [Abstract]
Accounts Receivable, Net	$ 1,300	$ 1,300		$ 1,300
Related Party Transactions		8,700	$ 2,100
Noncash Contribution Expense	$ 6,895	$ 6,895	$ 0

Revenue from Contracts with Cus

Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Service charges and fees	$ 5,267	$ 5,248	$ 16,684	$ 15,189
Accounts Receivable, Net	1,300		1,300		$ 1,300
Debit and credit card interchange fees	1,834	1,250	4,990	3,714
Success fees (2)	675	701	2,370	1,162
Other income	84	127	497	373
Total revenue from contracts with customers	7,860	7,326	24,541	20,438
Revenues outside the scope of ASC 606 (3)	(3,442)	3,130	4,964	11,218
Total non-interest income	4,418	10,456	29,505	31,656
Operating Segments [Member] | HOA Services [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	208	136	525	416
Debit and credit card interchange fees	6	0	15	0
Success fees (2)	0	0	0	0
Other income	1	0	3	1
Total revenue from contracts with customers	215	136	543	417
Revenues outside the scope of ASC 606 (3)	0	0	0	0
Total non-interest income	215	136	543	417
Operating Segments [Member] | Public and Non-Profit Finance [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	0	0	0	0
Debit and credit card interchange fees	0	0	0	0
Success fees (2)	0	0	0	0
Other income	0	0	0	0
Total revenue from contracts with customers	0	0	0	0
Revenues outside the scope of ASC 606 (3)	159	183	159	415
Total non-interest income	159	183	159	415
Operating Segments [Member] | Technology and Innovation [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	643	762	2,197	2,319
Debit and credit card interchange fees	0	0	0	0
Success fees (2)	675	599	2,349	915
Other income	0	0	0	3
Total revenue from contracts with customers	1,318	1,361	4,546	3,237
Revenues outside the scope of ASC 606 (3)	1,518	494	4,972	2,452
Total non-interest income	2,836	1,855	9,518	5,689
Operating Segments [Member] | HFF Loan Portfolio [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	0	0	0	0
Debit and credit card interchange fees	0	0	0	0
Success fees (2)	0	0	0	0
Other income	0	0	0	0
Total revenue from contracts with customers	0	0	0	0
Revenues outside the scope of ASC 606 (3)	0	0	12	0
Total non-interest income	0	0	12	0
Operating Segments [Member] | Other National Business Lines [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	0	0	0	0
Debit and credit card interchange fees	0	0	0	0
Success fees (2)	0	0	0	0
Other income	0	0	1	113
Total revenue from contracts with customers	0	0	1	113
Revenues outside the scope of ASC 606 (3)	549	379	1,181	1,519
Total non-interest income	549	379	1,182	1,632
Reportable Geographical Components [Member] | ARIZONA
Disaggregation of Revenue [Line Items]
Service charges and fees	917	765	2,826	2,095
Debit and credit card interchange fees	284	232	822	661
Success fees (2)	0	0	0	0
Other income	29	61	139	99
Total revenue from contracts with customers	1,230	1,058	3,787	2,855
Revenues outside the scope of ASC 606 (3)	1,000	207	2,115	712
Total non-interest income	2,230	1,265	5,902	3,567
Reportable Geographical Components [Member] | NEVADA
Disaggregation of Revenue [Line Items]
Service charges and fees	1,967	1,952	6,143	5,544
Debit and credit card interchange fees	381	246	995	723
Success fees (2)	0	0	0	0
Other income	34	(4)	153	(4)
Total revenue from contracts with customers	2,382	2,194	7,291	6,263
Revenues outside the scope of ASC 606 (3)	191	160	1,294	537
Total non-interest income	2,573	2,354	8,585	6,800
Reportable Geographical Components [Member] | Southern California [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	634	628	2,053	1,749
Debit and credit card interchange fees	171	138	471	400
Success fees (2)	0	0	0	0
Other income	7	32	51	43
Total revenue from contracts with customers	812	798	2,575	2,192
Revenues outside the scope of ASC 606 (3)	119	173	323	410
Total non-interest income	931	971	2,898	2,602
Reportable Geographical Components [Member] | Northern California [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	905	1,011	2,945	3,069
Debit and credit card interchange fees	992	634	2,687	1,930
Success fees (2)	0	102	21	247
Other income	18	34	134	107
Total revenue from contracts with customers	1,915	1,781	5,787	5,353
Revenues outside the scope of ASC 606 (3)	397	15	1,494	486
Total non-interest income	2,312	1,796	7,281	5,839
Corporate & Other
Disaggregation of Revenue [Line Items]
Service charges and fees	(7)	(6)	(5)	(3)
Debit and credit card interchange fees	0	0	0	0
Success fees (2)	0	0	0	0
Other income	(5)	4	16	11
Total revenue from contracts with customers	(12)	(2)	11	8
Revenues outside the scope of ASC 606 (3)	(7,375)	1,519	(6,586)	4,687
Total non-interest income	$ (7,387)	$ 1,517	$ (6,575)	$ 4,695

Uncategorized Items - wal-20180

Label	Element	Value
Supplemental Employee Retirement Plan [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax	$ 469,000
Additional Paid-in Capital [Member]
Stockholders' Equity Attributable to Parent	us-gaap_StockholdersEquity	1,400,140,000
Stockholders' Equity Attributable to Parent	us-gaap_StockholdersEquity	1,424,540,000
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax	(12,556,000)
AOCI Attributable to Parent [Member]
Stockholders' Equity Attributable to Parent	us-gaap_StockholdersEquity	(4,695,000)
Stockholders' Equity Attributable to Parent	us-gaap_StockholdersEquity	$ (4,203,000)
Common Stock [Member]
Shares, Issued	us-gaap_SharesIssued	105,071,000
Shares, Issued	us-gaap_SharesIssued	105,487,000
Stockholders' Equity Attributable to Parent	us-gaap_StockholdersEquity	$ 10,000
Stockholders' Equity Attributable to Parent	us-gaap_StockholdersEquity	10,000
Treasury Stock [Member]
Stockholders' Equity Attributable to Parent	us-gaap_StockholdersEquity	(26,362,000)
Stockholders' Equity Attributable to Parent	us-gaap_StockholdersEquity	(40,173,000)
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax	7,740,000
Accumulated Other-than-Temporary Impairment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax	144,000
Retained Earnings [Member]
Stockholders' Equity Attributable to Parent	us-gaap_StockholdersEquity	522,974,000
Stockholders' Equity Attributable to Parent	us-gaap_StockholdersEquity	$ 849,524,000