Prosperity Bancshares (PB) 10-Q 8 May 17 2017 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2017	May 04, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	PROSPERITY BANCSHARES INC
Entity Central Index Key	1,068,851
Trading Symbol	PB
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		69,489,262
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Amendment Flag	false

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
ASSETS
Cash and due from banks	$ 324,797	$ 436,203
Federal funds sold	945	1,178
Total cash and cash equivalents	325,742	437,381
Available for sale securities, at fair value	209,427	221,176
Held to maturity securities, at cost (fair value of $9,517,764 and $9,339,455, respectively)	9,644,693	9,504,910
Total securities	9,854,120	9,726,086
Loans held for sale	21,896	26,975
Loans held for investment	9,717,357	9,595,085
Total loans	9,739,253	9,622,060
Less: allowance for credit losses	(84,095)	(85,326)
Loans, net	9,655,158	9,536,734
Accrued interest receivable	49,721	53,310
Goodwill	1,900,845	1,900,845
Core deposit intangibles, net	43,869	45,784
Bank premises and equipment, net	257,558	262,083
Other real estate owned	15,698	15,463
Bank owned life insurance (BOLI)	250,775	247,116
Federal Home Loan Bank of Dallas stock	74,129	55,430
Other assets	49,804	50,840
TOTAL ASSETS	22,477,419	22,331,072
Deposits:
Noninterest-bearing	5,299,264	5,190,973
Interest-bearing	11,736,308	12,116,329
Total deposits	17,035,572	17,307,302
Other borrowings	1,270,644	990,781
Securities sold under repurchase agreements	335,875	320,430
Accrued interest payable	2,228	2,319
Other liabilities	144,018	67,929
Total liabilities	18,788,337	18,688,761
COMMITMENTS AND CONTINGENCIES
SHAREHOLDERS’ EQUITY:
Preferred stock, $1 par value; 20,000,000 shares authorized; none issued or outstanding
Common stock, $1 par value; 200,000,000 shares authorized; 69,479,912 shares issued and outstanding at March 31, 2017; 69,491,012 shares issued and outstanding at December 31, 2016	69,480	69,491
Capital surplus	2,029,950	2,028,129
Retained earnings	1,588,222	1,543,280
Accumulated other comprehensive income—net unrealized gain on available for sale securities, net of tax of $770 and $760, respectively	1,430	1,411
Total shareholders’ equity	3,689,082	3,642,311
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 22,477,419	$ 22,331,072

Consolidated Balance Sheets (U3

Consolidated Balance Sheets (Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Held to maturity securities, fair value	$ 9,517,764	$ 9,339,455
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	69,479,912	69,491,012
Common stock, shares outstanding (in shares)	69,479,912	69,491,012
Accumulated other comprehensive income-net unrealized gain on available for sale securities, tax	$ 770	$ 760

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
INTEREST INCOME:
Loans, including fees	$ 111,710	$ 124,522
Securities	53,157	52,573
Federal funds sold	183	96
Total interest income	165,050	177,191
INTEREST EXPENSE:
Deposits	9,908	10,206
Other borrowings	2,476	482
Securities sold under repurchase agreements	231	212
Junior subordinated debentures		34
Total interest expense	12,615	10,934
NET INTEREST INCOME	152,435	166,257
PROVISION FOR CREDIT LOSSES	2,675	14,000
NET INTEREST INCOME AFTER PROVISION FOR CREDIT LOSSES	149,760	152,257
NONINTEREST INCOME:
Nonsufficient funds (NSF) fees	8,089	8,189
Credit card, debit card and ATM card income	5,953	5,827
Service charges on deposit accounts	5,421	4,590
Trust income	2,155	2,027
Mortgage income	1,266	1,471
Brokerage income	488	1,290
Net gain on sale of assets	1,759	1,020
Other	5,693	6,379
Total noninterest income	30,824	30,793
NONINTEREST EXPENSE:
Salaries and employee benefits	48,444	50,114
Net occupancy and equipment	5,503	5,624
Credit and debit card, data processing and software amortization	4,085	4,430
Regulatory assessments and FDIC insurance	3,549	3,430
Core deposit intangibles amortization	1,915	2,222
Depreciation	3,103	3,349
Communications	2,702	2,939
Other real estate expense	85	42
Other	8,676	8,378
Total noninterest expense	78,062	80,528
INCOME BEFORE INCOME TAXES	102,522	102,522
PROVISION FOR INCOME TAXES	33,957	33,571
NET INCOME	$ 68,565	$ 68,951
EARNINGS PER SHARE:
Basic	$ 0.99	$ 0.98
Diluted	$ 0.99	$ 0.98

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 68,565	$ 68,951
Securities available for sale:
Change in unrealized gain during period	29	148
Total other comprehensive gain	29	148
Deferred taxes related to other comprehensive gain	(10)	(52)
Other comprehensive gain, net of tax	19	96
Comprehensive income	$ 68,584	$ 69,047

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Tradition Bancshares, Inc [Member]	Common Stock [Member]	Common Stock [Member]Tradition Bancshares, Inc [Member]	Capital Surplus [Member]	Capital Surplus [Member]Tradition Bancshares, Inc [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]
BALANCE at Dec. 31, 2015	$ 3,462,910		$ 70,059		$ 2,036,378		$ 1,355,040	$ 2,040	$ (607)
BALANCE (in shares) at Dec. 31, 2015			70,058,761
Net income	68,951						68,951
Other comprehensive income	96							96
Common stock issued in connection with the exercise of stock options and restricted stock awards, net (in shares)			1,750
Common stock issued in connection with the exercise of stock options and restricted stock awards, net			$ 2		(2)
Common stock issued in connection with the acquisition (in shares)				679,528
Common stock issued in connection with the acquisition		$ 32,522		$ 679		$ 31,843
Stock repurchase (in shares)			(1,159,586)
Stock repurchase	(47,182)		$ (1,160)		(46,022)
Stock based compensation expense	2,652				2,652
Cash dividends declared	(20,889)						(20,889)
BALANCE at Mar. 31, 2016	3,499,060		$ 69,580		2,024,849		1,403,102	2,136	$ (607)
BALANCE (in shares) at Mar. 31, 2016			69,580,453
BALANCE at Dec. 31, 2016	3,642,311		$ 69,491		2,028,129		1,543,280	1,411
BALANCE (in shares) at Dec. 31, 2016			69,491,012
Net income	68,565						68,565
Other comprehensive income	19							19
Common stock issued in connection with the exercise of stock options and restricted stock awards, net (in shares)			(11,100)
Common stock issued in connection with the exercise of stock options and restricted stock awards, net	148		$ (11)		159
Stock based compensation expense	1,662				1,662
Cash dividends declared	(23,623)						(23,623)
BALANCE at Mar. 31, 2017	$ 3,689,082		$ 69,480		$ 2,029,950		$ 1,588,222	$ 1,430
BALANCE (in shares) at Mar. 31, 2017			69,479,912

Consolidated Statements of Cha7

Consolidated Statements of Changes in Shareholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Retained Earnings [Member]
Cash dividend declared, per share (in dollars per share)	$ 0.3400	$ 0.3000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 68,565	$ 68,951
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and core deposit intangibles amortization	5,018	5,571
Provision for credit losses	2,675	14,000
Net amortization of premium on investments	9,883	10,253
Gain on sale of other real estate	(10)	(14)
Gain on sale of assets	(1,759)	(1,020)
Net accretion of discount on loans	(4,753)	(14,494)
Net accretion of discount on deposits	(99)	(182)
Gain on sale of loans	(1,162)	(1,341)
Proceeds from sale of loans held for sale	59,037	58,460
Originations of loans held for sale	(52,904)	(56,903)
Stock based compensation expense	1,662	2,652
(Increase) decrease in accrued interest receivable and other assets	(17,703)	62,906
Increase in accrued interest payable and other liabilities	75,998	12,159
Net cash provided by operating activities	144,448	160,998
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities and principal paydowns of held to maturity securities	424,808	414,681
Purchase of held to maturity securities	(574,333)	(132,952)
Proceeds from maturities and principal paydowns of available for sale securities	1,211,622	2,506,849
Purchase of available for sale securities	(1,199,985)	(2,499,989)
Net (increase) decrease in loans held for investment	(121,679)	12,730
Purchase of bank premises and equipment	(1,123)	(1,778)
Proceeds from sale of bank premises, equipment and other real estate	4,401	1,832
Net cash (used in) provided by investing activities	(256,289)	292,410
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase (decrease) in noninterest-bearing deposits	108,291	(333,615)
Net (decrease) increase in interest-bearing deposits	(379,922)	36,517
Net proceeds (repayments) from other short-term borrowings	280,000	(305,000)
Repayments of other long-term borrowings	(137)	(174)
Net increase (decrease) in securities sold under repurchase agreements	15,445	(11,049)
Proceeds from stock option exercises	148	0
Repurchase of common stock		(47,182)
Payments of cash dividends	(23,623)	(20,889)
Net cash provided by (used in) financing activities	202	(681,392)
NET DECREASE IN CASH AND CASH EQUIVALENTS	(111,639)	(227,984)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	437,381	563,962
CASH AND CASH EQUIVALENTS, END OF PERIOD	325,742	335,978
NONCASH ACTIVITIES:
Acquisition of real estate through foreclosure of collateral	320	12,953
SUPPLEMENTAL INFORMATION:
Income taxes paid		5,400
Interest paid	$ 12,706	10,666
Tradition Bancshares, Inc [Member]
CASH FLOWS FROM INVESTING ACTIVITIES:
Net cash used in the purchase of Tradition Bancshares, Inc.		(8,963)
NONCASH ACTIVITIES:
Stock issued in connection with the acquisition		$ 32,522

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation	1. BASIS OF PRESENTATION The consolidated financial statements include the accounts of Prosperity Bancshares, Inc. ® ® The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for financial information and with the rules and regulations of the Securities and Exchange Commission. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, the statements reflect all adjustments necessary for a fair presentation of the financial position, results of operations and cash flows of the Company on a consolidated basis, and all such adjustments are of a normal recurring nature. These financial statements and the notes thereto should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2016. Operating results for the three-month period ended March 31, 2017 are not necessarily indicative of the results that may be expected for the year ending December 31, 2017 or any other period.

Income Per Common Share

Income Per Common Share	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Income Per Common Share	2. INCOME PER COMMON SHARE Outstanding stock options issued by the Company represent the only dilutive effect reflected in diluted weighted average shares. The following table illustrates the computation of basic and diluted earnings per share: Three Months Ended March 31, 2017 2016 Amount Per Share Amount Amount Per Share Amount (Amounts in thousands, except per share data) Net income $ 68,565 $ 68,951 Basic: Weighted average shares outstanding 69,480 $ 0.99 70,174 $ 0.98 Diluted: Add incremental shares for: Effect of dilutive securities - options 2 7 Total 69,482 $ 0.99 70,181 $ 0.98 There were no stock options exercisable during the three months ended March 31, 2017 or 2016 that would have had an anti-dilutive effect on the above computation.

New Accounting Standards

New Accounting Standards	3 Months Ended
	Mar. 31, 2017
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
New Accounting Standards	3. NEW ACCOUNTING STANDARDS Accounting Standards Updates (“ASU”) ASU 2017-08, “Receivables—Nonrefundable Fees and Other Costs (Subtopic 310-20).” ASU 2017-08 shortens the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. ASU 2017-08 will be effective for the Company on January 1, 2019 on a modified retrospective basis with a cumulative-effect adjustment as of the beginning of the period of adoption. The Company is currently evaluating the potential impact of ASU 2017-08 on the Company’s financial statements. ASU 2017-04, “Intangibles—Goodwill and Other (Topic 350).” ASU 2017-04 simplifies the subsequent measurement of goodwill by eliminating the second step of the goodwill impairment test, which required computing the implied fair value of goodwill. Under the amendments in this update, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An impairment charge should be recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. ASU 2017-04 will be effective for the Company on January 1, 2020 and is not expected to have a significant impact on the Company’s financial statements. ASU 2017-01, “Business Combinations (Topic 805).” ASU 2017-01 is intended to clarify or correct unintended application of ASU 2014-09 “Revenue from Contracts with Customers (Topic 606).” ASU 2017-01 clarifies 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. Additionally, the amendments in this update provide a more robust framework to assist entities in evaluating whether a set of assets and activities constitutes a business. Lastly, the amendments in this update narrow the definition of the term output so that the term is consistent with how outputs are described in Topic 606. ASU 2017-01 will be effective for the Company on January 1, 2018 and is not expected to have a significant impact on the Company’s financial statements. ASU 2016-18, “Statement of Cash Flows (Topic 230) – Restricted Cash.” ASU 2016-18 requires the Statement of Cash Flows to explain the change during the period in the total of cash, cash equivalents and amounts generally described as restricted cash or restricted cash equivalents. Therefore, restricted cash or cash equivalents should be included with cash and cash equivalents when recording the beginning-of-period and end-of-period total amounts on the Statement of Cash Flows. ASU 2016-18 will be effective for the Company on January 1, 2018 and is not expected to have a significant impact on the Company’s financial statements. ASU 2016-15, ASU 2016-15 addresses certain cash receipts and cash payments with the objective of reducing the existing diversity in practice. ASU 2016‑15 will be effective for the Company on January 1, 2018 and is not expected to have a significant impact on the Company's financial statements. ASU 2016-13, “Financial Instruments – Credit Losses (Topic 326)—Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires a financial asset (or a group of financial assets) measured at amortized cost basis to be presented at the net amount expected to be collected. The measurement of expected credit losses is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. An entity must use judgment in determining the relevant information and estimation methods that are appropriate in its circumstances. Additionally, available for sale debt securities may realize value either through collection of contractual cash flows or through sale of the security at fair value. Therefore, the amendments limit the amount of the allowance for credit losses to the difference between amortized cost and fair value. ASU 2016-13 will be effective for the Company as of January 1, 2020. The Company is currently evaluating the potential impact of ASU 2016-13 on the Company’s financial statements. ASU 2016-12, “Revenue from Contracts with Customers (Topic 606)—Narrow-Scope Improvements and Practical Expedients.” ASU 2016-12 addresses narrow-scope improvements to the guidance on collectability, noncash consideration and completed contracts at transition. Additionally, the amendments in this update provide a practical expedient for contract modifications at transition and an accounting policy election related to the presentation of sales taxes and other similar taxes collected from customers. The amendments in this update affect the guidance in , which is effective January 1, 2018. The Company is in the process of evaluating the impact of this guidance and does not currently anticipate a significant impact on the Company’s financial statements. ASU 2016-10, “Revenue from Contracts with Customers (Topic 606)—Identifying Performance Obligations and Licensing.” ASU 2016-10 clarifies two aspects of ” (i) identifying performance obligations and (ii) the licensing implementation guidance. This ASU adds guidance on how to identify the promised goods or services in the contract and how to evaluate whether promised goods and services are distinct. Additionally, this update includes guidance on determining whether an entity’s promise to grant a license provides a customer with either a right to use the entity’s intellectual property (which is satisfied at a point in time) or a right to access the entity’s intellectual property (which is satisfied over time) and when to recognize revenue for a sales-based or use-based royalty promised in exchange for a license of intellectual property. The amendments in this update affect the guidance in ,” which is effective January 1, 2018. The Company is in the process of evaluating the impact of this guidance and does not currently anticipate a significant impact on the Company’s financial statements. ASU 2016-09, “Compensation - Stock Compensation (Topic 718) — Improvements to Employee Share-Based Payment Accounting.” ASU 2016-09 simplifies the accounting for share-based awards paid to employees. The amended guidance 1) requires excess tax benefits and tax deficiencies on share-based awards payments to employees to be recognized directly to income tax expense or benefit in the Consolidated Statement of Income rather than to capital surplus; 2) requires excess tax benefits to be included as operating activities on the Consolidated Statements of Cash Flows; 3) provides entities with the option of making an accounting policy election to account for forfeitures of share-based payments as they occur instead of estimating the awards expected to be forfeited; and 4) changes the threshold to qualify for equity classification to permit withholdings up to the maximum statutory tax rate in the applicable jurisdiction. In addition, excess tax benefits and tax deficiencies are considered discrete items in the reporting period they occur and are not included in the estimate of an entity’s annual effective tax rate. The Company adopted ASU 2016-09 on January 1, 2017 and elected to recognize forfeitures as they occur. Implementation of ASU 2016-09 will add volatility to tax expense as the Company’s stock price changes. The adoption of ASU 2016-09 did not have a significant impact on the Company’s financial statements. ASU 2016-08, “Revenue from Contracts with Customers (Topic 606)—Principal versus Agent Considerations (Reporting Revenue Gross versus Net).” ASU 2014-09, “Revenue from Contracts with Customers (Topic 606) ASU 2016-02, "Leases (Topic 842)." ASU 2016-02 requires that lessees and lessors recognize lease assets and lease liabilities on the balance sheet and disclose key information about leasing arrangements. ASU 2016-02 is effective for public companies for annual periods beginning January 1, 2019, including interim periods within those fiscal years. The Company is currently evaluating the potential impact of ASU 2016-02 on the Company’s financial statements. ASU 2016-01, “Financial Instruments—Overall (Subtopic 825-10) — Recognition and Measurement of Financial Assets and Financial Liabilities.” ASU 2016-01 addresses certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. ASU 2016-01 1) requires equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) 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 to disclose the fair value of financial instruments measured at amortized cost for entities that are not public business entities; 4) eliminates the requirement for public business entities to disclose the method(s) 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; 5) requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; 6) requires an entity to present separately in other comprehensive income 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; 7) requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset (that is, securities or loans and receivables) on the balance sheet or the accompanying notes to the financial statements; and 8) clarifies that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity’s other deferred tax assets. The amendments in this update affect all entities that hold financial assets or owe financial liabilities. ASU 2016-01 is effective for the Company beginning January 1, 2018, and is not expected to have a significant impact on the Company’s financial statements. ASU 2014-09, “Revenue from Contracts with Customers (Topic 606).” ASU 2014-09 supersedes the revenue recognition requirements in Revenue Recognition (Topic 605), and most industry-specific guidance throughout the Industry Topics of the Codification. Additionally, ASU 2014-09 supersedes some cost guidance included in Revenue Recognition—Construction-Type and Production-Type Contracts (Subtopic 605-35). In addition, the existing requirements for the recognition of a gain or loss on the transfer of nonfinancial assets that are not in a contract with a customer are amended to be consistent with the guidance on recognition and measurement. The core principle of ASU 2014-09 is 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. The Company will adopt ASU 2014-09, effective January 1, 2018, using the modified retrospective application with a cumulative-effect adjustment, if such adjustment is significant. The Company continues to evaluate the requirements of ASU 2014-09, but it is not expected to have a significant impact on the Company’s financial statements.

Securities

Securities	3 Months Ended
	Mar. 31, 2017
Investments Debt And Equity Securities [Abstract]
Securities	4. SECURITIES The amortized cost and fair value of investment securities were as follows: March 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) Available for Sale States and political subdivisions $ 1,815 $ 5 $ — $ 1,820 Collateralized mortgage obligations 115,235 648 (87 ) 115,796 Mortgage-backed securities 77,588 1,853 (153 ) 79,288 Other securities 12,588 22 (87 ) 12,523 Total $ 207,226 $ 2,528 $ (327 ) $ 209,427 Held to Maturity U.S. Treasury securities and obligations of U.S. Government agencies $ 33,561 $ 493 $ (3 ) $ 34,051 States and political subdivisions 363,139 4,268 (299 ) 367,108 Collateralized mortgage obligations 799 5 (3 ) 801 Mortgage-backed securities 9,247,094 31,618 (163,008 ) 9,115,704 Other securities 100 — — 100 Total $ 9,644,693 $ 36,384 $ (163,313 ) $ 9,517,764 December 31, 2016 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) Available for Sale States and political subdivisions $ 1,915 $ 5 $ — $ 1,920 Collateralized mortgage obligations 120,478 240 (119 ) 120,599 Mortgage-backed securities 84,024 2,004 (165 ) 85,863 Other securities 12,588 252 (46 ) 12,794 Total $ 219,005 $ 2,501 $ (330 ) $ 221,176 Held to Maturity U.S. Treasury securities and obligations of U.S. Government agencies $ 33,523 $ 497 $ — $ 34,020 States and political subdivisions 384,015 3,934 (1,328 ) 386,621 Collateralized mortgage obligations 850 6 (5 ) 851 Mortgage-backed securities 9,086,422 30,880 (199,439 ) 8,917,863 Other securities 100 — — 100 Total $ 9,504,910 $ 35,317 $ (200,772 ) $ 9,339,455 Management evaluates securities for other-than-temporary impairment (“OTTI”) at least on a quarterly basis, and more frequently when economic or market conditions warrant such an evaluation. The investment securities portfolio is evaluated for OTTI by segregating the portfolio into two general segments and applying the appropriate OTTI analysis. Investment securities classified as available for sale or held to maturity are evaluated for OTTI under Financial Accounting Standards Board (“FASB”): Accounting Standards Codification (“ASC”) Topic 320, “ Investments-Debt and Equity Securities.” In determining OTTI, management considers many factors, including: (1) the length of time and the extent to which the fair value has been less than cost, (2) the financial condition and near-term prospects of the issuer, (3) whether the market decline was affected by macroeconomic conditions and (4) whether the entity has the intent to sell the debt security or more likely than not will be required to sell the debt security before its anticipated recovery. The assessment of whether an other-than-temporary decline exists involves a high degree of subjectivity and judgment and is based on the information available to management at a point in time. When OTTI occurs, the amount of the OTTI recognized in earnings depends on whether an entity intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss. If an entity intends to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the OTTI will be recognized in earnings equal to the entire difference between the investment’s amortized cost basis and its fair value at the balance sheet date. If an entity does not intend to sell the security and it is not more likely than not that the entity will be required to sell the security before recovery of its amortized cost basis less any current-period loss, the OTTI will be separated into the amount representing the credit-related portion of the impairment loss (“credit loss”) and the noncredit portion of the impairment loss (“noncredit portion”). The amount of the total OTTI related to the credit loss is determined based on the difference between the present value of cash flows expected to be collected and the amortized cost basis and such difference is recognized in earnings. The amount of the total OTTI related to the noncredit portion is recognized in other comprehensive income, net of applicable taxes. The previous amortized cost basis less the OTTI recognized in earnings will become the new amortized cost basis of the investment. As of March 31, 2017, management does not have the intent to sell any of its investment securities and believes that it is more likely than not that the Company will not have to sell any such securities before a recovery of cost. The unrealized losses are largely due to increases in market interest rates over the yields available at the time the underlying securities were purchased. The fair value is expected to recover as the securities approach their maturity date or repricing date or if market yields for such investments decline. Management does not believe any of the securities are impaired due to reasons of credit quality. Accordingly, as of March 31, 2017, management believes any impairment in the Company’s securities is temporary, and therefore no impairment loss has been realized in the Company’s consolidated statement of income. Securities with unrealized losses, segregated by length of time, that have been in a continuous loss position were as follows: March 31, 2017 Less than 12 Months More than 12 Months Total Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses (Dollars in thousands) Available for Sale Collateralized mortgage obligations $ 5,865 $ (76 ) $ 1,413 $ (11 ) $ 7,278 $ (87 ) Mortgage-backed securities 42,178 (148 ) 2,285 (5 ) 44,463 (153 ) Other securities — — 1,649 (87 ) 1,649 (87 ) Total $ 48,043 $ (224 ) $ 5,347 $ (103 ) $ 53,390 $ (327 ) Held to Maturity U.S. Treasury securities and obligations of U.S. Government agencies $ 1,500 $ (3 ) $ — $ — $ 1,500 $ (3 ) States and political subdivisions 82,411 (262 ) 4,860 (37 ) 87,271 (299 ) Collateralized mortgage obligations 120 (2 ) 43 (1 ) 163 (3 ) Mortgage-backed securities 7,026,944 (159,742 ) 84,893 (3,266 ) 7,111,837 (163,008 ) Total $ 7,110,975 $ (160,009 ) $ 89,796 $ (3,304 ) $ 7,200,771 $ (163,313 ) December 31, 2016 Less than 12 Months More than 12 Months Total Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses (Dollars in thousands) Available for Sale Collateralized mortgage obligations $ 10,723 $ (119 ) $ — $ — $ 10,723 $ (119 ) Mortgage-backed securities 45,456 (160 ) 2,334 (5 ) 47,790 (165 ) Other securities — — 1,691 (46 ) 1,691 (46 ) Total $ 56,179 $ (279 ) $ 4,025 $ (51 ) $ 60,204 $ (330 ) Held to Maturity U.S. Treasury securities and obligations of U.S. Government agencies $ — $ — $ — $ — $ — $ — States and political subdivisions 115,132 (1,288 ) 5,080 (40 ) 120,212 (1,328 ) Collateralized mortgage obligations 589 (4 ) 44 (1 ) 633 (5 ) Mortgage-backed securities 6,903,919 (195,556 ) 90,293 (3,883 ) 6,994,212 (199,439 ) Total $ 7,019,640 $ (196,848 ) $ 95,417 $ (3,924 ) $ 7,115,057 $ (200,772 ) At March 31, 2017 and December 31, 2016, there were 254 securities and 276 securities, respectively, in an unrealized loss position for more than 12 months. The amortized cost and fair value of investment securities at March 31, 2017, by contractual maturity, are shown below. Actual maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations at any time with or without call or prepayment penalties. Held to Maturity Available for Sale Amortized Cost Fair Value Amortized Cost Fair Value (Dollars in thousands) Due in one year or less $ 32,844 $ 32,887 $ 12,588 $ 12,523 Due after one year through five years 184,021 185,335 1,815 1,820 Due after five years through ten years 158,481 161,282 — — Due after ten years 21,454 21,755 — — Subtotal 396,800 401,259 14,403 14,343 Mortgage-backed securities and collateralized mortgage obligations 9,247,893 9,116,505 192,823 195,084 Total $ 9,644,693 $ 9,517,764 $ 207,226 $ 209,427 The Company recorded no gain or loss on sale of securities for the three months ended March 31, 2017 and 2016. As of March 31, 2017, the Company did not own any non-agency collateralized mortgage obligations. At March 31, 2017 and December 31, 2016, the Company did not own securities of any one issuer (other than the U.S. government and its agencies) for which aggregate adjusted cost exceeded 10% of the consolidated shareholders’ equity at such respective dates. Securities with an amortized cost of $5.26 billion and $5.64 billion and a fair value of $5.16 billion and $5.51 billion at March 31, 2017 and December 31, 2016, respectively, were pledged to collateralize public deposits and for other purposes required or permitted by law.

Loans and Allowance for Credit

Loans and Allowance for Credit Losses	3 Months Ended
	Mar. 31, 2017
Receivables [Abstract]
Loans and Allowance for Credit Losses	5. LOANS AND ALLOWANCE FOR CREDIT LOSSES The loan portfolio consists of various types of loans and is categorized by major type as follows: March 31, 2017 December 31, 2016 (Dollars in thousands) Residential mortgage loans held for sale $ 21,896 $ 26,975 Commercial and industrial 1,554,661 1,539,439 Real estate: Construction, land development and other land loans 1,326,685 1,263,923 1-4 family residential (includes home equity) 2,683,935 2,690,856 Commercial real estate (includes multi-family residential) 3,226,978 3,162,109 Farmland 493,606 484,588 Agriculture 169,191 187,748 Consumer and other 262,301 266,422 Total loans held for investment 9,717,357 9,595,085 Total $ 9,739,253 $ 9,622,060 Concentrations of Credit. Most of the Company’s lending activity occurs within the states of Texas and Oklahoma. Commercial real estate loans, 1-4 family residential loans and construction, land development and other land loans make up 74.3% of the Company’s total loan portfolio. As of March 31, 2017 and December 31, 2016, there were no concentrations of loans related to any single industry in excess of 10% of total loans. Foreign Loans. The Company has U.S. dollar-denominated loans and commitments to borrowers in Mexico. The outstanding balance of these loans and the unfunded amounts available under these commitments were not significant at March 31, 2017 or December 31, 2016. Related Party Loans. As of March 31, 2017 and December 31, 2016, loans outstanding to directors, officers and their affiliates totaled $4.1 million and $4.5 million, respectively. All transactions between the Company and such related parties are conducted in the ordinary course of business and made on the same terms and conditions as similar transactions with unaffiliated persons. An analysis of activity with respect to these related party loans is as follows: As of and for the three months ended March 31, 2017 As of and for the year ended December (Dollars in thousands) Beginning balance on January 1 $ 4,493 $ 4,063 New loans — 699 Repayments and reclassified related loans (358 ) (269 ) Ending balance $ 4,135 $ 4,493 Nonperforming Assets and Nonaccrual and Past Due Loans. The Company has several procedures in place to assist it in maintaining the overall quality of its loan portfolio. The Company has established underwriting guidelines to be followed by its officers, including requiring appraisals on loans collateralized by real estate. The Company also monitors its delinquency levels for any negative or adverse trends. Nevertheless, the Company’s loan portfolio could become subject to increasing pressures from deteriorating borrower credit due to general economic conditions. The Company generally places a loan on nonaccrual status and ceases accruing interest when the payment of principal or interest is delinquent for 90 days, or earlier in some cases, unless the loan is in the process of collection and the underlying collateral fully supports the carrying value of the loan. With respect to potential problem loans, an evaluation of the borrower’s overall financial condition is made to determine the need, if any, for possible writedowns or appropriate additions to the allowance for credit losses. An aging analysis of past due loans, segregated by category of loan, is presented below: March 31, 2017 Loans Past Due and Still Accruing 30-89 Days 90 or More Days Total Past Due Loans Nonaccrual Loans Current Loans Total Loans (Dollars in thousands) Construction, land development and other land loans $ 11,658 $ — $ 11,658 $ 283 $ 1,314,744 $ 1,326,685 Agriculture and agriculture real estate (includes farmland) 1,559 — 1,559 534 660,704 662,797 1-4 family (includes home equity) (1) 4,600 495 5,095 3,192 2,697,544 2,705,831 Commercial real estate (includes multi-family residential) 15,100 384 15,484 2,084 3,209,410 3,226,978 Commercial and industrial 14,587 — 14,587 18,128 1,521,946 1,554,661 Consumer and other 1,198 1 1,199 139 260,963 262,301 Total $ 48,702 $ 880 $ 49,582 $ 24,360 $ 9,665,311 $ 9,739,253 December 31, 2016 Loans Past Due and Still Accruing 30-89 Days 90 or More Days Total Past Due Loans Nonaccrual Loans Current Loans Total Loans (Dollars in thousands) Construction, land development and other land loans $ 8,766 $ 514 $ 9,280 $ 73 $ 1,254,570 $ 1,263,923 Agriculture and agriculture real estate (includes farmland) 1,813 381 2,194 161 669,981 672,336 1-4 family (includes home equity) (1) 8,645 53 8,698 3,726 2,705,407 2,717,831 Commercial real estate (includes multi-family residential) 4,250 — 4,250 3,528 3,154,331 3,162,109 Commercial and industrial 8,290 8 8,298 23,999 1,507,142 1,539,439 Consumer and other 886 — 886 155 265,381 266,422 Total $ 32,650 $ 956 $ 33,606 $ 31,642 $ 9,556,812 $ 9,622,060 (1) Includes $21.9 million and $27.0 million of residential mortgage loans held for sale at March 31, 2017 and December 31, 2016, respectively. The following table presents information regarding nonperforming assets as of the dates indicated: March 31, 2017 December 31, 2016 (Dollars in thousands) Nonaccrual loans (1) $ 24,360 $ 31,642 Accruing loans 90 or more days past due 880 956 Total nonperforming loans 25,240 32,598 Repossessed assets 261 241 Other real estate 15,698 15,463 Total nonperforming assets $ 41,199 $ 48,302 Nonperforming assets to total loans and other real estate 0.42 % 0.50 % (1) Includes troubled debt restructurings of $8.7 million and $97 thousand as of March 31, 2017 and December 31, 2016, respectively. The Company had $41.2 million in nonperforming assets at March 31, 2017 compared with $48.3 million at December 31, 2016. This decrease was primarily due to three loans that were charged off and two loans that were paid off during the three months ended March 31, 2017. Nonperforming assets were 0.42% of total loans and other real estate at March 31, 2017 compared with 0.50% of total loans and other real estate at December 31, 2016. These low nonperforming assets to total loans and other real estate ratios are reflective of the Company’s conservative lending approach. If interest on nonaccrual loans had been accrued under the original loan terms, approximately $1.1 million and $3.2 million would have been recorded as income for the three months ended March 31, 2017 and 2016, respectively. Acquired Loans. Acquired loans were preliminarily recorded at fair value based on a discounted cash flow valuation methodology that considers, among other things, interest rates, projected default rates, loss given default, and recovery rates (no allowance for credit losses was carried over from the acquisition completed during 2016). During the valuation process, the Company identified Purchased Credit-Impaired (“PCI”) and Non-PCI loans in the acquired loan portfolios. Loans acquired with evidence of credit quality deterioration at acquisition for which it was probable that the Company would not be able to collect all contractual amounts due were accounted for as PCI. PCI loan identification considers the following factors: payment history and past due status, debt service coverage, loan grading, collateral values and other factors that may indicate deterioration of credit quality since origination. Non-PCI loan identification considers the following factors: account types, remaining terms, annual interest rates or coupons, current market rates, interest types, past delinquencies, timing of principal and interest payments, loan to value ratios, loss exposures and remaining balances. Accretion of purchased discounts on PCI loans will be based on estimated future cash flows, regardless of contractual maturities. Accretion of purchased discounts on Non-PCI loans will be recognized on a level-yield basis based on contractual maturity of individual loans. PCI Loans. The carrying amount of PCI loans included in the consolidated balance sheet and the related outstanding balance as of the dates indicated are presented in the table below. The outstanding balance represents the total amount owed as of March 31, 2017 and December 31, 2016. March 31, 2017 December 31, 2016 (Dollars in thousands) PCI loans: Outstanding balance $ 48,438 $ 51,640 Less: discount 22,395 24,007 Recorded investment $ 26,043 $ 27,633 Changes in the accretable yield for acquired PCI loans for the three months ended March 31, 2017 and 2016 were as follows: Three Months Ended March 31, 2017 2016 (Dollars in thousands) Balance at beginning of period $ 9,778 $ 5,664 Additions — 10,222 Reclassifications from nonaccretable 968 5,120 Accretion (1,483 ) (7,831 ) Balance at March 31 $ 9,263 $ 13,175 Income recognition on PCI loans is subject to the Company’s ability to reasonably estimate both the timing and amount of future cash flows. PCI loans for which the Company is accruing interest income are not considered non-performing or impaired. The non-accretable difference represents contractual principal and interest the Company does not expect to collect. Non-PCI Loans. The carrying amount of Non-PCI loans included in the consolidated balance sheet and the related outstanding balance as of the dates indicated are presented in the table below. The outstanding balance represents the total amount owed as of March 31, 2017 and December 31, 2016, including accrued but unpaid interest. March 31, 2017 December 31, 2016 (Dollars in thousands) Non-PCI loans: Outstanding balance $ 997,980 $ 1,115,061 Less: discount 32,129 35,401 Recorded investment $ 965,851 $ 1,079,660 Changes in the discount accretion for Non-PCI loans for the three months ended March 31, 2017 and 2016 were as follows: Three Months Ended March 31, 2017 2016 (Dollars in thousands) Balance at beginning of period $ 35,401 $ 54,734 Additions — 3,491 Accretion charge-offs (2 ) (1,053 ) Accretion (3,270 ) (6,663 ) Balance at March 31 $ 32,129 $ 50,509 Impaired Loans. Loans are considered impaired when, based on current information and events, it is probable the Company will be unable to collect all amounts due in accordance with the original contractual terms of the loan agreement, including scheduled principal and interest payments. Impairment is evaluated in total for smaller-balance loans of a similar nature and on an individual loan basis for other loans. If a loan is impaired, a specific valuation allowance is allocated, if necessary, so that the loan is reported net, at the present value of estimated future cash flows using the loan’s existing rate or at the fair value of collateral if repayment is expected solely from the collateral. Interest payments on impaired loans are typically applied to principal unless collectability of the principal amount is reasonably assured, in which case interest is recognized on a cash basis. Impaired loans, or portions thereof, are charged off when deemed uncollectible. Impaired loans are set forth in the following tables. No interest income was recognized on impaired loans subsequent to their classification as impaired. The average recorded investment presented in the tables below is reported on a year-to-date basis. March 31, 2017 Recorded Investment Unpaid Contractual Principal Balance Related Allowance Average Recorded Investment (Dollars in thousands) With no related allowance recorded: Construction, land development and other land loans $ 231 $ 239 $ — $ 123 Agriculture and agriculture real estate (includes farmland) 385 390 — 196 1-4 family (includes home equity) 2,788 3,029 — 2,619 Commercial real estate (includes multi-family residential) 2,043 2,078 — 2,614 Commercial and industrial 12,884 13,374 — 10,904 Consumer and other 108 168 — 113 Total 18,439 19,278 — 16,569 With an allowance recorded: Construction, land development and other land loans — — — — Agriculture and agriculture real estate (includes farmland) 149 180 10 151 1-4 family (includes home equity) 380 393 113 408 Commercial real estate (includes multi-family residential) — — — 144 Commercial and industrial 3,782 4,129 1,203 8,555 Consumer and other 31 38 1 18 Total 4,342 4,740 1,327 9,276 Total: Construction, land development and other land loans 231 239 — 123 Agriculture and agriculture real estate (includes farmland) 534 570 10 347 1-4 family (includes home equity) 3,168 3,422 113 3,027 Commercial real estate (includes multi-family residential) 2,043 2,078 — 2,758 Commercial and industrial 16,666 17,503 1,203 19,459 Consumer and other 139 206 1 131 $ 22,781 $ 24,018 $ 1,327 $ 25,845 December 31, 2016 Recorded Investment Unpaid Contractual Principal Balance Related Allowance Average Recorded Investment (Dollars in thousands) With no related allowance recorded: Construction, land development and other land loans $ 14 $ 220 $ — $ 24 Agriculture and agriculture real estate (includes farmland) 7 12 — 14 1-4 family (includes home equity) 2,450 2,682 — 1,828 Commercial real estate (includes multi-family residential) 3,184 3,327 — 9,150 Commercial and industrial 8,925 9,446 — 5,139 Consumer and other 119 157 — 88 Total 14,699 15,844 — 16,243 With an allowance recorded: Construction, land development and other land loans — — — 3 Agriculture and agriculture real estate (includes farmland) 154 181 17 171 1-4 family (includes home equity) 437 449 150 408 Commercial real estate (includes multi-family residential) 288 288 178 275 Commercial and industrial 13,327 13,821 2,851 13,961 Consumer and other 4 4 1 93 Total 14,210 14,743 3,197 14,911 Total: Construction, land development and other land loans 14 220 — 27 Agriculture and agriculture real estate (includes farmland) 161 193 17 185 1-4 family (includes home equity) 2,887 3,131 150 2,236 Commercial real estate (includes multi-family residential) 3,472 3,615 178 9,425 Commercial and industrial 22,252 23,267 2,851 19,100 Consumer and other 123 161 1 181 $ 28,909 $ 30,587 $ 3,197 $ 31,154 Credit Quality Indicators. As part of the on-going monitoring of the credit quality of the Company’s loan portfolio and methodology for calculating the allowance for credit losses, management assigns and tracks loan grades to be used as credit quality indicators. The following is a general description of the loan grades used: Grade 1— Credits in this category have risk potential that is virtually nonexistent. These loans may be secured by insured certificates of deposit, insured savings accounts, U.S. Government securities and highly rated municipal bonds. Grade 2— Credits in this category are of the highest quality. These borrowers represent top rated companies and individuals with unquestionable financial standing with excellent global cash flow coverage, net worth, liquidity and collateral coverage. Grade 3— Credits in this category are not immune from risk but are well protected by the collateral and paying capacity of the borrower. These loans may exhibit a minor unfavorable credit factor, but the overall credit is sufficiently strong to minimize the possibility of loss. Grade 4— Credits in this category are considered to be of acceptable credit quality with moderately greater risk than Grade 3 and receiving closer monitoring. Loans in this category have sources of repayment that remain sufficient to preclude a larger than normal probability of default and secondary sources are likewise currently of sufficient quantity, quality, and liquidity to protect the Company against loss of principal and interest. These borrowers have specific risk factors, but the overall strength of the credit is acceptable based on other mitigating credit and/or collateral factors and can repay the debt in the normal course of business. Grade 5— Credits in this category constitute an undue and unwarranted credit risk; however, the factors do not rise to a level of substandard. These credits have potential weaknesses and/or declining trends that, if not corrected, could expose the Bank to risk at a future date. These loans are monitored on the Bank’s internally-generated watch list and evaluated on a quarterly basis. Grade 6— Credits in this category are considered “substandard” but “non-impaired” loans in accordance with regulatory guidelines. Loans in this category have well-defined weakness that, if not corrected, could make default of principal and interest possible. Loans in this category are still accruing interest and may be dependent upon secondary sources of repayment and/or collateral liquidation. Grade 7— Credits in this category are deemed “substandard” and “impaired” pursuant to regulatory guidelines. As such, the Bank has determined that it is probable that less than 100% of the contractual principal and interest will be collected. These loans are individually evaluated for a specific reserve and will typically have the accrual of interest stopped. Grade 8— Credits in this category include “doubtful” loans in accordance with regulatory guidance. Such loans are no longer accruing interest and factors indicate a loss is imminent. These loans are also deemed “impaired.” While a specific reserve may be in place while the loan and collateral is being evaluated, these loans are typically charged down to an amount the Bank estimates is collectible. Grade 9— Credits in this category are deemed a “loss” in accordance with regulatory guidelines and have been charged off or charged down. The Bank may continue collection efforts and may have partial recovery in the future. The following table presents risk grades and PCI loans by category of loan at March 31, 2017. Impaired loans include loans in risk grades 7, 8 and 9, as well as any PCI loan that has a specific reserve allocated to it. Construction, Land Development and Other Agriculture and Agriculture Real Estate (includes Farmland) 1-4 Family (includes Home (1) Commercial Real Estate (includes Multi-Family Commercial and Industrial Consumer and Other Total (Dollars in thousands) Grade 1 $ — $ 13,972 $ — $ — $ 56,049 $ 40,907 $ 110,928 Grade 2 2,682 4,074 22,447 8,332 11,695 27,225 76,455 Grade 3 1,241,209 562,415 2,607,696 2,898,086 1,181,197 178,333 8,668,936 Grade 4 75,654 71,851 59,543 242,316 187,836 10,670 647,870 Grade 5 4,445 9,118 4,001 45,312 47,030 3,203 113,109 Grade 6 1,092 445 4,137 14,765 50,868 1,824 73,131 Grade 7 231 534 3,140 2,042 15,984 139 22,070 Grade 8 — — 29 — 682 — 711 Grade 9 — — — — — — — PCI Loans (2) 1,372 388 4,838 16,125 3,320 — 26,043 Total $ 1,326,685 $ 662,797 $ 2,705,831 $ 3,226,978 $ 1,554,661 $ 262,301 $ 9,739,253 (1) Includes $21.9 million of residential mortgage loans held for sale at March 31, 2017. (2) Of the total PCI loans, $1.6 million were classified as substandard at March 31, 2017, with no specific reserves allocated to them. The following table presents risk grades and PCI loans by category of loan at December 31, 2016. Impaired loans include loans in risk grades 7, 8 and 9, as well as any PCI loan that has a specific reserve allocated to it. Construction, Land Development and Other Agriculture and Agriculture Real Estate (includes Farmland) 1-4 Family (includes Home (1) Commercial Real Estate (includes Multi-Family Commercial and Industrial Consumer and Other Total (Dollars in thousands) Grade 1 $ — $ 14,616 $ — $ — $ 54,908 $ 40,688 $ 110,212 Grade 2 2,261 4,218 22,863 8,317 12,772 11,041 61,472 Grade 3 1,200,623 570,324 2,622,304 2,859,433 1,143,634 194,210 8,590,528 Grade 4 54,380 74,079 55,367 220,533 176,287 16,095 596,741 Grade 5 2,525 7,703 3,605 45,533 57,283 2,403 119,052 Grade 6 2,690 847 5,095 8,401 68,682 1,829 87,544 Grade 7 13 161 2,857 3,472 21,475 156 28,134 Grade 8 — — 30 — 714 — 744 Grade 9 — — — — — — — PCI Loans (2) 1,431 388 5,710 16,420 3,684 — 27,633 Total $ 1,263,923 $ 672,336 $ 2,717,831 $ 3,162,109 $ 1,539,439 $ 266,422 $ 9,622,060 (1) Includes $27.0 million of residential mortgage loans held for sale at December 31, 2016. (2) Of the total PCI loans, $2.7 million were classified as substandard at December 31, 2016, which includes $31 thousand with specific reserves allocated to them. Allowance for Credit Losses. The allowance for credit losses is a valuation established through charges to earnings in the form of a provision for credit losses. Management has established an allowance for credit losses which it believes is adequate as of March 31, 2017 for estimated losses in the Company’s loan portfolio. The amount of the allowance for credit losses is affected by the following: (1) charge-offs of loans that occur when loans are deemed uncollectible and decrease the allowance, (2) recoveries on loans previously charged off that increase the allowance and (3) provisions for credit losses charged to earnings that increase the allowance. Based on an evaluation of the loan portfolio and consideration of the factors listed below, management presents a quarterly review of the allowance for credit losses to the Bank’s Board of Directors, indicating any change in the allowance since the last review and any recommendations as to adjustments in the allowance. Although management believes it uses the best information available to make determinations with respect to the allowance for credit losses, future adjustments may be necessary if economic conditions or the borrower’s performance differ from the assumptions used in making the initial determinations. The Company’s allowance for credit losses consists of two components: (1) a specific valuation allowance based on probable losses on specifically identified loans and (2) a general valuation allowance based on historical loan loss experience, general economic conditions and other qualitative risk factors both internal and external to the Company. In setting the specific valuation allowance, the Company follows a loan review program to evaluate the credit risk in the total loan portfolio and assigns risk grades to each loan. Through this loan review process, the Company maintains an internal list of impaired loans, which along with the delinquency list of loans, helps management assess the overall quality of the loan portfolio and the adequacy of the allowance for credit losses. All loans that have been identified as impaired are reviewed on a quarterly basis in order to determine whether a specific reserve is required. For certain impaired loans, the Company allocates a specific loan loss reserve primarily based on the value of the collateral securing the impaired loan in accordance with ASC Topic 310-10, “ Receivables. In connection with this review of the loan portfolio, the Company considers risk elements attributable to particular loan types or categories in assessing the quality of individual loans. Some of the risk elements include: • for 1-4 family residential mortgage loans, the borrower’s ability to repay the loan, including a consideration of the debt to income ratio and employment and income stability, the loan to value ratio, and the age, condition and marketability of collateral; • for commercial real estate loans and multifamily residential loans, the debt service coverage ratio (income from the property in excess of operating expenses compared to loan payment requirements), operating results of the owner in the case of owner-occupied properties, the loan to value ratio, the age and condition of the collateral and the volatility of income, property value and future operating results typical of properties of that type; • for construction, land development and other land loans, the perceived feasibility of the project including the ability to sell developed lots or improvements constructed for resale or the ability to lease property constructed for lease, the quality and nature of contracts for presale or prelease, if any, experience and ability of the developer and loan to value ratio; • for commercial and industrial loans, the operating results of the commercial, industrial or professional enterprise, the borrower’s business, professional and financial ability and expertise, the specific risks and volatility of income and operating results typical for businesses in that category and the value, nature and marketability of collateral; • for agriculture real estate loans, the experience and financial capability of the borrower, projected debt service coverage of the operations of the borrower and loan to value ratio; and • for non-real estate agriculture loans, the operating results, experience and financial capability of the borrower, historical and expected market conditions and the value, nature and marketability of collateral. In addition, for each category, the Company considers secondary sources of income and the financial strength and credit history of the borrower and any guarantors. In determining the amount of the general valuation allowance, management considers factors such as historical loan loss experience, concentration risk of specific loan types, the volume, growth and composition of the Company’s loan portfolio, current economic conditions that may affect the borrower’s ability to pay and the value of collateral, the evaluation of the Company’s loan portfolio through its internal loan review process, general economic conditions, other qualitative risk factors both internal and external to the Company and other relevant factors in accordance with ASC Topic 450, “ Contingencies. The following table details activity in the allowance for credit losses by category of loan for the three months ended March 31, 2017 and 2016. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. Construction, Land Development and Other Land Loans Agriculture and Agriculture Real Estate (includes Farmland) 1-4 Family (includes Home Equity) Commercial Real Estate (includes Multi-Family Residential) Commercial and Industrial Consumer and Other Total (Dollars in thousands) Allowance for credit losses: Three Months Ended Balance $ 14,984 $ 4,073 $ 16,571 $ 12,256 $ 35,836 $ 1,606 $ 85,326 Provision for credit losses (386 ) (554 ) (895 ) (1,148 ) 5,341 317 2,675 Charge-offs — — (13 ) (133 ) (3,638 ) (824 ) (4,608 ) Recoveries 65 65 108 — 143 321 702 Net charge-offs 65 65 95 (133 ) (3,495 ) (503 ) (3,906 ) Balance $ 14,663 $ 3,584 $ 15,771 $ 10,975 $ 37,682 $ 1,420 $ 84,095 Allowance for credit losses: Three Months Ended Balance $ 14,882 $ 3,845 $ 14,891 $ 12,996 $ 33,409 $ 1,361 $ 81,384 Provision for credit losses (703 ) 6,689 (297 ) (546 ) 8,150 707 14,000 Charge-offs (7 ) (7,025 ) (49 ) (59 ) (6,277 ) (848 ) (14,265 ) Recoveries 193 63 19 — 1,881 439 2,595 Net charge-offs 186 (6,962 ) (30 ) (59 ) (4,396 ) (409 ) (11,670 ) Balance $ 14,365 $ 3,572 $ 14,564 $ 12,391 $ 37,163 $ 1,659 $ 83,714 The following table details the amount of the allowance for credit losses allocated to each category of loan as of March 31, 2017, December 31, 2016 and March 31, 2016, on the basis of the impairment methodology used by the Company. Construction, Land Development and Other Land Loans Agriculture and Agriculture Real Estate (includes Farmland) 1-4 Family (includes Home Equity) Commercial Real Estate (includes Multi-Family Residential) Commercial and Industrial Consumer and Other Total (Dollars in thousands) Allowance for credit losses related March 31, 2017 Individually evaluated for impairment $ — $ 10 $ 113 $ — $ 1,203 $ 1 $ 1,327 Collectively evaluated for impairment 14,663 3,574 15,658 10,975 36,479 1,419 82,768 PCI loans — — — — — — — Total allowance for credit losses $ 14,663 $ 3,584 $ 15,771 $ 10,975 $ 37,682 $ 1,420 $ 84,095 December 31, 2016 Individually evaluated for impairment $ — $ 17 $ 150 $ 178 $ 2,820 $ 1 $ 3,166 Collectively evaluated for impairment 14,984 4,056 16,421 12,078 32,985 1,605 82,129 PCI loans — — — — 31 — 31 Total allowance for credit losses $ 14,984 $ 4,073 $ 16,571 $ 12,256 $ 35,836 $ 1,606 $ 85,326 March 31, 2016 Individually evaluated for impairment $ 2 $ 37 $ 91 $ — $ 7,464 $ 27 $ 7,621 Collectively evaluated for impairment 14,363 3,535 14,473 12,391 28,531 1,632 74,925 PCI loans — — — — 1,168 — 1,168 Total allowance for credit losses $ 14,365 $ 3,572 $ 14,564 $ 12,391 $ 37,163 $ 1,659 $ 83,714 The following table details the recorded investment in loans as of March 31, 2017, December 31, 2016 and March 31, 2016, excluding $21.9 million, $27.0 million and $23.7 million, respectively, of residential mortgage loans held for sale, related to each balance in the allowance for credit losses by category of loan. Construction, Land Development and Other Land Loans Agriculture and Agriculture Real Estate (includes Farmland) 1-4 Family (includes Home Equity) Commercial Real Estate (includes Multi-Family Residential) Commercial and Industrial Consumer and Other Total (Dollars in thousands) Recorded investment in March 31, 2017 Individually evaluated for impairment $ 231 $ 534 $ 3,168 $ 2,043 $ 16,666 $ 139 $ 22,781 Collectively evaluated for impairment 1,325,082 661,875 2,675,929 3,208,810 1,534,675 262,162 9,668,533 PCI loans 1,372 388 4,838 16,125 3,320 — 26,043 Total loans evaluated for impairment $ 1,326,685 $ 662,797 $ 2,683,935 $ 3,226,978 $ 1,554,661 $ 262,301 $ 9,717,357 December 31, 2016 Individually evaluated for impairment $ 14 $ 161 $ 2,887 $ 3,472 $ 22,221 $ 123 $ 28,878 Collectively evaluated for impairment 1,262,478 671,787 2,682,259 3,142,217 1,513,534 266,299 9,538,574 PCI loans 1,431 388 5,710 16,420 3,684 — 27,633 Total loans evaluated for impairment $ 1,263,923 $ 672,336 $ 2,690,856 $ 3,162,109 $ 1,539,439 $ 266,422 $ 9,595,085 March 31, 2016 Individually evaluated for impairment $ 25 $ 5,691 $ 2,379 $ 9,159 $ 18,441 $ 227 $ 35,922 Collectively evaluated for impairment 1,170,405 635,208 2,630,719 3,200,625 1,671,822 246,454 9,555,233 PCI loans 3,094 394 6,374 19,922 9,752 — 39,536 Total loans evaluated for impairment $ 1,173,524 $ 641,293 $ 2,639,472 $ 3,229,706 $ 1,700,015 $ 246,681 $ 9,630,691 Troubled Debt Restructurings. The restructuring of a loan is considered a “troubled debt restructuring” if both (1) the borrower is experiencing financial difficulties and (2) the creditor has granted a concession. Concessions may include interest rate reductions or below market interest rates, principal forgiveness, restructuring amortization schedules and other actions intended to minimize potential losses. Under ASC topic 310-40 “ the Company evaluates all loan modifications to identify whether the restructuring constitutes a troubled debt restructuring. As of March 31, 2017 and 2016, the Company had $8.7 million and $593 thousand, respectively, in outstanding troubled debt restructurings. The following table presents information regarding the recorded investment of loans modified as troubled debt restructurings during the three months ended March 31, 2017 and 2016: Three Months Ended March 31, 2017 2016 Number of Loans Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Number of Loans Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment (Dollars in thousands) Troubled Debt Restructurings Construction, land development and other land loans — $ — $ — — $ — $ — Agriculture and agriculture real estate (includes farmland) — — — — — — 1-4 Family (includes home equity) — — — — — — Commercial real estate (includes multi-family residential) — — — — — — Commercial and industrial 3 8,656 8,650 — — — Consumer and other — — — — — — Total 3 $ 8,656 $ 8,650 — $ — $ — As of March 31, 2017, there have been no defaults on any loans that were modified as troubled debt restructurings during the preceding twelve months. Default is determined at 90 or more days past due. For three months ended March 31, 2017, the Company added 3 loans totaling $8.7 million as new troubled debt restructurings, of which $8.7 million was still outstanding at March 31, 2017. For three months ended March 31, 2016, the Company did not add any loans as new troubled debt restructurings. The modifications generally related to extending the amortization periods of the loans, which includes loans modified during bankruptcy. The Company did not grant principal reductions on any restructured loans. These modifications did not have a material impact on the Company’s determination of the allowance for credit losses.

Fair Value

Fair Value	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value	6. FAIR VALUE The Company uses fair value measurements to record fair value adjustments to certain assets and to determine fair value disclosures. Fair values represent the estimated price that would be received from selling an asset or paid to transfer a liability, otherwise known as an “exit price.” Securities available for sale are recorded at fair value on a recurring basis. Additionally, from time to time, the Company may be required to record other assets at fair value on a nonrecurring basis such as certain loans including residential mortgage loans held for sale, goodwill and other intangible assets and other real estate owned. These nonrecurring fair value adjustments typically involve application of lower-of-cost-or-market accounting or write downs of individual assets. ASC Topic 820 “ Fair Value Measurements and Disclosures Fair Value Hierarchy The Company groups financial assets and financial liabilities measured at fair value in three levels, based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. These levels are: • Level 1—Quoted prices in active markets for identical assets or liabilities. • Level 2—Other significant observable inputs (including quoted prices in active markets for similar assets or liabilities) or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. 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. The fair value disclosures below represent the Company’s estimates based on relevant market information and information about the financial instruments. Fair value estimates are based on judgments regarding current economic conditions, risk characteristics of the various instruments and other factors. These estimates are subjective in nature and involve uncertainties and matters of significant judgment and therefore cannot be determined with precision. Changes in the above methodologies and assumptions could significantly affect the estimates. The following tables present fair values for assets and liabilities measured at fair value on a recurring basis: As of March 31, 2017 Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets: Available for sale securities: States and political subdivisions $ — $ 1,820 $ — $ 1,820 Collateralized mortgage obligations — 115,796 — 115,796 Mortgage-backed securities — 79,288 — 79,288 Other securities 12,523 — — 12,523 Total $ 12,523 $ 196,904 $ — $ 209,427 As of December 31, 2016 Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets: Available for sale securities: States and political subdivisions $ — $ 1,920 $ — $ 1,920 Collateralized mortgage obligations — 120,599 — 120,599 Mortgage-backed securities — 85,863 — 85,863 Other securities 12,794 — — 12,794 Total $ 12,794 $ 208,382 $ — $ 221,176 Certain assets and liabilities are measured at fair value on a nonrecurring basis; that is, the instruments 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). These instruments include other real estate owned, repossessed assets, held to maturity debt securities, loans held for sale and impaired loans, which are included as loans held for investment. For the three months ended March 31, 2017, the Company had additions to other real estate owned of $320 thousand, all of which was still outstanding as of March 31, 2017. For the three months ended March 31, 2017, the Company had additions to impaired loans of $1.7 million, all of which was still outstanding as of March 31, 2017. The remaining financial assets and liabilities measured at fair value on a non-recurring basis that were recorded in 2017 and remained outstanding at March 31, 2017 were not significant. The following table presents carrying and fair value information of financial instruments as of the dates indicated: As of March 31, 2017 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total Assets (Dollars in thousands) Cash and due from banks $ 324,797 $ 324,797 $ — $ — $ 324,797 Federal funds sold 945 945 — — 945 Held to maturity securities 9,644,693 — 9,517,764 — 9,517,764 Loans held for sale 21,896 — 21,896 — 21,896 Loans held for investment, net of allowance 9,633,262 — — 9,679,257 9,679,257 Other real estate owned 15,698 — 15,698 — 15,698 Liabilities Deposits: Noninterest-bearing $ 5,299,264 $ — $ 5,299,264 $ — $ 5,299,264 Interest-bearing 11,736,308 — 11,740,990 — 11,740,990 Other borrowings 1,270,644 — 1,271,004 — 1,271,004 Securities sold under repurchase agreements 335,875 — 335,864 — 335,864 As of December 31, 2016 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total Assets (Dollars in thousands) Cash and due from banks $ 436,203 $ 436,203 $ — $ — $ 436,203 Federal funds sold 1,178 1,178 — — 1,178 Held to maturity securities 9,504,910 — 9,339,455 — 9,339,455 Loans held for sale 26,975 — 26,975 — 26,975 Loans held for investment, net of allowance 9,509,759 — — 9,533,310 9,533,310 Other real estate owned 15,463 — 15,463 — 15,463 Liabilities Deposits: Noninterest-bearing $ 5,190,973 $ — $ 5,190,973 $ — $ 5,190,973 Interest-bearing 12,116,329 — 12,121,157 — 12,121,157 Other borrowings 990,781 — 991,181 — 991,181 Securities sold under repurchase agreements 320,430 — 320,428 — 320,428 The following is a description of the fair value estimates, methods and assumptions that are used by the Company in estimating the fair values of financial instruments. Cash and due from banks —For these short-term instruments, the carrying amount is a reasonable estimate of fair value. The Company classifies the estimated fair value of these instruments as Level 1. Federal funds sold —For these short-term instruments, the carrying amount is a reasonable estimate of fair value. The Company classifies the estimated fair value of these instruments as Level 1. Securities — Fair value measurements based upon quoted prices are considered Level 1 inputs. Level 1 securities consist of U.S. Treasury securities and certain equity securities which are included in the available for sale portfolio. For all other available for sale and held to maturity securities, if quoted prices are not available, fair values are measured using Level 2 inputs. For these securities, the Company generally 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. The Company reviews the prices supplied by the independent pricing service, as well as their underlying pricing methodologies, for reasonableness. Securities available for sale are recorded at fair value on a recurring basis. Loans held for sale — Loans held for sale are carried at the lower of cost or estimated fair value. Fair value for consumer mortgages held for sale is based on commitments on hand from investors or prevailing market prices. As such, the Company classifies loans subjected to nonrecurring fair value adjustments as Level 2. Loans held for investment — The Company does not record loans at fair value on a recurring basis. As such, valuation techniques discussed herein for loans are primarily for estimating fair value disclosures. However, from time to time, the Company records nonrecurring fair value adjustments to impaired loans to reflect (1) partial write downs that are based on the observable market price or current appraised value of the collateral, or (2) the full charge-off of the loan carrying value. Where appraisals are not available, estimated cash flows are discounted using a rate commensurate with the credit risk associated with those cash flows. Assumptions regarding credit risk, cash flows and discount rates are judgmentally determined using available market information and specific borrower information. The estimated fair value approximates carrying value for variable-rate loans that reprice frequently and with no significant change in credit risk. The fair value of fixed-rate loans and variable-rate loans which reprice on an infrequent basis is estimated by discounting future cash flows using the current interest rates at which similar loans with similar terms would be made to borrowers of similar credit quality. An overall valuation adjustment is made for specific credit risks as well as general portfolio credit risk. The Company classifies the estimated fair value of loans held for investment as Level 3. Other real estate owned — Other real estate owned is primarily foreclosed properties securing residential loans and commercial real estate. Foreclosed assets are adjusted to fair value less estimated costs to sell upon transfer of the loans to other real estate owned. Subsequently, these assets are carried at the lower of carrying value or fair value less estimated costs to sell. Other real estate carried at fair value based on an observable market price or a current appraised value is classified by the Company as Level 2. When management determines that the fair value of other real estate requires additional adjustments, either as a result of a non-current appraisal or when there is no observable market price, the Company classifies the other real estate as Level 3. Deposits —The fair value of demand deposits, savings accounts and certain money market deposits is the amount payable on demand at the reporting date. The fair value of fixed-maturity certificates of deposit is estimated using the rates currently offered for deposits of similar remaining maturities. Deposits fair value measurements utilize Level 2 inputs. Other borrowings —Rates currently available to the Company for debt with similar terms and remaining maturities are used to estimate the fair value of other borrowings using a discounted cash flows methodology and are measured utilizing Level 2 inputs. Securities sold under repurchase agreements —The fair value of securities sold under repurchase agreements is the amount payable on demand at the reporting date and are measured utilizing Level 2 inputs. Off-balance sheet financial instruments —The fair value of commitments to extend credit and standby letters of credit is estimated using the fees currently charged to enter into similar agreements, taking into account the remaining terms of the agreement and the present creditworthiness of the counterparties. The Company has reviewed the unfunded portion of commitments to extend credit as well as standby and other letters of credit, and has determined that the fair value of such financial instruments is not material. The Company classifies the estimated fair value of credit-related financial instruments as Level 3. The fair value estimates presented herein are based on pertinent information available to management at March 31, 2017. Although management is not aware of any factors that would significantly affect the estimated fair value amounts, such amounts have not been comprehensively revalued for purposes of these financial statements since those dates and, therefore, current estimates of fair value may differ significantly from the amounts presented herein.

Goodwill and Core Deposit Intan

Goodwill and Core Deposit Intangibles	3 Months Ended
	Mar. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Core Deposit Intangibles	7. GOODWILL AND CORE DEPOSIT INTANGIBLES Changes in the carrying amount of the Company’s goodwill and core deposit intangibles for the three months ended March 31, 2017 and the year ended December 31, 2016 were as follows: Goodwill Core Deposit Intangibles (Dollars in thousands) Balance as of December 31, 2015 $ 1,868,827 $ 49,417 Less: Amortization — (9,200 ) Add: Acquisition of Tradition Bancshares, Inc. 32,018 5,567 Balance as of December 31, 2016 1,900,845 45,784 Less: Amortization — (1,915 ) Add: Measurement period adjustments — — Balance as of March 31, 2017 $ 1,900,845 $ 43,869 Goodwill is recorded on the acquisition date of each entity. The Company may record subsequent adjustments to goodwill for amounts undeterminable at acquisition date, such as deferred taxes and real estate valuations, and therefore the goodwill amounts may change accordingly. The Company initially records the total premium paid on acquisitions as goodwill. After finalizing the valuation, core deposit intangibles are identified and reclassified from goodwill to core deposit intangibles on the balance sheet. This reclassification has no effect on total assets, liabilities, shareholders’ equity, net income or cash flows. Management performs an evaluation annually, and more frequently if a triggering event occurs, of whether any impairment of the goodwill and core deposit intangibles has occurred. If any such impairment is determined, a write-down is recorded. As of March 31, 2017, there was no impairment recorded on goodwill and core deposit intangibles. The measurement period for the Company to determine the fair value of acquired identifiable assets and assumed liabilities will be at the end of the earlier of (1) twelve months from the date of acquisition or (2) as soon as the Company receives the information it was seeking about facts and circumstances that existed as of the date of acquisition. Core deposit intangibles are being amortized on a non-pro rata basis over their estimated lives, which the Company believes is between 10 and 15 years. Amortization expense related to intangible assets totaled $1.9 million and $2.2 million for the three months ended March 31, 2017 and 2016, respectively. The estimated aggregate future amortization expense for core deposit intangibles remaining as of March 31, 2017 is as follows (dollars in thousands): Remaining 2017 $ 5,027 2018 5,959 2019 5,051 2020 4,483 2021 4,022 Thereafter 19,327 Total $ 43,869

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	8. STOCK–BASED COMPENSATION At March 31, 2017, the Company had two stock-based employee compensation plans with awards outstanding. One of these plans has expired and therefore no additional awards may be issued under that plan. During 2004, Bancshares’ Board of Directors established the Prosperity Bancshares, Inc. 2004 Stock Incentive Plan (the “2004 Plan”) which was approved by Bancshares’ shareholders and authorized the issuance of up to 1,250,000 shares of common stock upon the exercise of options granted under the 2004 Plan or upon the grant or exercise, as the case may be, of other awards granted under the 2004 Plan. The 2004 Plan provided for grants of incentive and nonqualified stock options to employees and nonqualified stock options to directors who are not employees. The 2004 Plan also provided for grants of shares of restricted stock, stock appreciation rights, phantom stock awards and performance awards on substantially similar terms. The 2004 Plan has expired and therefore no additional shares may be issued from the 2004 Plan. During 2012, Bancshares’ Board of Directors established the Prosperity Bancshares, Inc. 2012 Stock Incentive Plan (the “2012 Plan”), which was approved by Bancshares’ shareholders and authorized the issuance of up to 1,250,000 shares of common stock upon the exercise of options granted under the 2012 Plan or pursuant to the grant or exercise, as the case may be, of other awards granted under the 2012 Plan, including restricted stock, stock appreciation rights, phantom stock awards and performance awards. A total of 341,435 shares have been granted under the 2012 Plan as of March 31, 2017. The Company received $148 thousand from the exercise of stock options during the three-month period ended March 31, 2017. The Company received no cash from the exercise of stock options during the three-month period ended March 31, 2016. There was no tax benefit realized from option exercises of the stock-based payment arrangements during the three-month periods ended March 31, 2017 and 2016. As of March 31, 2017, there was $9.47 million of total unrecognized compensation expense related to stock-based compensation arrangements. That cost is expected to be recognized over a weighted average period of 1.31 years.

Contractual Obligations and Off

Contractual Obligations and Off-Balance Sheet Items	3 Months Ended
	Mar. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Contractual Obligations and Off-Balance Sheet Items	9. CONTRACTUAL OBLIGATIONS AND OFF-BALANCE SHEET ITEMS Contractual Obligations The following table summarizes the Company’s contractual obligations and other commitments to make future payments as of March 31, 2017 (other than deposit obligations and securities sold under repurchase agreements). The Company’s future cash payments associated with its contractual obligations pursuant to its FHLB notes payable and operating leases as of March 31, 2017 are summarized below. Payments for FHLB notes payable include interest of $596 thousand that will be paid over the future periods. Payments related to leases are based on actual payments specified in underlying contracts. 1 year or less More than 1 year but less than 3 years 3 years or more but less than 5 years 5 years or more Total (Dollars in thousands) Federal Home Loan Bank notes payable $ 1,265,871 $ 4,648 $ 523 $ 198 $ 1,271,240 Operating leases 5,185 7,495 3,887 3,837 20,404 Total $ 1,271,056 $ 12,143 $ 4,410 $ 4,035 $ 1,291,644 Off-Balance Sheet Items In the normal course of business, the Company enters into various transactions, which, in accordance with GAAP, are not included in its consolidated balance sheets. The Company enters into these transactions to meet the financing needs of its customers. These transactions include commitments to extend credit and standby letters of credit, which involve, to varying degrees, elements of credit risk and interest rate risk in excess of the amounts recognized in the consolidated balance sheets. The Company’s commitments associated with outstanding standby letters of credit and commitments to extend credit expiring by periods as of March 31, 2017 are summarized below. Since commitments associated with letters of credit and commitments to extend credit may expire unused, the amounts shown do not necessarily reflect the actual future cash funding requirements. 1 year or less More than 1 year but less than 3 years 3 years or more but less than 5 years 5 years or more Total (Dollars in thousands) Standby letters of credit $ 55,466 $ 21,513 $ 544 $ — $ 77,523 Commitments to extend credit 993,282 333,635 166,589 586,811 2,080,317 Total $ 1,048,748 $ 355,148 $ 167,133 $ 586,811 $ 2,157,840

Other Comprehensive Income

Other Comprehensive Income	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Other Comprehensive Income	10. OTHER COMPREHENSIVE INCOME The tax effects allocated to each component of other comprehensive income were as follows: Three Months Ended March 31, 2017 2016 Before Tax Amount Tax Effect Net of Tax Amount Before Tax Amount Tax Effect Net of Tax Amount (Dollars in thousands) Other comprehensive income: Securities available for sale: Change in unrealized gain during period $ 29 $ (10 ) $ 19 $ 148 $ (52 ) $ 96 Total securities available for sale 29 (10 ) 19 148 (52 ) 96 Total other comprehensive income $ 29 $ (10 ) $ 19 $ 148 $ (52 ) $ 96 Activity in accumulated other comprehensive income associated with securities available for sale, net of tax, was as follows: Securities Available for Sale Accumulated Other Comprehensive Income (Dollars in thousands) Balance at January 1, 2017 $ 1,411 $ 1,411 Other comprehensive income 19 19 Balance at March 31, 2017 $ 1,430 $ 1,430 Balance at January 1, 2016 $ 2,040 $ 2,040 Other comprehensive income 96 96 Balance at March 31, 2016 $ 2,136 $ 2,136

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2017
Business Combinations [Abstract]
Acquisitions	11. ACQUISITIONS Acquisition of Tradition Bancshares, Inc. — On January 1, 2016, the Company completed the acquisition of Tradition and its wholly-owned subsidiary Tradition Bank, headquartered in Houston, Texas. Tradition Bank operated 7 banking offices in the Houston, Texas area, including its main office in Bellaire, 3 banking centers in Katy and 1 banking center in The Woodlands. The acquisition was not considered significant to the Company’s financial statements and therefore pro forma financial data and related disclosures are not included. Under the terms of the definitive agreement, Bancshares issued 679,528 shares of its common stock plus $39.0 million in cash for all outstanding shares of Tradition capital stock, for total merger consideration of $71.5 million, based on Bancshares’ closing stock price of $47.86 on December 31, 2015. As of March 31, 2017, total goodwill related to the Tradition acquisition was $32.0 million. Goodwill is calculated as the excess of both the consideration exchanged and liabilities assumed as compared to the fair value of identifiable assets acquired, none of which is expected to be deductible for tax purposes. Additionally, the Company recognized $5.6 million of core deposit intangibles during 2016.

New Accounting Standards (Polic

New Accounting Standards (Policies)	3 Months Ended
	Mar. 31, 2017
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
Accounting Standards Updates (“ASU”)	Accounting Standards Updates (“ASU”) ASU 2017-08, “Receivables—Nonrefundable Fees and Other Costs (Subtopic 310-20).” ASU 2017-08 shortens the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. ASU 2017-08 will be effective for the Company on January 1, 2019 on a modified retrospective basis with a cumulative-effect adjustment as of the beginning of the period of adoption. The Company is currently evaluating the potential impact of ASU 2017-08 on the Company’s financial statements. ASU 2017-04, “Intangibles—Goodwill and Other (Topic 350).” ASU 2017-04 simplifies the subsequent measurement of goodwill by eliminating the second step of the goodwill impairment test, which required computing the implied fair value of goodwill. Under the amendments in this update, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An impairment charge should be recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. ASU 2017-04 will be effective for the Company on January 1, 2020 and is not expected to have a significant impact on the Company’s financial statements. ASU 2017-01, “Business Combinations (Topic 805).” ASU 2017-01 is intended to clarify or correct unintended application of ASU 2014-09 “Revenue from Contracts with Customers (Topic 606).” ASU 2017-01 clarifies 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. Additionally, the amendments in this update provide a more robust framework to assist entities in evaluating whether a set of assets and activities constitutes a business. Lastly, the amendments in this update narrow the definition of the term output so that the term is consistent with how outputs are described in Topic 606. ASU 2017-01 will be effective for the Company on January 1, 2018 and is not expected to have a significant impact on the Company’s financial statements. ASU 2016-18, “Statement of Cash Flows (Topic 230) – Restricted Cash.” ASU 2016-18 requires the Statement of Cash Flows to explain the change during the period in the total of cash, cash equivalents and amounts generally described as restricted cash or restricted cash equivalents. Therefore, restricted cash or cash equivalents should be included with cash and cash equivalents when recording the beginning-of-period and end-of-period total amounts on the Statement of Cash Flows. ASU 2016-18 will be effective for the Company on January 1, 2018 and is not expected to have a significant impact on the Company’s financial statements. ASU 2016-15, ASU 2016-15 addresses certain cash receipts and cash payments with the objective of reducing the existing diversity in practice. ASU 2016‑15 will be effective for the Company on January 1, 2018 and is not expected to have a significant impact on the Company's financial statements. ASU 2016-13, “Financial Instruments – Credit Losses (Topic 326)—Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires a financial asset (or a group of financial assets) measured at amortized cost basis to be presented at the net amount expected to be collected. The measurement of expected credit losses is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. An entity must use judgment in determining the relevant information and estimation methods that are appropriate in its circumstances. Additionally, available for sale debt securities may realize value either through collection of contractual cash flows or through sale of the security at fair value. Therefore, the amendments limit the amount of the allowance for credit losses to the difference between amortized cost and fair value. ASU 2016-13 will be effective for the Company as of January 1, 2020. The Company is currently evaluating the potential impact of ASU 2016-13 on the Company’s financial statements. ASU 2016-12, “Revenue from Contracts with Customers (Topic 606)—Narrow-Scope Improvements and Practical Expedients.” ASU 2016-12 addresses narrow-scope improvements to the guidance on collectability, noncash consideration and completed contracts at transition. Additionally, the amendments in this update provide a practical expedient for contract modifications at transition and an accounting policy election related to the presentation of sales taxes and other similar taxes collected from customers. The amendments in this update affect the guidance in , which is effective January 1, 2018. The Company is in the process of evaluating the impact of this guidance and does not currently anticipate a significant impact on the Company’s financial statements. ASU 2016-10, “Revenue from Contracts with Customers (Topic 606)—Identifying Performance Obligations and Licensing.” ASU 2016-10 clarifies two aspects of ” (i) identifying performance obligations and (ii) the licensing implementation guidance. This ASU adds guidance on how to identify the promised goods or services in the contract and how to evaluate whether promised goods and services are distinct. Additionally, this update includes guidance on determining whether an entity’s promise to grant a license provides a customer with either a right to use the entity’s intellectual property (which is satisfied at a point in time) or a right to access the entity’s intellectual property (which is satisfied over time) and when to recognize revenue for a sales-based or use-based royalty promised in exchange for a license of intellectual property. The amendments in this update affect the guidance in ,” which is effective January 1, 2018. The Company is in the process of evaluating the impact of this guidance and does not currently anticipate a significant impact on the Company’s financial statements. ASU 2016-09, “Compensation - Stock Compensation (Topic 718) — Improvements to Employee Share-Based Payment Accounting.” ASU 2016-09 simplifies the accounting for share-based awards paid to employees. The amended guidance 1) requires excess tax benefits and tax deficiencies on share-based awards payments to employees to be recognized directly to income tax expense or benefit in the Consolidated Statement of Income rather than to capital surplus; 2) requires excess tax benefits to be included as operating activities on the Consolidated Statements of Cash Flows; 3) provides entities with the option of making an accounting policy election to account for forfeitures of share-based payments as they occur instead of estimating the awards expected to be forfeited; and 4) changes the threshold to qualify for equity classification to permit withholdings up to the maximum statutory tax rate in the applicable jurisdiction. In addition, excess tax benefits and tax deficiencies are considered discrete items in the reporting period they occur and are not included in the estimate of an entity’s annual effective tax rate. The Company adopted ASU 2016-09 on January 1, 2017 and elected to recognize forfeitures as they occur. Implementation of ASU 2016-09 will add volatility to tax expense as the Company’s stock price changes. The adoption of ASU 2016-09 did not have a significant impact on the Company’s financial statements. ASU 2016-08, “Revenue from Contracts with Customers (Topic 606)—Principal versus Agent Considerations (Reporting Revenue Gross versus Net).” ASU 2014-09, “Revenue from Contracts with Customers (Topic 606) ASU 2016-02, "Leases (Topic 842)." ASU 2016-02 requires that lessees and lessors recognize lease assets and lease liabilities on the balance sheet and disclose key information about leasing arrangements. ASU 2016-02 is effective for public companies for annual periods beginning January 1, 2019, including interim periods within those fiscal years. The Company is currently evaluating the potential impact of ASU 2016-02 on the Company’s financial statements. ASU 2016-01, “Financial Instruments—Overall (Subtopic 825-10) — Recognition and Measurement of Financial Assets and Financial Liabilities.” ASU 2016-01 addresses certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. ASU 2016-01 1) requires equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) 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 to disclose the fair value of financial instruments measured at amortized cost for entities that are not public business entities; 4) eliminates the requirement for public business entities to disclose the method(s) 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; 5) requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; 6) requires an entity to present separately in other comprehensive income 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; 7) requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset (that is, securities or loans and receivables) on the balance sheet or the accompanying notes to the financial statements; and 8) clarifies that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity’s other deferred tax assets. The amendments in this update affect all entities that hold financial assets or owe financial liabilities. ASU 2016-01 is effective for the Company beginning January 1, 2018, and is not expected to have a significant impact on the Company’s financial statements. ASU 2014-09, “Revenue from Contracts with Customers (Topic 606).” ASU 2014-09 supersedes the revenue recognition requirements in Revenue Recognition (Topic 605), and most industry-specific guidance throughout the Industry Topics of the Codification. Additionally, ASU 2014-09 supersedes some cost guidance included in Revenue Recognition—Construction-Type and Production-Type Contracts (Subtopic 605-35). In addition, the existing requirements for the recognition of a gain or loss on the transfer of nonfinancial assets that are not in a contract with a customer are amended to be consistent with the guidance on recognition and measurement. The core principle of ASU 2014-09 is 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. The Company will adopt ASU 2014-09, effective January 1, 2018, using the modified retrospective application with a cumulative-effect adjustment, if such adjustment is significant. The Company continues to evaluate the requirements of ASU 2014-09, but it is not expected to have a significant impact on the Company’s financial statements.

Income Per Common Share (Tables

Income Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table illustrates the computation of basic and diluted earnings per share: Three Months Ended March 31, 2017 2016 Amount Per Share Amount Amount Per Share Amount (Amounts in thousands, except per share data) Net income $ 68,565 $ 68,951 Basic: Weighted average shares outstanding 69,480 $ 0.99 70,174 $ 0.98 Diluted: Add incremental shares for: Effect of dilutive securities - options 2 7 Total 69,482 $ 0.99 70,181 $ 0.98

Securities (Tables)

Securities (Tables)	3 Months Ended
	Mar. 31, 2017
Investments Debt And Equity Securities [Abstract]
Schedule of Amortized Cost and Fair Value of Investment Securities	The amortized cost and fair value of investment securities were as follows: March 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) Available for Sale States and political subdivisions $ 1,815 $ 5 $ — $ 1,820 Collateralized mortgage obligations 115,235 648 (87 ) 115,796 Mortgage-backed securities 77,588 1,853 (153 ) 79,288 Other securities 12,588 22 (87 ) 12,523 Total $ 207,226 $ 2,528 $ (327 ) $ 209,427 Held to Maturity U.S. Treasury securities and obligations of U.S. Government agencies $ 33,561 $ 493 $ (3 ) $ 34,051 States and political subdivisions 363,139 4,268 (299 ) 367,108 Collateralized mortgage obligations 799 5 (3 ) 801 Mortgage-backed securities 9,247,094 31,618 (163,008 ) 9,115,704 Other securities 100 — — 100 Total $ 9,644,693 $ 36,384 $ (163,313 ) $ 9,517,764 December 31, 2016 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) Available for Sale States and political subdivisions $ 1,915 $ 5 $ — $ 1,920 Collateralized mortgage obligations 120,478 240 (119 ) 120,599 Mortgage-backed securities 84,024 2,004 (165 ) 85,863 Other securities 12,588 252 (46 ) 12,794 Total $ 219,005 $ 2,501 $ (330 ) $ 221,176 Held to Maturity U.S. Treasury securities and obligations of U.S. Government agencies $ 33,523 $ 497 $ — $ 34,020 States and political subdivisions 384,015 3,934 (1,328 ) 386,621 Collateralized mortgage obligations 850 6 (5 ) 851 Mortgage-backed securities 9,086,422 30,880 (199,439 ) 8,917,863 Other securities 100 — — 100 Total $ 9,504,910 $ 35,317 $ (200,772 ) $ 9,339,455
Securities in Continuous Loss Position	Securities with unrealized losses, segregated by length of time, that have been in a continuous loss position were as follows: March 31, 2017 Less than 12 Months More than 12 Months Total Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses (Dollars in thousands) Available for Sale Collateralized mortgage obligations $ 5,865 $ (76 ) $ 1,413 $ (11 ) $ 7,278 $ (87 ) Mortgage-backed securities 42,178 (148 ) 2,285 (5 ) 44,463 (153 ) Other securities — — 1,649 (87 ) 1,649 (87 ) Total $ 48,043 $ (224 ) $ 5,347 $ (103 ) $ 53,390 $ (327 ) Held to Maturity U.S. Treasury securities and obligations of U.S. Government agencies $ 1,500 $ (3 ) $ — $ — $ 1,500 $ (3 ) States and political subdivisions 82,411 (262 ) 4,860 (37 ) 87,271 (299 ) Collateralized mortgage obligations 120 (2 ) 43 (1 ) 163 (3 ) Mortgage-backed securities 7,026,944 (159,742 ) 84,893 (3,266 ) 7,111,837 (163,008 ) Total $ 7,110,975 $ (160,009 ) $ 89,796 $ (3,304 ) $ 7,200,771 $ (163,313 ) December 31, 2016 Less than 12 Months More than 12 Months Total Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses Estimated Fair Value Unrealized Losses (Dollars in thousands) Available for Sale Collateralized mortgage obligations $ 10,723 $ (119 ) $ — $ — $ 10,723 $ (119 ) Mortgage-backed securities 45,456 (160 ) 2,334 (5 ) 47,790 (165 ) Other securities — — 1,691 (46 ) 1,691 (46 ) Total $ 56,179 $ (279 ) $ 4,025 $ (51 ) $ 60,204 $ (330 ) Held to Maturity U.S. Treasury securities and obligations of U.S. Government agencies $ — $ — $ — $ — $ — $ — States and political subdivisions 115,132 (1,288 ) 5,080 (40 ) 120,212 (1,328 ) Collateralized mortgage obligations 589 (4 ) 44 (1 ) 633 (5 ) Mortgage-backed securities 6,903,919 (195,556 ) 90,293 (3,883 ) 6,994,212 (199,439 ) Total $ 7,019,640 $ (196,848 ) $ 95,417 $ (3,924 ) $ 7,115,057 $ (200,772 )
Investment Securities by Contractual Maturity	The amortized cost and fair value of investment securities at March 31, 2017, by contractual maturity, are shown below. Actual maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations at any time with or without call or prepayment penalties. Held to Maturity Available for Sale Amortized Cost Fair Value Amortized Cost Fair Value (Dollars in thousands) Due in one year or less $ 32,844 $ 32,887 $ 12,588 $ 12,523 Due after one year through five years 184,021 185,335 1,815 1,820 Due after five years through ten years 158,481 161,282 — — Due after ten years 21,454 21,755 — — Subtotal 396,800 401,259 14,403 14,343 Mortgage-backed securities and collateralized mortgage obligations 9,247,893 9,116,505 192,823 195,084 Total $ 9,644,693 $ 9,517,764 $ 207,226 $ 209,427

Loans and Allowance for Credi23

Loans and Allowance for Credit Losses (Tables)	3 Months Ended
	Mar. 31, 2017
Receivables [Abstract]
Types of Loans in Loan Portfolio	The loan portfolio consists of various types of loans and is categorized by major type as follows: March 31, 2017 December 31, 2016 (Dollars in thousands) Residential mortgage loans held for sale $ 21,896 $ 26,975 Commercial and industrial 1,554,661 1,539,439 Real estate: Construction, land development and other land loans 1,326,685 1,263,923 1-4 family residential (includes home equity) 2,683,935 2,690,856 Commercial real estate (includes multi-family residential) 3,226,978 3,162,109 Farmland 493,606 484,588 Agriculture 169,191 187,748 Consumer and other 262,301 266,422 Total loans held for investment 9,717,357 9,595,085 Total $ 9,739,253 $ 9,622,060
Related Party Loans	An analysis of activity with respect to these related party loans is as follows: As of and for the three months ended March 31, 2017 As of and for the year ended December (Dollars in thousands) Beginning balance on January 1 $ 4,493 $ 4,063 New loans — 699 Repayments and reclassified related loans (358 ) (269 ) Ending balance $ 4,135 $ 4,493
Aging Analysis of Past Due Loans	An aging analysis of past due loans, segregated by category of loan, is presented below: March 31, 2017 Loans Past Due and Still Accruing 30-89 Days 90 or More Days Total Past Due Loans Nonaccrual Loans Current Loans Total Loans (Dollars in thousands) Construction, land development and other land loans $ 11,658 $ — $ 11,658 $ 283 $ 1,314,744 $ 1,326,685 Agriculture and agriculture real estate (includes farmland) 1,559 — 1,559 534 660,704 662,797 1-4 family (includes home equity) (1) 4,600 495 5,095 3,192 2,697,544 2,705,831 Commercial real estate (includes multi-family residential) 15,100 384 15,484 2,084 3,209,410 3,226,978 Commercial and industrial 14,587 — 14,587 18,128 1,521,946 1,554,661 Consumer and other 1,198 1 1,199 139 260,963 262,301 Total $ 48,702 $ 880 $ 49,582 $ 24,360 $ 9,665,311 $ 9,739,253 December 31, 2016 Loans Past Due and Still Accruing 30-89 Days 90 or More Days Total Past Due Loans Nonaccrual Loans Current Loans Total Loans (Dollars in thousands) Construction, land development and other land loans $ 8,766 $ 514 $ 9,280 $ 73 $ 1,254,570 $ 1,263,923 Agriculture and agriculture real estate (includes farmland) 1,813 381 2,194 161 669,981 672,336 1-4 family (includes home equity) (1) 8,645 53 8,698 3,726 2,705,407 2,717,831 Commercial real estate (includes multi-family residential) 4,250 — 4,250 3,528 3,154,331 3,162,109 Commercial and industrial 8,290 8 8,298 23,999 1,507,142 1,539,439 Consumer and other 886 — 886 155 265,381 266,422 Total $ 32,650 $ 956 $ 33,606 $ 31,642 $ 9,556,812 $ 9,622,060 (1) Includes $21.9 million and $27.0 million of residential mortgage loans held for sale at March 31, 2017 and December 31, 2016, respectively.
Non-performing Assets	The following table presents information regarding nonperforming assets as of the dates indicated: March 31, 2017 December 31, 2016 (Dollars in thousands) Nonaccrual loans (1) $ 24,360 $ 31,642 Accruing loans 90 or more days past due 880 956 Total nonperforming loans 25,240 32,598 Repossessed assets 261 241 Other real estate 15,698 15,463 Total nonperforming assets $ 41,199 $ 48,302 Nonperforming assets to total loans and other real estate 0.42 % 0.50 % (1) Includes troubled debt restructurings of $8.7 million and $97 thousand as of March 31, 2017 and December 31, 2016, respectively.
Carrying Amount of PCI Loans and Related Outstanding Balance	The carrying amount of PCI loans included in the consolidated balance sheet and the related outstanding balance as of the dates indicated are presented in the table below. The outstanding balance represents the total amount owed as of March 31, 2017 and December 31, 2016. March 31, 2017 December 31, 2016 (Dollars in thousands) PCI loans: Outstanding balance $ 48,438 $ 51,640 Less: discount 22,395 24,007 Recorded investment $ 26,043 $ 27,633
Changes in Accretable Yield for Acquired PCI Loans	Changes in the accretable yield for acquired PCI loans for the three months ended March 31, 2017 and 2016 were as follows: Three Months Ended March 31, 2017 2016 (Dollars in thousands) Balance at beginning of period $ 9,778 $ 5,664 Additions — 10,222 Reclassifications from nonaccretable 968 5,120 Accretion (1,483 ) (7,831 ) Balance at March 31 $ 9,263 $ 13,175
Carrying Amount of Non-PCI Loans and Related Outstanding Balance	The carrying amount of Non-PCI loans included in the consolidated balance sheet and the related outstanding balance as of the dates indicated are presented in the table below. The outstanding balance represents the total amount owed as of March 31, 2017 and December 31, 2016, including accrued but unpaid interest. March 31, 2017 December 31, 2016 (Dollars in thousands) Non-PCI loans: Outstanding balance $ 997,980 $ 1,115,061 Less: discount 32,129 35,401 Recorded investment $ 965,851 $ 1,079,660
Changes in Discount Accretion for Non-PCI Loans	Changes in the discount accretion for Non-PCI loans for the three months ended March 31, 2017 and 2016 were as follows: Three Months Ended March 31, 2017 2016 (Dollars in thousands) Balance at beginning of period $ 35,401 $ 54,734 Additions — 3,491 Accretion charge-offs (2 ) (1,053 ) Accretion (3,270 ) (6,663 ) Balance at March 31 $ 32,129 $ 50,509
Summary of Impaired Loans	Impaired loans are set forth in the following tables. No interest income was recognized on impaired loans subsequent to their classification as impaired. The average recorded investment presented in the tables below is reported on a year-to-date basis. March 31, 2017 Recorded Investment Unpaid Contractual Principal Balance Related Allowance Average Recorded Investment (Dollars in thousands) With no related allowance recorded: Construction, land development and other land loans $ 231 $ 239 $ — $ 123 Agriculture and agriculture real estate (includes farmland) 385 390 — 196 1-4 family (includes home equity) 2,788 3,029 — 2,619 Commercial real estate (includes multi-family residential) 2,043 2,078 — 2,614 Commercial and industrial 12,884 13,374 — 10,904 Consumer and other 108 168 — 113 Total 18,439 19,278 — 16,569 With an allowance recorded: Construction, land development and other land loans — — — — Agriculture and agriculture real estate (includes farmland) 149 180 10 151 1-4 family (includes home equity) 380 393 113 408 Commercial real estate (includes multi-family residential) — — — 144 Commercial and industrial 3,782 4,129 1,203 8,555 Consumer and other 31 38 1 18 Total 4,342 4,740 1,327 9,276 Total: Construction, land development and other land loans 231 239 — 123 Agriculture and agriculture real estate (includes farmland) 534 570 10 347 1-4 family (includes home equity) 3,168 3,422 113 3,027 Commercial real estate (includes multi-family residential) 2,043 2,078 — 2,758 Commercial and industrial 16,666 17,503 1,203 19,459 Consumer and other 139 206 1 131 $ 22,781 $ 24,018 $ 1,327 $ 25,845 December 31, 2016 Recorded Investment Unpaid Contractual Principal Balance Related Allowance Average Recorded Investment (Dollars in thousands) With no related allowance recorded: Construction, land development and other land loans $ 14 $ 220 $ — $ 24 Agriculture and agriculture real estate (includes farmland) 7 12 — 14 1-4 family (includes home equity) 2,450 2,682 — 1,828 Commercial real estate (includes multi-family residential) 3,184 3,327 — 9,150 Commercial and industrial 8,925 9,446 — 5,139 Consumer and other 119 157 — 88 Total 14,699 15,844 — 16,243 With an allowance recorded: Construction, land development and other land loans — — — 3 Agriculture and agriculture real estate (includes farmland) 154 181 17 171 1-4 family (includes home equity) 437 449 150 408 Commercial real estate (includes multi-family residential) 288 288 178 275 Commercial and industrial 13,327 13,821 2,851 13,961 Consumer and other 4 4 1 93 Total 14,210 14,743 3,197 14,911 Total: Construction, land development and other land loans 14 220 — 27 Agriculture and agriculture real estate (includes farmland) 161 193 17 185 1-4 family (includes home equity) 2,887 3,131 150 2,236 Commercial real estate (includes multi-family residential) 3,472 3,615 178 9,425 Commercial and industrial 22,252 23,267 2,851 19,100 Consumer and other 123 161 1 181 $ 28,909 $ 30,587 $ 3,197 $ 31,154
Risk Grades and PCI Loans by Category of Loan	The following table presents risk grades and PCI loans by category of loan at March 31, 2017. Impaired loans include loans in risk grades 7, 8 and 9, as well as any PCI loan that has a specific reserve allocated to it. Construction, Land Development and Other Agriculture and Agriculture Real Estate (includes Farmland) 1-4 Family (includes Home (1) Commercial Real Estate (includes Multi-Family Commercial and Industrial Consumer and Other Total (Dollars in thousands) Grade 1 $ — $ 13,972 $ — $ — $ 56,049 $ 40,907 $ 110,928 Grade 2 2,682 4,074 22,447 8,332 11,695 27,225 76,455 Grade 3 1,241,209 562,415 2,607,696 2,898,086 1,181,197 178,333 8,668,936 Grade 4 75,654 71,851 59,543 242,316 187,836 10,670 647,870 Grade 5 4,445 9,118 4,001 45,312 47,030 3,203 113,109 Grade 6 1,092 445 4,137 14,765 50,868 1,824 73,131 Grade 7 231 534 3,140 2,042 15,984 139 22,070 Grade 8 — — 29 — 682 — 711 Grade 9 — — — — — — — PCI Loans (2) 1,372 388 4,838 16,125 3,320 — 26,043 Total $ 1,326,685 $ 662,797 $ 2,705,831 $ 3,226,978 $ 1,554,661 $ 262,301 $ 9,739,253 (1) Includes $21.9 million of residential mortgage loans held for sale at March 31, 2017. (2) Of the total PCI loans, $1.6 million were classified as substandard at March 31, 2017, with no specific reserves allocated to them. The following table presents risk grades and PCI loans by category of loan at December 31, 2016. Impaired loans include loans in risk grades 7, 8 and 9, as well as any PCI loan that has a specific reserve allocated to it. Construction, Land Development and Other Agriculture and Agriculture Real Estate (includes Farmland) 1-4 Family (includes Home (1) Commercial Real Estate (includes Multi-Family Commercial and Industrial Consumer and Other Total (Dollars in thousands) Grade 1 $ — $ 14,616 $ — $ — $ 54,908 $ 40,688 $ 110,212 Grade 2 2,261 4,218 22,863 8,317 12,772 11,041 61,472 Grade 3 1,200,623 570,324 2,622,304 2,859,433 1,143,634 194,210 8,590,528 Grade 4 54,380 74,079 55,367 220,533 176,287 16,095 596,741 Grade 5 2,525 7,703 3,605 45,533 57,283 2,403 119,052 Grade 6 2,690 847 5,095 8,401 68,682 1,829 87,544 Grade 7 13 161 2,857 3,472 21,475 156 28,134 Grade 8 — — 30 — 714 — 744 Grade 9 — — — — — — — PCI Loans (2) 1,431 388 5,710 16,420 3,684 — 27,633 Total $ 1,263,923 $ 672,336 $ 2,717,831 $ 3,162,109 $ 1,539,439 $ 266,422 $ 9,622,060 (1) Includes $27.0 million of residential mortgage loans held for sale at December 31, 2016. (2) Of the total PCI loans, $2.7 million were classified as substandard at December 31, 2016, which includes $31 thousand with specific reserves allocated to them.
Allowance for Credit Losses by Category of Loan	The following table details activity in the allowance for credit losses by category of loan for the three months ended March 31, 2017 and 2016. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. Construction, Land Development and Other Land Loans Agriculture and Agriculture Real Estate (includes Farmland) 1-4 Family (includes Home Equity) Commercial Real Estate (includes Multi-Family Residential) Commercial and Industrial Consumer and Other Total (Dollars in thousands) Allowance for credit losses: Three Months Ended Balance $ 14,984 $ 4,073 $ 16,571 $ 12,256 $ 35,836 $ 1,606 $ 85,326 Provision for credit losses (386 ) (554 ) (895 ) (1,148 ) 5,341 317 2,675 Charge-offs — — (13 ) (133 ) (3,638 ) (824 ) (4,608 ) Recoveries 65 65 108 — 143 321 702 Net charge-offs 65 65 95 (133 ) (3,495 ) (503 ) (3,906 ) Balance $ 14,663 $ 3,584 $ 15,771 $ 10,975 $ 37,682 $ 1,420 $ 84,095 Allowance for credit losses: Three Months Ended Balance $ 14,882 $ 3,845 $ 14,891 $ 12,996 $ 33,409 $ 1,361 $ 81,384 Provision for credit losses (703 ) 6,689 (297 ) (546 ) 8,150 707 14,000 Charge-offs (7 ) (7,025 ) (49 ) (59 ) (6,277 ) (848 ) (14,265 ) Recoveries 193 63 19 — 1,881 439 2,595 Net charge-offs 186 (6,962 ) (30 ) (59 ) (4,396 ) (409 ) (11,670 ) Balance $ 14,365 $ 3,572 $ 14,564 $ 12,391 $ 37,163 $ 1,659 $ 83,714 The following table details the amount of the allowance for credit losses allocated to each category of loan as of March 31, 2017, December 31, 2016 and March 31, 2016, on the basis of the impairment methodology used by the Company. Construction, Land Development and Other Land Loans Agriculture and Agriculture Real Estate (includes Farmland) 1-4 Family (includes Home Equity) Commercial Real Estate (includes Multi-Family Residential) Commercial and Industrial Consumer and Other Total (Dollars in thousands) Allowance for credit losses related March 31, 2017 Individually evaluated for impairment $ — $ 10 $ 113 $ — $ 1,203 $ 1 $ 1,327 Collectively evaluated for impairment 14,663 3,574 15,658 10,975 36,479 1,419 82,768 PCI loans — — — — — — — Total allowance for credit losses $ 14,663 $ 3,584 $ 15,771 $ 10,975 $ 37,682 $ 1,420 $ 84,095 December 31, 2016 Individually evaluated for impairment $ — $ 17 $ 150 $ 178 $ 2,820 $ 1 $ 3,166 Collectively evaluated for impairment 14,984 4,056 16,421 12,078 32,985 1,605 82,129 PCI loans — — — — 31 — 31 Total allowance for credit losses $ 14,984 $ 4,073 $ 16,571 $ 12,256 $ 35,836 $ 1,606 $ 85,326 March 31, 2016 Individually evaluated for impairment $ 2 $ 37 $ 91 $ — $ 7,464 $ 27 $ 7,621 Collectively evaluated for impairment 14,363 3,535 14,473 12,391 28,531 1,632 74,925 PCI loans — — — — 1,168 — 1,168 Total allowance for credit losses $ 14,365 $ 3,572 $ 14,564 $ 12,391 $ 37,163 $ 1,659 $ 83,714 The following table details the recorded investment in loans as of March 31, 2017, December 31, 2016 and March 31, 2016, excluding $21.9 million, $27.0 million and $23.7 million, respectively, of residential mortgage loans held for sale, related to each balance in the allowance for credit losses by category of loan. Construction, Land Development and Other Land Loans Agriculture and Agriculture Real Estate (includes Farmland) 1-4 Family (includes Home Equity) Commercial Real Estate (includes Multi-Family Residential) Commercial and Industrial Consumer and Other Total (Dollars in thousands) Recorded investment in March 31, 2017 Individually evaluated for impairment $ 231 $ 534 $ 3,168 $ 2,043 $ 16,666 $ 139 $ 22,781 Collectively evaluated for impairment 1,325,082 661,875 2,675,929 3,208,810 1,534,675 262,162 9,668,533 PCI loans 1,372 388 4,838 16,125 3,320 — 26,043 Total loans evaluated for impairment $ 1,326,685 $ 662,797 $ 2,683,935 $ 3,226,978 $ 1,554,661 $ 262,301 $ 9,717,357 December 31, 2016 Individually evaluated for impairment $ 14 $ 161 $ 2,887 $ 3,472 $ 22,221 $ 123 $ 28,878 Collectively evaluated for impairment 1,262,478 671,787 2,682,259 3,142,217 1,513,534 266,299 9,538,574 PCI loans 1,431 388 5,710 16,420 3,684 — 27,633 Total loans evaluated for impairment $ 1,263,923 $ 672,336 $ 2,690,856 $ 3,162,109 $ 1,539,439 $ 266,422 $ 9,595,085 March 31, 2016 Individually evaluated for impairment $ 25 $ 5,691 $ 2,379 $ 9,159 $ 18,441 $ 227 $ 35,922 Collectively evaluated for impairment 1,170,405 635,208 2,630,719 3,200,625 1,671,822 246,454 9,555,233 PCI loans 3,094 394 6,374 19,922 9,752 — 39,536 Total loans evaluated for impairment $ 1,173,524 $ 641,293 $ 2,639,472 $ 3,229,706 $ 1,700,015 $ 246,681 $ 9,630,691
Troubled Debt Restructurings	The following table presents information regarding the recorded investment of loans modified as troubled debt restructurings during the three months ended March 31, 2017 and 2016: Three Months Ended March 31, 2017 2016 Number of Loans Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Number of Loans Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment (Dollars in thousands) Troubled Debt Restructurings Construction, land development and other land loans — $ — $ — — $ — $ — Agriculture and agriculture real estate (includes farmland) — — — — — — 1-4 Family (includes home equity) — — — — — — Commercial real estate (includes multi-family residential) — — — — — — Commercial and industrial 3 8,656 8,650 — — — Consumer and other — — — — — — Total 3 $ 8,656 $ 8,650 — $ — $ —

Fair Value (Tables)

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Assets and Liabilities Measured on Recurring Basis	The following tables present fair values for assets and liabilities measured at fair value on a recurring basis: As of March 31, 2017 Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets: Available for sale securities: States and political subdivisions $ — $ 1,820 $ — $ 1,820 Collateralized mortgage obligations — 115,796 — 115,796 Mortgage-backed securities — 79,288 — 79,288 Other securities 12,523 — — 12,523 Total $ 12,523 $ 196,904 $ — $ 209,427 As of December 31, 2016 Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets: Available for sale securities: States and political subdivisions $ — $ 1,920 $ — $ 1,920 Collateralized mortgage obligations — 120,599 — 120,599 Mortgage-backed securities — 85,863 — 85,863 Other securities 12,794 — — 12,794 Total $ 12,794 $ 208,382 $ — $ 221,176
Financial Instruments Fair Value	The following table presents carrying and fair value information of financial instruments as of the dates indicated: As of March 31, 2017 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total Assets (Dollars in thousands) Cash and due from banks $ 324,797 $ 324,797 $ — $ — $ 324,797 Federal funds sold 945 945 — — 945 Held to maturity securities 9,644,693 — 9,517,764 — 9,517,764 Loans held for sale 21,896 — 21,896 — 21,896 Loans held for investment, net of allowance 9,633,262 — — 9,679,257 9,679,257 Other real estate owned 15,698 — 15,698 — 15,698 Liabilities Deposits: Noninterest-bearing $ 5,299,264 $ — $ 5,299,264 $ — $ 5,299,264 Interest-bearing 11,736,308 — 11,740,990 — 11,740,990 Other borrowings 1,270,644 — 1,271,004 — 1,271,004 Securities sold under repurchase agreements 335,875 — 335,864 — 335,864 As of December 31, 2016 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total Assets (Dollars in thousands) Cash and due from banks $ 436,203 $ 436,203 $ — $ — $ 436,203 Federal funds sold 1,178 1,178 — — 1,178 Held to maturity securities 9,504,910 — 9,339,455 — 9,339,455 Loans held for sale 26,975 — 26,975 — 26,975 Loans held for investment, net of allowance 9,509,759 — — 9,533,310 9,533,310 Other real estate owned 15,463 — 15,463 — 15,463 Liabilities Deposits: Noninterest-bearing $ 5,190,973 $ — $ 5,190,973 $ — $ 5,190,973 Interest-bearing 12,116,329 — 12,121,157 — 12,121,157 Other borrowings 990,781 — 991,181 — 991,181 Securities sold under repurchase agreements 320,430 — 320,428 — 320,428

Goodwill and Core Deposit Int25

Goodwill and Core Deposit Intangibles (Tables)	3 Months Ended
	Mar. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Core Deposit Intangibles	Changes in the carrying amount of the Company’s goodwill and core deposit intangibles for the three months ended March 31, 2017 and the year ended December 31, 2016 were as follows: Goodwill Core Deposit Intangibles (Dollars in thousands) Balance as of December 31, 2015 $ 1,868,827 $ 49,417 Less: Amortization — (9,200 ) Add: Acquisition of Tradition Bancshares, Inc. 32,018 5,567 Balance as of December 31, 2016 1,900,845 45,784 Less: Amortization — (1,915 ) Add: Measurement period adjustments — — Balance as of March 31, 2017 $ 1,900,845 $ 43,869
Estimated Aggregate Future Amortization Expense for Core Deposit Intangibles	The estimated aggregate future amortization expense for core deposit intangibles remaining as of March 31, 2017 is as follows (dollars in thousands): Remaining 2017 $ 5,027 2018 5,959 2019 5,051 2020 4,483 2021 4,022 Thereafter 19,327 Total $ 43,869

Contractual Obligations and O26

Contractual Obligations and Off-Balance Sheet Items (Tables)	3 Months Ended
	Mar. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Schedule of Contractual Obligations and Other Commitments	The following table summarizes the Company’s contractual obligations and other commitments to make future payments as of March 31, 2017 (other than deposit obligations and securities sold under repurchase agreements). The Company’s future cash payments associated with its contractual obligations pursuant to its FHLB notes payable and operating leases as of March 31, 2017 are summarized below. Payments for FHLB notes payable include interest of $596 thousand that will be paid over the future periods. Payments related to leases are based on actual payments specified in underlying contracts. 1 year or less More than 1 year but less than 3 years 3 years or more but less than 5 years 5 years or more Total (Dollars in thousands) Federal Home Loan Bank notes payable $ 1,265,871 $ 4,648 $ 523 $ 198 $ 1,271,240 Operating leases 5,185 7,495 3,887 3,837 20,404 Total $ 1,271,056 $ 12,143 $ 4,410 $ 4,035 $ 1,291,644
Summary of Commitments Associated with Outstanding Standby Letters of Credit and Commitments to Extend Credit	The Company’s commitments associated with outstanding standby letters of credit and commitments to extend credit expiring by periods as of March 31, 2017 are summarized below. Since commitments associated with letters of credit and commitments to extend credit may expire unused, the amounts shown do not necessarily reflect the actual future cash funding requirements. 1 year or less More than 1 year but less than 3 years 3 years or more but less than 5 years 5 years or more Total (Dollars in thousands) Standby letters of credit $ 55,466 $ 21,513 $ 544 $ — $ 77,523 Commitments to extend credit 993,282 333,635 166,589 586,811 2,080,317 Total $ 1,048,748 $ 355,148 $ 167,133 $ 586,811 $ 2,157,840

Other Comprehensive Income (Tab

Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Tax Effects Allocated to Each Component of Other Comprehensive Income	The tax effects allocated to each component of other comprehensive income were as follows: Three Months Ended March 31, 2017 2016 Before Tax Amount Tax Effect Net of Tax Amount Before Tax Amount Tax Effect Net of Tax Amount (Dollars in thousands) Other comprehensive income: Securities available for sale: Change in unrealized gain during period $ 29 $ (10 ) $ 19 $ 148 $ (52 ) $ 96 Total securities available for sale 29 (10 ) 19 148 (52 ) 96 Total other comprehensive income $ 29 $ (10 ) $ 19 $ 148 $ (52 ) $ 96
Activity in Accumulated Other Comprehensive Income Associated with Securities Available for Sale, Net of Tax	Activity in accumulated other comprehensive income associated with securities available for sale, net of tax, was as follows: Securities Available for Sale Accumulated Other Comprehensive Income (Dollars in thousands) Balance at January 1, 2017 $ 1,411 $ 1,411 Other comprehensive income 19 19 Balance at March 31, 2017 $ 1,430 $ 1,430 Balance at January 1, 2016 $ 2,040 $ 2,040 Other comprehensive income 96 96 Balance at March 31, 2016 $ 2,136 $ 2,136

Income Per Common Share - Sched

Income Per Common Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Net income	$ 68,565	$ 68,951
Weighted average shares outstanding (in shares)	69,480,000	70,174,000
Weighted average shares outstanding (in dollars per share)	$ 0.99	$ 0.98
Effect of dilutive securities - options (in shares)	2,000	7,000
Total (in shares)	69,482,000	70,181,000
Total (in dollars per share)	$ 0.99	$ 0.98

Income Per Common Share Additio

Income Per Common Share Additional Information (Details) - shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	0

Securities - Schedule of Amorti

Securities - Schedule of Amortized Cost and Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Available for Sale Securities, Amortized Cost Basis	$ 207,226	$ 219,005
Available for Sale, Gross Unrealized Gains	2,528	2,501
Available for Sale, Gross Unrealized Losses	(327)	(330)
Available for Sale Securities	209,427	221,176
Held to Maturity, amortized cost, total	9,644,693	9,504,910
Held to Maturity, Gross Unrealized Gains	36,384	35,317
Held to Maturity, Gross Unrealized Losses	(163,313)	(200,772)
Held to Maturity securities	9,517,764	9,339,455
US States and Political Subdivisions Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale Securities, Amortized Cost Basis	1,815	1,915
Available for Sale, Gross Unrealized Gains	5	5
Available for Sale Securities	1,820	1,920
Held to Maturity, amortized cost, total	363,139	384,015
Held to Maturity, Gross Unrealized Gains	4,268	3,934
Held to Maturity, Gross Unrealized Losses	(299)	(1,328)
Held to Maturity securities	367,108	386,621
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale Securities, Amortized Cost Basis	115,235	120,478
Available for Sale, Gross Unrealized Gains	648	240
Available for Sale, Gross Unrealized Losses	(87)	(119)
Available for Sale Securities	115,796	120,599
Held to Maturity, amortized cost, total	799	850
Held to Maturity, Gross Unrealized Gains	5	6
Held to Maturity, Gross Unrealized Losses	(3)	(5)
Held to Maturity securities	801	851
Collateralized Mortgage Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale Securities, Amortized Cost Basis	77,588	84,024
Available for Sale, Gross Unrealized Gains	1,853	2,004
Available for Sale, Gross Unrealized Losses	(153)	(165)
Available for Sale Securities	79,288	85,863
Held to Maturity, amortized cost, total	9,247,094	9,086,422
Held to Maturity, Gross Unrealized Gains	31,618	30,880
Held to Maturity, Gross Unrealized Losses	(163,008)	(199,439)
Held to Maturity securities	9,115,704	8,917,863
Other Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale Securities, Amortized Cost Basis	12,588	12,588
Available for Sale, Gross Unrealized Gains	22	252
Available for Sale, Gross Unrealized Losses	(87)	(46)
Available for Sale Securities	12,523	12,794
Held to Maturity, amortized cost, total	100	100
Held to Maturity securities	100	100
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Schedule Of Available For Sale Securities [Line Items]
Held to Maturity, amortized cost, total	33,561	33,523
Held to Maturity, Gross Unrealized Gains	493	497
Held to Maturity, Gross Unrealized Losses	(3)
Held to Maturity securities	$ 34,051	$ 34,020

Securities - Additional Informa

Securities - Additional Information (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017USD ($)SegmentSecurity	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)Security
Schedule Of Held To Maturity Securities [Line Items]
Gain (Loss) on Sale of Securities, Net	$ 0	$ 0
Available for Sale Securities, Amortized Cost Basis	207,226		$ 219,005
Available for sale securities, at fair value	$ 209,427		$ 221,176
Securities Concentration Risk [Member] | Stockholders' Equity, Total [Member]
Schedule Of Held To Maturity Securities [Line Items]
Concentration Risk, Percentage	10.00%		10.00%
Collateralized Securities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Number of Investment Securities Segments | Segment	2
Other than Temporary Impairment Losses, Investments	$ 0
Securities in Unrealized Loss Positions Qualitative Disclosure Number of Positions Greater Than or Equal to One Year | Security	254		276
Available for Sale Securities, Amortized Cost Basis	$ 5,260,000		$ 5,640,000
Available for sale securities, at fair value	$ 5,160,000		$ 5,510,000

Securities - Securities in Cont

Securities - Securities in Continuous Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Estimated Fair Value, Less than 12 Months	$ 48,043	$ 56,179
Available for Sale, Unrealized Losses, Less than 12 Months	(224)	(279)
Available for Sale, Estimated Fair Value, More than 12 Months	5,347	4,025
Available for Sale, Unrealized Losses, More than 12 Months	(103)	(51)
Available for Sale, Estimated Fair Value, Total	53,390	60,204
Available for Sale, Unrealized Losses, Total	(327)	(330)
Held to Maturity, Estimated Fair Value, Less than 12 Months	7,110,975	7,019,640
Held to Maturity, Unrealized Losses, Less than 12 Months	(160,009)	(196,848)
Held to Maturity, Estimated Fair Value, More than 12 Months	89,796	95,417
Held to Maturity, Unrealized Losses, More than 12 Months	(3,304)	(3,924)
Held to Maturity, Estimated Fair Value, Total	7,200,771	7,115,057
Held to Maturity, Unrealized Losses, Total	(163,313)	(200,772)
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Estimated Fair Value, Less than 12 Months	5,865	10,723
Available for Sale, Unrealized Losses, Less than 12 Months	(76)	(119)
Available for Sale, Estimated Fair Value, More than 12 Months	1,413
Available for Sale, Unrealized Losses, More than 12 Months	(11)
Available for Sale, Estimated Fair Value, Total	7,278	10,723
Available for Sale, Unrealized Losses, Total	(87)	(119)
Held to Maturity, Estimated Fair Value, Less than 12 Months	120	589
Held to Maturity, Unrealized Losses, Less than 12 Months	(2)	(4)
Held to Maturity, Estimated Fair Value, More than 12 Months	43	44
Held to Maturity, Unrealized Losses, More than 12 Months	(1)	(1)
Held to Maturity, Estimated Fair Value, Total	163	633
Held to Maturity, Unrealized Losses, Total	(3)	(5)
Collateralized Mortgage Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Estimated Fair Value, Less than 12 Months	42,178	45,456
Available for Sale, Unrealized Losses, Less than 12 Months	(148)	(160)
Available for Sale, Estimated Fair Value, More than 12 Months	2,285	2,334
Available for Sale, Unrealized Losses, More than 12 Months	(5)	(5)
Available for Sale, Estimated Fair Value, Total	44,463	47,790
Available for Sale, Unrealized Losses, Total	(153)	(165)
Held to Maturity, Estimated Fair Value, Less than 12 Months	7,026,944	6,903,919
Held to Maturity, Unrealized Losses, Less than 12 Months	(159,742)	(195,556)
Held to Maturity, Estimated Fair Value, More than 12 Months	84,893	90,293
Held to Maturity, Unrealized Losses, More than 12 Months	(3,266)	(3,883)
Held to Maturity, Estimated Fair Value, Total	7,111,837	6,994,212
Held to Maturity, Unrealized Losses, Total	(163,008)	(199,439)
Other Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Estimated Fair Value, More than 12 Months	1,649	1,691
Available for Sale, Unrealized Losses, More than 12 Months	(87)	(46)
Available for Sale, Estimated Fair Value, Total	1,649	1,691
Available for Sale, Unrealized Losses, Total	(87)	(46)
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Schedule Of Available For Sale Securities [Line Items]
Held to Maturity, Estimated Fair Value, Less than 12 Months	1,500
Held to Maturity, Unrealized Losses, Less than 12 Months	(3)
Held to Maturity, Estimated Fair Value, Total	1,500
Held to Maturity, Unrealized Losses, Total	(3)
US States and Political Subdivisions Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Held to Maturity, Estimated Fair Value, Less than 12 Months	82,411	115,132
Held to Maturity, Unrealized Losses, Less than 12 Months	(262)	(1,288)
Held to Maturity, Estimated Fair Value, More than 12 Months	4,860	5,080
Held to Maturity, Unrealized Losses, More than 12 Months	(37)	(40)
Held to Maturity, Estimated Fair Value, Total	87,271	120,212
Held to Maturity, Unrealized Losses, Total	$ (299)	$ (1,328)

Securities - Investment Securit

Securities - Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Investments Debt And Equity Securities [Abstract]
Held to Maturity, amortized cost, due in one year or less	$ 32,844
Held to Maturity, amortized cost, due after one year through five years	184,021
Held to Maturity, amortized cost, due after five years through ten years	158,481
Held to Maturity, amortized cost, due after ten years	21,454
Held to Maturity, amortized cost, subtotal	396,800
Held to Maturity, amortized cost, mortgage-backed securities and collateralized mortgage obligations	9,247,893
Held to Maturity, amortized cost, total	9,644,693	$ 9,504,910
Held to Maturity, fair value, due in one year or less	32,887
Held to Maturity, fair value, due after one year through five years	185,335
Held to Maturity, fair value, due after five years through ten years	161,282
Held to Maturity, fair value, due after ten years	21,755
Held to Maturity, fair value, subtotal	401,259
Held to Maturity, fair value, mortgage-backed securities and collateralized mortgage obligations	9,116,505
Held to Maturity, fair value, total	9,517,764	$ 9,339,455
Available for Sale, amortized cost, due in one year or less	12,588
Available for Sale, amortized cost, due after one year through five years	1,815
Available for Sale, amortized cost, subtotal	14,403
Available for Sale, amortized cost, mortgage-backed securities and collateralized mortgage obligations	192,823
Available for Sale, amortized cost, total	207,226
Available for Sale, fair value, due in one year or less	12,523
Available for Sale, fair value, due after one year through five years	1,820
Available for Sale, fair value, subtotal	14,343
Available for Sale, fair value, mortgage-backed securities and collateralized mortgage obligations	195,084
Available for Sale securities, at fair value	$ 209,427

Loans and Allowance for Credi34

Loans and Allowance for Credit Losses - Types of Loans in Loan Portfolio (Details) - USD ($) $ in Thousands		Mar. 31, 2017		Dec. 31, 2016		Mar. 31, 2016
Accounts Notes And Loans Receivable [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage		$ 21,896		$ 26,975
Total loans held for investment		9,717,357		9,595,085		$ 9,630,691
Total		9,739,253		9,622,060
Residential Portfolio Segment [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage		21,896		26,975
Commercial and Industrial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		1,554,661		1,539,439		1,700,015
Total		1,554,661		1,539,439
Construction, Land Development and Other Land Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		1,326,685		1,263,923		1,173,524
Total		1,326,685		1,263,923
1-4 Family Residential (Includes Home Equity) [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage		21,896		26,975		23,717
Total loans held for investment		2,683,935		2,690,856		2,639,472
Total	[1]	2,705,831	[2]	2,717,831	[3]
Commercial Real Estate (Includes Multi-Family Residential) [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		3,226,978		3,162,109		3,229,706
Total		3,226,978		3,162,109
Farmland [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		493,606		484,588
Agriculture [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		169,191		187,748
Consumer and Other [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		262,301		266,422		$ 246,681
Total		$ 262,301		$ 266,422
[1]	Includes $21.9 million and $27.0 million of residential mortgage loans held for sale at March 31, 2017 and December 31, 2016, respectively.
[2]	Includes $21.9 million of residential mortgage loans held for sale at March 31, 2017.
[3]	(1)Includes $27.0 million of residential mortgage loans held for sale at December 31, 2016.

Loans and Allowance for Credi35

Loans and Allowance for Credit Losses - Additional Information (Details)	3 Months Ended
	Mar. 31, 2017USD ($)contract	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Accounts Notes And Loans Receivable [Line Items]
Percentage of real estate loans aggregating to company loan portfolio	74.30%
Loans held for investment	$ 9,717,357,000	$ 9,630,691,000	$ 9,595,085,000
Financing Receivable Ratio of Non-performing Loans to All Loans and Other Real Estate	0.42%		0.50%
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	$ 1,100,000	3,200,000
Nonaccrual loans	$ 24,360,000		$ 31,642,000
Troubled debt restructurings, number of loans | contract	3
Troubled debt restructurings, pre-modification outstanding recorded investment	$ 8,656,000
Troubled Debt Restructuring [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	8,700	593,000
Nonperforming Financial Instruments [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	$ 41,199,000		48,302,000
Substandard [Member]
Accounts Notes And Loans Receivable [Line Items]
Percentage of Loans Related to Single Industry on Loans	10.00%
Loans and Leases Receivable, Related Parties	$ 4,135,000		4,493,000	$ 4,063,000
Minimum Period for Ceases Accruing Interest	90 days
Financing Receivable, Allowance for Credit Losses	$ 84,100,000		$ 85,300,000
Allowance for Credit Losses as Percentage of Loans	0.86%		0.89%
Loan to be Considered as Payment Default in Period	90 days
Troubled debt restructurings, number of loans | contract	3
Troubled debt restructurings, pre-modification outstanding recorded investment	$ 8,700,000	$ 0
Financing Receivable, Modifications, Recorded Investment	$ 8,700,000

Loans and Allowance for Credi36

Loans and Allowance for Credit Losses - Related Party Loans (Details) - Substandard [Member] - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Accounts Notes And Loans Receivable [Line Items]
Beginning balance on January 1	$ 4,493	$ 4,063
New loans		699
Repayments and reclassified related loans	(358)	(269)
Ending balance	$ 4,135	$ 4,493

Loans and Allowance for Credi37

Loans and Allowance for Credit Losses - Aging Analysis of Past Due Loans (Details) - USD ($) $ in Thousands		Mar. 31, 2017		Dec. 31, 2016
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		$ 49,582		$ 33,606
Nonaccrual loans		24,360		31,642
Current loans		9,665,311		9,556,812
Total loans		9,739,253		9,622,060
Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		48,702		32,650
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		880		956
Construction, Land Development and Other Land Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		11,658		9,280
Nonaccrual loans		283		73
Current loans		1,314,744		1,254,570
Total loans		1,326,685		1,263,923
Construction, Land Development and Other Land Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		11,658		8,766
Construction, Land Development and Other Land Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing				514
Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		1,559		2,194
Nonaccrual loans		534		161
Current loans		660,704		669,981
Total loans		662,797		672,336
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		1,559		1,813
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing				381
1-4 Family Residential (Includes Home Equity) [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing	[1]	5,095		8,698
Nonaccrual loans	[1]	3,192		3,726
Current loans	[1]	2,697,544		2,705,407
Total loans	[1]	2,705,831	[2]	2,717,831	[3]
1-4 Family Residential (Includes Home Equity) [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing	[1]	4,600		8,645
1-4 Family Residential (Includes Home Equity) [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing	[1]	495		53
Commercial Real Estate (Includes Multi-Family Residential) [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		15,484		4,250
Nonaccrual loans		2,084		3,528
Current loans		3,209,410		3,154,331
Total loans		3,226,978		3,162,109
Commercial Real Estate (Includes Multi-Family Residential) [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		15,100		4,250
Commercial Real Estate (Includes Multi-Family Residential) [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		384
Commercial and Industrial [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		14,587		8,298
Nonaccrual loans		18,128		23,999
Current loans		1,521,946		1,507,142
Total loans		1,554,661		1,539,439
Commercial and Industrial [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		14,587		8,290
Commercial and Industrial [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing				8
Consumer and Other [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		1,199		886
Nonaccrual loans		139		155
Current loans		260,963		265,381
Total loans		262,301		266,422
Consumer and Other [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		1,198		$ 886
Consumer and Other [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		$ 1
[1]	Includes $21.9 million and $27.0 million of residential mortgage loans held for sale at March 31, 2017 and December 31, 2016, respectively.
[2]	Includes $21.9 million of residential mortgage loans held for sale at March 31, 2017.
[3]	(1)Includes $27.0 million of residential mortgage loans held for sale at December 31, 2016.

Loans and Allowance for Credi38

Loans and Allowance for Credit Losses - Aging Analysis of Past Due Loans (Parenthetical) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Accounts Notes And Loans Receivable [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage	$ 21,896	$ 26,975
Residential Mortgage Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage	$ 21,896	$ 26,975

Loans and Allowance for Credi39

Loans and Allowance for Credit Losses - Nonperforming Assets (Details) - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 9,717,357	$ 9,595,085	$ 9,630,691
Nonperforming assets to total loans and other real estate		0.42%	0.50%
Nonperforming Financial Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 25,240	$ 32,598
Nonperforming Financial Loans [Member] | Finance Receivable Nonaccrual Status [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	[1]	24,360	31,642
Nonperforming Financial Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		880	956
Nonperforming Financial Instruments [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		41,199	48,302
Nonperforming Financial Instruments [Member] | Repossessed Assets [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		261	241
Nonperforming Financial Instruments [Member] | Other Real Assets [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 15,698	$ 15,463
[1]	Includes troubled debt restructurings of $8.7 million and $97 thousand as of March 31, 2017 and December 31, 2016, respectively.

Loans and Allowance for Credi40

Loans and Allowance for Credit Losses - Nonperforming Assets (Parenthetical) (Details) - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 9,717,357	$ 9,595,085	$ 9,630,691
Nonperforming Financial Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		25,240	32,598
Nonperforming Financial Loans [Member] | Finance Receivable Nonaccrual Status [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	[1]	24,360	31,642
Troubled Debt Restructuring [Member] | Nonperforming Financial Loans [Member] | Finance Receivable Nonaccrual Status [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 8,700	$ 97
[1]	Includes troubled debt restructurings of $8.7 million and $97 thousand as of March 31, 2017 and December 31, 2016, respectively.

Loans and Allowance for Credi41

Loans and Allowance for Credit Losses - Carrying Amount of PCI Loans and Related Outstanding Balance (Details) - Receivables Acquired with Deteriorated Credit Quality [Member] - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable Impaired [Line Items]
Outstanding balance	$ 48,438	$ 51,640
Less: discount	22,395	24,007
Recorded investment	$ 26,043	$ 27,633

Loans and Allowance for Credi42

Loans and Allowance for Credit Losses - Changes in Accretable Yield for Acquired PCI Loans (Details) - Receivables Acquired with Deteriorated Credit Quality [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Financing Receivable Impaired [Line Items]
Balance	$ 9,778	$ 5,664
Additions		10,222
Reclassifications from nonaccretable	968	5,120
Accretion	(1,483)	(7,831)
Balance	$ 9,263	$ 13,175

Loans and Allowance for Credi43

Loans and Allowance for Credit Losses - Carrying Amount of Non-PCI Loans and Related Outstanding Balance (Details) - Non PCI Loans [Member] - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable Impaired [Line Items]
Outstanding balance	$ 997,980	$ 1,115,061
Less: discount	32,129	35,401
Recorded investment	$ 965,851	$ 1,079,660

Loans and Allowance for Credi44

Loans and Allowance for Credit Losses - Changes in Discount Accretion for Non-PCI Loans (Details) - Non PCI Loans [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Financing Receivable Impaired [Line Items]
Balance	$ 35,401	$ 54,734
Additions		3,491
Accretion charge-offs	(2)	(1,053)
Accretion	(3,270)	(6,663)
Balance	$ 32,129	$ 50,509

Loans and Allowance for Credi45

Loans and Allowance for Credit Losses - Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	$ 18,439	$ 14,699
Impaired loans with no related allowance, unpaid contractual principal balance	19,278	15,844
Impaired loans with no related allowance, average recorded investment	16,569	16,243
Impaired loans with related allowance, recorded investment	4,342	14,210
Impaired loans with related allowance, unpaid contractual principal balance	4,740	14,743
Impaired loans with related allowance, related allowance	1,327	3,197
Impaired loans with related allowance, average recorded investment	9,276	14,911
Impaired loans, recorded investment	22,781	28,909
Impaired loans, unpaid contractual principal balance	24,018	30,587
Impaired loans, average recorded investment	25,845	31,154
Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	231	14
Impaired loans with no related allowance, unpaid contractual principal balance	239	220
Impaired loans with no related allowance, average recorded investment	123	24
Impaired loans with related allowance, average recorded investment		3
Impaired loans, recorded investment	231	14
Impaired loans, unpaid contractual principal balance	239	220
Impaired loans, average recorded investment	123	27
Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	385	7
Impaired loans with no related allowance, unpaid contractual principal balance	390	12
Impaired loans with no related allowance, average recorded investment	196	14
Impaired loans with related allowance, recorded investment	149	154
Impaired loans with related allowance, unpaid contractual principal balance	180	181
Impaired loans with related allowance, related allowance	10	17
Impaired loans with related allowance, average recorded investment	151	171
Impaired loans, recorded investment	534	161
Impaired loans, unpaid contractual principal balance	570	193
Impaired loans, average recorded investment	347	185
1-4 Family Residential (Includes Home Equity) [Member]
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	2,788	2,450
Impaired loans with no related allowance, unpaid contractual principal balance	3,029	2,682
Impaired loans with no related allowance, average recorded investment	2,619	1,828
Impaired loans with related allowance, recorded investment	380	437
Impaired loans with related allowance, unpaid contractual principal balance	393	449
Impaired loans with related allowance, related allowance	113	150
Impaired loans with related allowance, average recorded investment	408	408
Impaired loans, recorded investment	3,168	2,887
Impaired loans, unpaid contractual principal balance	3,422	3,131
Impaired loans, average recorded investment	3,027	2,236
Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	2,043	3,184
Impaired loans with no related allowance, unpaid contractual principal balance	2,078	3,327
Impaired loans with no related allowance, average recorded investment	2,614	9,150
Impaired loans with related allowance, recorded investment		288
Impaired loans with related allowance, unpaid contractual principal balance		288
Impaired loans with related allowance, related allowance		178
Impaired loans with related allowance, average recorded investment	144	275
Impaired loans, recorded investment	2,043	3,472
Impaired loans, unpaid contractual principal balance	2,078	3,615
Impaired loans, average recorded investment	2,758	9,425
Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	12,884	8,925
Impaired loans with no related allowance, unpaid contractual principal balance	13,374	9,446
Impaired loans with no related allowance, average recorded investment	10,904	5,139
Impaired loans with related allowance, recorded investment	3,782	13,327
Impaired loans with related allowance, unpaid contractual principal balance	4,129	13,821
Impaired loans with related allowance, related allowance	1,203	2,851
Impaired loans with related allowance, average recorded investment	8,555	13,961
Impaired loans, recorded investment	16,666	22,252
Impaired loans, unpaid contractual principal balance	17,503	23,267
Impaired loans, average recorded investment	19,459	19,100
Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	108	119
Impaired loans with no related allowance, unpaid contractual principal balance	168	157
Impaired loans with no related allowance, average recorded investment	113	88
Impaired loans with related allowance, recorded investment	31	4
Impaired loans with related allowance, unpaid contractual principal balance	38	4
Impaired loans with related allowance, related allowance	1	1
Impaired loans with related allowance, average recorded investment	18	93
Impaired loans, recorded investment	139	123
Impaired loans, unpaid contractual principal balance	206	161
Impaired loans, average recorded investment	$ 131	$ 181

Loans and Allowance for Credi46

Loans and Allowance for Credit Losses - Risk Grades and PCI Loans by Category of Loan (Details) - USD ($) $ in Thousands		Mar. 31, 2017		Dec. 31, 2016
Financing Receivable Impaired [Line Items]
Loans		$ 9,739,253		$ 9,622,060
Grade 1 [Member]
Financing Receivable Impaired [Line Items]
Loans		110,928		110,212
Grade 2 [Member]
Financing Receivable Impaired [Line Items]
Loans		76,455		61,472
Grade 3 [Member]
Financing Receivable Impaired [Line Items]
Loans		8,668,936		8,590,528
Grade 4 [Member]
Financing Receivable Impaired [Line Items]
Loans		647,870		596,741
Grade 5 [Member]
Financing Receivable Impaired [Line Items]
Loans		113,109		119,052
Grade 6 [Member]
Financing Receivable Impaired [Line Items]
Loans		73,131		87,544
Grade 7 [Member]
Financing Receivable Impaired [Line Items]
Loans		22,070		28,134
Grade 8 [Member]
Financing Receivable Impaired [Line Items]
Loans		711		744
PCI Loans [Member]
Financing Receivable Impaired [Line Items]
Loans		26,043	[1]	27,633	[2]
Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
Loans		1,326,685		1,263,923
Construction, Land Development and Other Land Loans [Member] | Grade 2 [Member]
Financing Receivable Impaired [Line Items]
Loans		2,682		2,261
Construction, Land Development and Other Land Loans [Member] | Grade 3 [Member]
Financing Receivable Impaired [Line Items]
Loans		1,241,209		1,200,623
Construction, Land Development and Other Land Loans [Member] | Grade 4 [Member]
Financing Receivable Impaired [Line Items]
Loans		75,654		54,380
Construction, Land Development and Other Land Loans [Member] | Grade 5 [Member]
Financing Receivable Impaired [Line Items]
Loans		4,445		2,525
Construction, Land Development and Other Land Loans [Member] | Grade 6 [Member]
Financing Receivable Impaired [Line Items]
Loans		1,092		2,690
Construction, Land Development and Other Land Loans [Member] | Grade 7 [Member]
Financing Receivable Impaired [Line Items]
Loans		231		13
Construction, Land Development and Other Land Loans [Member] | PCI Loans [Member]
Financing Receivable Impaired [Line Items]
Loans		1,372	[1]	1,431	[2]
Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
Loans		662,797		672,336
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Grade 1 [Member]
Financing Receivable Impaired [Line Items]
Loans		13,972		14,616
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Grade 2 [Member]
Financing Receivable Impaired [Line Items]
Loans		4,074		4,218
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Grade 3 [Member]
Financing Receivable Impaired [Line Items]
Loans		562,415		570,324
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Grade 4 [Member]
Financing Receivable Impaired [Line Items]
Loans		71,851		74,079
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Grade 5 [Member]
Financing Receivable Impaired [Line Items]
Loans		9,118		7,703
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Grade 6 [Member]
Financing Receivable Impaired [Line Items]
Loans		445		847
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Grade 7 [Member]
Financing Receivable Impaired [Line Items]
Loans		534		161
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | PCI Loans [Member]
Financing Receivable Impaired [Line Items]
Loans		388	[1]	388	[2]
1-4 Family Residential (Includes Home Equity) [Member]
Financing Receivable Impaired [Line Items]
Loans	[3]	2,705,831	[4]	2,717,831	[5]
1-4 Family Residential (Includes Home Equity) [Member] | Grade 2 [Member]
Financing Receivable Impaired [Line Items]
Loans		22,447	[4]	22,863	[5]
1-4 Family Residential (Includes Home Equity) [Member] | Grade 3 [Member]
Financing Receivable Impaired [Line Items]
Loans		2,607,696	[4]	2,622,304	[5]
1-4 Family Residential (Includes Home Equity) [Member] | Grade 4 [Member]
Financing Receivable Impaired [Line Items]
Loans		59,543	[4]	55,367	[5]
1-4 Family Residential (Includes Home Equity) [Member] | Grade 5 [Member]
Financing Receivable Impaired [Line Items]
Loans		4,001	[4]	3,605	[5]
1-4 Family Residential (Includes Home Equity) [Member] | Grade 6 [Member]
Financing Receivable Impaired [Line Items]
Loans		4,137	[4]	5,095	[5]
1-4 Family Residential (Includes Home Equity) [Member] | Grade 7 [Member]
Financing Receivable Impaired [Line Items]
Loans		3,140	[4]	2,857	[5]
1-4 Family Residential (Includes Home Equity) [Member] | Grade 8 [Member]
Financing Receivable Impaired [Line Items]
Loans		29	[4]	30	[5]
1-4 Family Residential (Includes Home Equity) [Member] | PCI Loans [Member]
Financing Receivable Impaired [Line Items]
Loans		4,838	[1],[4]	5,710	[2],[5]
Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
Loans		3,226,978		3,162,109
Commercial Real Estate (Includes Multi-Family Residential) [Member] | Grade 2 [Member]
Financing Receivable Impaired [Line Items]
Loans		8,332		8,317
Commercial Real Estate (Includes Multi-Family Residential) [Member] | Grade 3 [Member]
Financing Receivable Impaired [Line Items]
Loans		2,898,086		2,859,433
Commercial Real Estate (Includes Multi-Family Residential) [Member] | Grade 4 [Member]
Financing Receivable Impaired [Line Items]
Loans		242,316		220,533
Commercial Real Estate (Includes Multi-Family Residential) [Member] | Grade 5 [Member]
Financing Receivable Impaired [Line Items]
Loans		45,312		45,533
Commercial Real Estate (Includes Multi-Family Residential) [Member] | Grade 6 [Member]
Financing Receivable Impaired [Line Items]
Loans		14,765		8,401
Commercial Real Estate (Includes Multi-Family Residential) [Member] | Grade 7 [Member]
Financing Receivable Impaired [Line Items]
Loans		2,042		3,472
Commercial Real Estate (Includes Multi-Family Residential) [Member] | PCI Loans [Member]
Financing Receivable Impaired [Line Items]
Loans		16,125	[1]	16,420	[2]
Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
Loans		1,554,661		1,539,439
Commercial and Industrial [Member] | Grade 1 [Member]
Financing Receivable Impaired [Line Items]
Loans		56,049		54,908
Commercial and Industrial [Member] | Grade 2 [Member]
Financing Receivable Impaired [Line Items]
Loans		11,695		12,772
Commercial and Industrial [Member] | Grade 3 [Member]
Financing Receivable Impaired [Line Items]
Loans		1,181,197		1,143,634
Commercial and Industrial [Member] | Grade 4 [Member]
Financing Receivable Impaired [Line Items]
Loans		187,836		176,287
Commercial and Industrial [Member] | Grade 5 [Member]
Financing Receivable Impaired [Line Items]
Loans		47,030		57,283
Commercial and Industrial [Member] | Grade 6 [Member]
Financing Receivable Impaired [Line Items]
Loans		50,868		68,682
Commercial and Industrial [Member] | Grade 7 [Member]
Financing Receivable Impaired [Line Items]
Loans		15,984		21,475
Commercial and Industrial [Member] | Grade 8 [Member]
Financing Receivable Impaired [Line Items]
Loans		682		714
Commercial and Industrial [Member] | PCI Loans [Member]
Financing Receivable Impaired [Line Items]
Loans		3,320	[1]	3,684	[2]
Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
Loans		262,301		266,422
Consumer and Other [Member] | Grade 1 [Member]
Financing Receivable Impaired [Line Items]
Loans		40,907		40,688
Consumer and Other [Member] | Grade 2 [Member]
Financing Receivable Impaired [Line Items]
Loans		27,225		11,041
Consumer and Other [Member] | Grade 3 [Member]
Financing Receivable Impaired [Line Items]
Loans		178,333		194,210
Consumer and Other [Member] | Grade 4 [Member]
Financing Receivable Impaired [Line Items]
Loans		10,670		16,095
Consumer and Other [Member] | Grade 5 [Member]
Financing Receivable Impaired [Line Items]
Loans		3,203		2,403
Consumer and Other [Member] | Grade 6 [Member]
Financing Receivable Impaired [Line Items]
Loans		1,824		1,829
Consumer and Other [Member] | Grade 7 [Member]
Financing Receivable Impaired [Line Items]
Loans		$ 139		$ 156
[1]	(2)Of the total PCI loans, $1.6 million were classified as substandard at March 31, 2017, with no specific reserves allocated to them.
[2]	(2)Of the total PCI loans, $2.7 million were classified as substandard at December 31, 2016, which includes $31 thousand with specific reserves allocated to them.
[3]	Includes $21.9 million and $27.0 million of residential mortgage loans held for sale at March 31, 2017 and December 31, 2016, respectively.
[4]	Includes $21.9 million of residential mortgage loans held for sale at March 31, 2017.
[5]	(1)Includes $27.0 million of residential mortgage loans held for sale at December 31, 2016.

Loans and Allowance for Credi47

Loans and Allowance for Credit Losses - Risk Grades and Impaired Loans by Class of Loan (Parenthetical) (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Financing Receivable Impaired [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage	$ 21,896,000	$ 26,975,000
Substandard [Member]
Financing Receivable Impaired [Line Items]
Loans Receivable, Fair Value Disclosure	1,600,000	2,700,000
Allocated Specific Reserves	0	31,000
1-4 Family Residential (Includes Home Equity) [Member]
Financing Receivable Impaired [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage	$ 21,896,000	$ 26,975,000	$ 23,717,000

Loans and Allowance for Credi48

Loans and Allowance for Credit Losses - Allowance for Credit Losses by Category of Loan (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Allowance for credit losses:
Allowance for credit losses, beginning balance	$ 85,326	$ 81,384
Provision for credit losses	2,675	14,000
Charge-offs	(4,608)	(14,265)
Recoveries	702	2,595
Net charge-offs	(3,906)	(11,670)
Allowance for credit losses, ending balance	84,095	83,714
Allowance for credit losses related to:
Allowance for credit losses, individually evaluated for impairment			$ 1,327	$ 3,166	$ 7,621
Allowance for credit losses, collectively evaluated for impairment			82,768	82,129	74,925
Allowance for credit losses, PCI loans				31	1,168
Total allowance for credit losses	84,095	81,384	84,095	85,326	83,714
Recorded investment in loans:
Loans, individually evaluated for impairment			22,781	28,878	35,922
Loans, collectively evaluated for impairment			9,668,533	9,538,574	9,555,233
PCI loans			26,043	27,633	39,536
Total loans evaluated for impairment			9,717,357	9,595,085	9,630,691
Construction, Land Development and Other Land Loans [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	14,984	14,882
Provision for credit losses	(386)	(703)
Charge-offs		(7)
Recoveries	65	193
Net charge-offs	65	186
Allowance for credit losses, ending balance	14,663	14,365
Allowance for credit losses related to:
Allowance for credit losses, individually evaluated for impairment					2
Allowance for credit losses, collectively evaluated for impairment			14,663	14,984	14,363
Total allowance for credit losses	14,984	14,882	14,663	14,984	14,365
Recorded investment in loans:
Loans, individually evaluated for impairment			231	14	25
Loans, collectively evaluated for impairment			1,325,082	1,262,478	1,170,405
PCI loans			1,372	1,431	3,094
Total loans evaluated for impairment			1,326,685	1,263,923	1,173,524
Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	4,073	3,845
Provision for credit losses	(554)	6,689
Charge-offs		(7,025)
Recoveries	65	63
Net charge-offs	65	(6,962)
Allowance for credit losses, ending balance	3,584	3,572
Allowance for credit losses related to:
Allowance for credit losses, individually evaluated for impairment			10	17	37
Allowance for credit losses, collectively evaluated for impairment			3,574	4,056	3,535
Total allowance for credit losses	4,073	3,845	3,584	4,073	3,572
Recorded investment in loans:
Loans, individually evaluated for impairment			534	161	5,691
Loans, collectively evaluated for impairment			661,875	671,787	635,208
PCI loans			388	388	394
Total loans evaluated for impairment			662,797	672,336	641,293
1-4 Family Residential (Includes Home Equity) [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	16,571	14,891
Provision for credit losses	(895)	(297)
Charge-offs	(13)	(49)
Recoveries	108	19
Net charge-offs	95	(30)
Allowance for credit losses, ending balance	15,771	14,564
Allowance for credit losses related to:
Allowance for credit losses, individually evaluated for impairment			113	150	91
Allowance for credit losses, collectively evaluated for impairment			15,658	16,421	14,473
Total allowance for credit losses	16,571	14,891	15,771	16,571	14,564
Recorded investment in loans:
Loans, individually evaluated for impairment			3,168	2,887	2,379
Loans, collectively evaluated for impairment			2,675,929	2,682,259	2,630,719
PCI loans			4,838	5,710	6,374
Total loans evaluated for impairment			2,683,935	2,690,856	2,639,472
Commercial Real Estate (Includes Multi-Family Residential) [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	12,256	12,996
Provision for credit losses	(1,148)	(546)
Charge-offs	(133)	(59)
Net charge-offs	(133)	(59)
Allowance for credit losses, ending balance	10,975	12,391
Allowance for credit losses related to:
Allowance for credit losses, individually evaluated for impairment				178
Allowance for credit losses, collectively evaluated for impairment			10,975	12,078	12,391
Total allowance for credit losses	12,256	12,996	10,975	12,256	12,391
Recorded investment in loans:
Loans, individually evaluated for impairment			2,043	3,472	9,159
Loans, collectively evaluated for impairment			3,208,810	3,142,217	3,200,625
PCI loans			16,125	16,420	19,922
Total loans evaluated for impairment			3,226,978	3,162,109	3,229,706
Commercial and Industrial [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	35,836	33,409
Provision for credit losses	5,341	8,150
Charge-offs	(3,638)	(6,277)
Recoveries	143	1,881
Net charge-offs	(3,495)	(4,396)
Allowance for credit losses, ending balance	37,682	37,163
Allowance for credit losses related to:
Allowance for credit losses, individually evaluated for impairment			1,203	2,820	7,464
Allowance for credit losses, collectively evaluated for impairment			36,479	32,985	28,531
Allowance for credit losses, PCI loans				31	1,168
Total allowance for credit losses	35,836	33,409	37,682	35,836	37,163
Recorded investment in loans:
Loans, individually evaluated for impairment			16,666	22,221	18,441
Loans, collectively evaluated for impairment			1,534,675	1,513,534	1,671,822
PCI loans			3,320	3,684	9,752
Total loans evaluated for impairment			1,554,661	1,539,439	1,700,015
Consumer and Other [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	1,606	1,361
Provision for credit losses	317	707
Charge-offs	(824)	(848)
Recoveries	321	439
Net charge-offs	(503)	(409)
Allowance for credit losses, ending balance	1,420	1,659
Allowance for credit losses related to:
Allowance for credit losses, individually evaluated for impairment			1	1	27
Allowance for credit losses, collectively evaluated for impairment			1,419	1,605	1,632
Total allowance for credit losses	$ 1,606	$ 1,361	1,420	1,606	1,659
Recorded investment in loans:
Loans, individually evaluated for impairment			139	123	227
Loans, collectively evaluated for impairment			262,162	266,299	246,454
Total loans evaluated for impairment			$ 262,301	$ 266,422	$ 246,681

Loans and Allowance for Credi49

Loans and Allowance for Credit Losses - Allowance for Credit Losses by Category of Loan (Parenthetical) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Accounts Notes And Loans Receivable [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage	$ 21,896	$ 26,975
1-4 Family Residential (Includes Home Equity) [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage	$ 21,896	$ 26,975	$ 23,717

Loans and Allowance for Credi50

Loans and Allowance for Credit Losses - Troubled Debt Restructurings (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017USD ($)contract
Financing Receivable Modifications [Line Items]
Troubled debt restructurings, number of loans | contract	3
Troubled debt restructurings, pre-modification outstanding recorded investment	$ 8,656
Troubled debt restructurings, post-modification outstanding recorded investment	$ 8,650
Commercial and Industrial [Member]
Financing Receivable Modifications [Line Items]
Troubled debt restructurings, number of loans | contract	3
Troubled debt restructurings, pre-modification outstanding recorded investment	$ 8,656
Troubled debt restructurings, post-modification outstanding recorded investment	$ 8,650

Fair Value - Fair Value Assets

Fair Value - Fair Value Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Available for sale securities:
Available for sale securities, at fair value	$ 209,427	$ 221,176
Fair Value, Measurements, Recurring [Member]
Available for sale securities:
Available for sale securities, at fair value	209,427	221,176
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Available for sale securities:
Available for sale securities, at fair value	12,523	12,794
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Available for sale securities:
Available for sale securities, at fair value	196,904	208,382
Fair Value, Measurements, Recurring [Member] | States and Political Subdivisions [Member]
Available for sale securities:
Available for sale securities, at fair value	1,820	1,920
Fair Value, Measurements, Recurring [Member] | States and Political Subdivisions [Member] | Level 2 [Member]
Available for sale securities:
Available for sale securities, at fair value	1,820	1,920
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Obligations [Member]
Available for sale securities:
Available for sale securities, at fair value	115,796	120,599
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Obligations [Member] | Level 2 [Member]
Available for sale securities:
Available for sale securities, at fair value	115,796	120,599
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities [Member]
Available for sale securities:
Available for sale securities, at fair value	79,288	85,863
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities [Member] | Level 2 [Member]
Available for sale securities:
Available for sale securities, at fair value	79,288	85,863
Fair Value, Measurements, Recurring [Member] | Other Securities [Member]
Available for sale securities:
Available for sale securities, at fair value	12,523	12,794
Fair Value, Measurements, Recurring [Member] | Other Securities [Member] | Level 1 [Member]
Available for sale securities:
Available for sale securities, at fair value	$ 12,523	$ 12,794

Fair Value - Additional Informa

Fair Value - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017USD ($)
Fair Value Disclosures [Abstract]
Other real estate, additions	$ 320
Real estate owned outstanding	320
Additions to impaired loans	1,700
Impaired loans outstanding	$ 1,700

Fair Value - Financial Instrume

Fair Value - Financial Instruments Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Assets
Cash and due from banks	$ 324,797	$ 436,203
Federal funds sold	945	1,178
Held to Maturity securities	9,517,764	9,339,455
Loans held for sale	21,896	26,975
Other real estate owned	15,698	15,463
Liabilities
Noninterest-bearing	5,299,264	5,190,973
Interest-bearing	11,736,308	12,116,329
Other borrowings	1,270,644	990,781
Securities sold under repurchase agreements	335,875	320,430
Carrying Amount [Member]
Assets
Cash and due from banks	324,797	436,203
Federal funds sold	945	1,178
Held to Maturity securities	9,644,693	9,504,910
Loans held for sale	21,896	26,975
Loans held for investment, net of allowance	9,633,262	9,509,759
Other real estate owned	15,698	15,463
Liabilities
Noninterest-bearing	5,299,264	5,190,973
Interest-bearing	11,736,308	12,116,329
Other borrowings	1,270,644	990,781
Securities sold under repurchase agreements	335,875	320,430
Estimated Fair Value [Member]
Assets
Cash and due from banks	324,797	436,203
Federal funds sold	945	1,178
Held to Maturity securities	9,517,764	9,339,455
Loans held for sale	21,896	26,975
Loans held for investment, net of allowance	9,679,257	9,533,310
Other real estate owned	15,698	15,463
Liabilities
Noninterest-bearing	5,299,264	5,190,973
Interest-bearing	11,740,990	12,121,157
Other borrowings	1,271,004	991,181
Securities sold under repurchase agreements	335,864	320,428
Estimated Fair Value [Member] | Level 1 [Member]
Assets
Cash and due from banks	324,797	436,203
Federal funds sold	945	1,178
Estimated Fair Value [Member] | Level 2 [Member]
Assets
Held to Maturity securities	9,517,764	9,339,455
Loans held for sale	21,896	26,975
Other real estate owned	15,698	15,463
Liabilities
Noninterest-bearing	5,299,264	5,190,973
Interest-bearing	11,740,990	12,121,157
Other borrowings	1,271,004	991,181
Securities sold under repurchase agreements	335,864	320,428
Estimated Fair Value [Member] | Level 3 [Member]
Assets
Loans held for investment, net of allowance	$ 9,679,257	$ 9,533,310

Goodwill and Core Deposit Int54

Goodwill and Core Deposit Intangibles - Goodwill and Core Deposit Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Schedule Of Intangible Assets And Goodwill [Line Items]
Goodwill, Beginning balance	$ 1,900,845	$ 1,868,827	$ 1,868,827
Goodwill, Acquisition of Tradition Bancshares, Inc.			32,018
Goodwill, Ending balance	1,900,845		1,900,845
Core Deposit Intangibles, Beginning balance	45,784
Core Deposit Intangibles, Amortization	(1,915)	(2,222)
Core Deposit Intangibles, Ending balance	43,869		45,784
Core Deposit Intangibles [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Core Deposit Intangibles, Beginning balance	45,784	49,417	49,417
Core Deposit Intangibles, Amortization	(1,915)	$ (2,200)	(9,200)
Core Deposit Intangibles, Acquisition of Tradition Bancshares, Inc.			5,567
Core Deposit Intangibles, Ending balance	$ 43,869		$ 45,784

Goodwill and Core Deposit Int55

Goodwill and Core Deposit Intangibles - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Schedule Of Intangible Assets And Goodwill [Line Items]
Amortization expense related to intangible assets	$ 1,915,000	$ 2,222,000
Core Deposit Intangibles [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Impairment recorded on goodwill and core deposit intangibles	0
Amortization expense related to intangible assets	$ 1,915,000	$ 2,200,000	$ 9,200,000
Core Deposit Intangibles [Member] | Minimum [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Finite-lived intangible assets, useful life	10 years
Core Deposit Intangibles [Member] | Maximum [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Finite-lived intangible assets, useful life	15 years

Goodwill and Core Deposit Int56

Goodwill and Core Deposit Intangibles - Estimated Aggregate Future Amortization Expense for Core Deposit Intangibles (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite Lived Intangible Assets [Line Items]
Total	$ 43,869	$ 45,784
Core Deposits [Member]
Finite Lived Intangible Assets [Line Items]
Remaining 2,017	5,027
2,018	5,959
2,019	5,051
2,020	4,483
2,021	4,022
Thereafter	19,327
Total	$ 43,869	$ 45,784	$ 49,417

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017USD ($)Planshares	Mar. 31, 2016USD ($)	Dec. 31, 2012shares	Dec. 31, 2004shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Stock-Based Employee Compensation Plans | Plan	2
Number of Stock-Based Employee Compensation Plans Expired | Plan	1
Proceeds from stock option exercises | $	$ 148	$ 0
Tax benefit realized from exercises of stock-based compensation arrangements | $	0	$ 0
Total unrecognized compensation expense related to stock-based compensation arrangements | $	$ 9,470
Weighted-average period of cost expected to be recognized	1 year 3 months 22 days
2004 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized				1,250,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	0
2012 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized			1,250,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	341,435

Contractual Obligations and O58

Contractual Obligations and Off-Balance Sheet Items - Additional Information (Details) $ in Thousands	Mar. 31, 2017USD ($)
Federal Home Loan Bank Notes Payable [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
Interest payable	$ 596

Contractual Obligations and O59

Contractual Obligations and Off-Balance Sheet Items - Contractual Obligations and Other Commitments (Details) - Lease Total [Member] $ in Thousands	Mar. 31, 2017USD ($)
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	$ 1,271,056
More than 1 year but less than 3 years	12,143
3 years or more but less than 5 years	4,410
5 years or more	4,035
Total	1,291,644
Federal Home Loan Bank Notes Payable [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	1,265,871
More than 1 year but less than 3 years	4,648
3 years or more but less than 5 years	523
5 years or more	198
Total	1,271,240
Operating Leases [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	5,185
More than 1 year but less than 3 years	7,495
3 years or more but less than 5 years	3,887
5 years or more	3,837
Total	$ 20,404

Contractual Obligations and O60

Contractual Obligations and Off-Balance Sheet Items - Summary of Commitments Associated with Outstanding Standby Letters of Credit and Commitments to Extend Credit (Details) - Guarantee Obligations [Member] $ in Thousands	Mar. 31, 2017USD ($)
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	$ 1,048,748
More than 1 year but less than 3 years	355,148
3 years or more but less than 5 years	167,133
5 years or more	586,811
Total	2,157,840
Financial Guarantee [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	993,282
More than 1 year but less than 3 years	333,635
3 years or more but less than 5 years	166,589
5 years or more	586,811
Total	2,080,317
Standby Letters of Credit [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	55,466
More than 1 year but less than 3 years	21,513
3 years or more but less than 5 years	544
5 years or more	0
Total	$ 77,523

Other Comprehensive Income - Ta

Other Comprehensive Income - Tax Effects Allocated to Each Component of Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Equity [Abstract]
Change in unrealized gain during period, before tax	$ 29	$ 148
Change in unrealized gain during period, tax	(10)	(52)
Change in unrealized gain during period, net of tax	19	96
Total securities available for sale, before tax	29	148
Total securities available for sale, tax	(10)	(52)
Total securities available for sale, net of tax	19	96
Total other comprehensive Income	29	148
Deferred taxes related to other comprehensive gain	(10)	(52)
Other comprehensive gain, net of tax	$ 19	$ 96

Other Comprehensive Income - Ac

Other Comprehensive Income - Activity in Accumulated Other Comprehensive Income Associated with Securities Available for Sale, Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Beginning balance, accumulated other comprehensive income	$ 1,411	$ 2,040
Other comprehensive income	19	96
Ending balance, accumulated other comprehensive income	1,430	2,136
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Beginning balance, accumulated other comprehensive income	1,411	2,040
Other comprehensive income	19	96
Ending balance, accumulated other comprehensive income	$ 1,430	$ 2,136

Acquisitions - Additional Infor

Acquisitions - Additional Information (Details) $ / shares in Units, $ in Thousands	Jan. 01, 2016USD ($)Bankshares	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)$ / shares
Business Acquisition [Line Items]
Goodwill		$ 1,900,845	$ 1,900,845	$ 1,868,827
Core Deposit Intangibles [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired			$ 5,567
Tradition Bancshares, Inc [Member]
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares (in Shares) | shares	679,528
Payments to Acquire Businesses, Gross	$ 39,000
Business Combination, Consideration Transferred	$ 71,500
Business Acquisition, Share Price | $ / shares				$ 47.86
Goodwill		32,000
Tradition Bancshares, Inc [Member] | Core Deposit Intangibles [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired		$ 5,600
Tradition Bancshares, Inc [Member] | Houston [Member]
Business Acquisition [Line Items]
Number of Operating Banking Offices | Bank	7
Tradition Bancshares, Inc [Member] | Katy [Member]
Business Acquisition [Line Items]
Number of Operating Banking Offices | Bank	3
Tradition Bancshares, Inc [Member] | The Woodlands [Member]
Business Acquisition [Line Items]
Number of Operating Banking Offices | Bank	1