Western Alliance Bancorporation (WAL) 10-K 16 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Feb. 10, 2016	Jun. 30, 2015
Entity Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	WAL
Entity Registrant Name	WESTERN ALLIANCE BANCORPORATION
Entity Central Index Key	1,212,545
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		103,418,400
Entity Public Float			$ 2,357.3

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets:
Cash and due from banks	$ 133,709	$ 125,329
Interest-bearing deposits in other financial institutions	90,931	39,067
Cash and cash equivalents	224,640	164,396
Money Market Funds, at Carrying Value	122	451
Investment securities - measured at fair value; amortized cost of $1,389 at December 31, 2015 and $1,734 at December 31, 2014	1,481	1,858
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	1,982,523	1,520,237
Investments in restricted stock, at cost	58,111	25,275
Trade and Loans Receivables Held-for-sale, Net, Not Part of Disposal Group	23,809	0
Loans:
Loans, net of deferred loan fees and costs	11,112,854	8,398,265
Less: Allowance for credit losses	(119,068)	(110,216)
Net loans held for investment	10,993,786	8,288,049
Premises and equipment, net	118,535	113,818
Other assets acquired through foreclosure, net	43,942	57,150
Bank owned life insurance	162,458	141,969
Goodwill	289,638	23,224
Other intangible assets, net	15,716	2,689
Deferred tax assets, net	86,352	62,686
Other assets	273,976	198,696
Total assets	14,275,089	10,600,498
Deposits:
Non-interest-bearing demand	4,093,976	2,288,048
Interest-bearing	7,936,648	6,642,995
Total deposits	12,030,624	8,931,043
Customer repurchase agreements	38,155	54,899
Other borrowings	150,000	390,263
Qualifying debt	210,328	40,437
Other liabilities	254,480	182,928
Total liabilities	$ 12,683,587	$ 9,599,570
Commitments and Contingencies
Stockholders’ equity:
Preferred stock - par value $0.0001 and liquidation value per share of $1,000; 20,000,000 authorized; zero shares issued and outstanding at December 31, 2015 and 70,500 at December 31, 2014	$ 0	$ 70,500
Common stock - par value $0.0001; 200,000,000 authorized; 103,087,044 shares issued and outstanding at December 31, 2015 and 88,691,249 at December 31, 2014	10	9
Additional paid in capital	1,306,594	828,327
Accumulated other comprehensive income	262,638	85,453
Retained earnings	22,260	16,639
Total stockholders’ equity	1,591,502	1,000,928
Total liabilities and stockholders’ equity	$ 14,275,089	$ 10,600,498

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Amortized cost of investment securities available for sale	$ 1,899,580	$ 1,493,648
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, liquidation value	$ 1,000	$ 1,000
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred Stock, Shares Issued	70,500	141,000
Preferred stock, shares outstanding	70,500	141,000
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	103,087,044	88,691,249
Common stock, shares outstanding	103,087,044	88,691,249

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interest income:
Loans, including fees	$ 476,417	$ 370,922	$ 326,714
Investment securities	37,888	38,603	30,382
Dividends	10,317	6,562	4,454
Other	522	292	1,105
Total interest income	525,144	416,379	362,655
Interest expense:
Deposits	21,795	20,012	16,335
Other borrowings	5,678	9,639	11,506
Qualifying debt	5,007	1,754	1,823
Other	88	81	96
Total interest expense	32,568	31,486	29,760
Net interest income	492,576	384,893	332,895
Provision for credit losses	3,200	4,726	13,220
Net interest income after provision for credit losses	489,376	380,167	319,675
Non-interest income:
Service charges and fees	14,639	10,567	10,123
Income from bank owned life insurance	3,899	4,508	4,809
Card income	3,679	3,310	2,626
Lending related fees	1,948	71	0
Gain (Loss) on Sale of Securities, Net	615	757	(1,195)
Gains (Losses) on Extinguishment of Debt	(81)	(502)	(1,387)
Gain (loss) on sales of investment securities, net	47	1,212	(6,483)
Business Combination, Bargain Purchase, Gain Recognized, Amount	0	0	10,044
Other income	5,022	4,728	3,660
Total non-interest income	29,768	24,651	22,197
Non-interest expense:
Salaries and employee benefits	149,828	126,630	113,434
Occupancy	22,180	18,155	19,378
Legal, professional, and directors' fees	18,548	14,278	13,633
Data processing	14,776	10,057	8,589
Insurance	11,003	8,862	8,094
Marketing	4,377	4,423	4,198
Card expense	2,764	2,417	1,805
Marketing Expense	2,885	2,300	2,581
Intangible amortization	1,970	1,461	2,388
Intangible amortization	(2,070)	(5,350)	(2,387)
Acquisition / restructure expense	8,836	198	5,752
Other expense	25,509	23,888	18,751
Total non-interest expense	260,606	207,319	196,216
Income from continuing operations before provision for income taxes	258,538	197,499	145,656
Income tax expense	64,294	48,390	29,830
Income from continuing operations	194,244	149,109	115,826
(Loss) from discontinued operations, net of tax	0	(1,158)	(861)
Net income	194,244	147,951	114,965
Dividends on preferred stock	750	1,387	1,410
Net income available to common stockholders	$ 193,494	$ 146,564	$ 113,555
Earnings per share from continuing operations:
Basic	$ 2.05	$ 1.70	$ 1.34
Diluted	2.03	1.69	1.32
Loss per share from discontinued operations:
Basic	0	(0.01)	(0.01)
Diluted	0	(0.02)	(0.01)
Earnings per share available to common stockholders:
Basic	2.05	1.69	1.33
Diluted	$ 2.03	$ 1.67	$ 1.31
Weighted average number of common shares outstanding:
Basic	94,570	86,693	85,682
Diluted	95,219	87,506	86,541
Dividends declared per common share	$ 0	$ 0	$ 0

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 194,244	$ 147,951	$ 114,965
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	0	8,976	0
Other comprehensive income (loss), net:
Unrealized (loss) gain on AFS securities, net of tax effect of $3,922, $(17,749), and $18,240, respectively	(6,117)	29,683	(30,503)
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	0	0	(17)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	90	0	0
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Subordinated Debt	(4,276)	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	(4,276)
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(6,523)	1,380	(5,900)
Realized (gain) loss on sale of AFS securities included in income, net of tax effect of $230, $283, and $(447), respectively	(385)	(474)	748
Net other comprehensive (loss) income	(10,688)	38,185	(29,772)
Comprehensive income	$ 183,556	$ 186,136	$ 85,193

CONSOLIDATED STATEMENTS OF COM6

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Tax	$ 0	$ (5,367)
Unrealized gain on securities available-for-sale securities, tax	(3,922)	17,749
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax	(52)	0
Realized gain on sale of securities, tax	$ 230	$ 283

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($)		Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated (Deficit) [Member]	Bridge Capital Holdings [Member]	[2]	Bridge Capital Holdings [Member]Common Stock [Member]		Bridge Capital Holdings [Member]Additional Paid in Capital [Member]	[2]
Beginning balance at Dec. 31, 2012		$ 759,421,000	$ 141,000,000	$ 9,000	$ 784,852,000	$ 8,226,000	$ (174,666,000)
Beginning balance, shares at Dec. 31, 2012			141,000	86,465,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		114,965,000					114,965,000
Exercise of stock options, shares				440,000
Exercise of stock options		4,595,000			4,595,000
Restricted stock grants, net, shares				281,000
Restricted stock grants, net		7,699,000			7,699,000
Dividends on preferred stock		(1,410,000)					(1,410,000)
Other comprehensive (loss) income, net		(29,772,000)				(29,772,000)
Ending balance at Dec. 31, 2013		855,498,000	$ 141,000,000	$ 9,000	797,146,000	(21,546,000)	(61,111,000)
Ending balance, shares at Dec. 31, 2013			141,000	87,186,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		147,951,000					147,951,000
Exercise of stock options, shares				625,000
Exercise of stock options		8,294,000			8,294,000
Restricted stock grants, net, shares				332,000
Restricted stock grants, net		9,141,000			9,141,000
Stock Issued During Period, Shares, New Issues				548,122
Stock Issued During Period, Value, New Issues		$ 13,746,000		$ 14,200,000	13,746,000
Stock Redeemed or Called During Period, Shares		(70,500)	(70,000)
Stock Redeemed or Called During Period, Value		$ (70,500,000)	$ (70,500,000)
Dividends on preferred stock		(1,387,000)					(1,387,000)
Other comprehensive (loss) income, net		38,185,000				38,185,000
Ending balance at Dec. 31, 2014		1,000,928,000	$ 70,500,000	$ 9,000	828,327,000	16,639,000	85,453,000
Ending balance, shares at Dec. 31, 2014			71,000	88,691,000
Adjusted balance at Dec. 31, 2014	[1]	1,000,928,000	$ 70,500,000	$ 9,000	828,327,000	32,948,000	69,144,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		$ 194,244,000					194,244,000
Exercise of stock options, shares		182,000		182,000
Exercise of stock options		$ 1,935,000			1,935,000
Restricted stock grants, net, shares				457,000
Restricted stock grants, net		17,014,000			17,014,000
Stock Issued During Period, Shares, New Issues				760,000						12,997,000
Stock Issued During Period, Value, New Issues		$ 28,288,000			28,288,000			$ 431,031,000		$ 1,000	[2]	$ 431,030,000
Stock Redeemed or Called During Period, Shares		(70,500)	(71,000)
Stock Redeemed or Called During Period, Value		$ (70,500,000)	$ (70,500,000)
Dividends on preferred stock		(750,000)					(750,000)
Other comprehensive (loss) income, net		(10,688,000)				(10,688,000)
Ending balance at Dec. 31, 2015		$ 1,591,502,000	$ 0	$ 10,000	$ 1,306,594,000	$ 22,260,000	$ 262,638,000
Ending balance, shares at Dec. 31, 2015			0	103,087,000
[1]	As adjusted, see "Note 10. Qualifying Debt" to the Consolidated Financial Statements describing the $16.3 million reclassification made between retained earnings and AOCI.
[2]	Includes value of certain share-based awards replaced in connection with the acquisition.

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS	12 Months Ended
	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Cash flows from operating activities:
Net income	$ 194,244,000	$ 147,951,000	$ 114,965,000
Adjustments to reconcile net income to cash provided by operating activities:
Provision for credit losses	3,200,000	4,726,000	13,220,000
Depreciation and amortization	8,466,000	6,166,000	6,859,000
Stock-based compensation	17,930,000	12,465,000	7,699,000
Excess tax benefit of stock-based compensation	(5,874,000)	(4,194,000)	(1,552,000)
Deferred income taxes	3,254,000	(7,182,000)	(13,717,000)
Amortization of net premiums for investment securities	9,775,000	8,035,000	9,727,000
Accretion And Amortization Fair Market Value Adjustments Relating To Acquisitions of Loans	(17,144,000)	(17,014,000)	(10,917,000)
Accretion and Amortization Fair Market Value Adjustments Relating to Acquisitions of Other Assets and Liabilities	1,279,000	(552,000)	437,000
Income from bank owned life insurance	(3,899,000)	(4,508,000)	(4,809,000)
Unrealized losses on assets and liabilities measured at fair value, net	(47,000)	(1,212,000)	6,483,000
(Gains) / Losses on:
Sales of investment securities	(615,000)	(757,000)	1,195,000
Business Combination, Bargain Purchase, Gain Recognized, Amount	0	0	(10,044,000)
Gains (Losses) on Extinguishment of Debt	81,000	502,000	1,387,000
Other assets acquired through foreclosure, net	(2,628,000)	(2,866,000)	(5,924,000)
Valuation adjustments of other repossessed assets, net	182,000	294,000	3,743,000
Sale of premises, equipment, and other assets, net	376,000	(2,778,000)	(206,000)
Changes in, net of acquisitions:
Other assets	(9,999,000)	9,242,000	33,185,000
Other liabilities	14,231,000	14,971,000	13,318,000
Net cash provided by operating activities	212,812,000	163,289,000	165,049,000
Investment securities - measured at fair value
Principal pay downs and maturities	347,000	1,144,000	1,881,000
Investment securities - AFS
Purchases	(827,002,000)	(143,052,000)	(729,768,000)
Principal pay downs and maturities	273,950,000	226,455,000	208,228,000
Proceeds from sales	132,546,000	95,826,000	63,153,000
Principal pay downs and maturities of held-to-maturity securities	0	6,600,000	5,375,000
Purchase of investment tax credits	(29,437,000)	(32,484,000)	(40,355,000)
Proceeds from Sale (Payments to Purchase) Investment In Money Market	330,000	2,181,000	(1,968,000)
Proceeds from Life Insurance Policies	797,000	1,046,000	2,582,000
(Purchase) liquidation of restricted stock	(25,821,000)	4,911,000	750,000
Payments for (Proceeds from) Loans and Leases	(1,269,351,000)	(1,560,633,000)	(728,793,000)
Purchase of premises, equipment, and other assets, net	(10,856,000)	(13,925,000)	(18,873,000)
Proceeds from sale of other real estate owned and repossessed assets, net	45,627,000	25,918,000	43,242,000
Cash Acquired from Acquisition	342,427,000	0	21,204,000
Net cash used in investing activities	(1,366,443,000)	(1,386,013,000)	(1,173,342,000)
Cash flows from financing activities:
Net increase in deposits	1,357,855,000	1,093,353,000	1,045,173,000
Proceeds from Issuance of Subordinated Long-term Debt	150,000,000	0	0
Net (increase) decrease in borrowings	(257,038,000)	40,407,000	70,159,000
Payments of Debt Extinguishment Costs	0	(6,501,000)	(10,887,000)
Proceeds from exercise of common stock options	1,935,000	8,294,000	4,595,000
Redemption Of Preferred Stock	(70,500,000)	(70,500,000)	0
Excess tax benefit of stock-based compensation	5,874,000	4,194,000	1,552,000
Cash dividends paid on preferred stock	(750,000)	(1,387,000)	(1,410,000)
Proceeds from Issuance of Common Stock	28,288,000	13,746,000	0
Net cash provided by financing activities	1,213,875,000	1,081,606,000	1,109,182,000
Net increase (decrease) in cash and cash equivalents	60,244,000	(141,118,000)	100,889,000
Cash and cash equivalents at beginning of period	164,396,000	305,514,000	204,625,000
Cash and cash equivalents at end of period	224,640,000	164,396,000	305,514,000
Cash paid during the period for:
Interest	28,831,000	26,516,000	28,613,000
Income taxes	54,590,000	35,556,000	19,105,000
Non-cash investing and financing activity:
Transfers to other assets acquired through foreclosure, net	28,566,000	13,777,000	24,911,000
Change in unfunded LIHTC and SBIC commitments	39,617,000	9,798,000	50,000,000
Non-cash assets acquired in acquisition	1,587,186,000	0	410,827,000
Non-cash liabilities acquired in acquisition	1,764,996,000	0	421,987,000
Change in unrealized gain on AFS securities, net of tax	(6,502,000)	29,209,000	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	(4,276,000)
Change in unfunded obligations	(27,325,000)	(28,522,000)	(29,755,000)
Transfer of HTM securities to AFS, amortized cost	0	275,300,000	0
Unrealized gain on transfer of HTM securities to AFS, net of tax	0	$ 8,976,000	$ 0
Subordinated Debt [Member]
Cash flows from financing activities:
Proceeds from Debt, Net of Issuance Costs	$ 148,211,000

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of operation WAL is a bank holding company headquartered in Phoenix, Arizona, incorporated under the laws of the state of Delaware. WAL provides a full spectrum of deposit, lending, treasury management, and online banking products and services through its wholly-owned banking subsidiary, WAB. On June 30, 2015, WAL acquired Bridge Capital Holdings and its wholly-owned subsidiary, Bridge Bank. Upon acquisition, Bridge Capital Holdings merged into WAL and its principal operating subsidiary, Bridge Bank, merged into WAB. Effective as of July 1, 2015, the existing Bridge offices and the two previously existing WAB Northern California offices are operating as a combined division, with their results reported under the Company's Northern California operating segment. WAB operates the following full-service banking divisions: ABA in Arizona, BON in Southern Nevada, Bridge in Northern California, FIB in Northern Nevada, and TPB in Southern California. The Company also serves business customers through a national platform of specialized financial services including AAB, Corporate Finance, Equity Fund Resources, Life Sciences Group, Mortgage Warehouse Lending, Public Finance, Renewable Energy Group, Resort Finance, and Technology Finance. In addition, the Company has one non-bank subsidiary, LVSP, which holds and manages certain non-performing loans and OREO. Basis of presentation The accounting and reporting policies of the Company are in accordance with GAAP and conform to practices within the financial services industry. The accounts of the Company and its consolidated subsidiaries are included in the Consolidated Financial Statements. Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Material estimates that are particularly susceptible to significant changes in the near term relate to the determination of the allowance for credit losses; estimated cash flows related to PCI loans; fair value determinations related to acquisitions and other assets and liabilities carried at fair value; and accounting for income taxes. Although management believes these estimates to be reasonably accurate, actual amounts may differ. In the opinion of management, all adjustments considered necessary have been reflected in the Consolidated Financial Statements. Principles of consolidation On December 31, 2013, the Company consolidated its three bank subsidiaries under one bank charter, WAB. As the subsidiary bank mergers did not meet the definition of a business combination under the guidance of ASC 805, Business Combinations , the entities were combined in a method similar to a pooling of interests. As of December 31, 2015 , WAL has ten wholly-owned subsidiaries: WAB, LVSP, and eight unconsolidated subsidiaries used as business trusts in connection with the issuance of trust-preferred securities. The Bank has the following significant wholly-owned subsidiaries: WAB Investments, Inc., BON Investments, Inc., and TPB Investments, Inc., which hold certain investment securities, municipal and non-profit loans, and leases; and BW Real Estate, Inc., which operates as a real estate investment trust and holds certain of WAB's real estate loans and related securities. BW Nevada Holdings, LLC was dissolved on June 12, 2015 after distributing the Company’s 2700 West Sahara Avenue, Las Vegas, Nevada office building to WAB. The Company does not have any other significant entities that should be considered for consolidation. All significant intercompany balances and transactions have been eliminated in consolidation. Reclassifications Certain amounts in the Consolidated Financial Statements as of and for the years ended December 31, 2015 , 2014 , and 2013 may have been reclassified to conform to the current presentation. The reclassifications have no effect on net income or stockholders’ equity as previously reported. Business combinations Business combinations are accounted for under the acquisition method of accounting in accordance with ASC 805, Business Combinations. Under the acquisition method, the acquiring entity in a business combination recognizes all of the acquired assets and assumed liabilities at their estimated fair values as of the date of acquisition. Any excess of the purchase price over the fair value of net assets and other identifiable intangible assets acquired is recorded as goodwill. To the extent the fair value of net assets acquired, including identified intangible assets, exceeds the purchase price, a bargain purchase gain is recognized. Assets acquired and liabilities assumed from contingencies are also recognized at fair value if the fair value can be determined during the measurement period. Results of operations of an acquired business are included in the Consolidated Income Statement from the date of acquisition. Acquisition-related costs, including conversion and restructuring charges, are expensed as incurred. Cash and cash equivalents For purposes of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from banks (including cash items in process of clearing), and federal funds sold. Cash flows from loans originated by the Company and customer deposit accounts are reported net. The Company maintains amounts due from banks, which at times may exceed federally insured limits. The Company has not experienced any losses in such accounts. Cash reserve requirements Depository institutions are required by law to maintain reserves against their transaction deposits. The reserves must be held in cash or with the FRB. Banks are permitted to meet this requirement by maintaining the specified amount as an average balance over a two-week period. The total of reserve balances was approximately $37.9 million and $11.6 million as of December 31, 2015 and 2014 , respectively. Investment securities Investment securities may be classified as HTM, AFS, or measured at fair value. The appropriate classification is initially decided at the time of purchase. Securities classified as HTM are those debt securities that the Company has both the intent and ability to hold to maturity regardless of changes in market conditions, liquidity needs, or general economic conditions. These securities are carried at amortized cost. The sale of a security within three months of its maturity date or after the majority of the principal outstanding has been collected is considered a maturity for purposes of classification and disclosure. Securities classified as AFS or trading securities measured at fair value are reported as an asset in the Consolidated Balance Sheet at their estimated fair value. As the fair value of AFS securities changes, the changes are reported net of income tax as an element of OCI, except for other-than-temporarily-impaired securities. When AFS securities are sold, the unrealized gain or loss is reclassified from OCI to non-interest income. The changes in the fair values of trading securities are reported in non-interest income. Securities classified as AFS are both equity and debt securities that the Company intends to hold for an indefinite period of time, but not necessarily to maturity. Any decision to sell a security classified as AFS would be based on various factors, including significant movements in interest rates, changes in the maturity mix of the Company’s assets and liabilities, liquidity needs, decline in credit quality, and regulatory capital considerations. Interest income is recognized based on the coupon rate and increased by accretion of discounts earned or decreased by the amortization of premiums paid over the contractual life of the security, adjusted for prepayment estimates, using the interest method. In estimating whether there are any OTTI losses, management considers the 1) length of time and the extent to which the fair value has been less than amortized cost; 2) financial condition and near term prospects of the issuer; 3) impact of changes in market interest rates; and 4) intent and ability of the Company to retain its investment for a period of time sufficient to allow for any anticipated recovery in fair value and whether it is not more likely than not the Company would be required to sell the security. Declines in the fair value of individual AFS debt securities that are deemed to be other-than-temporary are reflected in earnings when identified. The fair value of the debt security then becomes the new cost basis. For individual debt securities where the Company does not intend to sell the security and it is not more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis, the other-than-temporary decline in fair value of the debt security related to 1) credit loss is recognized in earnings; and 2) interest rate, market, or other factors is recognized in other comprehensive income or loss. For individual debt securities where the Company either intends to sell the security or more likely than not will not recover all of its amortized cost, the OTTI is recognized in earnings equal to the entire difference between the security's cost basis and its fair value at the balance sheet date. For individual debt securities for which a credit loss has been recognized in earnings, interest accruals and amortization and accretion of premiums and discounts are suspended when the credit loss is recognized. Interest received after accruals have been suspended is recognized on a cash basis. Restricted stock On January 30, 2015, WAB became a member of the Federal Reserve System and, as part of its membership, is required to maintain stock in the FRB in a specified ratio to its capital. In addition, WAB is a member of the FHLB system and, accordingly, maintains an investment in capital stock of the FHLB based on the borrowing capacity used. The Bank also maintains an investment in its primary correspondent bank. All of these investments are considered equity securities with no actively traded market. Therefore, the shares are considered restricted investment securities. These investments are carried at cost, which is equal to the value at which they may be redeemed. The dividend income received from the stock is reported in interest income. The Company conducts a periodic review and evaluation of its restricted stock to determine if any impairment exists. No impairment has been recorded to date. Loans, held for sale Loans, held for sale consist primarily of SBA and CRE loans that the Company originates (or acquires) and intends to sell. These loans are carried at the lower of aggregate cost or fair value. Fair value is determined based on available market data for similar assets, expected cash flows, and appraisals of underlying collateral or the credit quality of the borrower. Gains and losses on the sale of loans are recognized pursuant to ASC 860, Transfers and Servicing . Interest income of these loans is accrued daily and loan origination fees and costs are deferred and included in the cost basis of the loan. The Company issues various representations and warranties associated with these loan sales. The Company has not experienced any losses as a result of these representations and warranties. Loans, held for investment The Company generally holds loans for investment and has the intent and ability to hold loans until their maturity. Therefore, they are reported at book value. Net loans are stated at the amount of unpaid principal, reduced by net deferred fees and costs, purchase accounting fair value adjustments, and an allowance for credit losses. In addition, the book value of loans that are subject to a fair value hedge is adjusted for changes in value attributable to the effective portion of the hedged benchmark interest rate risk. Purchased loans are recorded at estimated fair value on the date of purchase, comprised of unpaid principal less estimated credit losses and interest rate fair value adjustments. The Company may acquire loans through a business combination or in a purchase for which differences may exist between the contractual cash flows and the cash flows expected to be collected, which are due, at least in part, to credit quality. Loans are evaluated individually to determine if there has been credit deterioration since origination. Such loans may then be aggregated and accounted for as a pool of loans based on common characteristics. When the Company acquires such loans, the yield that may be accreted (accretable yield) is limited to the excess of the Company’s estimate of undiscounted cash flows expected to be collected over the Company’s initial investment in the loan. The excess of contractual cash flows over the cash flows expected to be collected may not be recognized as an adjustment to yield, loss, or a valuation allowance. Subsequent increases in cash flows expected to be collected generally are recognized prospectively through adjustment of the loan’s yield over the remaining life. Subsequent decreases to cash flows expected to be collected are recognized as impairment. The Company may not carry over or create a valuation allowance in the initial accounting for loans acquired under these circumstances. For purchased loans that are not deemed impaired, fair value adjustments attributable to both credit and interest rates are accreted (or amortized) over the contractual life of the individual loan. For additional information, see " Note 4. Loans, Leases and Allowance for Credit Losses " of these Notes to Consolidated Financial Statements. Loan fees collected for the origination of loans less direct loan origination costs (net deferred loan fees) are amortized over the contractual life of the loan through interest income. If the loan has scheduled payments, the amortization of the net deferred loan fee is calculated using the interest method over the contractual life of the loan. If the loan does not have scheduled payments, such as a line of credit, the net deferred loan fee is recognized as interest income on a straight-line basis over the contractual life of the loan commitment. Commitment fees based on a percentage of a customer’s unused line of credit and fees related to standby letters of credit are recognized over the commitment period. When loans are repaid, any remaining unamortized balances of premiums, discounts, or net deferred fees are recognized as interest income. Non-accrual loans: For all loan types except credit cards, when a borrower discontinues making payments as contractually required by the note, the Company must determine whether it is appropriate to continue to accrue interest. The Company ceases accruing interest income when the loan has become delinquent by more than 90 days or when management determines that the full repayment of principal and collection of interest according to contractual terms is no longer likely. The Company may decide to continue to accrue interest on certain loans more than 90 days delinquent if the loans are well secured by collateral and in the process of collection. Credit card loans and other personal loans are typically charged off no later than 180 days delinquent. For all loan types, when a loan is placed on non-accrual status, all interest accrued but uncollected is reversed against interest income in the period in which the status is changed and, the Company makes a loan-level decision to apply either the cash basis or cost recovery method. The Company recognizes income on a cash basis only for those non-accrual loans for which the collection of the remaining principal balance is not in doubt. Under the cost recovery method, subsequent payments received from the customer are applied to principal and generally no further interest income is recognized until the principal has been paid in full or until circumstances have changed such that payments are again consistently received as contractually required. Impaired loans: A loan is identified as impaired when it is no longer probable that interest and principal will be collected according to the contractual terms of the original loan agreement. Generally, impaired loans are classified as non-accrual. However, in certain instances, impaired loans may continue on an accrual basis, if full repayment of all principal and interest is expected and the loan is both well secured and in the process of collection. Impaired loans are measured for reserve requirements in accordance with ASC 310, Receivables, based on the present value of expected future cash flows discounted at the loan's effective interest rate or, as a practical expedient, at the loan's observable market price or the fair value of the collateral less applicable disposition costs if the loan is collateral dependent. The amount of an impairment reserve, if any, and any subsequent changes are recorded as a provision for credit losses. Losses are recorded as a charge-off when losses are confirmed. In addition to management's internal loan review process, regulators may from time to time direct the Company to modify loan grades, loan impairment calculations, or loan impairment methodology. Troubled Debt Restructured Loans : A TDR loan is a loan on which the Company, for reasons related to a borrower’s financial difficulties, grants a concession to the borrower that the Company would not otherwise consider. The loan terms that have been modified or restructured due to a borrower’s financial situation include, but are not limited to, a reduction in the stated interest rate, an extension of the maturity or renewal of the loan at an interest rate below current market, a reduction in the face amount of the debt, a reduction in the accrued interest, or deferral of interest payments. A TDR loan is also considered impaired. A TDR loan may be returned to accrual status when the loan is brought current, has performed in accordance with the contractual restructured terms for a reasonable period of time (generally six months) and the ultimate collectability of the total contractual restructured principal and interest is no longer in doubt. However, such loans continue to be considered impaired. Consistent with regulatory guidance, a TDR loan that is subsequently modified in another restructuring agreement but has shown sustained performance and classification as a TDR, will be removed from TDR status provided that the modified terms were market-based at the time of modification. Allowance for credit losses Credit risk is inherent in the business of extending loans and leases to borrowers, for which the Company must maintain an adequate allowance for credit losses. The allowance for credit losses is established through a provision for credit losses recorded to expense. Loans are charged against the allowance for credit losses when management believes that the contractual principal or interest will not be collected. Subsequent recoveries, if any, are credited to the allowance. The allowance is an amount believed adequate to absorb estimated probable losses on existing loans that may become uncollectable, based on evaluation of the collectability of loans and prior credit loss experience, together with other factors. The Company formally re-evaluates and establishes the appropriate level of the allowance for credit losses on a quarterly basis. The allowance consists of specific and general components. The specific allowance applies to impaired loans. For impaired collateral dependent loans, the reserve is calculated based on the collateral value, net of estimated disposition costs. Generally, the Company obtains independent collateral valuation analysis for each loan every twelve months. Loans not collateral dependent are evaluated based on the expected future cash flows discounted at the original contractual interest rate. The Company's impairment analysis also incorporates various valuation considerations, including loan type, loss experience, and geographic criteria. The general allowance covers all non-impaired loans and is based on historical loss experience adjusted for the various qualitative and quantitative factors listed above. The Company’s allowance for credit loss methodology incorporates several quantitative and qualitative risk factors used to establish the appropriate allowance for credit losses at each reporting date. Quantitative factors include: 1) the Company's historical loss experience; 2) levels of and trends in delinquencies and impaired loans; 3) levels of and trends in charge-offs and recoveries; 4) trends in volume and terms of loans; 5) changes in underwriting standards or lending policies; 6) experience, ability, depth of lending staff; 7) national and local economic trends and conditions; 8) changes in credit concentrations; 9) out-of-market exposures; 10) changes in quality of loan review system; and 11) changes in the value of underlying collateral. An internal ten -year loss history is also incorporated into the allowance calculation model. Due to the credit concentration of our loan portfolio in real estate secured loans, the value of collateral is heavily dependent on real estate values in Nevada, Arizona, and California. While management uses the best information available to make its evaluation, future adjustments to the allowance may be necessary if there are significant changes in economic or other conditions. In addition, regulators, as an integral part of their examination processes, periodically review the Bank's allowance for credit losses, and may require us to make additions to the allowance based on their judgment about information available to them at the time of their examination. Management regularly reviews the assumptions and formulae used in determining the allowance and makes adjustments if required to reflect the current risk profile of the portfolio. Transfers of financial assets Transfers of financial assets are accounted for as sales when control over the assets has been surrendered. Control over transferred assets is deemed surrendered when the 1) assets have been isolated from the Company; 2) transferee obtains the right to pledge or exchange the transferred assets; and 3) Company no longer maintains effective control over the transferred assets through an agreement to repurchase the transferred assets before maturity. Premises and equipment Premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is computed principally by the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized over the terms of the lease or the estimated lives of the improvements, whichever is shorter. Depreciation and amortization is computed using the following estimated lives: Years Bank premises 31 Furniture, fixtures, and equipment 3 - 10 Leasehold improvements (1) 3 - 10 (1) Depreciation is recorded over the lesser of 3 to 10 years or the term of the lease. Management periodically reviews premises and equipment in order to determine if facts and circumstances suggest that the value of an asset is not recoverable. Goodwill and other intangible assets The Company records as goodwill the excess of the purchase price over the fair value of the identifiable net assets acquired in accordance with applicable guidance. The Company performs its annual goodwill and intangibles impairment tests as of October 1 each year, or more often if events or circumstances indicate that the carrying value may not be recoverable. The Company can first elect to assess, through qualitative factors, whether it is more likely than not that goodwill is impaired. Pursuant to this guidance, if the qualitative assessment indicates potential impairment, the Company will proceed with the two-step process. The first step tests for impairment, while the second step, if necessary, measures the impairment. The resulting impairment amount, if any, is charged to current period earnings as non-interest expense. The Company’s intangible assets consist primarily of core deposit intangible assets that are amortized over periods ranging from 5 to 10 years. The Company considers the remaining useful lives of its core deposit intangible assets each reporting period, as required by ASC 350, Intangibles—Goodwill and Other, to determine whether events and circumstances warrant a revision to the remaining period of amortization. If the estimate of an intangible asset’s remaining useful life has changed, the remaining carrying amount of the intangible asset is amortized prospectively over the revised remaining useful life. The Company has not revised its estimates of the useful lives of its core deposit intangibles during the years ended December 31, 2015 , 2014 , or 2013 . Other assets acquired through foreclosure Other assets acquired through foreclosure consist primarily of properties acquired as a result of, or in-lieu-of, foreclosure. Properties or other assets (primarily repossessed assets formerly leased) are classified as OREO and other repossessed property and are initially reported at fair value of the asset less estimated selling costs. Subsequent adjustments are based on the lower of carrying value or fair value less estimated costs to sell the property. Costs related to the development or improvement of the assets are capitalized and costs related to holding the assets are charged to non-interest expense. Property is evaluated regularly to ensure the recorded amount is supported by its current fair value and valuation allowances. Investments in low income housing credits The Company invests in Limited Partnerships formed for the purpose of investing in low income housing projects, which qualify for federal LIHTC. These investments are expected to generate tax credits over a ten-year period. The Company adopted the amended guidance in ASU 2014-01, Accounting for Investments in Qualified Affordable Housing Projects, beginning on January 1, 2014 and accounts for these investments using the proportional amortization method. See " Note 15. Income Taxes " for the additional disclosures required under these amendments. Bank owned life insurance BOLI is carried at its cash surrender value with changes recorded in other non-interest income in the Consolidated Income Statements. The face amount of the underlying policies including death benefits was $361.7 million and $321.9 million as of December 31, 2015 and 2014 , respectively. There are no loans offset against cash surrender values, and there are no restrictions as to the use of proceeds. Customer repurchase agreements The Company enters into repurchase agreements with customers, whereby it pledges securities against overnight investments made from the customer’s excess collected funds. The Company records these at the amount of cash received in connection with the transaction. Stock compensation plans The Company has the Incentive Plan, as amended, which is described more fully in " Note 11. Stockholders' Equity " of these Notes to Consolidated Financial Statements. Compensation expense for stock options and non-vested restricted stock awards is based on the fair value of the award on the measurement date which, for the Company, is the date of the grant and is recognized ratably over the service period of the award. The Company utilizes the Black-Scholes option-pricing model to calculate the fair value of stock options. The fair value of non-vested restricted stock awards is the market price of the Company’s stock on the date of grant. See " Note 11. Stockholders' Equity " of these Notes to Consolidated Financial Statements for further discussion of stock options and restricted stock awards. Derivative financial instruments The Company uses interest-rate swaps to mitigate interest-rate risk associated with changes to 1) the fair value of certain fixed-rate financial instruments (fair value hedges) and 2) certain cash flows related to future interest payments on variable rate financial instruments (cash flow hedges). The Company recognizes derivatives as assets or liabilities in the Consolidated Balance Sheet at their fair value in accordance with ASC 815, Derivatives and Hedging . The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and further, on the type of hedging relationship. On the date the derivative contract is entered into, the Company designates the derivative as a fair value hedge or cash flow hedge. Derivative instruments designated in a hedge relationship to mitigate exposure to changes in the fair value of an asset or liability attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivative instruments designated in a hedge relationship to mitigate exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. Changes in the fair value of a derivative that is designated and qualifies as a fair value hedge, along with changes in the fair value of the hedged asset or liability that are attributable to the hedged risk are recorded in current-period earnings. For a cash flow hedge, the effective portion of the change in the fair value of the derivative is recorded in AOCI and reclassified into earnings in the same period or periods during which the hedged transaction affects earnings. Any ineffective portion of the change in fair value of a cash flow hedge is recognized immediately in non-interest income in the Consolidated Income Statement. Under both the fair value and cash flow hedge scenarios, changes in the fair value of derivatives not considered to be highly effective in hedging the change in fair value or the expected cash flows of the hedged item are recognized in earnings as non-interest income during the period of the change. The Company documents its hedge relationships, including identification of the hedging instruments and the hedged items, as well as its risk management objectives and strategies for undertaking the hedge transaction at the time the derivative contract is executed. Both at inception and at least quarterly thereafter, the Company assesses whether the derivatives used in hedging transactions are highly effective (as defined in the guidance) in offsetting changes in either the fair value or cash flows of the hedged item. Retroactive effectiveness is assessed, as well as the continued expectation that the hedge will remain effective prospectively. The Company discontinues hedge accounting prospectively when it is determined that a hedge is no longer highly effective. When hedge accounting is discontinued on a fair value hedge that no longer qualifies as an effective hedge, the derivative continues to be reported at fair value in the Consolidated Balance Sheet, but the carrying amount of the hedged item is no longer adjusted for future changes in fair value. The adjustment to the carrying amount of the hedged item that existed at the date hedge accounting is discontinued is amortized over the remaining life of the hedged item into earnings. Derivative instruments that are not designated as hedges, so called free-standing derivatives, are reported in the Consolidated Balance Sheet at fair value and the changes in fair value are recognized in earnings as non-interest income during the period of change. The Company may in the normal course of business purchase a financial instrument or originate a loan that contains an embedded derivative instrument. Upon purchasing the instrument or originating the loan, the Company assesses whether the economic characteristics of the embedded derivative are clearly and closely related to the economic characteristics of the remaining component of the financial instrument (i.e., the host contract) and whether a separate instrument with the same terms as the embedded instrument would meet the definition of a derivative instrument. When it is determined that the embedded derivative possesses economic characteristics that are not clearly and closely related to the economic characteristics of the host contract and a separate instrument with the same terms would qualify as a derivative instrument, the embedded derivative is separated from the host contract and carried at fair value. However, in cases where the host contract is measured at fair value, with c

Mergers, Acquisitions and Dispo

Mergers, Acquisitions and Dispositions	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Mergers, Acquisitions and Dispositions	2. MERGERS, ACQUISITIONS AND DISPOSITIONS Acquisition of Bridge Capital Holdings On June 30, 2015, the Company completed its acquisition of Bridge Capital Holdings and its wholly-owned subsidiary, Bridge Bank, headquartered in San Jose, California. Under the terms of the acquisition, each outstanding share of Bridge common stock was exchanged for 0.8145 shares of WAL's common stock plus $2.39 in cash. The Company paid $36.5 million in cash and issued 12.5 million common shares for all equity interests in Bridge. The merger was undertaken, in part, because Bridge strengthens the Company's Northern California presence and provides new avenues for growth in technology and international services. Bridge’s results of operations have been included in the Company’s results beginning July 1, 2015. Acquisition / restructure expenses related to the Bridge acquisition of $8.8 million for the year ended December 31, 2015 , have been included in non-interest expense, of which approximately $0.9 million are acquisition related costs as defined by ASC 805. The acquisition was accounted for under the acquisition method of accounting in accordance with ASC 805. Assets purchased and liabilities assumed were recorded at their respective acquisition date estimated fair values. The fair values of assets acquired and liabilities assumed are subject to adjustment during the first twelve months after the acquisition date if additional information becomes available to indicate a more accurate or appropriate value for an asset or liability. The following table shows the recognized amounts of identifiable assets acquired and liabilities assumed at their as adjusted acquisition date fair values, which include all measurement period adjustments identified and recognized since July 1, 2015: As Adjusted (in thousands) Assets: Cash and cash equivalents (1) $ 378,966 Investment securities - AFS 61,299 Investments in restricted stock 7,015 Loans 1,439,930 Premises and equipment 1,519 Other assets acquired through foreclosure 1,407 Bank owned life insurance 17,385 Investment in LIHTC 5,354 Intangible assets 14,997 Deferred tax assets, net 18,287 Other assets 19,993 Total assets $ 1,966,152 Liabilities: Deposits $ 1,742,031 Qualifying debt 11,287 Other liabilities 11,678 Total liabilities 1,764,996 Net assets acquired $ 201,156 Consideration paid Common stock (12,451,240 shares at $33.76 per share) $ 420,354 Fair value of equity awards related to pre-combination vesting 10,676 Cash 36,539 Fair value of total consideration 467,569 Goodwill $ 266,413 (1) Cash and cash equivalents is net of a $6.2 million payment made by Bridge related to the cash out of vested, unexercised stock options at the date of closing. Cash acquired, less cash consideration paid of $36.5 million , resulted in net cash and cash equivalents increasing by $342.4 million following the acquisition. The Company identified $6.8 million in measurement period adjustments since July 1, 2015, which have been reflected as an adjustment to increase goodwill. Due to early adoption of the amended guidance within ASU 2015-16, Simplifying the Accounting for Measurement-Period Adjustments , as discussed in " Note 1. Summary of Significant Accounting Policies ," these adjustments to provisional amounts identified during the measurement period are recognized in the reporting period in which the adjustment amounts are determined, rather than retrospectively adjusting the provisional amounts at the acquisition date. Any effects on earnings from changes in the provisional amounts have been appropriately reflected in the Consolidated Income Statement for the year ended December 31, 2015. The significant measurement period adjustments relate to loans, net deferred tax assets, and other liabilities. The fair value of loans decreased as there were further adjustments made to the interest and credit marks on Bridge loans. The net deferred tax assets balance was adjusted to account for the tax effects of all the changes in the fair values of assets acquired and liabilities assumed. Other liabilities also increased to accrue for unrecorded expenses and other liabilities incurred prior to acquisition. Although further measurement period adjustments are not expected to be significant, the estimated fair value of tax related items and other liabilities are still preliminary and are subject to additional measurement period adjustments. Loans acquired in the Bridge acquisition consist of loans that are not considered impaired (non-PCI loans) and loans that have shown evidence of credit deterioration since origination (PCI loans) as of the acquisition date. All loans were recorded net of fair value adjustments (interest rate and credit marks), which were determined using discounted contractual cash flow models. The fair value of non-PCI loans acquired totals $1.43 billion , which is net of interest and credit marks of $26.0 million . The fair value of PCI loans totals $10.9 million , which is net of interest and credit marks of $5.7 million . See " Note 4. Loans, Leases and Allowance for Credit Losses " of these Notes to Consolidated Financial Statements for additional detail of the acquired loans. In connection with the Bridge acquisition, the Company acquired intangible assets of $15.0 million , consisting primarily of core deposit intangibles. The core deposit intangible asset balance has been allocated to the Northern California and CBL segments based on their respective core deposit balances at June 30, 2015, and is subject to amortization over its estimated useful life of 10 years. Goodwill related to the acquisition totaled $266.4 million , which includes $6.8 million of measurement period adjustments identified and recognized since July 1, 2015. Goodwill has been allocated to the Northern California and CBL segments based on their proportionate loan and deposit balances as of June 30, 2015. Management believes this methodology allocates goodwill to the reporting units in a manner consistent with the expected synergies of the combination. None of the goodwill recognized as part of the acquisition is expected to be deductible for income tax purposes. Qualifying debt assumed from Bridge is comprised of junior subordinated debt with a contractual balance of $17.5 million and is recorded net of a $6.2 million fair value mark that will be amortized over the remaining life of the trusts. See " Note 10. Qualifying Debt " of these Notes to Consolidated Financial Statements for further detail and discussion of the debt. In connection with the acquisition, the Company assumed Bridge's SERP, an unfunded noncontributory defined benefit pension plan. The SERP provides retirement benefits to certain Bridge officer's based on years of service and final average salary. Pursuant to the terms of the SERP agreements, if the officer's service is terminated by Bridge or by the officer for "good reason" (as defined in the SERP agreements) within 24 months following a change in control, such as the Bridge acquisition, the officer is entitled to full vesting of the normal benefit under the SERP agreement, and such SERP benefits will be made in installment payments commencing on the first business day of January of the year following the officer's attainment of age 55 or, if the officer is already age 55 as of such termination of employment, on the first business day of January of the year following the officer's termination of employment. As of June 30, 2015, a $7.1 million liability included in other liabilities was recorded in the Company's Consolidated Balance Sheet related to the SERP. A discount rate of 5.75% and an employee compensation rate increase of 4.00% were used in determining the SERP liability as of June 30, 2015. See " Note 19. Employee Benefit Plans " of these Notes to the Consolidated Financial Statements for further detail and discussion of the SERP. The following table presents pro forma information as if the Bridge acquisition was completed on January 1, 2014. The pro forma information includes adjustments for interest income on loans and securities acquired, amortization of intangibles arising from the transaction and interest expense on deposits acquired. The pro forma information is not necessarily indicative of the results of operations as they would have been had the transactions been effected on the assumed dates. Year Ended December 31, 2015 2014 (in thousands, except per share amounts) Interest income $ 560,292 $ 495,235 Non-interest income 37,073 38,768 Net income available to common stockholders (1) 205,099 164,165 Earnings per share - basic 1.90 1.64 Earnings per share - diluted 1.87 1.62 (1) Excludes acquisition / restructure related costs incurred by the Company of $8.8 million for the year ended December 31, 2015 , respectively, and acquisition / restructure related costs incurred by Bridge of $6.8 million for the year ended December 31, 2015 , respectively, and related tax effects. PartnersFirst Discontinued Operations The Company discontinued its affinity credit card business and presented these activities as discontinued operations. During the second quarter 2014, the Company shut down its remaining affinity credit card operations. Therefore, no additional discontinued operations have been reported. The following table summarizes the operating results of the discontinued operations for the year ended December 31, 2014 and 2013 : Year Ended December 31, 2014 2013 (in thousands) Operating revenue $ (358 ) $ 3,345 Non-interest expenses (1,369 ) (4,855 ) Loss before income taxes (1,727 ) (1,510 ) Income tax benefit (569 ) (649 ) Net loss $ (1,158 ) $ (861 )

Investment Securities

Investment Securities	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Investment Securities	3. INVESTMENT SECURITIES The carrying amounts and fair values of investment securities at December 31, 2015 and 2014 are summarized as follows: December 31, 2015 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (in thousands) Available-for-sale Collateralized debt obligations $ 50 $ 10,059 $ (49 ) $ 10,060 Commercial MBS issued by GSEs 19,147 72 (105 ) 19,114 Corporate debt securities 12,769 482 — 13,251 CRA investments 34,722 — (37 ) 34,685 Municipal obligations 320,087 14,743 — 334,830 Preferred stock 108,417 4,286 (1,467 ) 111,236 Private label commercial MBS 4,685 6 — 4,691 Private label residential MBS 261,530 5 (4,407 ) 257,128 Residential MBS issued by GSEs 1,169,631 5,254 (4,664 ) 1,170,221 Trust preferred securities 32,000 — (7,686 ) 24,314 U.S. treasury securities 2,996 — (3 ) 2,993 Total AFS securities $ 1,966,034 $ 34,907 $ (18,418 ) $ 1,982,523 Securities measured at fair value Residential MBS issued by GSEs $ 1,481 December 31, 2014 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (in thousands) Available-for-sale Collateralized debt obligations $ 50 $ 11,395 $ — $ 11,445 Commercial MBS issued by GSEs 2,047 100 — 2,147 Corporate debt securities 52,773 717 (1,001 ) 52,489 CRA investments 24,302 30 — 24,332 Municipal obligations 285,398 13,688 (49 ) 299,037 Mutual funds 37,449 500 (247 ) 37,702 Preferred stock 83,192 2,099 (2,679 ) 82,612 Private label commercial MBS 5,017 132 — 5,149 Private label residential MBS 70,985 379 (1,121 ) 70,243 Residential MBS issued by GSEs 881,734 11,440 (1,985 ) 891,189 Trust preferred securities 32,000 — (6,454 ) 25,546 U.S. government-sponsored agency securities 18,701 — (355 ) 18,346 Total AFS securities $ 1,493,648 $ 40,480 $ (13,891 ) $ 1,520,237 Securities measured at fair value Residential MBS issued by GSEs $ 1,858 For additional information on the fair value changes of securities measured at fair value, see the trading securities table in " Note 17. Fair Value Accounting " of these Notes to Consolidated Financial Statements. The Company conducts an OTTI analysis on a quarterly basis. The initial indication of OTTI for both debt and equity securities is a decline in the market value below the amount recorded for an investment, and taking into account the severity and duration of the decline. Another potential indication of OTTI is a downgrade below investment grade. In determining whether an impairment is OTTI, the Company considers the length of time and the extent to which the market value has been below cost, recent events specific to the issuer, including investment downgrades by rating agencies and economic conditions of its industry, and the Company’s ability and intent to hold the investment for a period of time sufficient to allow for any anticipated recovery. For marketable equity securities, the Company also considers the issuer’s financial condition, capital strength, and near-term prospects. For debt securities, for the purpose of an OTTI analysis, the Company also considers the cause of the price decline (general level of interest rates, credit spreads, and industry and issuer-specific factors), the issuer’s financial condition, near-term prospects, and current ability to make future payments in a timely manner, as well as the issuer’s ability to service debt, and any change in agencies’ ratings at the evaluation date from the acquisition date and any likely imminent action. The Company has reviewed securities for which there is an unrealized loss in accordance with its accounting policy for OTTI described above and determined that there were no impairment charges for the years ended December 31, 2015 , 2014 , and 2013 . The Company does not consider any securities to be other-than-temporarily impaired as of December 31, 2015 and 2014 . No assurance can be made that OTTI will not occur in future periods. Information pertaining to securities with gross unrealized losses at December 31, 2015 and 2014 , aggregated by investment category and length of time that individual securities have been in a continuous loss position follows: December 31, 2015 Less Than Twelve Months More Than Twelve Months Total Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (in thousands) Available-for-sale Collateralized debt obligations $ 49 $ 1 $ — $ — $ 49 $ 1 Commercial MBS issued by GSEs 105 17,051 — — 105 17,051 CRA investments 37 24,729 — — 37 24,729 Preferred stock 377 10,542 1,090 14,761 1,467 25,303 Private label residential MBS 3,733 226,720 674 30,372 4,407 257,092 Residential MBS issued by GSEs 3,566 536,515 1,098 38,338 4,664 574,853 Trust preferred securities — — 7,686 24,314 7,686 24,314 U.S. treasury securities 3 2,006 — — 3 2,006 Total AFS securities $ 7,870 $ 817,564 $ 10,548 $ 107,785 $ 18,418 $ 925,349 December 31, 2014 Less Than Twelve Months More Than Twelve Months Total Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (in thousands) Available-for-sale Corporate debt securities $ 139 $ 9,860 $ 862 $ 29,139 $ 1,001 $ 38,999 Municipal obligations — — 49 4,430 49 4,430 Mutual funds 247 25,855 — — 247 25,855 Preferred stock 232 13,811 2,447 28,109 2,679 41,920 Private label residential MBS 157 24,056 964 26,614 1,121 50,670 Residential MBS issued by GSEs 227 49,217 1,758 97,296 1,985 146,513 Trust preferred securities — — 6,454 25,546 6,454 25,546 U.S. government sponsored agency securities — — 355 18,346 355 18,346 Total AFS securities $ 1,002 $ 122,799 $ 12,889 $ 229,480 $ 13,891 $ 352,279 At December 31, 2015 and 2014 , the Company’s unrealized losses relate primarily to interest rate fluctuations, credit spread widening, and reduced liquidity in applicable markets. The total number of securities in an unrealized loss position at December 31, 2015 was 146 , compared to 109 at December 31, 2014 . In analyzing an issuer’s financial condition, management considers whether the securities are issued by the federal government or its agencies, whether downgrades by bond rating agencies have occurred, and industry analysis reports. Since material downgrades have not occurred and management does not intend to sell the debt securities in an unrealized loss position in the foreseeable future, none of the securities described in the above table or in this paragraph were deemed to be OTTI. The preferred stock and trust preferred securities have yields based on floating rate LIBOR, which are highly correlated to the federal funds rate and have been negatively affected by the low rate environment. This has resulted in unrealized losses for these securities. The amortized cost and fair value of securities as of December 31, 2015 , by contractual maturities, are shown below. MBS are shown separately as individual MBS are comprised of pools of loans with varying maturities. Therefore, these securities are listed separately in the maturity summary. December 31, 2015 Amortized Cost Estimated Fair Value (in thousands) Available-for-sale Due in one year or less $ 62,852 $ 63,114 After one year through five years 77,273 81,090 After five years through ten years 68,935 72,283 After ten years 301,981 314,882 Mortgage-backed securities 1,454,993 1,451,154 Total AFS securities $ 1,966,034 $ 1,982,523 The following tables summarize the carrying amount of the Company’s investment ratings position as of December 31, 2015 and 2014 : December 31, 2015 AAA Split-rated AAA/AA+ AA+ to AA- A+ to A- BBB+ to BBB- BB+ and below Unrated Totals (in thousands) Available-for-sale Collateralized debt obligations $ — $ — $ — $ — $ — $ 10,060 $ — $ 10,060 Commercial MBS issued by GSEs — 19,114 — — — — — 19,114 Corporate debt securities — — 2,721 5,489 5,041 — — 13,251 CRA investments — — — — — — 34,685 34,685 Municipal obligations 7,949 — 180,460 131,110 6,243 180 8,888 334,830 Preferred stock — — — — 79,955 23,655 7,626 111,236 Private label commercial MBS 4,691 — — — — — — 4,691 Private label residential MBS 235,605 — 40 3,186 1,750 2,705 13,842 257,128 Residential MBS issued by GSEs — 1,170,221 — — — — — 1,170,221 Trust preferred securities — — — — 24,314 — — 24,314 U.S. treasury securities — 2,993 — — — — — 2,993 Total AFS securities (1) $ 248,245 $ 1,192,328 $ 183,221 $ 139,785 $ 117,303 $ 36,600 $ 65,041 $ 1,982,523 Securities measured at fair value Residential MBS issued by GSEs $ — $ 1,481 $ — $ — $ — $ — $ — $ 1,481 (1) The Company uses the average credit rating of the combination of S&P, Moody’s, and Fitch, where ratings differ. December 31, 2014 AAA Split-rated AAA/AA+ AA+ to AA- A+ to A- BBB+ to BBB- BB+ and below Unrated Totals (in thousands) Available-for-sale Collateralized debt obligations $ — $ — $ — $ — $ — $ 11,445 $ — $ 11,445 Commercial MBS issued by GSEs — 2,147 — — — — — 2,147 Corporate debt securities — — 2,759 5,570 44,160 — — 52,489 CRA investments — — — — — — 24,332 24,332 Municipal obligations 8,168 — 138,256 146,155 6,263 195 — 299,037 Mutual funds (2) — — — — 37,702 — — 37,702 Preferred stock — — — — 54,585 17,632 10,395 82,612 Private label commercial MBS 5,149 — — — — — — 5,149 Private label residential MBS 59,944 — 68 3,439 3,595 3,197 — 70,243 Residential MBS issued by GSEs — 891,189 — — — — — 891,189 Trust preferred securities — — — — 25,546 — — 25,546 U.S. government sponsored agency securities — 18,346 — — — — — 18,346 Total AFS securities (1) $ 73,261 $ 911,682 $ 141,083 $ 155,164 $ 171,851 $ 32,469 $ 34,727 $ 1,520,237 Securities measured at fair value Residential MBS issued by GSEs $ — $ 1,858 $ — $ — $ — $ — $ — $ 1,858 (1) The Company uses the average credit rating of the combination of S&P, Moody’s, and Fitch, where ratings differ. (2) At least 80% of mutual funds are investment grade corporate debt securities. Securities with carrying amounts of approximately $830.7 million and $755.5 million at December 31, 2015 and 2014 , respectively, were pledged for various purposes as required or permitted by law. The following table presents gross gains and losses on sales of investment securities: Year Ended December 31, 2015 2014 2013 (in thousands) Gross gains $ 1,144 $ 1,118 $ 1,569 Gross losses (529 ) (361 ) (2,764 ) Net gains on sales of investment securities $ 615 $ 757 $ (1,195 )

Loans, Leases and Allowance for

Loans, Leases and Allowance for Credit Losses	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Loans, Leases and Allowance for Credit Losses	4. LOANS, LEASES AND ALLOWANCE FOR CREDIT LOSSES The composition of the Company’s loan portfolio is as follows: December 31, 2015 2014 (in thousands) Loans, HFI Commercial and industrial $ 5,114,257 $ 3,326,708 Commercial real estate - non-owner occupied 2,283,536 2,052,566 Commercial real estate - owner occupied 2,083,285 1,732,888 Construction and land development 1,133,439 748,053 Residential real estate 322,939 299,402 Commercial leases 148,493 205,639 Consumer 26,905 33,009 Loans, net of deferred loan fees and costs 11,112,854 8,398,265 Allowance for credit losses (119,068 ) (110,216 ) Total loans HFI $ 10,993,786 $ 8,288,049 Net deferred loan fees and costs as of December 31, 2015 and 2014 total $19.2 million and $12.5 million , respectively. Net unamortized discounts on loans total $8.2 million and $7.5 million as of December 31, 2015 and 2014 , respectively. Total loans held for investment are also net of interest rate and credit marks on acquired loans totaling $40.5 million and $27.1 million as of December 31, 2015 and 2014 , respectively. As of December 31, 2015 , the Company also has $23.8 million of HFS loans. The following table presents the contractual aging of the recorded investment in past due loans held for investment by class of loans: December 31, 2015 Current 30-59 Days 60-89 Days Over 90 days Total Total (in thousands) Commercial real estate Owner occupied $ 2,078,968 $ 445 $ 362 $ 3,510 $ 4,317 $ 2,083,285 Non-owner occupied 2,099,274 2,481 — 2,822 5,303 2,104,577 Multi-family 178,959 — — — — 178,959 Commercial and industrial Commercial 5,066,197 26,358 14,124 7,578 48,060 5,114,257 Leases 145,905 — — 2,588 2,588 148,493 Construction and land development Construction 694,527 — — — — 694,527 Land 438,495 — — 417 417 438,912 Residential real estate 317,677 888 159 4,215 5,262 322,939 Consumer 26,587 12 91 215 318 26,905 Total loans $ 11,046,589 $ 30,184 $ 14,736 $ 21,345 $ 66,265 $ 11,112,854 December 31, 2014 Current 30-59 Days 60-89 Days Over 90 days Total Total (in thousands) Commercial real estate Owner occupied $ 1,730,164 $ 1,406 $ 180 $ 1,138 $ 2,724 $ 1,732,888 Non-owner occupied 1,855,454 2,389 3,361 8,737 14,487 1,869,941 Multi-family 182,180 — 445 — 445 182,625 Commercial and industrial Commercial 3,324,132 1,523 15 1,038 2,576 3,326,708 Leases 205,639 — — — — 205,639 Construction and land development Construction 388,399 — — — — 388,399 Land 356,209 — 2,640 805 3,445 359,654 Residential real estate 292,065 2,347 205 4,785 7,337 299,402 Consumer 32,540 177 21 271 469 33,009 Total loans $ 8,366,782 $ 7,842 $ 6,867 $ 16,774 $ 31,483 $ 8,398,265 The following table presents the recorded investment in non-accrual loans and loans past due ninety days or more and still accruing interest by class of loans: December 31, 2015 December 31, 2014 Non-accrual loans Loans past due 90 days or more and still accruing Non-accrual loans Loans past due 90 days or more and still accruing Current Past Due/ Total Current Past Due/ Total (in thousands) Commercial real estate Owner occupied $ 749 $ 3,253 $ 4,002 $ 339 $ 13,630 $ — $ 13,630 $ 1,138 Non-owner occupied 11,851 2,822 14,673 — 30,226 8,601 38,827 2,171 Multi-family — — — — — — — — Commercial and industrial Commercial 3,263 15,026 18,289 2,671 2,621 496 3,117 703 Leases — 2,588 2,588 — 373 — 373 — Construction and land development Construction — — — — — — — — Land 1,892 417 2,309 — 2,686 2,640 5,326 805 Residential real estate 1,835 4,489 6,324 — 1,332 4,841 6,173 232 Consumer — 196 196 18 25 188 213 83 Total $ 19,590 $ 28,791 $ 48,381 $ 3,028 $ 50,893 $ 16,766 $ 67,659 $ 5,132 The reduction in interest income associated with loans on non-accrual status was approximately $2.5 million , $3.8 million , and $5.4 million for the years ended December 31, 2015 , 2014 , and 2013 , respectively. The Company utilizes an internal asset classification system as a means of reporting problem and potential problem loans. Under the Company’s risk rating system, the Company classifies problem and potential problem loans as Special Mention, Substandard, Doubtful, and Loss. Substandard loans include those characterized by well-defined weaknesses and carry the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. Loans classified as Doubtful, or risk rated eight, have all the weaknesses inherent in those classified as Substandard with the added characteristic that the weaknesses present make collection or liquidation in full, on the basis of currently existing facts, conditions and values, highly questionable and improbable. The final rating of Loss covers loans considered uncollectible and having such little recoverable value that it is not practical to defer writing off the asset. Loans that do not currently expose the Company to sufficient risk to warrant classification in one of the aforementioned categories, but possess weaknesses that warrant management’s close attention, are deemed to be Special Mention. Risk ratings are updated, at a minimum, quarterly. The following tables present gross loans by risk rating: December 31, 2015 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Commercial real estate Owner occupied $ 2,032,932 $ 28,422 $ 20,814 $ 1,117 $ — $ 2,083,285 Non-owner occupied 2,054,428 14,867 35,282 — — 2,104,577 Multi-family 178,959 — — — — 178,959 Commercial and industrial Commercial 4,962,930 76,283 74,294 750 — 5,114,257 Leases 140,531 4,580 794 2,588 — 148,493 Construction and land development Construction 678,438 16,089 — — — 694,527 Land 420,819 362 17,731 — — 438,912 Residential real estate 310,067 776 12,096 — — 322,939 Consumer 26,438 209 258 — — 26,905 Total $ 10,805,542 $ 141,588 $ 161,269 $ 4,455 $ — $ 11,112,854 December 31, 2015 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Current (up to 29 days past due) $ 10,799,558 $ 140,932 $ 104,232 $ 1,867 $ — $ 11,046,589 Past due 30 - 59 days 1,907 271 28,006 — — 30,184 Past due 60 - 89 days 4,077 385 10,274 — — 14,736 Past due 90 days or more — — 18,757 2,588 — 21,345 Total $ 10,805,542 $ 141,588 $ 161,269 $ 4,455 $ — $ 11,112,854 December 31, 2014 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Commercial real estate Owner occupied $ 1,664,270 $ 28,072 $ 39,222 $ 1,324 $ — $ 1,732,888 Non-owner occupied 1,771,138 35,752 62,611 440 — 1,869,941 Multi-family 182,180 — 445 — — 182,625 Commercial and industrial Commercial 3,295,027 14,380 17,146 155 — 3,326,708 Leases 202,772 2,494 373 — — 205,639 Construction and land development Construction 383,677 4,241 481 — — 388,399 Land 328,278 10,289 21,087 — — 359,654 Residential real estate 284,052 2,044 13,306 — — 299,402 Consumer 32,419 233 357 — — 33,009 Total $ 8,143,813 $ 97,505 $ 155,028 $ 1,919 $ — $ 8,398,265 December 31, 2014 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Current (up to 29 days past due) $ 8,140,140 $ 95,091 $ 129,787 $ 1,764 $ — $ 8,366,782 Past due 30 - 59 days 2,771 198 4,718 155 — 7,842 Past due 60 - 89 days 385 37 6,445 — — 6,867 Past due 90 days or more 517 2,179 14,078 — — 16,774 Total $ 8,143,813 $ 97,505 $ 155,028 $ 1,919 $ — $ 8,398,265 The table below reflects the recorded investment in loans classified as impaired: December 31, 2015 2014 (in thousands) Impaired loans with a specific valuation allowance under ASC 310 (1) $ 24,287 $ 124,928 Impaired loans without a specific valuation allowance under ASC 310 (2) 104,587 41,822 Total impaired loans $ 128,874 $ 166,750 Valuation allowance related to impaired loans (3) $ (4,658 ) $ (10,765 ) (1) Includes TDR loans of $3.0 million and $103.3 million at December 31, 2015 and 2014 , respectively. (2) Includes TDR loans of $85.9 million and $35.0 million at December 31, 2015 and 2014 , respectively. (3) Includes valuation allowance related to TDR loans of $0.3 million and $8.9 million at December 31, 2015 and 2014 , respectively. The following table presents impaired loans by class: December 31, 2015 2014 (in thousands) Commercial real estate Owner occupied $ 23,153 $ 44,893 Non-owner occupied 41,081 66,324 Multi-family — — Commercial and industrial Commercial 26,513 13,749 Leases 2,896 373 Construction and land development Construction — — Land 18,322 21,748 Residential real estate 16,575 19,300 Consumer 334 363 Total $ 128,874 $ 166,750 A valuation allowance is established for an impaired loan when the fair value of the loan is less than the recorded investment. In certain cases, portions of impaired loans are charged-off to realizable value instead of establishing a valuation allowance and are included, when applicable, in the table above as “Impaired loans without a specific valuation allowance under ASC 310.” However, before concluding that an impaired loan needs no associated valuation allowance, an assessment is made to consider all available and relevant information for the method used to evaluate impairment and the type of loan being assessed. The valuation allowance disclosed above is included in the allowance for credit losses reported in the Consolidated Balance Sheets as of December 31, 2015 and 2014 . The following table presents the average investment in impaired loans and income recognized on impaired loans: Year Ended December 31, 2015 2014 2013 (in thousands) Average balance on impaired loans $ 150,151 $ 169,758 $ 182,670 Interest income recognized on impaired loans 4,794 5,494 6,235 Interest recognized on non-accrual loans, cash basis 1,634 2,536 1,916 The following table presents average investment in impaired loans by loan class: Year Ended December 31, 2015 2014 2013 (in thousands) Commercial real estate Owner occupied $ 34,912 $ 37,048 $ 49,452 Non-owner occupied 56,360 68,821 56,110 Multi-family — — 89 Commercial and industrial Commercial 17,534 16,168 15,023 Leases 2,948 410 727 Construction and land development Construction — — — Land 19,561 21,580 27,326 Residential real estate 18,453 25,223 33,339 Consumer 383 508 604 Total $ 150,151 $ 169,758 $ 182,670 The average investment in TDR loans included in the average investment in impaired loans table above for the years ended December 31, 2015 , 2014 , and 2013 was $113.9 million , $126.6 million , and $141.8 million , respectively. The following table presents interest income on impaired loans by class: Year Ended December 31, 2015 2014 2013 (in thousands) Commercial real estate Owner occupied $ 1,575 $ 1,550 $ 1,726 Non-owner occupied 1,560 1,484 2,043 Multi-family — 1 — Commercial and industrial Commercial 288 745 1,087 Leases — — — Construction and land development Construction — — — Land 785 1,021 1,288 Residential real estate 579 646 62 Consumer 7 47 29 Total $ 4,794 $ 5,494 $ 6,235 The Company is not committed to lend significant additional funds on these impaired loans. The following table summarizes nonperforming assets: December 31, 2015 2014 (in thousands) Non-accrual loans (1) $ 48,381 $ 67,659 Loans past due 90 days or more on accrual status 3,028 5,132 Troubled debt restructured loans (2) 70,707 84,720 Total nonperforming loans 122,116 157,511 Other assets acquired through foreclosure, net 43,942 57,150 Total nonperforming assets $ 166,058 $ 214,661 (1) Includes non-accrual TDR loans of $18.2 million and $53.6 million at December 31, 2015 and 2014 , respectively. (2) Includes accruing TDR loans only. Loans Acquired in Bridge Acquisition The following table presents information regarding the contractually required principal and interest payments receivable, cash flows expected to be collected, and the estimated fair value of loans acquired in the Bridge acquisition, as of June 30, 2015, the closing date of the transaction. The estimated fair value was decreased by $7.2 million for measurement period adjustments recognized during the six months ended December 31, 2015 : As Adjusted Commercial and Industrial Commercial Real Estate Construction and Land Development Residential Real Estate Consumer Total (in thousands) Contractually required principal and interest payments: PCI $ 17,899 $ 3,127 $ — $ 2,509 $ — $ 23,535 Non-PCI 1,225,837 340,762 106,851 26,999 987 1,701,436 Total loans acquired 1,243,736 343,889 106,851 29,508 987 1,724,971 Cash flows expected to be collected: PCI 10,066 1,570 — 2,088 — 13,724 Non-PCI 1,186,076 304,944 102,240 26,629 989 1,620,878 Total loans acquired 1,196,142 306,514 102,240 28,717 989 1,634,602 Fair value of loans acquired: PCI 7,362 1,417 — 2,075 — 10,854 Non-PCI 1,076,742 229,306 99,080 23,023 925 1,429,076 Total loans acquired $ 1,084,104 $ 230,723 $ 99,080 $ 25,098 $ 925 $ 1,439,930 Loans Acquired with Deteriorated Credit Quality Changes in the accretable yield for loans acquired with deteriorated credit quality in the Centennial, Western Liberty, and Bridge acquisitions are as follows: Year Ended December 31, 2015 2014 2013 (in thousands) Balance, at beginning of period $ 19,156 $ 28,164 $ 7,072 Additions due to acquisition of Bridge 857 — — Measurement period adjustments 38 — 22,318 Reclassifications from non-accretable to accretable yield (1) 1,747 6,052 9,817 Accretion to interest income (3,996 ) (7,185 ) (7,182 ) Reversal of fair value adjustments upon disposition of loans (1,877 ) (7,875 ) (3,861 ) Balance, at end of period $ 15,925 $ 19,156 $ 28,164 (1) The primary drivers of reclassification from non-accretable to accretable yield resulted from changes in estimated cash flows. Allowance for Credit Losses The following table summarizes the changes in the allowance for credit losses by portfolio type: Year Ended December 31, Construction and Land Development Commercial Real Estate Residential Real Estate Commercial and Industrial Consumer Total (in thousands) 2015 Beginning Balance $ 18,558 $ 28,783 $ 7,456 $ 54,566 $ 853 $ 110,216 Charge-offs — — 820 5,550 127 6,497 Recoveries (1,872 ) (4,139 ) (2,181 ) (3,754 ) (203 ) (12,149 ) Provision (1,454 ) (9,762 ) (3,539 ) 18,411 (456 ) 3,200 Ending balance $ 18,976 $ 23,160 $ 5,278 $ 71,181 $ 473 $ 119,068 2014 Beginning Balance $ 14,519 $ 32,064 $ 11,640 $ 39,657 $ 2,170 $ 100,050 Charge-offs 87 964 1,728 4,370 513 7,662 Recoveries (2,160 ) (3,859 ) (1,896 ) (4,728 ) (459 ) (13,102 ) Provision 1,966 (6,176 ) (4,352 ) 14,551 (1,263 ) 4,726 Ending balance $ 18,558 $ 28,783 $ 7,456 $ 54,566 $ 853 $ 110,216 2013 Beginning Balance $ 10,554 $ 34,982 $ 15,237 $ 32,860 $ 1,794 $ 95,427 Charge-offs 1,538 8,648 5,922 4,000 1,371 21,479 Recoveries (2,060 ) (2,758 ) (2,097 ) (5,037 ) (930 ) (12,882 ) Provision 3,443 2,972 228 5,760 817 13,220 Ending balance $ 14,519 $ 32,064 $ 11,640 $ 39,657 $ 2,170 $ 100,050 The following table presents impairment method information related to loans and allowance for credit losses by loan portfolio segment: Commercial Real Estate-Owner Occupied Commercial Real Estate-Non-Owner Occupied Commercial and Industrial Residential Real Estate Construction and Land Development Commercial Leases Consumer Total Loans (in thousands) Loans as of December 31, 2015: Recorded Investment: Impaired loans with an allowance recorded $ 2,778 $ 2,344 $ 18,230 $ 914 $ — $ — $ 21 $ 24,287 Impaired loans with no allowance recorded 20,375 38,737 8,283 15,661 18,322 2,896 313 104,587 Total loans individually evaluated for impairment 23,153 41,081 26,513 16,575 18,322 2,896 334 128,874 Loans collectively evaluated for impairment 2,044,934 2,180,250 5,085,299 303,372 1,115,117 145,597 26,571 10,901,140 Loans acquired with deteriorated credit quality 15,198 62,205 2,445 2,992 — — — 82,840 Total recorded investment $ 2,083,285 $ 2,283,536 $ 5,114,257 $ 322,939 $ 1,133,439 $ 148,493 $ 26,905 $ 11,112,854 Unpaid Principal Balance Impaired loans with an allowance recorded $ 2,778 $ 2,344 $ 19,233 $ 969 $ — $ — $ 21 $ 25,345 Impaired loans with no allowance recorded 63,709 61,692 71,773 44,142 82,800 5,229 3,923 333,268 Total loans individually evaluated for impairment 66,487 64,036 91,006 45,111 82,800 5,229 3,944 358,613 Loans collectively evaluated for impairment 2,044,934 2,180,250 5,085,299 303,372 1,115,117 145,597 26,571 10,901,140 Loans acquired with deteriorated credit quality 20,227 88,181 7,820 3,536 — — — 119,764 Total unpaid principal balance $ 2,131,648 $ 2,332,467 $ 5,184,125 $ 352,019 $ 1,197,917 $ 150,826 $ 30,515 $ 11,379,517 Related Allowance for Credit Losses Impaired loans with an allowance recorded $ 858 $ 11 $ 3,518 $ 270 $ — $ — $ 1 $ 4,658 Impaired loans with no allowance recorded — — — — — — — — Total loans individually evaluated for impairment 858 11 3,518 270 — — 1 4,658 Loans collectively evaluated for impairment 10,953 11,302 65,806 5,008 18,976 1,857 472 114,374 Loans acquired with deteriorated credit quality — 36 — — — — — 36 Total allowance for credit losses $ 11,811 $ 11,349 $ 69,324 $ 5,278 $ 18,976 $ 1,857 $ 473 $ 119,068 Commercial Real Estate-Owner Occupied Commercial Real Estate-Non-Owner Occupied Commercial and Industrial Residential Real Estate Construction and Land Development Commercial Leases Consumer Total Loans (in thousands) Loans as of December 31, 2014: Recorded Investment: Impaired loans with an allowance recorded $ 28,024 $ 44,937 $ 11,399 $ 19,300 $ 21,052 $ 41 $ 175 $ 124,928 Impaired loans with no allowance recorded 16,869 21,387 2,350 — 696 332 188 41,822 Total loans individually evaluated for impairment 44,893 66,324 13,749 19,300 21,748 373 363 166,750 Loans collectively evaluated for impairment 1,670,083 1,910,420 3,312,629 277,692 726,305 205,266 32,646 8,135,041 Loans acquired with deteriorated credit quality 17,912 75,822 330 2,410 — — — 96,474 Total recorded investment $ 1,732,888 $ 2,052,566 $ 3,326,708 $ 299,402 $ 748,053 $ 205,639 $ 33,009 $ 8,398,265 Unpaid Principal Balance Impaired loans with an allowance recorded $ 31,292 $ 45,853 $ 11,829 $ 24,420 $ 21,169 $ 41 $ 187 $ 134,791 Impaired loans with no allowance recorded 17,010 21,550 4,104 — 885 483 188 44,220 Total loans individually evaluated for impairment 48,302 67,403 15,933 24,420 22,054 524 375 179,011 Loans collectively evaluated for impairment 1,670,083 1,910,420 3,312,629 277,692 726,305 205,266 32,646 8,135,041 Loans acquired with deteriorated credit quality 24,273 108,935 1,150 3,439 — — — 137,797 Total unpaid principal balance $ 1,742,658 $ 2,086,758 $ 3,329,712 $ 305,551 $ 748,359 $ 205,790 $ 33,021 $ 8,451,849 Related Allowance for Credit Losses Impaired loans with an allowance recorded $ 2,082 $ 2,537 $ 1,926 $ 1,052 $ 3,112 $ 39 $ 17 $ 10,765 Impaired loans with no allowance recorded — — — — — — — — Total loans individually evaluated for impairment 2,082 2,537 1,926 1,052 3,112 39 17 10,765 Loans collectively evaluated for impairment 10,198 13,734 49,809 6,404 15,446 2,761 836 99,188 Loans acquired with deteriorated credit quality 174 58 31 — — — — 263 Total allowance for credit losses $ 12,454 $ 16,329 $ 51,766 $ 7,456 $ 18,558 $ 2,800 $ 853 $ 110,216 Troubled Debt Restructurings A TDR loan is a loan on which the Company, for reasons related to a borrower’s financial difficulties, grants a concession to the borrower that the Company would not otherwise consider. The loan terms that have been modified or restructured due to a borrower’s financial situation include, but are not limited to, a reduction in the stated interest rate, an extension of the maturity or renewal of the loan at an interest rate below current market, a reduction in the face amount of the debt, a reduction in the accrued interest, or deferral of interest payments. The majority of the Company's modifications are extensions in terms or deferral of payments which result in no lost principal or interest followed by reductions in interest rates or accrued interest. A TDR loan is also considered impaired. Consistent with regulatory guidance, a TDR loan that is subsequently modified in another restructuring agreement but has shown sustained performance and classification as a TDR, will be removed from TDR status provided that the modified terms were market-based at the time of modification. The following table presents information on the financial effects of TDR loans by class for the periods presented: Year Ended December 31, 2015 Number of Loans Pre-Modification Outstanding Recorded Investment Forgiven Principal Balance Lost Interest Income Post-Modification Outstanding Recorded Investment Waived Fees and Other Expenses (dollars in thousands) Commercial real estate Owner occupied — $ — $ — $ — $ — $ — Non-owner occupied 1 193 — — 193 — Multi-family — — — — — — Commercial and industrial Commercial 1 256 — — 256 — Leases — — — — — — Construction and land development Construction — — — — — — Land — — — — — — Residential real estate 1 81 — 3 78 4 Consumer — — — — — — Total 3 $ 530 $ — $ 3 $ 527 $ 4 Year Ended December 31, 2014 Number of Loans Pre-Modification Outstanding Recorded Investment Forgiven Principal Balance Lost Interest Income Post-Modification Outstanding Recorded Investment Waived Fees and Other Expenses (dollars in thousands) Commercial real estate Owner occupied 6 $ 14,646 $ 378 $ 257 $ 14,011 $ 33 Non-owner occupied 5 16,976 — 60 16,916 15 Multi-family — — — — — — Commercial and industrial Commercial 6 2,655 — — 2,655 4 Leases — — — — — — Construction and land development Construction — — — — — — Land 2 2,687 — 47 2,640 — Residential real estate 5 1,966 447 70 1,449 15 Consumer — — — — — — Total 24 $ 38,930 $ 825 $ 434 $ 37,671 $ 67 Year Ended December 31, 2013 Number of Loans Pre-Modification Outstanding Recorded Investment Forgiven Principal Balance Lost Interest Income Post-Modification Outstanding Recorded Investment Waived Fees and Other Expenses (dollars in thousands) Commercial real estate Owner occupied 8 $ 3,681 $ — $ 54 $ 3,627 $ 28 Non-owner occupied 5 10,735 1,030 63 9,642 14 Multi-family — — — — — — Commercial and industrial Commercial 13 4,809 — 19 4,790 11 Leases — — — — — — Construction and land development Construction — — — — — — Land 2 286 — — 286 1 Residential real estate 13 5,434 267 887 4,280 24 Consumer 2 74 — 5 69 3 Total 43 $ 25,019 $ 1,297 $ 1,028 $ 22,694 $ 81 The following table presents TDR loans by class for which there was a payment default during the period: Year Ended December 31, 2015 2014 2013 Number of Loans Recorded Investment Number of Loans Recorded Investment Number of Loans Recorded Investment (dollars in thousands) Commercial real estate Owner occupied — $ — 2 $ 395 3 $ 2,506 Non-owner occupied — — 2 984 3 1,490 Multi-family — — — — — — Commercial and industrial Commercial — — 3 369 3 1,089 Leases — — — — — — Construction and land development Construction 1 137 — — — — Land — — — — 2 330 Residential real estate 3 1,047 1 202 4 955 Consumer — — — — — — Total 4 $ 1,184 8 $ 1,950 15 $ 6,370 A TDR loan is deemed to have a payment default when it becomes past due 90 days, goes on non-accrual, or is restructured again. Payment defaults, along with other qualitative indicators, are considered by management in the determination of the allowance for credit losses. At December 31, 2015 and 2014 , there was $0.1 million and $1.2 million , respectively, in loan commitments outstanding on TDR loans. Loan Purchases and Sales For the years ended December 31, 2015 and 2014 , secondary market loan purchases totaled $137.2 million and $166.4 million , respectively. For 2015 , these purchased loans consisted of $117.1 million of commercial and industrial loans, $13.2 million of commercial real estate loans, $6.8 million in commercial leases, and $0.1 million of construction and land development loans. For 2014 , these purchased loans consisted primarily of commercial and industrial loans. In addition, the Company periodically acquires newly originated loans at closing through participations or loan syndications. During the year ended December 31, 2015 , the Company sold loans, which consisted primarily of commercial and industrial and commercial mortgage-backed securities loans, with a carrying value of $102.2 million and recognized a gain of $0.5 million on the sales. The Company had no significant loan sales in 2014 .

Premises and Equipment (Notes)

Premises and Equipment (Notes)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment Disclosure [Text Block]	5. PREMISES AND EQUIPMENT The following is a summary of the major categories of premises and equipment: December 31, 2015 2014 (in thousands) Bank premises $ 83,431 $ 82,494 Land and improvements 33,971 33,971 Furniture, fixtures, and equipment 40,025 51,320 Leasehold improvements 18,958 18,160 Construction in progress 1,999 848 Total 178,384 186,793 Accumulated depreciation and amortization (59,849 ) (72,975 ) Premises and equipment, net $ 118,535 $ 113,818 Lease Obligations The Company leases certain premises and equipment under non-cancelable operating leases expiring through 2025. The following is a schedule of future minimum rental payments under these leases at December 31, 2015 : (in thousands) 2016 $ 8,547 2017 7,999 2018 7,536 2019 6,628 2020 4,986 Thereafter 8,879 Total future minimum rental payments $ 44,575 The Company leases the majority of its office locations and many of these leases contain multiple renewal options and provisions for increased rents. Total rent expense of $8.1 million , $6.2 million , and $6.9 million is included in occupancy expense for the years ended December 31, 2015 , 2014 , and 2013 , respectively. Total depreciation expense of $7.7 million , $6.0 million , and $6.0 million is included in occupancy expense for the years ended December 31, 2015 , 2014 , and 2013 , respectively.

Other Assets Acquired Through F

Other Assets Acquired Through Foreclosure	12 Months Ended
	Dec. 31, 2015
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Other Assets Acquired Through Foreclosure	6. OTHER ASSETS ACQUIRED THROUGH FORECLOSURE The following table represents the changes in other assets acquired through foreclosure: Year Ended December 31, 2015 Gross Balance Valuation Allowance Net Balance (in thousands) Balance, beginning of period $ 71,421 $ (14,271 ) $ 57,150 Additions from acquisition of Bridge 1,407 — 1,407 Transfers to other assets acquired through foreclosure, net 28,566 — 28,566 Proceeds from sale of other real estate owned and repossessed assets, net (51,038 ) 5,411 (45,627 ) Valuation adjustments, net — (182 ) (182 ) Gains, net (1) 2,628 — 2,628 Balance, end of period $ 52,984 $ (9,042 ) $ 43,942 2014 Balance, beginning of period $ 88,421 $ (21,702 ) $ 66,719 Transfers to other assets acquired through foreclosure, net 13,777 — 13,777 Proceeds from sale of other real estate owned and repossessed assets, net (33,643 ) 7,725 (25,918 ) Valuation adjustments, net — (294 ) (294 ) Gains, net (1) 2,866 — 2,866 Balance, end of period $ 71,421 $ (14,271 ) $ 57,150 2013 Balance, beginning of period $ 113,474 $ (36,227 ) $ 77,247 Additions from acquisition of Centennial 5,622 — 5,622 Transfers to other assets acquired through foreclosure, net 24,911 — 24,911 Proceeds from sale of other real estate owned and repossessed assets, net (61,510 ) 18,268 (43,242 ) Valuation adjustments, net — (3,743 ) (3,743 ) Gains, net (1) 5,924 — 5,924 Balance, end of period $ 88,421 $ (21,702 ) $ 66,719 (1) Includes net gains related to initial transfers to other assets of $0.9 million , $0.1 million , and $0.9 million during the years ended December 31, 2015 , 2014 , and 2013 respectively, pursuant to accounting guidance. At December 31, 2015 , 2014 , and 2013 , the majority of the Company’s repossessed assets consisted of properties located in Nevada. The Company held 39 properties at December 31, 2015 , compared to 67 at December 31, 2014 .

Deposits (Notes)

Deposits (Notes)	12 Months Ended
	Dec. 31, 2015
Deposit [Abstract]
Deposits [Abstract]	8. DEPOSITS The table below summarizes deposits by type: December 31, 2015 2014 (in thousands) Non-interest-bearing demand $ 4,093,976 $ 2,288,048 Interest-bearing demand 1,028,073 854,935 Savings and money market 5,296,921 3,869,699 Certificate of deposit ($250,000 or more) 1,569,525 1,339,238 Other time deposits 42,129 579,123 Total deposits $ 12,030,624 $ 8,931,043 The summary of the contractual maturities for all time deposits as of December 31, 2015 is as follows: December 31, 2015 (in thousands) 2016 $ 1,507,050 2017 88,184 2018 9,633 2019 3,552 2020 3,235 Total $ 1,611,654 WAB is a member of CDARS and ICS, which provide mechanisms for obtaining FDIC insurance on large deposits. Federal banking law and regulation places restrictions on depository institutions regarding brokered deposits because of the general concern that these deposits are not relationship based and are at a greater risk of being withdrawn, thus posing liquidity risk for institutions that gather brokered deposits in significant amounts. At December 31, 2015 and 2014 , the Company had $517.5 million and $700.7 million , respectively, of reciprocal CDARS deposits and $714.4 million and $481.2 million , respectively, of ICS deposits. At December 31, 2015 and 2014 , the Company had $184.2 million and $257.0 million , respectively, of wholesale brokered deposits. There were also $365.6 million and $202.4 million of additional deposits as of December 31, 2015 and 2014 , respectively, that the Company considers core deposits, but which are classified as brokered deposits for regulatory reporting purposes.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Accumulated Other Comprehensive Income	12. ACCUMULATED OTHER COMPREHENSIVE INCOME The following table summarizes the changes in accumulated other comprehensive income (loss) by component, net of tax, for the periods indicated: Unrealized holding gains (losses) on AFS Unrealized holding gains (losses) on SERP Unrealized holding gains (losses) on junior subordinated debt Impairment loss on securities Unrealized gain on cash flow hedge Total (in thousands) Balance, December 31, 2012 $ 8,065 $ — $ — $ 144 $ 17 $ 8,226 Other comprehensive income before reclassifications (30,503 ) — — — (17 ) (30,520 ) Amounts reclassified from accumulated other comprehensive income 748 — — — — 748 Net current-period other comprehensive (loss) (29,755 ) — — — (17 ) (29,772 ) Balance, December 31, 2013 $ (21,690 ) $ — $ — $ 144 $ — $ (21,546 ) Transfer of HTM securities to AFS 8,976 — — — — 8,976 Other comprehensive income before reclassifications 29,683 — — — — 29,683 Amounts reclassified from accumulated other comprehensive income (474 ) — — — — (474 ) Net current-period other comprehensive income 38,185 — — — — 38,185 Balance, December 31, 2014 $ 16,495 $ — $ — $ 144 $ — $ 16,639 Balance, January 1, 2015 (1) 16,495 — 16,309 144 — 32,948 Transfer of HTM securities to AFS — — — — — — Other comprehensive income before reclassifications (6,117 ) 90 (4,276 ) — — (10,303 ) Amounts reclassified from accumulated other comprehensive income (385 ) — — — — (385 ) Net current-period other comprehensive (loss) income (6,502 ) 90 (4,276 ) — — (10,688 ) Balance, December 31, 2015 $ 9,993 $ 90 $ 12,033 $ 144 $ — $ 22,260 (1) As adjusted, see " Note 10. Qualifying Debt " for further discussion. The following table presents reclassifications out of accumulated other comprehensive income: Year Ended December 31, Income Statement Classification 2015 2014 2013 (in thousands) Gain (loss) on sales of investment securities, net $ 615 $ 757 $ (1,195 ) Income tax (expense) benefit (230 ) (283 ) 447 Net of tax $ 385 $ 474 $ (748 )

Other Borrowings

Other Borrowings	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Other Borrowings	9. OTHER BORROWINGS The following table summarizes the Company’s borrowings as of December 31, 2015 and 2014 : December 31, 2015 2014 (in thousands) Short-Term: Revolving line of credit $ — $ 25,000 FHLB advances 150,000 96,987 Other short-term debt — 58,182 Total short-term borrowings $ 150,000 $ 180,169 Long-Term: FHLB advances $ — $ 210,094 Total long-term borrowings $ — $ 210,094 The Company maintains other lines of credit with correspondent banks totaling $70.0 million , of which $25.0 million is secured by pledged securities and has a floating interest rate of one-month or three-month LIBOR plus 1.50%. The remaining $45.0 million is unsecured and has a floating interest rate of one-month LIBOR plus 3.25%. As of December 31, 2015 , there were no outstanding balances on the Company's lines of credit. At December 31, 2014 , the Company had revolving lines of credit with other institutions with outstanding advances totaling $25.0 million , at an interest rate of 1.75% . In addition, the Bank has entered into federal funds credit line agreements with correspondent banks under which it can borrow up to $100.0 million on an unsecured basis at the federal funds rate in effect at the time of borrowing. There were no amounts outstanding on these lines of credit as of December 31, 2015 and 2014 . The lending institutions will determine the interest rate charged on funds at the time of the borrowing. The Company maintains lines of credit with the FHLB and the FRB. The Company’s borrowing capacity is determined based on collateral pledged, generally consisting of investment securities and loans, at the time of the borrowing. At December 31, 2015 , there were $150.0 million in short-term FHLB advances, consisting primarily of overnight advances. The weighted average interest rate on these FHLB advances as of December 31, 2015 was 0.36% . At December 31, 2014 , short-term FHLB advances of $97.0 million had a weighted average interest rate of 1.24% . At December 31, 2014 , Senior Notes had a carrying value of $58.2 million . During the year ended December 31, 2015 , the Senior Notes matured, resulting in a $58.2 million decrease to other short-term debt. During 2015 , the Company paid off $200.0 million of FHLB advances classified as long-term for a loss on extinguishment of $0.1 million . As of December 31, 2014 , long-term FHLB advances of $210.1 million had a weighted average interest rate of 1.06% . As of December 31, 2015 and 2014 , the Company had additional available credit with the FHLB of approximately $1.54 billion and $935.0 million , respectively, and with the FRB of approximately $1.21 billion and $1.15 billion , respectively.

Qualifying Debt Qualifying Debt

Qualifying Debt Qualifying Debt (Notes)	12 Months Ended
	Dec. 31, 2015
Qualifying Debt Disclosure [Abstract]
Subordinated Borrowings Disclosure [Text Block]	10. QUALIFYING DEBT Subordinated Debt On June 29, 2015, the Company issued $150.0 million of subordinated debt, which was recorded net of debt issuance costs of $1.8 million , and matures July 15, 2025. The subordinated debt has a fixed interest rate of 5.00% through June 30, 2020 and then converts to a variable rate of 3.20% plus three-month LIBOR through maturity. The carrying value of subordinated debt also includes the effective portion of related hedges and is $152.0 million at December 31, 2015 . Junior Subordinated Debt The Company has formed or acquired through mergers, eight statutory business trusts, including two new business trusts, Bridge Capital Trust I and Bridge Capital Trust II, acquired in the acquisition of Bridge on June 30, 2015. These trusts exist for the exclusive purpose of issuing Cumulative Trust Preferred Securities. All of the funds raised from the issuance of these securities were passed to the Company and are reflected in the accompanying Consolidated Balance Sheets as junior subordinated debt, with a carrying value of $58.4 million as of December 31, 2015 . The junior subordinated debt has contractual balances and maturity dates as follows: December 31, Name of Trust Maturity 2015 2014 At fair value (in thousands) BankWest Nevada Capital Trust II 2033 $ 15,464 $ 15,464 Intermountain First Statutory Trust I 2034 10,310 10,310 First Independent Statutory Trust I 2035 7,217 7,217 WAL Trust No. 1 2036 20,619 20,619 WAL Statutory Trust No. 2 2037 5,155 5,155 WAL Statutory Trust No. 3 2037 7,732 7,732 Total contractual balance 66,497 66,497 FVO on junior subordinated debt (19,569 ) (26,060 ) Junior subordinated debt, at fair value $ 46,928 $ 40,437 At amortized cost Bridge Capital Holdings Trust I 2035 $ 12,372 $ — Bridge Capital Holdings Trust II 2036 5,155 — Total contractual balance 17,527 — Purchase accounting adjustment, net of accretion (1) (6,085 ) — Junior subordinated debt, at amortized cost $ 11,442 $ — Total junior subordinated debt $ 58,370 $ 40,437 (1) The purchase accounting adjustment will be accreted over the remaining life of the trusts, pursuant to accounting guidance. With the exception of debt issued by Bridge Capital Trust I and Bridge Capital Trust II, junior subordinated debt is recorded at fair value at each reporting date due to the FVO election made by the Company under ASC 825. The Bridge junior subordinated debt was initially recorded at a fair value of $11.3 million on June 30, 2015, which includes a fair market value purchase accounting adjustment of $6.2 million that will be accreted over the remaining life of the debt. The Company did not make the FVO election for the Bridge junior subordinated debt. Accordingly, the carrying value of these trusts at each future reporting date will not reflect the current fair value of the debt. The weighted average interest rate of all junior subordinated debt as of December 31, 2015 was 2.95% , which is three-month LIBOR plus the contractual spread of 2.34%, compared to a weighted average interest rate of 2.73% at December 31, 2014 . In the event of certain changes or amendments to regulatory requirements or federal tax rules, the debt is redeemable in whole. The obligations under these instruments are fully and unconditionally guaranteed by the Company and rank subordinate and junior in right of payment to all other liabilities of the Company. Based on guidance issued by the FRB, the Company's securities continue to qualify as Tier 1 Capital. Adoption of ASU 2016-01 The following table presents the impact of the Company's election to early adopt an element of ASU 2016-01 issued by the FASB in January 2016 related to changes in the fair value of a liability resulting from a change in the instrument-specific credit risk when the fair value option for financial instruments has been elected and its retrospective application for the periods indicated. The cumulative effect of adoption of this guidance at January 1, 2015 was a decrease to retained earnings of $16.3 million and a corresponding increase to accumulated other comprehensive income. Sep 30, 2015 Jun 30, 2015 Mar 31, 2015 (in thousands) Consolidated Balance Sheet: Stockholders' equity Accumulated other comprehensive income As previously reported $ 20,643 $ 15,348 $ 23,423 As reported under new guidance 35,276 26,707 39,538 Retained earnings As previously reported 218,897 159,939 125,467 As reported under new guidance 204,264 148,580 109,352 Three Months Ended Sep 30, 2015 Jun 30, 2015 Mar 31, 2015 (in thousands, except per share data) Consolidated Income Statement: Non-interest income As previously reported $ 13,826 $ (2,191 ) $ 5,933 As reported under new guidance 8,502 5,545 6,242 Income tax expense As previously reported 19,183 10,599 14,118 As reported under new guidance 17,133 13,579 14,234 Net income As previously reported 59,134 34,719 40,190 As reported under new guidance 55,860 39,475 40,383 Net income available to common shareholders As previously reported 58,958 34,472 40,014 As reported under new guidance 55,684 39,228 40,207 Earnings per share applicable to common shareholders--basic As previously reported 0.59 0.39 0.46 As reported under new guidance 0.55 0.44 0.46 Earnings per share applicable to common shareholders--diluted As previously reported 0.58 0.39 0.45 As reported under new guidance 0.55 0.44 0.45

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Stockholder's Equity	11. STOCKHOLDERS' EQUITY Preferred Stock On September 27, 2011, the Company received $141.0 million from the issuance of 141,000 shares of non-cumulative perpetual preferred stock, Series B, par value of $0.0001 per share and a liquidation preference of $1,000 per share, to the U.S. Treasury Department under the SBLF. On December 31, 2014, the Company redeemed 70,500 of its 141,000 shares of non-cumulative perpetual preferred stock, Series B. The shares were redeemed at their liquidation value of $1,000 per share plus accrued dividends for a total redemption price of $70.7 million . On December 18, 2015, the Company redeemed its remaining 70,500 shares of non-cumulative perpetual preferred stock, Series B. The shares were redeemed at their liquidation value of $1,000 per share plus accrued dividends for a total redemption price of $70.7 million . Common Stock Issuance In Connection with Bridge Acquisition Under the terms of the Bridge merger agreement, each share of Bridge common stock issued and outstanding as of June 30, 2015, the acquisition date, was exchanged for 0.8145 shares of WAL common stock and $2.39 in cash. This resulted in the issuance of 12,451,240 shares, or $420.4 million , of the Company's common stock and payment of $36.5 million in cash. Under ATM Distribution Agreement On June 4, 2014, the Company entered into a distribution agency agreement with Credit Suisse Securities (USA) LLC, under which the Company may sell shares of its common stock up to an aggregate offering price of $100.0 million on the New York Stock Exchange. The parties executed an Amended and Restated Distribution Agency Agreement on October 30, 2014. The Company pays Credit Suisse Securities (USA) LLC a mutually agreed rate, not to exceed 2% of the gross offering proceeds of the shares. The common stock will be sold at prevailing market prices at the time of the sale or at negotiated prices and, as a result, prices will vary. Sales in the ATM offering were previously being made pursuant to a prospectus dated May 14, 2012 and a prospectus supplement filed with the SEC on June 4, 2014, in connection with one or more offerings of shares from the Company's shelf registration statement on Form S-3 (No. 333-181128), which expired on May 14, 2015. On May 7, 2015, the Company filed with the SEC a new shelf registration statement on Form S-3 (No. 333-203959). During the year ended December 31, 2015 , the Company sold 760,376 shares under the ATM offering at a weighted-average selling price of $38.13 per share for gross proceeds of $29.0 million . Total related offering costs were $0.7 million , of which $0.5 million relates to compensation costs paid to Credit Suisse Securities (USA) LLC. During the year ended December 31, 2014 , the Company sold 548,122 shares under the ATM offering at a weighted-average selling price of $25.96 per share for gross proceeds of $14.2 million . Total related offering costs were $0.5 million , of which $0.2 million relates to compensation costs paid to Credit Suisse Securities (USA) LLC. Stock-Based Compensation Equity Awards Assumed in Bridge Acquisition In connection with the Bridge acquisition, the Company assumed unvested restricted stock awards and stock options originally granted by Bridge and converted them into WAL restricted stock awards and stock options. Bridge equity awards were converted into WAL equity awards at a conversion ratio of 0.905 , resulting in the issuance of 546,151 shares of WAL restricted stock and 213,091 of WAL options. The portion of the fair value of these equity awards associated with prior service of Bridge employees represents a component of the total consideration for the Bridge acquisition, which totaled $10.7 million . Bridge's restricted stock awards generally had an original vesting period of five years. The remaining vesting period of these awards remained unchanged upon conversion. The value of restricted stock replacement awards were based on WAL's stock price as of the acquisition date and totaled $17.0 million as of June 30, 2015, of which $9.0 million is considered purchase price consideration for pre-combination service and $8.0 million is post-combination compensation service expense that will be recognized over the remaining vesting period of the awards. During the year ended December 31, 2015 , the Company recognized $1.7 million in compensation expense related to these awards. Bridge's stock options had an original vesting period of four years and a contractual term of ten years. Stock option replacement awards were valued using the Black-Scholes option valuation model, using the following weighted average assumptions. June 30, 2015 Dividend yield — % Volatility 33.96 % Risk-free interest rate 2.11 % Expected life in years 7.66 Weighted average fair value of assumed options $ 19.06 The value of assumed stock options as of June 30, 2015 totaled $4.1 million , of which $1.7 million is considered purchase price consideration for pre-combination service and $2.4 million is post-combination compensation service expense that will be recognized over the remaining vesting period of the options. During the year ended December 31, 2015 , the Company recognized $0.5 million in compensation expense related to these awards. Stock Awards and Stock Options The Incentive Plan, as amended, gives the Board of Directors the authority to grant up to 10.5 million stock awards consisting of unrestricted stock, stock units, dividend equivalent rights, stock options (incentive and non-qualified), stock appreciation rights, restricted stock, and performance and annual incentive awards. Stock awards available for grant at December 31, 2015 were 3.2 million. The Incentive Plan contains certain individual limits on the maximum amount that can be paid in cash under the Incentive Plan and on the maximum number of shares of common stock that may be issued pursuant to the Incentive Plan in a calendar year. In 2012, stockholders approved an amendment to the Incentive Plan that 1) increased by 2,000,000 the maximum number of shares available for issuance thereunder; 2) increased the maximum number of shares of stock that can be awarded to any person eligible for an award thereunder to 300,000 per calendar year; and 3) provided for additional business criteria upon which performance-based awards may be based thereunder. In 2014, stockholders approved an amendment to the Incentive Plan that increased the maximum number of shares available for issuance by 2,000,000. Restricted stock awards granted to employees in 2015 and 2014 generally vest over a three -year period. Stock grants made to non-employee WAL and WAB directors during 2015 includes both the annual grant that was fully vested at June 30, 2015 and a special grant to WAB directors that immediately vested in December 2015. The Company estimates the compensation cost for stock grants based upon the grant date fair value. Stock compensation cost is recognized on a straight-line basis over the requisite service period for the entire award. The aggregate grant date fair value for the stock issued during the year ended December 31, 2015 was $12.6 million . For the year ended December 31, 2015 , the Company recognized $9.3 million in stock-based compensation expense related to these stock grants, compared to $6.8 million in 2014 . In addition, the Company granted 52,200 shares of restricted stock to certain members of executive management that have both performance and service conditions that affect vesting. The performance condition was based on achieving an EPS target for fiscal year 2015. This EPS target was met as of December 31, 2015 and therefore the restricted stock awards will vest over a remaining two-year service period. The grant date fair value of the awards was $1.4 million . For the year ended December 31, 2015 , the Company recognized $0.5 million in stock-based compensation expense related to these performance-based restricted stock grants, compared to no such stock-based compensation expense in 2014 or 2013 . A summary of the status of the Company’s unvested shares of restricted stock, including those issued in connection with the Bridge acquisition, and changes during the years then ended is presented below: December 31, 2015 2014 Shares Weighted Average Grant Date Fair Value Shares Weighted Average Grant Date Fair Value (in thousands, except per share amounts) Balance, beginning of period 1,050 $ 16.19 1,204 $ 9.71 Granted 509 27.55 508 23.90 Issued in acquisition of Bridge 546 14.70 — — Vested (528 ) 13.02 (566 ) 9.57 Forfeited (85 ) 21.63 (96 ) 15.05 Balance, end of period 1,492 $ 20.46 1,050 $ 16.19 The weighted average grant date fair value of stock awards granted during the years ended December 31, 2015 , 2014 , and 2013 was $12.6 million , $12.2 million , and $6.7 million , respectively. The total fair value of restricted stock that vested during the years ended December 31, 2015 , 2014 , and 2013 was $14.6 million , $13.3 million , and 6.8 million , respectively. As of December 31, 2015 , there was $18.5 million of total unrecognized compensation cost related to unvested share-based compensation arrangements granted under the Incentive Plan. That cost is expected to be recognized over a weighted average period of 2.19 years. As of December 31, 2015 , the Company has stock option awards outstanding related to options granted in 2011 as well as stock option awards converted in connection with the Bridge acquisition. The options granted in 2011 had a vesting period of 4 years, a contractual life of 7 years, and became fully vested in January 2015. The fair value of each option award was estimated on the date of grant using the Black-Scholes option valuation model. A summary of option activity during the year ended December 31, 2015 is presented below: December 31, 2015 Shares Weighted Average Exercise Price (per share) Weighted Average Remaining Contractual Term (in years) Aggregate (in thousands, except exercise price and contractual terms) Outstanding options, beginning of period 217 $ 9.70 Granted — — Issued in acquisition of Bridge 213 22.02 Exercised (182 ) 10.62 Forfeited or expired (24 ) 23.89 Options outstanding, end of period 224 $ 19.15 6.41 $ 3,738 Options exercisable, end of period 94 $ 11.72 3.67 $ 2,278 Options expected to vest, end of period 97 $ 24.49 8.38 $ 1,691 The total intrinsic value of options exercised during the years ended December 31, 2015 , 2014 , and 2013 was $3.6 million , $7.1 million , and $2.8 million , respectively. Performance Stock Units The Company grants members of its executive management committee performance stock units that do not vest unless the Company achieves a specified cumulative EPS target over a three-year performance period. The number of shares issued will vary based on the cumulative EPS target that is achieved. The Company estimates the cost of performance stock units based upon the grant date fair value and expected vesting percentage over the three-year performance period. For the year ended December 31, 2015 , the Company recognized $4.8 million in stock-based compensation expense related to these performance stock units, compared to $3.6 million in stock-based compensation expense for such units in 2014 . The three-year performance period for the 2012 grant ended on December 31, 2014, and the Company's cumulative EPS for the performance period exceeded the level required for a maximum award under the terms of the grant. As a result, on February 18, 2015, executive management committee members were granted 285,000 of fully vested common shares. The three-year performance period for the 2013 grant ended on December 31, 2015, and the Company's cumulative EPS for the performance period exceeded the level required for a maximum award under the terms of the grant. As a result, 308,400 shares will become fully vested and be paid out to members of the executive management committee in February 2016. As of December 31, 2015 , outstanding performance stock unit grants made in 2014 and 2015 are expected to pay out at the maximum award amount, or 414,650 common shares.

Derivatives and Hedging

Derivatives and Hedging	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging Activities	13. DERIVATIVES AND HEDGING ACTIVITIES The Company is a party to various derivative instruments through its subsidiary, WAB. Derivative instruments are contracts between two or more parties that have a notional amount and an underlying variable, require a small or no initial investment, and allow for the net settlement of positions. A derivative’s notional amount serves as the basis for the payment provision of the contract and takes the form of units, such as shares or dollars. A derivative’s underlying variable is a specified interest rate, security price, commodity price, foreign exchange rate, index, or other variable. The interaction between the notional amount and the underlying variable determines the number of units to be exchanged between the parties and influences the fair value of the derivative contract. The primary type of derivatives that the Company uses are interest rate swaps. Generally, these instruments are used to help manage the Company's exposure to interest rate risk and meet client financing and hedging needs. Derivatives are recorded at fair value in the Consolidated Balance Sheets, after taking into account the effects of bilateral collateral and master netting agreements. These agreements allow the Company to settle all derivative contracts held with the same counterparty on a net basis, and to offset net derivative positions with related cash collateral, where applicable. As of December 31, 2015 , 2014 , and 2013 , the Company does not have any significant outstanding cash flow hedges or free-standing derivatives. Derivatives Designated in Hedge Relationships The Company utilizes derivatives that have been designated as part of a hedge relationship in accordance with the applicable accounting guidance to minimize the exposure to changes in benchmark interest rates and volatility of net interest income and EVE to interest rate fluctuations. The primary derivative instruments used to manage interest rate risk are interest rate swaps, which convert the contractual interest rate index of agreed-upon amounts of assets and liabilities (i.e., notional amounts) to another interest rate index. The Company designates its “pay fixed/receive variable” interest rate swaps as fair value hedges. These contracts convert certain fixed-rate long-term loan assets into variable-rate assets, thereby modifying the Company's exposure to changes in interest rates. As a result, the Company receives variable-rate interest payments in exchange for making fixed-rate payments over the lives of the contracts without exchanging the notional amounts. The Company entered into a "pay variable/receive fixed" interest rate swap agreement, designated as a fair value hedge, to hedge the interest rate exposure on its subordinated debt issuance. As a result, the Company is paying a floating rate of three month LIBOR plus 3.16% and is receiving semi-annual fixed payments of 5.00% to match the payments on the debt. Fair Values, Volume of Activity, and Gain/Loss Information Related to Derivative Instruments The following table summarizes the fair values of the Company's derivative instruments on a gross and net basis as of December 31, 2015 , 2014 , and 2013 . The change in the notional amounts of these derivatives from December 31, 2013 to December 31, 2015 indicates the volume of the Company's derivative transaction activity during these periods. The derivative asset and liability balances are presented on a gross basis, prior to the application of bilateral collateral and master netting agreements. Total derivative assets and liabilities are adjusted to take into account the impact of legally enforceable master netting agreements that allow the Company to settle all derivative contracts with the same counterparty on a net basis and to offset the net derivative position with the related collateral. Where master netting agreements are not in effect or are not enforceable under bankruptcy laws, the Company does not adjust those derivative amounts with counterparties. The fair value of derivative contracts, after taking into account the effects of master netting agreements, is included in other assets or other liabilities in the Consolidated Balance Sheets, as indicated in the following table: December 31, 2015 December 31, 2014 December 31, 2013 Fair Value Fair Value Fair Value Notional Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities (in thousands) Derivatives designated as hedging instruments: Fair value hedges Interest rate swaps $ 800,478 $ 3,569 $ 64,785 $ 647,703 $ 7 $ 57,820 $ 294,997 $ 2,386 $ 788 Total 800,478 3,569 64,785 647,703 7 57,820 294,997 2,386 788 Netting adjustments (1) — — — — — — — 384 384 Net derivatives in the balance sheet $ 800,478 $ 3,569 $ 64,785 $ 647,703 $ 7 $ 57,820 $ 294,997 $ 2,002 $ 404 (1) Netting adjustments represent the amounts recorded to convert our derivative balances from a gross basis to a net basis in accordance with the applicable accounting guidance. Fair value hedges An assessment of effectiveness is performed at initiation of a hedge and on a quarterly basis thereafter. All of the Company's fair value hedges remained “highly effective” as of December 31, 2015 , 2014 , and 2013 . The following table summarizes the pre-tax net gains (losses) on fair value hedges for the years ended December 31, 2015 , 2014 , and 2013 which are recorded in unrealized (losses) gains on assets and liabilities measured at fair value, net in the income statement. Year Ended December 31, 2015 2014 2013 (in thousands) Hedge of Fixed Rate Loans (a) Loss on "pay fixed" swap $ (6,965 ) $ (60,377 ) $ 3,308 Gain on receive fixed rate loans 7,044 60,208 (3,317 ) Net ineffectiveness $ 79 $ (169 ) $ (9 ) Hedge of Fixed Rate Subordinated Debt (a) Gain on "receive fixed" swap $ 3,569 $ — $ — Loss on subordinated debt (3,569 ) — — Net ineffectiveness $ — $ — $ — (a) The fair value of derivatives contracts are carried as other assets and other liabilities in the Consolidated Balance Sheets. The effective portion of hedging gains (losses) are recorded as basis adjustments to the underlying hedged asset or liability. Gains and losses on both the hedging derivative and hedged item are recorded through non-interest expense with a resulting net income impact for the amount of ineffectiveness. Counterparty Credit Risk Like other financial instruments, derivatives contain an element of credit risk. This risk is measured as the expected positive replacement value of the contracts. Management generally enters into bilateral collateral and master netting agreements that provide for the net settlement of all contracts with the same counterparty. Additionally, management monitors counterparty credit risk exposure on each contract to determine appropriate limits on the Company's total credit exposure across all product types. In general, the Company has a zero credit threshold with regard to derivative exposure with counterparties. Management reviews the Company's collateral positions on a daily basis and exchanges collateral with counterparties in accordance with standard ISDA documentation and other related agreements. The Company generally holds collateral in the form of highly rated securities issued by the U.S. Treasury or government-sponsored enterprises, such as GNMA, FNMA, and FHLMC. The total collateral netted against net derivative liabilities totaled $61.7 million at December 31, 2015 , $57.8 million at December 31, 2014 , and $0.3 million at December 31, 2013 . The following table summarizes our largest exposure to an individual counterparty at the dates indicated: December 31, 2015 2014 2013 (in thousands) Largest gross exposure (derivative asset) to an individual counterparty $ 3,569 $ 7 $ 2,378 Collateral posted by this counterparty 4,680 — 2,002 Derivative liability with this counterparty — — 346 Collateral pledged to this counterparty 1,340 — — Net exposure after netting adjustments and collateral $ 229 $ 7 $ — Credit Risk Contingent Features Management has entered into certain derivative contracts that require the Company to post collateral to the counterparties when these contracts are in a net liability position. Conversely, the counterparties post collateral when these contracts are in a net asset position. The amount of collateral to be posted is based on the amount of the net liability and exposure thresholds. As of December 31, 2015 , 2014 , and 2013 the aggregate fair value of all derivative contracts with credit risk contingent features (i.e., those containing collateral posting provisions) held by the Company that were in a net liability position totaled $64.8 million , $57.8 million , and $0.4 million , respectively. As of December 31, 2015 , the Company was in an over-collateralized net position of $15.5 million after considering $77.2 million of collateral held in the form of securities. As of December 31, 2014 and 2013 , the Company was in an over-collateralized position of $14.2 million and $12.4 million , respectively.

Earnings per Share (Notes)

Earnings per Share (Notes)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Share	14. EARNINGS PER SHARE Diluted EPS is based on the weighted average outstanding common shares during each period, including common stock equivalents. Basic EPS is based on the weighted average outstanding common shares during the period. The following table presents the calculation of basic and diluted EPS: Year Ended December 31, 2015 2014 2013 (in thousands, except per share amounts) Weighted average shares - basic 94,570 86,693 85,682 Dilutive effect of stock awards 649 813 859 Weighted average shares - diluted 95,219 87,506 86,541 Net income available to common stockholders $ 193,494 $ 146,564 $ 113,555 Earnings per share - basic 2.05 1.69 1.33 Earnings per share - diluted 2.03 1.67 1.31 The Company had zero , 1,500 , and 163,300 stock options outstanding as of December 31, 2015 , 2014 , and 2013 , respectively, which were not included in the computation of diluted earnings per common share because their effect would be anti-dilutive.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	15. INCOME TAXES The provision for income taxes charged to operations consists of the following: Year Ended December 31, 2015 2014 2013 (in thousands) Current $ 61,040 $ 55,572 $ 43,547 Deferred 3,254 (7,182 ) (13,717 ) Total tax provision $ 64,294 $ 48,390 $ 29,830 The reconciliation between the statutory federal income tax rate and the Company’s effective tax rate are summarized as follows: Year Ended December 31, 2015 2014 2013 (in thousands) Income tax at statutory rate $ 90,489 $ 69,125 $ 50,979 Increase (decrease) resulting from: State income taxes, net of federal benefits 5,783 4,904 3,016 Bank owned life insurance (1,365 ) (1,578 ) (1,683 ) Tax-exempt income (20,226 ) (15,006 ) (7,308 ) Deferred tax asset valuation allowance (2,290 ) (2,104 ) (2,391 ) Bargain purchase gain — — (3,775 ) Low income housing tax credits (5,223 ) (3,872 ) (2,105 ) Tax benefit related to Western Liberty acquisition — — (3,738 ) Other, net (2,874 ) (3,079 ) (3,165 ) Total tax provision $ 64,294 $ 48,390 $ 29,830 The effective tax rate for the year ended December 31, 2015 was 24.87% , compared to 24.50% for the year ended December 31, 2014 , and 20.48% for the year ended December 31, 2013 . There was not a significant change in the effective tax rate from 2014 compared to 2015. The increase in the effective tax rate from 2013 compared to 2014 is primarily due to the increase in pre-tax book income and the absence of acquisition related benefits for the year ended December 31, 2014 compared to 2013 . The cumulative tax effects of the primary temporary differences are shown in the following table: December 31, 2015 2014 (in thousands) Deferred tax assets: Allowance for credit losses $ 47,431 $ 42,038 Fair market value adjustment related to acquired loans 13,930 8,250 Stock-based compensation 12,069 4,749 Net operating loss carryovers 9,255 8,453 Tax credit carryovers 9,052 9,617 Startup costs and other amortization 4,771 5,113 Allowance for other assets acquired through foreclosure, net 4,280 7,343 Section 382 limited NUBILs 3,284 3,657 Other 13,686 8,188 Total gross deferred tax assets 117,758 97,408 Deferred tax asset valuation allowance — (2,290 ) Total deferred tax assets 117,758 95,118 Deferred tax liabilities: Unrealized gain on debt instruments measured at fair value (7,537 ) — Deferred loan costs (7,400 ) (6,041 ) Unrealized gain on AFS securities (6,353 ) (9,949 ) Core deposit intangible (6,093 ) (1,006 ) Premises and equipment (2,039 ) (4,049 ) Unrealized gains on financial instruments measured at fair value (1,000 ) (9,798 ) Other (984 ) (1,589 ) Total deferred tax liabilities (31,406 ) (32,432 ) Deferred tax assets, net $ 86,352 $ 62,686 Deferred tax assets and liabilities are included in the Consolidated Financial Statements at currently enacted income tax rates applicable to the period in which the deferred tax assets or liabilities are expected to be reversed. As changes in tax laws or rates are enacted, deferred tax assets and liabilities are adjusted through the provision for income taxes. For the year ended December 31, 2015 , the net deferred tax assets increased $23.7 million to $86.4 million . This overall increase in the net deferred tax asset was primarily the result of increases to deferred tax assets from the effects of the Bridge acquisition; a change in fair market value of junior subordinated debt and AFS securities; and the increase in the allowance for credit losses. Although realization is not assured, the Company believes that the realization of the recognized deferred tax asset of $86.4 million at December 31, 2015 is more-likely-than-not based on expectations as to future taxable income and based on available tax planning strategies within the meaning of ASC 740, Income Taxes , that could be implemented if necessary to prevent a carryover from expiring. As of December 31, 2015 and 2014 , the Company had a deferred tax valuation allowance of zero and $1.8 million , respectively, related to net capital loss carryovers from the sale of preferred stock investments and zero and $0.5 million , respectively, related to IRC Section 382 limitations associated with the Company's acquisition of Western Liberty. The deferred tax asset related to federal and state NOL carryovers outstanding at December 31, 2015 and 2014 available to reduce the tax liability in future years totaled $9.3 million and $8.5 million , respectively. The respective $9.3 million and $8.5 million of tax benefits relate entirely to federal NOL carryovers (subject to an annual limitation imposed by IRC Section 382). The Company’s ability to use federal NOL carryovers, as well as its ability to use certain future tax deductions called NUBILs associated with the Company's acquisitions of Western Liberty and Centennial, will be subject to separate annual limitations of $1.8 million and $1.6 million of deductions from taxable income, respectively. In management’s opinion, it is more-likely-than-not that the results of future operations will generate sufficient taxable income to realize all of the deferred tax benefits related to these NOL carryovers and NUBILs. The Company files income tax returns in the U.S. federal jurisdiction and in various states. With few exceptions, the Company is no longer subject to U.S. federal, state, or local income tax examinations by tax authorities for years before 2011 . When tax returns are filed, it is highly certain that some positions taken would be sustained upon examination by the taxing authorities, while others are subject to uncertainty about the merits of the position taken or the amount of the position that would be ultimately sustained. The benefit of a tax position is recognized in the Consolidated Financial Statements in the period in which, based on all available evidence, management believes it is more-likely-than-not that the position will be sustained upon examination, including the resolution of appeals or litigation processes, if any. Tax positions taken are not offset or aggregated with other positions. Tax positions that meet the more-likely-than-not recognition threshold are measured as the largest amount of tax benefit that is more than 50% likely of being realized upon settlement with the applicable taxing authority. The portion of the benefits associated with tax positions taken that exceeds the amount measured as described above would be reflected as a liability for unrecognized tax benefits in the accompanying Consolidated Balance Sheet along with any associated interest and penalties that would be payable to the taxing authorities upon examination. The total gross activity of unrecognized tax benefits related to uncertain tax positions are shown in the following table: December 31, 2015 2014 (in thousands) Beginning balance $ — $ — Gross Increases Tax positions in prior periods 1,038 — Current period tax positions — — Gross decreases Tax positions in prior periods — — Settlements — — Lapse of statute of limitations — — Ending balance $ 1,038 $ — As of December 31, 2015 , the total amount of unrecognized tax benefits, net of associated deferred tax benefit, that would impact the effective tax rate, if recognized, is $0.7 million . There were no unrecognized tax benefits as of December 31, 2014 . Interest and penalties related to unrecognized tax benefits are recognized in the provision for income taxes. During the year ended December 31, 2015 , the Company recognized as part of its provision for income taxes, $0.1 million in penalties associated with unrecognized tax benefits and no amounts for interest. There were no amounts for interest and penalties recognized during the years ended December 31, 2014 and 2013 . As of December 31, 2015 , the Company has accrued a $0.1 million liability for penalties and a $0.1 million liability for interest. As of December 31, 2014 , there were no amounts accrued for interest or penalties. Investments in LIHTC The Company invests in LIHTC funds that are designed to generate a return primarily through the realization of federal tax credits. Investments in LIHTC and unfunded LIHTC obligations are included as part of other assets and other liabilities, respectively, in the Consolidated Balance Sheets and total $152.7 million and $61.2 million , respectively, as of December 31, 2015 , compared to $126.6 million and $51.4 million as of December 31, 2014 . For the years ended December 31, 2015 , 2014 , and 2013 , $14.4 million , $10.6 million , and $5.9 million of amortization related to LIHTC investments was recognized as a component of income tax expense, respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	16. COMMITMENTS AND CONTINGENCIES Unfunded Commitments and Letters of Credit The Company is party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit and standby letters of credit. They involve, to varying degrees, elements of credit risk in excess of amounts recognized in the Consolidated Balance Sheets. Lines of credit are obligations to lend money to a borrower. Credit risk arises when the borrower's current financial condition may indicate less ability to pay than when the commitment was originally made. In the case of standby letters of credit, the risk arises from the potential failure of the customer to perform according to the terms of a contract. In such a situation, the third party might draw on the standby letter of credit to pay for completion of the contract and the Company would look to its customer to repay these funds with interest. To minimize the risk, the Company uses the same credit policies in making commitments and conditional obligations as it would for a loan to that customer. Standby letters of credit and financial guarantees are commitments issued by the Company to guarantee the performance of a customer to a third party in borrowing arrangements. The Company generally has recourse to recover from the customer any amounts paid under the guarantees. Typically, letters of credit issued have expiration dates within one year. A summary of the contractual amounts for unfunded commitments and letters of credit are as follows: December 31, 2015 2014 (in thousands) Commitments to extend credit, including unsecured loan commitments of $341,374 at December 31, 2015 and $232,863 at December 31, 2014 $ 3,624,578 $ 2,164,523 Credit card commitments and financial guarantees 57,966 42,038 Standby letters of credit, including unsecured letters of credit of $4,257 at December 31, 2015 and $5,166 at December 31, 2014 50,659 49,556 Total $ 3,733,203 $ 2,256,117 The following table represents the contractual commitments for lines and letters of credit by maturity at December 31, 2015 : Amount of Commitment Expiration per Period Total Amounts Committed Less Than 1 Year 1-3 Years 3-5 Years After 5 Years (in thousands) Commitments to extend credit $ 3,624,578 $ 1,588,558 $ 1,401,293 $ 267,284 $ 367,443 Credit card commitments and financial guarantees 57,966 57,966 — — — Standby letters of credit 50,659 42,749 5,749 2,161 — Total $ 3,733,203 $ 1,689,273 $ 1,407,042 $ 269,445 $ 367,443 Commitments to extend credit are agreements to lend to a customer provided that there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. The Company enters into credit arrangements that generally provide for the termination of advances in the event of a covenant violation or other event of default. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer’s creditworthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the Company upon extension of credit, is based on management’s credit evaluation of the party. The commitments are collateralized by the same types of assets used as loan collateral. The Company has exposure to credit losses from unfunded commitments and letters of credit. As funds have not been disbursed on these commitments, they are not reported as loans outstanding. Credit losses related to these commitments are not included in the allowance for credit losses reported in " Note 4. Loans, Leases and Allowance for Credit Losses " of these Consolidated Financial Statements and are accounted for as a separate loss contingency. This loss contingency for unfunded loan commitments and letters of credit was $3.3 million and $2.1 million as of December 31, 2015 and 2014 , respectively. Changes to this liability are adjusted through non-interest expense. Concentrations of Lending Activities The Company’s lending activities are driven in large part by the customers served in the market areas where the Company has branch offices in the states of Arizona, Nevada, and California. Despite the geographic concentration of lending activities, the Company does not have a single external customer from which it derives 10% or more of its revenues. The Company monitors concentrations within four broad categories: geography, industry, product, and collateral. The Company's loan portfolio includes significant credit exposure to the CRE market. As of December 31, 2015 and 2014 , CRE related loans accounted for approximately 49% and 54% of total loans, respectively. Substantially all of these loans are secured by first liens with an initial loan to value ratio of generally not more than 75% . Approximately 48% and 46% of these CRE loans, excluding construction and land loans, were owner-occupied at December 31, 2015 and 2014 , respectively. Contingencies The Company is involved in various lawsuits of a routine nature that are being handled and defended in the ordinary course of the Company’s business. Expenses are being incurred in connection with these lawsuits, but in the opinion of management, based in part on consultation with outside legal counsel, the resolution of these lawsuits and associated defense costs will not have a material impact on the Company’s financial position, results of operations, or cash flows. Other The Company has entered into change in control agreements with certain named executives and other employees designated as executives by the Board of Directors. Under these agreements, in the event of a qualifying termination, each executive is entitled to receive 1) accrued benefits, payable in accordance with the Company’s normal payroll practice; 2) a lump sum cash severance payment in an amount equal to the sum of a) two times the executive’s annual base salary plus b) two times the executive's annual bonus; 3) any unpaid bonus that was earned by the executive in the prior year; and 4) reimbursement of paid group health premiums up to 24 months.

Fair Value Accounting

Fair Value Accounting	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Accounting	17. FAIR VALUE ACCOUNTING The fair value of an asset or liability is the price that would be received to sell that asset or paid to transfer that liability in an orderly transaction occurring in the principal market (or most advantageous market in the absence of a principal market) for such asset or liability. In estimating fair value, the Company utilizes valuation techniques that are consistent with the market approach, the income approach, and/or the cost approach. Such valuation techniques are consistently applied. Inputs to valuation techniques include the assumptions that market participants would use in pricing an asset or liability. ASC 825 establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy under ASC 825 are described in " Note 1. Summary of Significant Accounting Policies " of these Notes to Consolidated Financial Statements. In general, fair value is based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. These adjustments may include amounts to reflect counterparty credit quality and the Company’s creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. The Company’s valuation methodologies may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. While management believes the Company’s valuation methodologies are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different estimate of fair value at the reporting date. Furthermore, the reported fair value amounts have not been comprehensively revalued since the presentation dates, and therefore, estimates of fair value after the balance sheet date may differ significantly from the amounts presented herein. A more detailed description of the valuation methodologies used for assets and liabilities measured at fair value is set forth below. Transfers between levels in the fair value hierarchy are recognized as of the end of the month following the event or change in circumstances that caused the transfer. Under ASC 825, the Company elected the FVO treatment for junior subordinated debt issued by WAL. This election is irrevocable and results in the recognition of unrealized gains and losses on these items in earnings at each reporting date. The Company did not elect FVO treatment for assumed Bridge junior subordinated debt. All securities for which the fair value measurement option had been elected are included in a separate line item in the Consolidated Balance Sheets as securities measured at fair value. For the years ended December 31, 2015 , 2014 , and 2013 securities gains and losses from fair value changes were as follows: Changes in Fair Values for Items Measured at Fair Value Unrealized Gain/(Loss) on Assets and Liabilities Measured at Fair Value, Net Interest Income on Securities Interest Expense on Junior Subordinated Debt Total Changes Included in Current-Period Earnings Total Changes Included in OCI (in thousands) Year Ended December 31, 2015 Securities measured at fair value $ (32 ) $ 2 $ — $ (30 ) $ — Junior subordinated debt (6,491 ) — (2,151 ) (2,151 ) (4,276 ) Total $ (6,523 ) $ 2 $ (2,151 ) $ (2,181 ) $ (4,276 ) Year Ended December 31, 2014 Securities measured at fair value $ (41 ) $ 7 $ — $ (34 ) $ — Junior subordinated debt 1,421 — (1,754 ) (333 ) — Total $ 1,380 $ 7 $ (1,754 ) $ (367 ) $ — Year Ended December 31, 2013 Securities measured at fair value $ (260 ) $ 6 $ — $ (254 ) $ — Junior subordinated debt (5,640 ) — (1,823 ) (7,463 ) — Total $ (5,900 ) $ 6 $ (1,823 ) $ (7,717 ) $ — (1) Due to the Company's election to early adopt an element of ASU 2016-01, changes in the fair value of junior subordinated debt are presented as part of OCI, net of tax, rather than included in earnings, effective January 1, 2015. See Note 10. Qualifying Debt for further discussion. There were no net gains or losses recognized during the years ended December 31, 2015 , 2014 , and 2013 on trading securities sold during the period. Interest income on securities measured at fair value is accounted for similarly to those classified as AFS. Any premiums or discounts are recognized in interest income over the term of the securities. For MBS, estimates of prepayments are considered in the constant yield calculations. Interest expense on junior subordinated debt is also determined under a constant yield calculation. Fair value on a recurring basis Financial assets and financial liabilities measured at fair value on a recurring basis include the following: Securities measured at fair value: All of the Company’s securities measured at fair value, which consist of MBS, are reported at fair value utilizing Level 2 inputs in the same manner as described below for AFS securities. AFS securities: Preferred stock, mutual funds, and CRA investments are reported at fair value utilizing Level 1 inputs. With the exception of CDO securities, other securities classified as AFS are reported at fair value utilizing Level 2 inputs. For these securities, the Company obtains fair value measurements from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information, and the bond’s terms and conditions, among other things. The Company estimates the fair value of CDO securities utilizing Level 3 inputs, which include pricing indications from comparable securities. Independent pricing service: Our independent pricing service provides pricing information on Level 1, 2, and 3 securities, and represents the pricing source for the majority of the portfolio. Management independently evaluates the fair value measurements received from the Company's third party pricing service through multiple review steps. First, management reviews what has transpired in the marketplace with respect to interest rates, credit spreads, volatility, and mortgage rates, among other things, and develops an expectation of changes to the securities' valuations from the previous quarter. Then, management obtains market values from additional sources. The pricing service provides management with observable market data including interest rate curves and mortgage prepayment speed grids, as well as dealer quote sheets, new bond offering sheets, and historical trade documentation. Management reviews the assumptions and decides whether they are reasonable. Management may compare interest rates, credit spreads, and prepayments speeds used as part of the assumptions to those that management believes are reasonable. Management may price securities using the provided assumptions to determine whether they can develop similar prices on like securities. Any discrepancies between management’s review and the prices provided by the vendor are discussed with the vendor and the Company’s other valuation advisors. Lastly, management selects a sample of investment securities and compares the values provided by its primary third party pricing service to the market values obtained from secondary sources and evaluates those with notable variances. Annually, the Company receives an SSAE 16 report from its independent pricing service attesting to the controls placed on the operations of the service from its auditor. Interest rate swaps: Interest rate swaps are reported at fair value utilizing Level 2 inputs. The Company obtains dealer quotations to value its interest rate swaps. Junior subordinated debt: The Company estimates the fair value of its junior subordinated debt using a discounted cash flow model which incorporates the effect of the Company’s own credit risk in the fair value of the liabilities (Level 3). The Company’s cash flow assumptions are based on contractual cash flows as the Company anticipates that it will pay the debt according to its contractual terms. As of March 31, 2015, junior subordinated debt issued by the parent was valued under an NPV approach with a discount rate equal to a derived credit spread of 5.96% plus three-month LIBOR. Subsequently, on June 29, 2015, WAB issued $150.0 million of subordinated debt at a credit spread of 3.20% over LIBOR. Management deemed this to be a new observable market input relative to the Company's own credit risk. As of June 30, 2015, the junior subordinated debt was valued with an adjusted credit spread of 4.69%. This credit spread of 4.69% represents a reduction of 1.27% from the credit spread as of March 31, 2015, and a premium of 1.49% over the recent subordinated debt issuance by WAB, with such premium resulting from terms and features reflecting the greater level of subordination of the junior subordinated debt issued by the parent. This spread reduction resulted in a non-cash, non-recurring debt valuation loss of $7.7 million during the three months ended June 30, 2015. This charge had no effect on regulatory capital. As of December 31, 2015 , utilizing the methodology described above, the Company estimated the discount rate at 5.67% , which represents an implied credit spread of 5.06% plus three-month LIBOR ( 0.61% ). As of December 31, 2014 , the Company estimated the discount rate at 6.24% , which was a 5.99% credit spread plus three-month LIBOR ( 0.25% ). The fair value of assets and liabilities measured at fair value on a recurring basis was determined using the following inputs as of the periods presented: Fair Value Measurements at the End of the Reporting Period Using: Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Fair Value (in thousands) December 31, 2015 Assets: Measured at fair value Residential MBS issued by GSEs $ — $ 1,481 $ — $ 1,481 Available-for-sale Collateralized debt obligations $ — $ — $ 10,060 $ 10,060 Commercial MBS issued by GSEs — 19,114 — 19,114 Corporate debt securities — 13,251 — 13,251 CRA investments 34,685 — — 34,685 Municipal obligations — 334,830 — 334,830 Preferred stock 111,236 — — 111,236 Private label commercial MBS — 4,691 — 4,691 Private label residential MBS — 257,128 — 257,128 Residential MBS issued by GSEs — 1,170,221 — 1,170,221 Trust preferred securities — 24,314 — 24,314 U.S. treasury securities 2,993 — — 2,993 Total AFS securities $ 148,914 $ 1,823,549 $ 10,060 $ 1,982,523 Loans - HFS $ — $ 23,809 $ — $ 23,809 Derivative assets (1) — 3,569 — 3,569 Liabilities: Junior subordinated debt (2) $ — $ — $ 46,928 $ 46,928 Derivative liabilities (1) — 64,785 — 64,785 (1) Derivative assets and liabilities relate to interest rate swaps, see " Note 13. Derivatives and Hedging Activities ." In addition, the carrying value of loans includes a net positive value of $64,184 and the net carrying value of subordinated debt includes a net negative value of $3,569 as of December 31, 2015 , which relates to the effective portion of the hedges put in place to mitigate against fluctuations in interest rates. (2) Includes only the portion of junior subordinated debt that is recorded at fair value at each reporting period pursuant to the election of FVO treatment. Fair Value Measurements at the End of the Reporting Period Using: Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value (in thousands) December 31, 2014 Assets: Measured at fair value Residential MBS issued by GSEs $ — $ 1,858 $ — $ 1,858 Available-for-sale Collateralized debt obligations $ — $ — $ 11,445 $ 11,445 Commercial MBS issued by GSEs — 2,147 — 2,147 Corporate debt securities — 52,489 — 52,489 CRA investments 24,332 — — 24,332 Municipal obligations — 299,037 — 299,037 Mutual funds 37,702 — — 37,702 Preferred stock 82,612 — — 82,612 Private label commercial MBS — 5,149 — 5,149 Private label residential MBS — 70,243 — 70,243 Residential MBS issued by GSEs — 891,189 — 891,189 Trust preferred securities — 25,546 — 25,546 U.S. government sponsored agency securities — 18,346 — 18,346 Total AFS securities $ 144,646 $ 1,364,146 $ 11,445 $ 1,520,237 Derivative assets (1) $ — $ 7 $ — $ 7 Liabilities: Junior subordinated debt $ — $ — $ 40,437 $ 40,437 Derivative liabilities (1) — 57,820 — 57,820 (1) Derivative assets and liabilities relate to interest rate swaps, see " Note 13. Derivatives and Hedging Activities ." In addition, the carrying value of loans includes a positive value of $57,140 as of December 31, 2014 , which relates to the effective portion of the hedges put in place to mitigate against fluctuations in interest rates. For the years ended December 31, 2015 , 2014 , and 2013 , the change in Level 3 assets and liabilities measured at fair value on a recurring basis was as follows: Junior Subordinated Debt Year Ended December 31, 2015 2014 2013 (in thousands) Beginning balance $ (40,437 ) $ (41,858 ) $ (36,218 ) Transfers into Level 3 — — — Total gains (losses) for the period Included in earnings (1) — 1,421 (5,640 ) Included in other comprehensive income (2) $ (6,491 ) $ — $ — Ending balance $ (46,928 ) $ (40,437 ) $ (41,858 ) (1) Total gains (losses) for the period are included in the non-interest income line, Unrealized gains (losses) on assets and liabilities measured at fair value, net. (2) Due to the Company's election to early adopt an element of ASU 2016-01, changes in the fair value of junior subordinated debt are presented as part of OCI rather than earnings effective January 1, 2015. Accordingly, total losses for 2015 are included in the other comprehensive income line, Unrealized gain (loss) on junior subordinated debt, which is net of tax. The above amount represents the gross loss from changes in fair value of junior subordinated debt. CDO Securities Year Ended December 31, 2015 2014 2013 (in thousands) Beginning balance $ 11,445 $ — $ — Transfers into Level 3 — 6,243 — Total gains (losses) for the period Included in other comprehensive income (3) (1,385 ) 5,202 — Ending balance $ 10,060 $ 11,445 $ — (3) Total gains (losses) for the period are included in the other comprehensive income line, Unrealized gain (loss) on AFS securities. For Level 3 liabilities measured at fair value on a recurring basis as of December 31, 2015 and 2014 , the significant unobservable inputs used in the fair value measurements were as follows: December 31, 2015 Valuation Technique Significant Unobservable Inputs (in thousands) Junior subordinated debt $ 46,928 Discounted cash flow Implied credit rating of the Company CDO securities 10,060 S&P Model Pricing indications from comparable securities December 31, 2014 Valuation Technique Significant Unobservable Inputs (in thousands) Junior subordinated debt $ 40,437 Discounted cash flow Adjusted Corporate Bond over Treasury Index with comparable credit spread CDO securities 11,445 S&P Model Pricing indications from comparable securities The significant unobservable inputs used in the fair value measurement of the Company’s junior subordinated debt as of December 31, 2015 was the "BB" rated financial over SWAP index and, as of December 31, 2014 , was the "BB" rated 20-Year over Treasury Index with comparable credit spread. The input value used in the fair value measurement of the Company's junior subordinated debt was 5.67% and 6.24% as of December 31, 2015 and 2014 , respectively. The significant unobservable inputs used in the fair value measurement of the Company's CDO securities include securities terms, conditions, and underlying collateral type, as well as trustee and servicer reports, trade data on comparable securities, and market quotes that are converted into spreads to benchmark LIBOR curves. Significant increases or decreases in these inputs could result in significantly different fair value measurements. Fair value on a nonrecurring basis Certain assets are measured at fair value on a nonrecurring basis. That is, the assets are not measured at fair value on an ongoing basis, but are subject to fair value adjustments in certain circumstances (for example, when there is evidence of impairment). The following table presents such assets carried on the balance sheet by caption and by level within the ASC 825 hierarchy: Fair Value Measurements at the End of the Reporting Period Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Active Markets for Similar Assets (Level 2) Unobservable Inputs (Level 3) (in thousands) As of December 31, 2015: Impaired loans with specific valuation allowance $ 19,629 $ — $ — $ 19,629 Impaired loans without specific valuation allowance (1) 66,754 — — 66,754 Other assets acquired through foreclosure 43,942 — — 43,942 As of December 31, 2014: Impaired loans with specific valuation allowance $ 114,163 $ — $ — $ 114,163 Impaired loans without specific valuation allowance (1) 38,019 — — 38,019 Other assets acquired through foreclosure 57,150 — — 57,150 (1) Excludes loan balances with charge-offs of $37.8 million and $3.8 million as of December 31, 2015 and 2014 , respectively. Impaired loans: The specific reserves for collateral dependent impaired loans are based on collateral value, net of estimated disposition costs and other identified quantitative inputs. Collateral value is determined based on third-party appraisals. Appraisals may utilize a single valuation approach or a combination of approaches, including comparable sales and the income approach. Fair value is determined, where possible, using market prices derived from an appraisal or evaluation, which are considered to be Level 2. However, certain assumptions and unobservable inputs are often used by the appraiser, therefore qualifying the assets as Level 3 in the fair value hierarchy. In some cases, adjustments are made to the appraised values due to various factors, including age of the appraisal (which are generally obtained every twelve months), age of comparables included in the appraisal, and known changes in the market and in the collateral. When significant adjustments are based on unobservable inputs, such as when a current appraised value is not available or management determines the fair value of the collateral is further impaired below the appraised value and there is no observable market price, the resulting fair value measurement has been categorized as a Level 3 measurement. These Level 3 impaired loans had an estimated fair value of $24.3 million and $124.9 million at December 31, 2015 and 2014 , respectively. The fair value of these Level 3 impaired loans reflects the carrying value of each loan, which has been reduced by any deficit in appraised value compared to book value, estimated disposition costs, and estimated losses of similar impaired loans based on historical loss experience. Specific reserves in the allowance for loan losses for these loans were $4.7 million and $10.8 million at December 31, 2015 and 2014 , respectively. Other assets acquired through foreclosure: Other assets acquired through foreclosure consist of properties acquired as a result of, or in-lieu-of, foreclosure. These assets are initially reported at the fair value determined by independent appraisals using appraised value less estimated cost to sell. Such properties are generally re-appraised every twelve months. There is risk for subsequent volatility. Costs relating to the development or improvement of the assets are capitalized and costs relating to holding the assets are charged to expense. The Company had $43.9 million and $57.2 million of such assets at December 31, 2015 and 2014 , respectively. Fair value is determined, where possible, using market prices derived from an appraisal or evaluation, which are considered to be Level 2. However, certain assumptions and unobservable inputs are often used by the appraiser, therefore qualifying the assets as Level 3 in the fair value hierarchy. When significant adjustments are based on unobservable inputs, such as when a current appraised value is not available or management determines the fair value of the collateral is further impaired below the appraised value and there is no observable market price, the resulting fair value measurement has been categorized as a Level 3 measurement. Credit vs. non-credit losses Under the provisions of ASC 320, Investments-Debt and Equity Securities , OTTI is separated into the amount of total impairment related to the credit loss and the amount of the total impairment related to all other factors. The amount of the total OTTI related to the credit loss is recognized in earnings. The amount of the total impairment related to all other factors is recognized in OCI. For the years ended December 31, 2015 , 2014 , and 2013 , the Company determined that no securities experienced credit losses. There is no OTTI balance recognized in comprehensive income as of December 31, 2015 and 2014 . FAIR VALUE OF FINANCIAL INSTRUMENTS The estimated fair value of the Company’s financial instruments is as follows: December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (in thousands) Financial assets: Investment securities: AFS $ 1,982,523 $ 148,914 $ 1,823,549 $ 10,060 $ 1,982,523 Trading 1,481 — 1,481 — 1,481 Derivative assets 3,569 — 3,569 — 3,569 Loans, net 11,017,595 — 10,766,826 86,383 10,853,209 Accrued interest receivable 54,445 — 54,445 — 54,445 Financial liabilities: Deposits $ 12,030,624 $ — $ 12,034,199 $ — $ 12,034,199 Customer repurchases 38,155 — 38,155 — 38,155 FHLB advances 150,000 — 150,000 — 150,000 Qualifying debt 210,328 — — 207,437 207,437 Derivative liabilities 64,785 — 64,785 — 64,785 Accrued interest payable 13,626 — 13,626 — 13,626 December 31, 2014 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (in thousands) Financial assets: Investment securities: AFS $ 1,520,237 $ 144,646 $ 1,364,146 $ 11,445 $ 1,520,237 Trading 1,858 — 1,858 — 1,858 Derivative assets 7 — 7 — 7 Loans, net 8,288,049 — 7,984,692 152,182 8,136,874 Accrued interest receivable 36,705 — 36,705 — 36,705 Financial liabilities: Deposits $ 8,931,043 $ — $ 8,935,566 $ — $ 8,935,566 Customer repurchases 54,899 — 54,899 — 54,899 FHLB advances 307,081 — 307,081 — 307,081 Other borrowed funds 83,182 — 25,000 61,074 86,074 Qualifying debt 40,437 — — 40,437 40,437 Derivative liabilities 57,820 — 57,820 — 57,820 Accrued interest payable 9,890 — 9,890 — 9,890 Interest rate risk The Company assumes interest rate risk (the risk to the Company’s earnings and capital from changes in interest rate levels) as a result of its normal operations. As a result, the fair values of the Company’s financial instruments as well as its future net interest income will change when interest rate levels change and that change may be either favorable or unfavorable to the Company. Interest rate risk exposure is measured using interest rate sensitivity analysis to determine our change in EVE and net interest income resulting from hypothetical changes in interest rates. If potential changes to EVE and net interest income resulting from hypothetical interest rate changes are not within the limits established by the BOD, the BOD may direct management to adjust the asset and liability mix to bring interest rate risk within BOD-approved limits. As of December 31, 2015 , the Company’s interest rate risk profile was within BOD-approved limits. WAB has an ALCO charged with managing interest rate risk within the BOD-approved limits. Limits are structured to prohibit an interest rate risk profile that does not conform to both management and BOD risk tolerances. There is also ALCO reporting at the Parent company level for reviewing interest rate risk for the Company, which gets reported to the BOD and the Finance and Investment Committee. Fair value of commitments The estimated fair value of standby letters of credit outstanding at December 31, 2015 and 2014 was insignificant. Loan commitments on which the committed interest rates were less than the current market rate were also insignificant at December 31, 2015 and 2014 .

Regulatory Capital Requirements

Regulatory Capital Requirements	12 Months Ended
	Dec. 31, 2015
Banking and Thrift [Abstract]
Regulatory Capital Requirements	18. REGULATORY CAPITAL REQUIREMENTS The Company and the Bank are subject to various regulatory capital requirements administered by the federal banking agencies. Failure to meet minimum capital requirements could trigger certain mandatory or discretionary actions that, if undertaken, could have a direct material effect on the Company’s business and financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Company and the Bank must meet specific capital guidelines that involve quantitative measures of their assets, liabilities, and certain off-balance sheet items as calculated under regulatory accounting practices. The capital amounts and classification are also subject to qualitative judgments by the regulators about components, risk weightings, and other factors. The capital framework under Basel III became effective for the Company on January 1, 2015. Under the Basel III final rules, minimum requirements have increased for both the quantity and quality of capital held by the Company. A new capital conservation buffer, comprised of Common Equity Tier 1 capital, is also established above the regulatory minimum capital requirements. This capital conservation buffer will be phased in beginning January 1, 2016 at 0.625% of risk-weighted assets and will increase each subsequent year by an additional 0.625% until reaching its final level of 2.5% on January 1, 2019. Strict eligibility requirements for regulatory capital instruments have been implemented under the final rules and the final rules also revise the definitions and calculations of Tier 1 capital, total capital, and risk-weighted assets. As of December 31, 2015 and 2014 , the Company and the Bank exceeded the capital levels necessary to be classified as well-capitalized, as defined by the federal banking agencies. The actual capital amounts and ratios for the Company and the Bank are presented in the following tables as of the periods indicated: Total Capital Tier 1 Capital Risk-Weighted Assets Tangible Average Assets Total Capital Ratio Tier 1 Capital Ratio Tier 1 Leverage Ratio Common Equity (dollars in thousands) Basel III December 31, 2015 WAL $ 1,603,472 $ 1,341,011 $ 13,193,563 $ 13,683,148 12.2 % 10.2 % 9.8 % 9.7 % WAB 1,485,070 1,213,304 13,073,394 13,561,251 11.4 9.3 9.0 9.3 Well-capitalized ratios 10.0 8.0 5.0 6.5 Minimum capital ratios 8.0 6.0 4.0 4.5 Basel I December 31, 2014 WAL $ 1,119,618 $ 1,007,278 $ 9,555,390 $ 10,367,575 11.7 % 10.5 % 9.7 % — WAB 1,057,253 945,687 9,435,459 10,232,297 11.2 10.0 9.2 — Well-capitalized ratios 10.0 6.0 5.0 — Minimum capital ratios 8.0 4.0 4.0 —

Segments

Segments	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segments	22. SEGMENTS The Company's reportable segments are aggregated primarily based on geographic location, services offered, and markets served. As a result of the Bridge acquisition on June 30, 2015, former Bridge activities were allocated between the newly formed Northern California segment and the CBL segment. As a substantial portion of Bridge's balance sheet is generated from nationally-focused business lines, the operations of these business lines are included in the CBL segment. Substantially all of the remaining assets and liabilities of Bridge are included in the Northern California segment. As the Bridge acquisition was completed on June 30, 2015, the results of operations of Bridge are included in the Company's Consolidated Income Statements beginning on July 1, 2015. The Southern California segment represents legacy Western Alliance operations in California, excluding two branches located in northern California, which are now included in the Northern California segment. Prior period amounts have been adjusted accordingly. The Arizona, Nevada, Southern California, and Northern California segments provide full service banking and related services to their respective markets although operations may not be domiciled in these states. The Company's CBL segment provides banking services to niche markets and, as of June 30, 2015, includes the operations of Bridge. These CBLs are managed centrally and are broader in geographic scope, though still predominately within the Company's core market areas. The Corporate & Other segment primarily relates to our Treasury division and also includes other corporate-related items, income and expense items not allocated to other reportable segments, and inter-segment eliminations. The Company's segment reporting process begins with the assignment of all loan and deposit accounts directly to the segments where these products are originated and/or serviced. Equity capital is assigned to each segment based on the risk profile of their assets and liabilities. With the exception of goodwill, which is assigned a 100% weighting, equity capital allocations ranged from 0% to 12% during the year, with a funds credit provided for the use of this equity as a funding source. Any excess or deficient equity not allocated to segments based on risk is assigned to the Corporate & Other segment. Net interest income, provision for credit losses, and non-interest expense amounts are recorded in their respective segment to the extent that the amounts are directly attributable to those segments. Net interest income is recorded in each segment on a TEB with a corresponding increase in income tax expense, which is eliminated in the Corporate & Other segment. Further, net interest income of a reportable segment includes a funds transfer pricing process that matches assets and liabilities with similar interest rate sensitivity and maturity characteristics. Using this funds transfer pricing methodology, liquidity is transferred between users and providers. A net user of funds has lending/investing in excess of deposits/borrowings and a net provider of funds has deposits/borrowings in excess of lending/investing. A segment that is a user of funds is charged for the use of funds, while a provider of funds is credited through funds transfer pricing, which is determined based on the average life of the assets or liabilities in the portfolio. Net income amounts for each reportable segment is further derived by the use of expense allocations. Certain expenses not directly attributable to a specific segment are allocated across all segments based on key metrics, such as number of employees, average loan balances, and average deposit balances. These types of expenses include information technology, operations, human resources, finance, risk management, credit administration, legal, and marketing. Income taxes are applied to each segment based on the effective tax rate for the geographic location of the segment. Any difference in the corporate tax rate and the aggregate effective tax rates in the segments are adjusted in the Corporate & Other segment. On December 31, 2013, the Company consolidated its three bank subsidiaries under one charter, WAB. As a result, the Company redefined its operating segments to reflect the new organizational and internal reporting structure. The realignment of the Company's segments resulted in significant differences from the old segmentation methodology. Consequently, the Company determined that recasting prior year segment information to conform to the new segmentation methodology would be impracticable due to the substantial time and cost that would be involved in recasting this information. Also, given the incomparability of the reporting segments between periods, the Company determined that disclosure of the reportable segment information for the year ended December 31, 2014 , as previously reported under the old basis, would not be beneficial to the reader as it does not assist the reader in better understanding the Company’s performance, assessing its prospects for future net cash flows or making more informed judgments about the Company as a whole, which are the primary objectives of ASC 280-10. The following is a summary of selected operating segment information for the years ended December 31, 2015 and 2014 . Arizona Nevada Southern California Northern California Central Business Lines Corporate & Other Consolidated Company At December 31, 2015 (dollars in millions) Assets: Cash, cash equivalents, and investment securities $ 2.3 $ 9.5 $ 2.4 $ 2.4 $ — $ 2,250.3 $ 2,266.9 Loans, net of deferred loan fees and costs 2,811.7 1,737.2 1,761.9 1,188.4 3,597.9 39.6 11,136.7 Less: allowance for credit losses (30.1 ) (18.6 ) (18.8 ) (12.7 ) (38.5 ) (0.4 ) (119.1 ) Total loans 2,781.6 1,718.6 1,743.1 1,175.7 3,559.4 39.2 11,017.6 Other assets acquired through foreclosure, net 8.4 20.8 — 0.3 — 14.4 43.9 Goodwill and other intangible assets, net — 24.8 — 158.2 122.4 — 305.4 Other assets 43.9 62.3 15.7 16.1 28.4 474.9 641.3 Total assets $ 2,836.2 $ 1,836.0 $ 1,761.2 $ 1,352.7 $ 3,710.2 $ 2,778.8 $ 14,275.1 Liabilities: Deposits $ 2,880.7 $ 3,382.8 $ 1,902.5 $ 1,541.1 $ 2,134.4 $ 189.1 $ 12,030.6 Borrowings and qualifying debt — — — — — 360.3 360.3 Other liabilities 12.2 29.0 7.8 11.2 105.1 127.4 292.7 Total liabilities 2,892.9 3,411.8 1,910.3 1,552.3 2,239.5 676.8 12,683.6 Allocated equity: 309.2 244.4 191.3 293.2 428.6 124.8 1,591.5 Total liabilities and stockholders' equity $ 3,202.1 $ 3,656.2 $ 2,101.6 $ 1,845.5 $ 2,668.1 $ 801.6 $ 14,275.1 Excess funds provided (used) 365.9 1,820.2 340.4 492.8 (1,042.1 ) (1,977.2 ) — Arizona Nevada Southern California Northern California Central Business Lines Corporate & Other Consolidated Company At December 31, 2014 (dollars in millions) Assets: Cash, cash equivalents, and investment securities $ 2.3 $ 5.0 $ 2.2 $ 0.3 $ — $ 1,702.4 $ 1,712.2 Loans, net of deferred loan fees and costs 2,341.9 1,668.7 1,553.1 198.6 2,590.0 46.0 8,398.3 Less: allowance for credit losses (30.7 ) (21.9 ) (17.9 ) (5.1 ) (34.0 ) (0.6 ) (110.2 ) Total loans 2,311.2 1,646.8 1,535.2 193.5 2,556.0 45.4 8,288.1 Other assets acquired through foreclosure, net 15.5 21.0 — — — 20.6 57.1 Goodwill and other intangible assets, net — 25.9 — — — — 25.9 Other assets 34.8 64.2 6.2 15.3 22.9 373.8 517.2 Total assets $ 2,363.8 $ 1,762.9 $ 1,543.6 $ 209.1 $ 2,578.9 $ 2,142.2 $ 10,600.5 Liabilities: Deposits $ 2,178.0 $ 3,230.6 $ 1,744.5 $ 584.0 $ 946.6 $ 247.3 $ 8,931.0 Borrowings and qualifying debt — — — — — 430.7 430.7 Other liabilities 17.4 40.8 8.9 0.2 72.4 98.2 237.9 Total liabilities 2,195.4 3,271.4 1,753.4 584.2 1,019.0 776.2 9,599.6 Allocated equity: 250.8 209.0 70.9 126.8 232.9 110.5 1,000.9 Total liabilities and stockholders' equity $ 2,446.2 $ 3,480.4 $ 1,824.3 $ 711.0 $ 1,251.9 $ 886.7 $ 10,600.5 Excess funds provided (used) 82.4 1,717.5 280.7 501.9 (1,327.0 ) (1,255.5 ) — Arizona Nevada Southern California Northern California Central Business Lines Corporate & Other Consolidated Company Year Ended December 31, 2015: (in thousands) Net interest income (expense) $ 129,914 $ 122,082 $ 94,585 $ 56,698 $ 124,222 $ (34,925 ) $ 492,576 Provision for (recovery of) credit losses 3,099 (6,887 ) 152 3,038 3,917 (119 ) 3,200 Net interest income (expense) after provision for credit losses 126,815 128,969 94,433 53,660 120,305 (34,806 ) 489,376 Non-interest income 4,204 9,202 2,697 5,161 4,110 4,394 29,768 Non-interest expense (59,917 ) (59,553 ) (47,549 ) (30,161 ) (45,831 ) (17,595 ) (260,606 ) Income (loss) from continuing operations before income taxes 71,102 78,618 49,581 28,660 78,584 (48,007 ) 258,538 Income tax expense (benefit) 27,893 27,516 20,849 12,051 29,469 (53,484 ) 64,294 Net income $ 43,209 $ 51,102 $ 28,732 $ 16,609 $ 49,115 $ 5,477 $ 194,244 Arizona Nevada Southern California Northern California Central Business Lines Corporate & Other Consolidated Company Year Ended December 31, 2014: (in thousands) Net interest income (expense) $ 112,128 $ 117,508 $ 91,090 $ 9,133 $ 71,010 $ (15,976 ) $ 384,893 Provision for (recovery of) credit losses 2,083 (7,542 ) (1,638 ) — 11,365 458 4,726 Net interest income (expense) after provision for credit losses 110,045 125,050 92,728 9,133 59,645 (16,434 ) 380,167 Non-interest income 3,586 8,944 3,917 184 1,742 6,278 24,651 Non-interest expense (54,859 ) (59,683 ) (49,764 ) (3,857 ) (27,804 ) (11,352 ) (207,319 ) Income (loss) from continuing operations before income taxes 58,772 74,311 46,881 5,460 33,583 (21,508 ) 197,499 Income tax expense (benefit) 23,053 26,009 19,711 2,296 12,594 (35,273 ) 48,390 Income from continuing operations 35,719 48,302 27,170 3,164 20,989 13,765 149,109 Loss from discontinued operations, net — — — — — (1,158 ) (1,158 ) Net income $ 35,719 $ 48,302 $ 27,170 $ 3,164 $ 20,989 $ 12,607 $ 147,951

Employee Benefit Plan (Notes)

Employee Benefit Plan (Notes)	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plans	19. EMPLOYEE BENEFIT PLANS The Company has a qualified 401(k) employee benefit plan for all eligible employees. Participants are able to defer between 1% and 100% (up to a maximum of $18,000 for those under 50 years of age and up to a maximum of $24,000 for those over 50 years of age in 2015 ) of their annual compensation. The Company may elect to match a discretionary amount each year, which was 50% of the first 6% of the participant’s compensation deferred into the plan. The Company’s total contribution was $2.2 million , $1.7 million , and $1.7 million for the years ended December 31, 2015 , 2014 , and 2013 , respectively. In addition, the Company maintains a non-qualified 401(k) restoration plan for the benefit of executives of the Company and certain affiliates. Participants are able to defer a portion of their annual salary and receive a matching contribution based primarily on the contribution structure in effect under the Company’s 401(k) plan, but without regard to certain statutory limitations applicable under the 401(k) plan. The Company’s total contribution to the restoration plan was $68,000 , $77,000 , and $64,000 for the years ended December 31, 2015 , 2014 , and 2013 , respectively. In connection with the Bridge acquisition, the Company assumed Bridge's SERP, an unfunded noncontributory defined benefit pension plan. The SERP provides retirement benefits to certain Bridge officers based on years of service and final average salary. The Company uses a December 31st measurement date for this plan. The following table reflects the accumulated benefit obligation and funded status of the SERP from the June 30, 2015 acquisition date through December 31, 2015 . Six Months Ended December 31, 2015 (in thousands) Change in benefit obligation Benefit obligation at acquisition $ 7,122 Service cost 334 Interest cost 202 Actuarial (gains)/losses (147 ) Expected benefits paid (67 ) Projected benefit obligation at end of year $ 7,444 Unfunded projected/accumulated benefit obligation (7,444 ) Additional liability $ — Weighted average assumptions to determine benefit obligation Discount rate 5.75 % Rate of compensation increase 4.00 % The components of net periodic benefit cost recognized from the acquisition date through December 31, 2015 and the amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit cost during 2016 are as follows: 2016 Six Months Ended December 31, 2015 (in thousands) Components of net periodic benefit cost Service cost $ 596 $ 334 Interest cost 426 202 Amortization of prior service cost 96 60 Amortization of actuarial (gains)/losses (96 ) (18 ) Net periodic benefit cost $ 1,022 $ 578 Other comprehensive income (cost) $ — $ 42

Related Parties (Notes)

Related Parties (Notes)	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related Party Transactions	20. RELATED PARTY TRANSACTIONS Principal stockholders, directors, and executive officers of the Company, together with the companies they control, are considered to be related parties. In the ordinary course of business, the Company has engaged in various related party transactions during the year, ranging from extending credit, accepting deposits as well as exchange of service transactions. Federal banking regulations require that any such extensions of credit not be offered on terms more favorable than would be offered to non-related party borrowers of similar creditworthiness. The following table summarizes the aggregate activity in such loans for the periods indicated: Year Ended December 31, 2015 2014 (in thousands) Balance, beginning $ 70,570 $ 30,783 New loans 10,678 35,341 Advances 18,614 23,559 Repayments and other (25,481 ) (19,113 ) Balance, ending $ 74,381 $ 70,570 None of these loans are past due, on non-accrual status or have been restructured to provide a reduction or deferral of interest or principal because of deterioration in the financial position of the borrower. There were no loans to a related party that were considered classified loans at December 31, 2015 or 2014 . The interest income associated with these loans was approximately $2.7 million and $1.9 million for the years ended December 31, 2015 and 2014 , respectively. Loan commitments outstanding with related parties totaled approximately $164.5 million and $151.8 million at December 31, 2015 and 2014 , respectively. The Company also accepts deposits from related parties which totaled $76.0 million and $47.7 million at December 31, 2015 and 2014 , respectively, with related interest expense totaling less than $100 thousand during each of the years ended December 31, 2015 and 2014 . In addition, the Company engages in certain activities with related parties for sponsorships, donations, and other services during the normal course of business. Those expenses totaled less than $1.0 million for the year ended December 31, 2015 and less than $2.0 million for the year ended December 31, 2014 .

Parent Company (Notes)

Parent Company (Notes)	12 Months Ended
	Dec. 31, 2015
Parent Company Financial Information [Abstract]
Parent Company Financial Information	21. PARENT COMPANY FINANCIAL INFORMATION The condensed financial statements of the holding company are presented in the following tables: WESTERN ALLIANCE BANCORPORATION Condensed Balance Sheets December 31, 2015 2014 (in thousands) ASSETS: Cash and cash equivalents $ 7,627 $ 11,855 Money market investments 122 451 Investment securities - AFS 50,507 51,335 Investment in bank subsidiaries 1,522,245 987,882 Investment in non-bank subsidiaries 2,424 9,827 Loans, net of deferred loan fees and costs and allowance for credit losses 35,635 39,221 Other assets acquired through foreclosure, net 14,471 16,318 Other assets 19,378 9,912 Total assets $ 1,652,409 $ 1,126,801 LIABILITIES AND STOCKHOLDERS' EQUITY: Other borrowings $ — $ 83,182 Qualifying debt 58,370 40,437 Accrued interest and other liabilities 2,537 2,254 Total liabilities 60,907 125,873 Total stockholders’ equity 1,591,502 1,000,928 Total liabilities and stockholders’ equity $ 1,652,409 $ 1,126,801 WESTERN ALLIANCE BANCORPORATION Condensed Income Statements Year Ended December 31, 2015 2014 2013 (in thousands) Income: Dividends from subsidiaries $ 140,900 $ 67,515 $ 71,529 Interest income 4,593 4,381 2,847 Non-interest income 586 1,235 3,995 Total income 146,079 73,131 78,371 Expense: Interest expense 6,671 8,776 10,833 Non-interest expense 11,397 10,348 32,001 Total expense 18,068 19,124 42,834 Income before income taxes and equity in undistributed earnings of subsidiaries 128,011 54,007 35,537 Income tax benefit 5,876 5,388 21,426 Income before equity in undistributed earnings of subsidiaries 133,887 59,395 56,963 Equity in undistributed earnings of subsidiaries 60,357 88,556 58,002 Net income 194,244 147,951 114,965 Dividends on preferred stock 750 1,387 1,410 Net income available to common stockholders $ 193,494 $ 146,564 $ 113,555 Western Alliance Bancorporation Condensed Statements of Cash Flows Year Ended December 31, 2015 2014 2013 (in thousands) Cash flows from operating activities: Net income $ 194,244 $ 147,951 $ 114,965 Adjustments to reconcile net income to net cash provided by operating activities: Equity in net undistributed earnings of subsidiaries (60,357 ) (88,556 ) (58,002 ) Excess tax benefit of stock-based compensation (1,945 ) (4,194 ) (1,552 ) Junior subordinated debt change in fair value — (1,421 ) 5,640 Loss on extinguishment of debt — 502 1,387 Other operating activities, net (4,734 ) (20,040 ) (4,011 ) Net cash provided by operating activities 127,208 34,242 58,427 Cash flows from investing activities: Purchases of securities — (23,431 ) (2,044 ) Principal pay downs, calls, maturities, and sales proceeds of securities, net 2,358 8,376 6,767 Proceeds from sale of other repossessed assets, net 4,138 9,610 9,844 Capital contributions to subsidiaries — — (40,000 ) Loans purchases, fundings, and principal collections, net 3,704 3,286 (35,979 ) Sale (purchase) of money market investments, net 330 2,181 (1,968 ) Sale (purchase) of premises, equipment, and other assets, net — 617 (481 ) Net cash and cash equivalents (used) in acquisition (1) (19,440 ) — — Net cash provided by (used in) investing activities (8,910 ) 639 (63,861 ) Cash flows from financing activities: Proceeds from other borrowings, net — 22,000 3,000 Excess tax benefit of stock-based compensation 1,945 4,194 1,552 Repayments on other borrowings (83,444 ) (6,501 ) (10,887 ) Proceeds from issuance of common stock 28,288 13,746 — Proceeds from exercise of stock options 1,935 8,294 4,595 Redemption of preferred stock (70,500 ) (70,500 ) — Cash dividends paid on preferred stock (750 ) (1,387 ) (1,410 ) Net cash used in financing activities (122,526 ) (30,154 ) (3,150 ) Net increase (decrease) in cash and cash equivalents (4,228 ) 4,727 (8,584 ) Cash and cash equivalents at beginning of year 11,855 7,128 15,712 Cash and cash equivalents at end of year $ 7,627 $ 11,855 $ 7,128 Supplemental disclosure: Cash paid during the year for: Interest $ 4,235 $ 9,067 $ 11,091 Income taxes 54,590 32,238 19,105 Non-cash investing and financing activity: Change in unrealized gain on AFS securities, net of tax 1,199 2,031 2,450 Change in unrealized (loss) on TRUPS securities, net of tax (4,276 ) — — Loan contributions to subsidiaries 183 2,663 — (1) Cash acquired, less cash consideration paid of $36.5 million , resulted in a net $19.4 million use of cash and cash equivalents in the acquisition.

Quarterly Financial Data (Notes

Quarterly Financial Data (Notes)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data Disclosure [Abstract]
Quarterly Financial Information	23. QUARTERLY FINANCIAL DATA (UNAUDITED) Year Ended December 31, 2015 Fourth Quarter Third Quarter Second Quarter First Quarter (in thousands, except share amounts) Interest income $ 151,331 $ 146,233 $ 116,618 $ 110,962 Interest expense 7,988 8,826 7,900 7,854 Net interest income 143,343 137,407 108,718 103,108 Provision for credit losses 2,500 — — 700 Net interest income after provision for credit losses 140,843 137,407 108,718 102,408 Non-interest income 9,479 8,502 5,545 6,242 Non-interest expense (72,448 ) (72,916 ) (61,209 ) (54,033 ) Income from continuing operations before provision for income taxes 77,874 72,993 53,054 54,617 Income tax expense 19,348 17,133 13,579 14,234 Net income 58,526 55,860 39,475 40,383 Dividends on preferred stock 151 176 247 176 Net income available to common stockholders $ 58,375 $ 55,684 $ 39,228 $ 40,207 Earnings per share: Basic $ 0.58 $ 0.55 $ 0.44 $ 0.46 Diluted $ 0.57 $ 0.55 $ 0.44 $ 0.45 (1) Due to the Company's election to early adopt an element of ASU 2016-01, changes in the fair value of junior subordinated debt are presented as part of OCI rather than earnings effective January 1, 2015. Accordingly, prior period 2015 amounts have been adjusted. Year Ended December 31, 2014 Fourth Quarter Third Quarter Second Quarter First Quarter (in thousands, except per share amounts) Interest income $ 110,151 $ 105,554 $ 101,973 $ 98,701 Interest expense 8,006 7,481 8,075 7,924 Net interest income 102,145 98,073 93,898 90,777 Provision for credit losses 300 419 507 3,500 Net interest income after provision for credit losses 101,845 97,654 93,391 87,277 Non-interest income 8,417 6,073 5,599 4,562 Non-interest expense (55,742 ) (49,859 ) (52,242 ) (49,476 ) Income from continuing operations before provision for income taxes 54,520 53,868 46,748 42,363 Income tax expense 14,111 12,949 10,706 10,624 Income from continuing operations 40,409 40,919 36,042 31,739 Loss from discontinued operations, net of tax — — (504 ) (654 ) Net income 40,409 40,919 35,538 31,085 Dividends on preferred stock 329 353 352 353 Net income available to common stockholders $ 40,080 $ 40,566 $ 35,186 $ 30,732 Earnings per share: Basic $ 0.46 $ 0.47 $ 0.41 $ 0.35 Diluted $ 0.46 $ 0.46 $ 0.40 $ 0.35

Summary of Significant Accoun31

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Nature of Operation	Nature of operation WAL is a bank holding company headquartered in Phoenix, Arizona, incorporated under the laws of the state of Delaware. WAL provides a full spectrum of deposit, lending, treasury management, and online banking products and services through its wholly-owned banking subsidiary, WAB. On June 30, 2015, WAL acquired Bridge Capital Holdings and its wholly-owned subsidiary, Bridge Bank. Upon acquisition, Bridge Capital Holdings merged into WAL and its principal operating subsidiary, Bridge Bank, merged into WAB. Effective as of July 1, 2015, the existing Bridge offices and the two previously existing WAB Northern California offices are operating as a combined division, with their results reported under the Company's Northern California operating segment. WAB operates the following full-service banking divisions: ABA in Arizona, BON in Southern Nevada, Bridge in Northern California, FIB in Northern Nevada, and TPB in Southern California. The Company also serves business customers through a national platform of specialized financial services including AAB, Corporate Finance, Equity Fund Resources, Life Sciences Group, Mortgage Warehouse Lending, Public Finance, Renewable Energy Group, Resort Finance, and Technology Finance. In addition, the Company has one non-bank subsidiary, LVSP, which holds and manages certain non-performing loans and OREO.
Basis of Presentation	Basis of presentation The accounting and reporting policies of the Company are in accordance with GAAP and conform to practices within the financial services industry. The accounts of the Company and its consolidated subsidiaries are included in the Consolidated Financial Statements.
Use of Estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Material estimates that are particularly susceptible to significant changes in the near term relate to the determination of the allowance for credit losses; estimated cash flows related to PCI loans; fair value determinations related to acquisitions and other assets and liabilities carried at fair value; and accounting for income taxes. Although management believes these estimates to be reasonably accurate, actual amounts may differ. In the opinion of management, all adjustments considered necessary have been reflected in the Consolidated Financial Statements.
Principles of Consolidation	Principles of consolidation On December 31, 2013, the Company consolidated its three bank subsidiaries under one bank charter, WAB. As the subsidiary bank mergers did not meet the definition of a business combination under the guidance of ASC 805, Business Combinations , the entities were combined in a method similar to a pooling of interests. As of December 31, 2015 , WAL has ten wholly-owned subsidiaries: WAB, LVSP, and eight unconsolidated subsidiaries used as business trusts in connection with the issuance of trust-preferred securities. The Bank has the following significant wholly-owned subsidiaries: WAB Investments, Inc., BON Investments, Inc., and TPB Investments, Inc., which hold certain investment securities, municipal and non-profit loans, and leases; and BW Real Estate, Inc., which operates as a real estate investment trust and holds certain of WAB's real estate loans and related securities. BW Nevada Holdings, LLC was dissolved on June 12, 2015 after distributing the Company’s 2700 West Sahara Avenue, Las Vegas, Nevada office building to WAB. The Company does not have any other significant entities that should be considered for consolidation. All significant intercompany balances and transactions have been eliminated in consolidation.
Reclassifications	Reclassifications Certain amounts in the Consolidated Financial Statements as of and for the years ended December 31, 2015 , 2014 , and 2013 may have been reclassified to conform to the current presentation. The reclassifications have no effect on net income or stockholders’ equity as previously reported.
Business Combinations	Business combinations Business combinations are accounted for under the acquisition method of accounting in accordance with ASC 805, Business Combinations. Under the acquisition method, the acquiring entity in a business combination recognizes all of the acquired assets and assumed liabilities at their estimated fair values as of the date of acquisition. Any excess of the purchase price over the fair value of net assets and other identifiable intangible assets acquired is recorded as goodwill. To the extent the fair value of net assets acquired, including identified intangible assets, exceeds the purchase price, a bargain purchase gain is recognized. Assets acquired and liabilities assumed from contingencies are also recognized at fair value if the fair value can be determined during the measurement period. Results of operations of an acquired business are included in the Consolidated Income Statement from the date of acquisition. Acquisition-related costs, including conversion and restructuring charges, are expensed as incurred.
Investment Securities	Investment securities Investment securities may be classified as HTM, AFS, or measured at fair value. The appropriate classification is initially decided at the time of purchase. Securities classified as HTM are those debt securities that the Company has both the intent and ability to hold to maturity regardless of changes in market conditions, liquidity needs, or general economic conditions. These securities are carried at amortized cost. The sale of a security within three months of its maturity date or after the majority of the principal outstanding has been collected is considered a maturity for purposes of classification and disclosure. Securities classified as AFS or trading securities measured at fair value are reported as an asset in the Consolidated Balance Sheet at their estimated fair value. As the fair value of AFS securities changes, the changes are reported net of income tax as an element of OCI, except for other-than-temporarily-impaired securities. When AFS securities are sold, the unrealized gain or loss is reclassified from OCI to non-interest income. The changes in the fair values of trading securities are reported in non-interest income. Securities classified as AFS are both equity and debt securities that the Company intends to hold for an indefinite period of time, but not necessarily to maturity. Any decision to sell a security classified as AFS would be based on various factors, including significant movements in interest rates, changes in the maturity mix of the Company’s assets and liabilities, liquidity needs, decline in credit quality, and regulatory capital considerations. Interest income is recognized based on the coupon rate and increased by accretion of discounts earned or decreased by the amortization of premiums paid over the contractual life of the security, adjusted for prepayment estimates, using the interest method. In estimating whether there are any OTTI losses, management considers the 1) length of time and the extent to which the fair value has been less than amortized cost; 2) financial condition and near term prospects of the issuer; 3) impact of changes in market interest rates; and 4) intent and ability of the Company to retain its investment for a period of time sufficient to allow for any anticipated recovery in fair value and whether it is not more likely than not the Company would be required to sell the security. Declines in the fair value of individual AFS debt securities that are deemed to be other-than-temporary are reflected in earnings when identified. The fair value of the debt security then becomes the new cost basis. For individual debt securities where the Company does not intend to sell the security and it is not more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis, the other-than-temporary decline in fair value of the debt security related to 1) credit loss is recognized in earnings; and 2) interest rate, market, or other factors is recognized in other comprehensive income or loss. For individual debt securities where the Company either intends to sell the security or more likely than not will not recover all of its amortized cost, the OTTI is recognized in earnings equal to the entire difference between the security's cost basis and its fair value at the balance sheet date. For individual debt securities for which a credit loss has been recognized in earnings, interest accruals and amortization and accretion of premiums and discounts are suspended when the credit loss is recognized. Interest received after accruals have been suspended is recognized on a cash basis.
Restricted Stock	Restricted stock On January 30, 2015, WAB became a member of the Federal Reserve System and, as part of its membership, is required to maintain stock in the FRB in a specified ratio to its capital. In addition, WAB is a member of the FHLB system and, accordingly, maintains an investment in capital stock of the FHLB based on the borrowing capacity used. The Bank also maintains an investment in its primary correspondent bank. All of these investments are considered equity securities with no actively traded market. Therefore, the shares are considered restricted investment securities. These investments are carried at cost, which is equal to the value at which they may be redeemed. The dividend income received from the stock is reported in interest income. The Company conducts a periodic review and evaluation of its restricted stock to determine if any impairment exists.
Finance, Loan and Lease Receivables, Held-for-sale, Policy [Policy Text Block]	Loans, held for sale Loans, held for sale consist primarily of SBA and CRE loans that the Company originates (or acquires) and intends to sell. These loans are carried at the lower of aggregate cost or fair value. Fair value is determined based on available market data for similar assets, expected cash flows, and appraisals of underlying collateral or the credit quality of the borrower. Gains and losses on the sale of loans are recognized pursuant to ASC 860, Transfers and Servicing . Interest income of these loans is accrued daily and loan origination fees and costs are deferred and included in the cost basis of the loan. The Company issues various representations and warranties associated with these loan sales. The Company has not experienced any losses as a result of these representations and warranties.
Loans, Interest and Fees from Loans	Loans, held for investment The Company generally holds loans for investment and has the intent and ability to hold loans until their maturity. Therefore, they are reported at book value. Net loans are stated at the amount of unpaid principal, reduced by net deferred fees and costs, purchase accounting fair value adjustments, and an allowance for credit losses. In addition, the book value of loans that are subject to a fair value hedge is adjusted for changes in value attributable to the effective portion of the hedged benchmark interest rate risk. Purchased loans are recorded at estimated fair value on the date of purchase, comprised of unpaid principal less estimated credit losses and interest rate fair value adjustments. The Company may acquire loans through a business combination or in a purchase for which differences may exist between the contractual cash flows and the cash flows expected to be collected, which are due, at least in part, to credit quality. Loans are evaluated individually to determine if there has been credit deterioration since origination. Such loans may then be aggregated and accounted for as a pool of loans based on common characteristics. When the Company acquires such loans, the yield that may be accreted (accretable yield) is limited to the excess of the Company’s estimate of undiscounted cash flows expected to be collected over the Company’s initial investment in the loan. The excess of contractual cash flows over the cash flows expected to be collected may not be recognized as an adjustment to yield, loss, or a valuation allowance. Subsequent increases in cash flows expected to be collected generally are recognized prospectively through adjustment of the loan’s yield over the remaining life. Subsequent decreases to cash flows expected to be collected are recognized as impairment. The Company may not carry over or create a valuation allowance in the initial accounting for loans acquired under these circumstances. For purchased loans that are not deemed impaired, fair value adjustments attributable to both credit and interest rates are accreted (or amortized) over the contractual life of the individual loan. For additional information, see " Note 4. Loans, Leases and Allowance for Credit Losses " of these Notes to Consolidated Financial Statements. Loan fees collected for the origination of loans less direct loan origination costs (net deferred loan fees) are amortized over the contractual life of the loan through interest income. If the loan has scheduled payments, the amortization of the net deferred loan fee is calculated using the interest method over the contractual life of the loan. If the loan does not have scheduled payments, such as a line of credit, the net deferred loan fee is recognized as interest income on a straight-line basis over the contractual life of the loan commitment. Commitment fees based on a percentage of a customer’s unused line of credit and fees related to standby letters of credit are recognized over the commitment period. When loans are repaid, any remaining unamortized balances of premiums, discounts, or net deferred fees are recognized as interest income. Non-accrual loans: For all loan types except credit cards, when a borrower discontinues making payments as contractually required by the note, the Company must determine whether it is appropriate to continue to accrue interest. The Company ceases accruing interest income when the loan has become delinquent by more than 90 days or when management determines that the full repayment of principal and collection of interest according to contractual terms is no longer likely. The Company may decide to continue to accrue interest on certain loans more than 90 days delinquent if the loans are well secured by collateral and in the process of collection. Credit card loans and other personal loans are typically charged off no later than 180 days delinquent. For all loan types, when a loan is placed on non-accrual status, all interest accrued but uncollected is reversed against interest income in the period in which the status is changed and, the Company makes a loan-level decision to apply either the cash basis or cost recovery method. The Company recognizes income on a cash basis only for those non-accrual loans for which the collection of the remaining principal balance is not in doubt. Under the cost recovery method, subsequent payments received from the customer are applied to principal and generally no further interest income is recognized until the principal has been paid in full or until circumstances have changed such that payments are again consistently received as contractually required. Impaired loans: A loan is identified as impaired when it is no longer probable that interest and principal will be collected according to the contractual terms of the original loan agreement. Generally, impaired loans are classified as non-accrual. However, in certain instances, impaired loans may continue on an accrual basis, if full repayment of all principal and interest is expected and the loan is both well secured and in the process of collection. Impaired loans are measured for reserve requirements in accordance with ASC 310, Receivables, based on the present value of expected future cash flows discounted at the loan's effective interest rate or, as a practical expedient, at the loan's observable market price or the fair value of the collateral less applicable disposition costs if the loan is collateral dependent. The amount of an impairment reserve, if any, and any subsequent changes are recorded as a provision for credit losses. Losses are recorded as a charge-off when losses are confirmed. In addition to management's internal loan review process, regulators may from time to time direct the Company to modify loan grades, loan impairment calculations, or loan impairment methodology. Troubled Debt Restructured Loans : A TDR loan is a loan on which the Company, for reasons related to a borrower’s financial difficulties, grants a concession to the borrower that the Company would not otherwise consider. The loan terms that have been modified or restructured due to a borrower’s financial situation include, but are not limited to, a reduction in the stated interest rate, an extension of the maturity or renewal of the loan at an interest rate below current market, a reduction in the face amount of the debt, a reduction in the accrued interest, or deferral of interest payments. A TDR loan is also considered impaired. A TDR loan may be returned to accrual status when the loan is brought current, has performed in accordance with the contractual restructured terms for a reasonable period of time (generally six months) and the ultimate collectability of the total contractual restructured principal and interest is no longer in doubt. However, such loans continue to be considered impaired. Consistent with regulatory guidance, a TDR loan that is subsequently modified in another restructuring agreement but has shown sustained performance and classification as a TDR, will be removed from TDR status provided that the modified terms were market-based at the time of modification.
Allowance for Credit Losses	Allowance for credit losses Credit risk is inherent in the business of extending loans and leases to borrowers, for which the Company must maintain an adequate allowance for credit losses. The allowance for credit losses is established through a provision for credit losses recorded to expense. Loans are charged against the allowance for credit losses when management believes that the contractual principal or interest will not be collected. Subsequent recoveries, if any, are credited to the allowance. The allowance is an amount believed adequate to absorb estimated probable losses on existing loans that may become uncollectable, based on evaluation of the collectability of loans and prior credit loss experience, together with other factors. The Company formally re-evaluates and establishes the appropriate level of the allowance for credit losses on a quarterly basis. The allowance consists of specific and general components. The specific allowance applies to impaired loans. For impaired collateral dependent loans, the reserve is calculated based on the collateral value, net of estimated disposition costs. Generally, the Company obtains independent collateral valuation analysis for each loan every twelve months. Loans not collateral dependent are evaluated based on the expected future cash flows discounted at the original contractual interest rate. The Company's impairment analysis also incorporates various valuation considerations, including loan type, loss experience, and geographic criteria. The general allowance covers all non-impaired loans and is based on historical loss experience adjusted for the various qualitative and quantitative factors listed above. The Company’s allowance for credit loss methodology incorporates several quantitative and qualitative risk factors used to establish the appropriate allowance for credit losses at each reporting date. Quantitative factors include: 1) the Company's historical loss experience; 2) levels of and trends in delinquencies and impaired loans; 3) levels of and trends in charge-offs and recoveries; 4) trends in volume and terms of loans; 5) changes in underwriting standards or lending policies; 6) experience, ability, depth of lending staff; 7) national and local economic trends and conditions; 8) changes in credit concentrations; 9) out-of-market exposures; 10) changes in quality of loan review system; and 11) changes in the value of underlying collateral. An internal ten -year loss history is also incorporated into the allowance calculation model. Due to the credit concentration of our loan portfolio in real estate secured loans, the value of collateral is heavily dependent on real estate values in Nevada, Arizona, and California. While management uses the best information available to make its evaluation, future adjustments to the allowance may be necessary if there are significant changes in economic or other conditions. In addition, regulators, as an integral part of their examination processes, periodically review the Bank's allowance for credit losses, and may require us to make additions to the allowance based on their judgment about information available to them at the time of their examination. Management regularly reviews the assumptions and formulae used in determining the allowance and makes adjustments if required to reflect the current risk profile of the portfolio.
Other Assets Acquired Through Foreclosure	Other assets acquired through foreclosure Other assets acquired through foreclosure consist primarily of properties acquired as a result of, or in-lieu-of, foreclosure. Properties or other assets (primarily repossessed assets formerly leased) are classified as OREO and other repossessed property and are initially reported at fair value of the asset less estimated selling costs. Subsequent adjustments are based on the lower of carrying value or fair value less estimated costs to sell the property. Costs related to the development or improvement of the assets are capitalized and costs related to holding the assets are charged to non-interest expense. Property is evaluated regularly to ensure the recorded amount is supported by its current fair value and valuation allowances.
Derivative Financial Instruments	Derivative financial instruments The Company uses interest-rate swaps to mitigate interest-rate risk associated with changes to 1) the fair value of certain fixed-rate financial instruments (fair value hedges) and 2) certain cash flows related to future interest payments on variable rate financial instruments (cash flow hedges). The Company recognizes derivatives as assets or liabilities in the Consolidated Balance Sheet at their fair value in accordance with ASC 815, Derivatives and Hedging . The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and further, on the type of hedging relationship. On the date the derivative contract is entered into, the Company designates the derivative as a fair value hedge or cash flow hedge. Derivative instruments designated in a hedge relationship to mitigate exposure to changes in the fair value of an asset or liability attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivative instruments designated in a hedge relationship to mitigate exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. Changes in the fair value of a derivative that is designated and qualifies as a fair value hedge, along with changes in the fair value of the hedged asset or liability that are attributable to the hedged risk are recorded in current-period earnings. For a cash flow hedge, the effective portion of the change in the fair value of the derivative is recorded in AOCI and reclassified into earnings in the same period or periods during which the hedged transaction affects earnings. Any ineffective portion of the change in fair value of a cash flow hedge is recognized immediately in non-interest income in the Consolidated Income Statement. Under both the fair value and cash flow hedge scenarios, changes in the fair value of derivatives not considered to be highly effective in hedging the change in fair value or the expected cash flows of the hedged item are recognized in earnings as non-interest income during the period of the change. The Company documents its hedge relationships, including identification of the hedging instruments and the hedged items, as well as its risk management objectives and strategies for undertaking the hedge transaction at the time the derivative contract is executed. Both at inception and at least quarterly thereafter, the Company assesses whether the derivatives used in hedging transactions are highly effective (as defined in the guidance) in offsetting changes in either the fair value or cash flows of the hedged item. Retroactive effectiveness is assessed, as well as the continued expectation that the hedge will remain effective prospectively. The Company discontinues hedge accounting prospectively when it is determined that a hedge is no longer highly effective. When hedge accounting is discontinued on a fair value hedge that no longer qualifies as an effective hedge, the derivative continues to be reported at fair value in the Consolidated Balance Sheet, but the carrying amount of the hedged item is no longer adjusted for future changes in fair value. The adjustment to the carrying amount of the hedged item that existed at the date hedge accounting is discontinued is amortized over the remaining life of the hedged item into earnings. Derivative instruments that are not designated as hedges, so called free-standing derivatives, are reported in the Consolidated Balance Sheet at fair value and the changes in fair value are recognized in earnings as non-interest income during the period of change. The Company may in the normal course of business purchase a financial instrument or originate a loan that contains an embedded derivative instrument. Upon purchasing the instrument or originating the loan, the Company assesses whether the economic characteristics of the embedded derivative are clearly and closely related to the economic characteristics of the remaining component of the financial instrument (i.e., the host contract) and whether a separate instrument with the same terms as the embedded instrument would meet the definition of a derivative instrument. When it is determined that the embedded derivative possesses economic characteristics that are not clearly and closely related to the economic characteristics of the host contract and a separate instrument with the same terms would qualify as a derivative instrument, the embedded derivative is separated from the host contract and carried at fair value. However, in cases where the host contract is measured at fair value, with changes in fair value reported in current earnings, or the Company is unable to reliably identify and measure an embedded derivative for separation from its host contract, the entire contract is carried in the Consolidated Balance Sheet at fair value and is not designated as a hedging instrument.
Income Taxes	Income taxes The Company is subject to income taxes in the United States and files a consolidated federal income tax return with all of its subsidiaries, with the exception of BW Real Estate, Inc. Deferred income taxes are recorded to reflect the effects of temporary differences between the financial reporting carrying amounts of assets and liabilities and their income tax bases using enacted tax rates that are expected to be in effect when the taxes are actually paid or recovered. As changes in tax laws or rates are enacted, deferred tax assets and liabilities are adjusted through the provision for income taxes. Net deferred tax assets are recorded to the extent that these assets will more-likely-than-not be realized. In making these determinations, all available positive and negative evidence is considered, including scheduled reversals of deferred tax liabilities, tax planning strategies, projected future taxable income, and recent operating results. If it is determined that deferred income tax assets to be realized in the future are in excess of their net recorded amount, an adjustment to the valuation allowance will be recorded, which will reduce the Company's provision for income taxes. A tax benefit related to uncertain tax positions may be recognized when it is more-likely-than-not that the position will be sustained upon examination, including related appeals or litigation, based on technical merits. Income tax benefits must meet a more-likely-than-not recognition threshold at the effective date to be recognized. Interest and penalties related to unrecognized tax benefits from uncertain tax positions are recognized as part of the provision for income taxes in the Consolidated Income Statement. Accrued interest and penalties are included in the related tax liability line with other liabilities in the Consolidated Balance Sheet. See " Note 15. Income Taxes " for further discussion on income taxes.
Off-Balance Sheet Instruments	Off-balance sheet instruments In the ordinary course of business, the Company has entered into off-balance sheet financial instrument arrangements consisting of commitments to extend credit and standby letters of credit. Such financial instruments are recorded in the Consolidated Financial Statements when they are funded. They involve, to varying degrees, elements of credit risk in excess of amounts recognized in the Consolidated Balance Sheet. Losses would be experienced when the Company is contractually obligated to make a payment under these instruments and must seek repayment from the borrower, which may not be as financially sound in the current period as they were when the commitment was originally made. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. The Company enters into credit arrangements that generally provide for the termination of advances in the event of a covenant violation or other event of default. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer’s creditworthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the Company upon extension of credit, is based on management’s credit evaluation of the party. The commitments are collateralized by the same types of assets used as loan collateral. As with outstanding loans, the Company applies qualitative factors and utilization rates to its off-balance sheet obligations in determining an estimate of losses inherent in these contractual obligations. The estimate for credit losses on off-balance sheet instruments is included in other liabilities and the charge to income that establishes this liability is included in non-interest expense.
Fair Values of Financial Instruments	Fair values of financial instruments The Company uses fair value measurements to record fair value adjustments to certain assets and liabilities. ASC 820, Fair Value Measurement , establishes a framework for measuring fair value and a three-level valuation hierarchy for disclosure of fair value measurement as well as enhances disclosure requirements for fair value measurements. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. The Company uses various valuation approaches, including market, income, and/or cost approaches. ASC 820 establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability developed based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the factors market participants would consider in pricing the asset or liability developed based on the best information available in the circumstances. The hierarchy is broken down into three levels based on the reliability of inputs, as follows: • Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. • Level 2 - Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. These might include quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (such as interest rates, prepayment speeds, volatilities, etc.) or model-based valuation techniques where all significant assumptions are observable, either directly or indirectly, in the market. • Level 3 - Valuation is generated from model-based techniques where one or more significant inputs are not observable, either directly or indirectly, in the market. These unobservable assumptions reflect the Company’s own estimates of assumptions that market participants would use in pricing the asset or liability. Valuation techniques may include use of matrix pricing, discounted cash flow models, and similar techniques. The availability of observable inputs varies based on the nature of the specific financial instrument. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, for disclosure purposes, the level in the fair value hierarchy within which the fair value measurement in its entirety falls is determined based on the lowest level input that is significant to the fair value measurement in its entirety. Fair value is a market-based measure considered from the perspective of a market participant who may purchase the asset or assume the liability rather than an entity-specific measure. When market assumptions are available, ASC 820 requires the Company to make assumptions regarding the assumptions that market participants would use to estimate the fair value of the financial instrument at the measurement date. ASC 825, Financial Instruments , requires disclosure of fair value information about financial instruments, whether or not recognized in the balance sheet, for which it is practicable to estimate that value. Management uses its best judgment in estimating the fair value of the Company’s financial instruments; however, there are inherent limitations in any estimation technique. Therefore, for substantially all financial instruments, the fair value estimates presented herein are not necessarily indicative of the amounts the Company could have realized in a sales transaction at December 31, 2015 and 2014 . The estimated fair value amounts for December 31, 2015 and 2014 have been measured as of period-end, and have not been re-evaluated or updated for purposes of these Consolidated Financial Statements subsequent to those dates. As such, the estimated fair values of these financial instruments subsequent to the reporting date may be different than the amounts reported at period-end. The information in " Note 17. Fair Value Accounting " in these Notes to Consolidated Financial Statements should not be interpreted as an estimate of the fair value of the entire Company since a fair value calculation is only required for a limited portion of the Company’s assets and liabilities. Due to the wide range of valuation techniques and the degree of subjectivity used in making the estimate, comparisons between the Company’s disclosures and those of other companies or banks may not be meaningful. The following methods and assumptions were used by the Company in estimating the fair value of its financial instruments: Cash and cash equivalents The carrying amounts reported in the Consolidated Balance Sheets for cash and due from banks approximate their fair value. Money market investments The carrying amounts reported in the Consolidated Balance Sheets for money market investments approximate their fair value. Investment securities The fair values of CRA investments, mutual funds, and exchange-listed preferred stock are based on quoted market prices and are categorized as Level 1 in the fair value hierarchy. The fair values of other investment securities were determined based on matrix pricing. Matrix pricing is a mathematical technique that utilizes observable market inputs including, for example, yield curves, credit ratings, and prepayment speeds. Fair values determined using matrix pricing are generally categorized as Level 2 in the fair value hierarchy. The Company owns certain CDOs for which quoted prices are not available. Quoted prices for similar assets are also not available for these investment securities. In order to determine the fair value of these securities, the Company engages a third party to estimate the future cash flows and discount rate using third party quotes adjusted based on assumptions a market participant would assume necessary for each specific security. As a result of the lack of an active market, the resulting fair values have been categorized as Level 3 in the fair value hierarchy. Restricted stock WAB is a member of the Federal Reserve System and the FHLB and, accordingly, maintains investments in the capital stock of the FRB and the FHLB. WAB also maintains an investment in its primary correspondent bank. These investments are carried at cost since no ready market exists for them, and they have no quoted market value. The Company conducts a periodic review and evaluation of its restricted stock to determine if any impairment exists. The fair values of these investments have been categorized as Level 2 in the fair value hierarchy. Loans The fair value of loans is estimated based on discounted cash flows using interest rates currently being offered for loans with similar terms to borrowers with similar credit quality and adjustments that the Company believes a market participant would consider in determining fair value based on a third party independent valuation. As a result, the fair value for certain loans is categorized as Level 2 in the fair value hierarchy, excluding impaired loans which are categorized as Level 3. Accrued interest receivable and payable The carrying amounts reported in the Consolidated Balance Sheets for accrued interest receivable and payable approximate their fair value. Derivative financial instruments All derivatives are recognized in the Consolidated Balance Sheets at their fair value. The fair value for derivatives is determined based on market prices, broker-dealer quotations on similar products, or other related input parameters. As a result, the fair values have been categorized as Level 2 in the fair value hierarchy. Deposits The fair value disclosed for demand and savings deposits is by definition equal to the amount payable on demand at their reporting date (that is, their carrying amount), which the Company believes a market participant would consider in determining fair value. The carrying amount for variable-rate deposit accounts approximates their fair value. Fair values for fixed-rate certificates of deposit are estimated using a discounted cash flow calculation that applies interest rates currently being offered on certificates to a schedule of aggregated expected monthly maturities on these deposits. The fair value measurement of the deposit liabilities is categorized as Level 2 in the fair value hierarchy. FHLB advances and other borrowed funds The fair values of the Company’s borrowings are estimated using discounted cash flow analyses, based on the market rates for similar types of borrowing arrangements. The FHLB advances have been categorized as Level 2 in the fair value hierarchy due to their short durations. Other borrowings have been categorized as Level 3 in the fair value hierarchy. Subordinated debt The fair value of subordinated debt is based on the market rate for the respective subordinated debt security. Subordinated debt has been categorized as Level 3 in the fair value hierarchy. Junior subordinated debt Junior subordinated debt is valued by comparing the BB Financial over SWAP index and discounting the contractual cash flows on the Company's debt using these market rates. Junior subordinated debt has been categorized as Level 3 in the fair value hierarchy. Off-balance sheet instruments The fair value of the Company’s off-balance sheet instruments (lending commitments and standby letters of credit) is based on quoted fees currently charged to enter into similar agreements, taking into account the remaining terms of the agreements, and the counterparties’ credit standing.
Recent Accounting Pronouncements	Recent accounting pronouncements In June 2014, the FASB issued guidance within ASU 2014-12, Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period . The amendments in ASU 2014-12 to Topic 718, Compensation - Stock Compensation, provide explicit guidance on whether to treat a performance target that could be achieved after the requisite service period as a performance condition that affects vesting or as a nonvesting condition that affects the grant-date fair value of an award. The amendments are effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Early adoption is permitted. An entity may elect to apply the amendments either prospectively to all awards granted or modified after the effective date or retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. The adoption of this guidance is not expected to have a material impact on the Company's Consolidated Financial Statements. In August 2014, the FASB issued guidance within ASU 2014-15, Presentation of Financial Statements - Going Concern . The amendments in ASU 2014-15 to Subtopic 205-40, Going Concern, provide guidance about management's responsibility to evaluate whether there is substantial doubt about an entity's ability to continue as a going concern. The amendments require management to assess an entity's ability to continue as a going concern by incorporating and expanding upon certain principles that are currently in U.S. auditing standards. The amendments are effective for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter. Early application is permitted. The adoption of this guidance is not expected to have a material impact on the Company’s Consolidated Financial Statements. In February 2015, the FASB issued guidance within ASU 2015-02, Amendments to the Consolidation Analysis . The amendments in ASU 2015-02 to Topic 810, Consolidation, change the analysis that a reporting entity must perform to determine whether it should consolidate certain types of legal entities. Specifically, the amendments modify the evaluation of whether limited partnerships and similar legal entities are variable interest entities or voting interest entities, eliminate the presumption that a general partner should consolidate a limited partnership, affect the consolidation analysis of reporting entities that are involved with variable interest entities, particularly those that have fee arrangements and related party relationships, and provide a scope exception from consolidation guidance for reporting entities with interests in legal entities that are required to comply with or operate in accordance with requirements that are similar to those in Rule 2a-7 of the Investment Company Act of 1940 for registered money market funds. The amendments are effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted. An entity may apply the amendments in this Update using a modified retrospective approach by recording a cumulative-effect adjustment to equity as of the beginning of the fiscal year of adoption or, may apply the amendments retrospectively. The adoption of this guidance is not expected to have a material impact on the Company's Consolidated Financial Statements. In November 2015, the FASB issued guidance within ASU 2015-17, Income Taxes . The amendments in ASU 2015-17 to Topic 740, Income Taxes, changes the presentation of deferred income tax liabilities and assets, from previously bifurcated current and noncurrent, to a single noncurrent amount on the classified statement of financial position. The amendment is effective from the annual period ending after December 15, 2016, and for and interim periods within those annual periods. Early application is permitted. The adoption of this guidance is not expected to have a material impact on the Company's Consolidated Financial Statements. In January 2016, the FASB issued guidance within ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities . The amendments in ASU 2016-01 to Subtopic 825-10, Financial Instruments, contain the following elements: 1) require equity investments to be measured at fair value with changes in fair value recognized in net income; 2) simplify the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; 3) eliminates the requirement for public entities to disclose the methods and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; 4) requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; 5) requires an entity to present separately in OCI the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments; 6) requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or accompanying notes to the financial statements; 7) clarifies that the entity should evaluate the need for a valuation allowance on a deferred tax asset related to AFS securities in combination with the entity's other deferred tax assets. The amendments are effective for fiscal years beginning after December 15, 2017, and for interim periods within those fiscal years. Except for the early application of the amendment noted in item 5) above, early adoption of the amendments in this Update is not permitted. See discussion in Recently adopted accounting guidance below for further discussion of the Company's election to early adopt this element of ASU 2016-01. Recently adopted accounting guidance In January 2014, the FASB issued guidance within ASU 2014-04, Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans upon Foreclosure . The objective of the amendments in ASU 2014-04 to Topic 310, Receivables - Troubled Debt Restructurings by Creditors, is to clarify when an in substance repossession or foreclosure occurs, that is, when a creditor should be considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan such that the loan receivable should be derecognized and the real estate property recognized. The amendments are effective for fiscal years, and interim periods within those years, beginning after December 31, 2014. An entity can elect to adopt the amendments using either a modified retrospective transition method or a prospective transition method. Early adoption is permitted. The adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In June 2014, the FASB issued guidance within ASU 2014-11, Repurchase-to-Maturity Transactions, Repurchase Financings, and Disclosures. The amendments in ASU 2014-11 to Topic 860, Transfers and Servicing, change the accounting for repurchase-to-maturity transactions to secured borrowing accounting and, for repurchase financing arrangements, the amendments require separate accounting for a transfer of a financial asset executed contemporaneously with a repurchase agreement with the same counterparty, which will result in secured borrowing accounting for the repurchase agreement. An entity is required to present changes in accounting for transactions outstanding on the effective date as a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption. The accounting changes are effective for the first interim or annual period beginning after December 15, 2014. The amendments also require disclosure of information about certain transactions accounted for as a sale in which the transferor retains substantially all of the exposure to the economic return on the transferred financial assets through an agreement with the same counterparty. An entity will also be required to disclose information about repurchase agreements, securities lending transactions, and repurchase-to-maturity transactions that are accounted for as secured borrowings. The disclosure for certain transactions accounted for as a sale is required to be presented for interim and annual periods beginning after December 15, 2014 and the disclosure for repurchase agreements, securities lending transactions, and repurchase-to-maturity transactions accounted for as secured borrowings is required to be presented for annual periods beginning after December 15, 2014, and for interim periods beginning after March 15, 2015. The adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In the second quarter of 2015, the Company adopted the amended guidance within ASU 2015-03, Simplifying the Presentation of Debt Issuance Costs . The amendments in ASU 2015-03 to Subtopic 835-30, Interest - Imputation of Interest, require that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. On June 29, 2015, the Company issued $150.0 million in subordinated debt. As a result of the adoption of this amended guidance, subordinated debt was recorded net of related issuance costs of $1.8 million . Prior period balances were not adjusted for the change in accounting principle as unamortized debt issuance costs were not significant. In the third quarter 2015, the Company elected early adoption of the amended guidance within ASU 2015-16, Simplifying the Accounting for Measurement-Period Adjustments . Under current GAAP, the acquirer is required to retrospectively adjust the provisional amounts recognized at the acquisition date with a corresponding adjustment to goodwill and is also required to revise comparative information for prior periods presented in the financial statements. The amendments in ASU 2015-16 to Topic 805, Business Combinations, require that an acquirer recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. The amendments in this Update also require that the acquirer record, in the same period's financial statements, the effect on earnings of changes in depreciation, amortization, or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date. An entity is required to present separately on the face of the income statement or disclose in the notes the portion of the amount recorded in current-period earnings by line item that would have been recorded in previous reporting periods if the adjustments to the provisional amounts had been recognized as of the acquisition date. As a result of the adoption of this amended guidance, all measurement period adjustments identified during the quarter have been recognized in the current reporting period. As the closing date of the Bridge acquisition was June 30, 2015, Bridge's results of operations were not included in the Company's results until July 1, 2015. Accordingly, there are no amounts recorded in current-period earnings that would have been recorded in previous reporting periods if the adjustments to the provisional amounts had been recognized as of the acquisition date. See " Note 2. Mergers, Acquisitions and Dispositions " for further discussion of the measurement period adjustments identified and recognized during the current reporting period. In January 2016, and effective January 1, 2015, the Company elected early adoption of an element of ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities , which relates to the accounting for changes in the fair value of its own liabilities when the fair value option for financial instruments has been elected. As mentioned above, under this portion of this amended standard, the portion of the total change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value is presented separately in other comprehensive income rather than being recognized in the income statement at each reporting period. As the Company's junior subordinated debt are variable rate instruments, that fair value movement relates to credit risk and therefore the fair value adjustment qualifies for presentation in other comprehensive income. See " Note 10. Qualifying Debt " for additional detail on the impact that adoption has had on the current reporting period.

Mergers, Acquisitions and Dis32

Mergers, Acquisitions and Dispositions (Tables)	12 Months Ended
	Dec. 31, 2015
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Business Acquisition, Pro Forma Information [Table Text Block]	The following table presents pro forma information as if the Bridge acquisition was completed on January 1, 2014. The pro forma information includes adjustments for interest income on loans and securities acquired, amortization of intangibles arising from the transaction and interest expense on deposits acquired. The pro forma information is not necessarily indicative of the results of operations as they would have been had the transactions been effected on the assumed dates. Year Ended December 31, 2015 2014 (in thousands, except per share amounts) Interest income $ 560,292 $ 495,235 Non-interest income 37,073 38,768 Net income available to common stockholders (1) 205,099 164,165 Earnings per share - basic 1.90 1.64 Earnings per share - diluted 1.87 1.62 (1) Excludes acquisition / restructure related costs incurred by the Company of $8.8 million for the year ended December 31, 2015 , respectively, and acquisition / restructure related costs incurred by Bridge of $6.8 million for the year ended December 31, 2015 , respectively, and related tax effects.
Business Combination Disclosure [Text Block]	The following table shows the recognized amounts of identifiable assets acquired and liabilities assumed at their as adjusted acquisition date fair values, which include all measurement period adjustments identified and recognized since July 1, 2015: As Adjusted (in thousands) Assets: Cash and cash equivalents (1) $ 378,966 Investment securities - AFS 61,299 Investments in restricted stock 7,015 Loans 1,439,930 Premises and equipment 1,519 Other assets acquired through foreclosure 1,407 Bank owned life insurance 17,385 Investment in LIHTC 5,354 Intangible assets 14,997 Deferred tax assets, net 18,287 Other assets 19,993 Total assets $ 1,966,152 Liabilities: Deposits $ 1,742,031 Qualifying debt 11,287 Other liabilities 11,678 Total liabilities 1,764,996 Net assets acquired $ 201,156 Consideration paid Common stock (12,451,240 shares at $33.76 per share) $ 420,354 Fair value of equity awards related to pre-combination vesting 10,676 Cash 36,539 Fair value of total consideration 467,569 Goodwill $ 266,413
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures	The following table summarizes the operating results of the discontinued operations for the year ended December 31, 2014 and 2013 : Year Ended December 31, 2014 2013 (in thousands) Operating revenue $ (358 ) $ 3,345 Non-interest expenses (1,369 ) (4,855 ) Loss before income taxes (1,727 ) (1,510 ) Income tax benefit (569 ) (649 ) Net loss $ (1,158 ) $ (861 )

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Carrying Amounts and Fair Values of Investment Securities	The carrying amounts and fair values of investment securities at December 31, 2015 and 2014 are summarized as follows: December 31, 2015 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (in thousands) Available-for-sale Collateralized debt obligations $ 50 $ 10,059 $ (49 ) $ 10,060 Commercial MBS issued by GSEs 19,147 72 (105 ) 19,114 Corporate debt securities 12,769 482 — 13,251 CRA investments 34,722 — (37 ) 34,685 Municipal obligations 320,087 14,743 — 334,830 Preferred stock 108,417 4,286 (1,467 ) 111,236 Private label commercial MBS 4,685 6 — 4,691 Private label residential MBS 261,530 5 (4,407 ) 257,128 Residential MBS issued by GSEs 1,169,631 5,254 (4,664 ) 1,170,221 Trust preferred securities 32,000 — (7,686 ) 24,314 U.S. treasury securities 2,996 — (3 ) 2,993 Total AFS securities $ 1,966,034 $ 34,907 $ (18,418 ) $ 1,982,523 Securities measured at fair value Residential MBS issued by GSEs $ 1,481 December 31, 2014 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (in thousands) Available-for-sale Collateralized debt obligations $ 50 $ 11,395 $ — $ 11,445 Commercial MBS issued by GSEs 2,047 100 — 2,147 Corporate debt securities 52,773 717 (1,001 ) 52,489 CRA investments 24,302 30 — 24,332 Municipal obligations 285,398 13,688 (49 ) 299,037 Mutual funds 37,449 500 (247 ) 37,702 Preferred stock 83,192 2,099 (2,679 ) 82,612 Private label commercial MBS 5,017 132 — 5,149 Private label residential MBS 70,985 379 (1,121 ) 70,243 Residential MBS issued by GSEs 881,734 11,440 (1,985 ) 891,189 Trust preferred securities 32,000 — (6,454 ) 25,546 U.S. government-sponsored agency securities 18,701 — (355 ) 18,346 Total AFS securities $ 1,493,648 $ 40,480 $ (13,891 ) $ 1,520,237 Securities measured at fair value Residential MBS issued by GSEs $ 1,858
Unrealized Losses and Fair Value of Investment Securities in Continuous Unrealized Loss Position	Information pertaining to securities with gross unrealized losses at December 31, 2015 and 2014 , aggregated by investment category and length of time that individual securities have been in a continuous loss position follows: December 31, 2015 Less Than Twelve Months More Than Twelve Months Total Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (in thousands) Available-for-sale Collateralized debt obligations $ 49 $ 1 $ — $ — $ 49 $ 1 Commercial MBS issued by GSEs 105 17,051 — — 105 17,051 CRA investments 37 24,729 — — 37 24,729 Preferred stock 377 10,542 1,090 14,761 1,467 25,303 Private label residential MBS 3,733 226,720 674 30,372 4,407 257,092 Residential MBS issued by GSEs 3,566 536,515 1,098 38,338 4,664 574,853 Trust preferred securities — — 7,686 24,314 7,686 24,314 U.S. treasury securities 3 2,006 — — 3 2,006 Total AFS securities $ 7,870 $ 817,564 $ 10,548 $ 107,785 $ 18,418 $ 925,349 December 31, 2014 Less Than Twelve Months More Than Twelve Months Total Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (in thousands) Available-for-sale Corporate debt securities $ 139 $ 9,860 $ 862 $ 29,139 $ 1,001 $ 38,999 Municipal obligations — — 49 4,430 49 4,430 Mutual funds 247 25,855 — — 247 25,855 Preferred stock 232 13,811 2,447 28,109 2,679 41,920 Private label residential MBS 157 24,056 964 26,614 1,121 50,670 Residential MBS issued by GSEs 227 49,217 1,758 97,296 1,985 146,513 Trust preferred securities — — 6,454 25,546 6,454 25,546 U.S. government sponsored agency securities — — 355 18,346 355 18,346 Total AFS securities $ 1,002 $ 122,799 $ 12,889 $ 229,480 $ 13,891 $ 352,279
Amortized Cost and Fair Value of Investment Securities by Contractual Maturities	The amortized cost and fair value of securities as of December 31, 2015 , by contractual maturities, are shown below. MBS are shown separately as individual MBS are comprised of pools of loans with varying maturities. Therefore, these securities are listed separately in the maturity summary. December 31, 2015 Amortized Cost Estimated Fair Value (in thousands) Available-for-sale Due in one year or less $ 62,852 $ 63,114 After one year through five years 77,273 81,090 After five years through ten years 68,935 72,283 After ten years 301,981 314,882 Mortgage-backed securities 1,454,993 1,451,154 Total AFS securities $ 1,966,034 $ 1,982,523
Investment Securities by Credit Rating Type	The following tables summarize the carrying amount of the Company’s investment ratings position as of December 31, 2015 and 2014 : December 31, 2015 AAA Split-rated AAA/AA+ AA+ to AA- A+ to A- BBB+ to BBB- BB+ and below Unrated Totals (in thousands) Available-for-sale Collateralized debt obligations $ — $ — $ — $ — $ — $ 10,060 $ — $ 10,060 Commercial MBS issued by GSEs — 19,114 — — — — — 19,114 Corporate debt securities — — 2,721 5,489 5,041 — — 13,251 CRA investments — — — — — — 34,685 34,685 Municipal obligations 7,949 — 180,460 131,110 6,243 180 8,888 334,830 Preferred stock — — — — 79,955 23,655 7,626 111,236 Private label commercial MBS 4,691 — — — — — — 4,691 Private label residential MBS 235,605 — 40 3,186 1,750 2,705 13,842 257,128 Residential MBS issued by GSEs — 1,170,221 — — — — — 1,170,221 Trust preferred securities — — — — 24,314 — — 24,314 U.S. treasury securities — 2,993 — — — — — 2,993 Total AFS securities (1) $ 248,245 $ 1,192,328 $ 183,221 $ 139,785 $ 117,303 $ 36,600 $ 65,041 $ 1,982,523 Securities measured at fair value Residential MBS issued by GSEs $ — $ 1,481 $ — $ — $ — $ — $ — $ 1,481 (1) The Company uses the average credit rating of the combination of S&P, Moody’s, and Fitch, where ratings differ. December 31, 2014 AAA Split-rated AAA/AA+ AA+ to AA- A+ to A- BBB+ to BBB- BB+ and below Unrated Totals (in thousands) Available-for-sale Collateralized debt obligations $ — $ — $ — $ — $ — $ 11,445 $ — $ 11,445 Commercial MBS issued by GSEs — 2,147 — — — — — 2,147 Corporate debt securities — — 2,759 5,570 44,160 — — 52,489 CRA investments — — — — — — 24,332 24,332 Municipal obligations 8,168 — 138,256 146,155 6,263 195 — 299,037 Mutual funds (2) — — — — 37,702 — — 37,702 Preferred stock — — — — 54,585 17,632 10,395 82,612 Private label commercial MBS 5,149 — — — — — — 5,149 Private label residential MBS 59,944 — 68 3,439 3,595 3,197 — 70,243 Residential MBS issued by GSEs — 891,189 — — — — — 891,189 Trust preferred securities — — — — 25,546 — — 25,546 U.S. government sponsored agency securities — 18,346 — — — — — 18,346 Total AFS securities (1) $ 73,261 $ 911,682 $ 141,083 $ 155,164 $ 171,851 $ 32,469 $ 34,727 $ 1,520,237 Securities measured at fair value Residential MBS issued by GSEs $ — $ 1,858 $ — $ — $ — $ — $ — $ 1,858 (1) The Company uses the average credit rating of the combination of S&P, Moody’s, and Fitch, where ratings differ. (2) At least 80% of mutual funds are investment grade corporate debt securities.
Gross Gains and (Losses) on Sales of Investment Securities	The following table presents gross gains and losses on sales of investment securities: Year Ended December 31, 2015 2014 2013 (in thousands) Gross gains $ 1,144 $ 1,118 $ 1,569 Gross losses (529 ) (361 ) (2,764 ) Net gains on sales of investment securities $ 615 $ 757 $ (1,195 )

Loans, Leases and Allowance f34

Loans, Leases and Allowance for Credit Losses (Tables)	12 Months Ended
	Dec. 31, 2015
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Table Text Block]	As Adjusted Commercial and Industrial Commercial Real Estate Construction and Land Development Residential Real Estate Consumer Total (in thousands) Contractually required principal and interest payments: PCI $ 17,899 $ 3,127 $ — $ 2,509 $ — $ 23,535 Non-PCI 1,225,837 340,762 106,851 26,999 987 1,701,436 Total loans acquired 1,243,736 343,889 106,851 29,508 987 1,724,971 Cash flows expected to be collected: PCI 10,066 1,570 — 2,088 — 13,724 Non-PCI 1,186,076 304,944 102,240 26,629 989 1,620,878 Total loans acquired 1,196,142 306,514 102,240 28,717 989 1,634,602 Fair value of loans acquired: PCI 7,362 1,417 — 2,075 — 10,854 Non-PCI 1,076,742 229,306 99,080 23,023 925 1,429,076 Total loans acquired $ 1,084,104 $ 230,723 $ 99,080 $ 25,098 $ 925 $ 1,439,930
Schedule of Held for Investment Loan Portfolio Composition of Loans, Leases and Allowance for Credit Losses	The composition of the Company’s loan portfolio is as follows: December 31, 2015 2014 (in thousands) Loans, HFI Commercial and industrial $ 5,114,257 $ 3,326,708 Commercial real estate - non-owner occupied 2,283,536 2,052,566 Commercial real estate - owner occupied 2,083,285 1,732,888 Construction and land development 1,133,439 748,053 Residential real estate 322,939 299,402 Commercial leases 148,493 205,639 Consumer 26,905 33,009 Loans, net of deferred loan fees and costs 11,112,854 8,398,265 Allowance for credit losses (119,068 ) (110,216 ) Total loans HFI $ 10,993,786 $ 8,288,049
Contractual Aging of Loan Portfolio by Class of Loans Including Loans Held for Sale and Excluding Deferred Fees/Costs	The following table presents the contractual aging of the recorded investment in past due loans held for investment by class of loans: December 31, 2015 Current 30-59 Days 60-89 Days Over 90 days Total Total (in thousands) Commercial real estate Owner occupied $ 2,078,968 $ 445 $ 362 $ 3,510 $ 4,317 $ 2,083,285 Non-owner occupied 2,099,274 2,481 — 2,822 5,303 2,104,577 Multi-family 178,959 — — — — 178,959 Commercial and industrial Commercial 5,066,197 26,358 14,124 7,578 48,060 5,114,257 Leases 145,905 — — 2,588 2,588 148,493 Construction and land development Construction 694,527 — — — — 694,527 Land 438,495 — — 417 417 438,912 Residential real estate 317,677 888 159 4,215 5,262 322,939 Consumer 26,587 12 91 215 318 26,905 Total loans $ 11,046,589 $ 30,184 $ 14,736 $ 21,345 $ 66,265 $ 11,112,854 December 31, 2014 Current 30-59 Days 60-89 Days Over 90 days Total Total (in thousands) Commercial real estate Owner occupied $ 1,730,164 $ 1,406 $ 180 $ 1,138 $ 2,724 $ 1,732,888 Non-owner occupied 1,855,454 2,389 3,361 8,737 14,487 1,869,941 Multi-family 182,180 — 445 — 445 182,625 Commercial and industrial Commercial 3,324,132 1,523 15 1,038 2,576 3,326,708 Leases 205,639 — — — — 205,639 Construction and land development Construction 388,399 — — — — 388,399 Land 356,209 — 2,640 805 3,445 359,654 Residential real estate 292,065 2,347 205 4,785 7,337 299,402 Consumer 32,540 177 21 271 469 33,009 Total loans $ 8,366,782 $ 7,842 $ 6,867 $ 16,774 $ 31,483 $ 8,398,265
Summary of Recorded Investment in Nonaccrual Loans and Loans Past Due 90 Days Still Accruing Interest by Loan Class	The following table presents the recorded investment in non-accrual loans and loans past due ninety days or more and still accruing interest by class of loans: December 31, 2015 December 31, 2014 Non-accrual loans Loans past due 90 days or more and still accruing Non-accrual loans Loans past due 90 days or more and still accruing Current Past Due/ Total Current Past Due/ Total (in thousands) Commercial real estate Owner occupied $ 749 $ 3,253 $ 4,002 $ 339 $ 13,630 $ — $ 13,630 $ 1,138 Non-owner occupied 11,851 2,822 14,673 — 30,226 8,601 38,827 2,171 Multi-family — — — — — — — — Commercial and industrial Commercial 3,263 15,026 18,289 2,671 2,621 496 3,117 703 Leases — 2,588 2,588 — 373 — 373 — Construction and land development Construction — — — — — — — — Land 1,892 417 2,309 — 2,686 2,640 5,326 805 Residential real estate 1,835 4,489 6,324 — 1,332 4,841 6,173 232 Consumer — 196 196 18 25 188 213 83 Total $ 19,590 $ 28,791 $ 48,381 $ 3,028 $ 50,893 $ 16,766 $ 67,659 $ 5,132
Loans by Risk Rating	The following tables present gross loans by risk rating: December 31, 2015 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Commercial real estate Owner occupied $ 2,032,932 $ 28,422 $ 20,814 $ 1,117 $ — $ 2,083,285 Non-owner occupied 2,054,428 14,867 35,282 — — 2,104,577 Multi-family 178,959 — — — — 178,959 Commercial and industrial Commercial 4,962,930 76,283 74,294 750 — 5,114,257 Leases 140,531 4,580 794 2,588 — 148,493 Construction and land development Construction 678,438 16,089 — — — 694,527 Land 420,819 362 17,731 — — 438,912 Residential real estate 310,067 776 12,096 — — 322,939 Consumer 26,438 209 258 — — 26,905 Total $ 10,805,542 $ 141,588 $ 161,269 $ 4,455 $ — $ 11,112,854 December 31, 2015 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Current (up to 29 days past due) $ 10,799,558 $ 140,932 $ 104,232 $ 1,867 $ — $ 11,046,589 Past due 30 - 59 days 1,907 271 28,006 — — 30,184 Past due 60 - 89 days 4,077 385 10,274 — — 14,736 Past due 90 days or more — — 18,757 2,588 — 21,345 Total $ 10,805,542 $ 141,588 $ 161,269 $ 4,455 $ — $ 11,112,854 December 31, 2014 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Commercial real estate Owner occupied $ 1,664,270 $ 28,072 $ 39,222 $ 1,324 $ — $ 1,732,888 Non-owner occupied 1,771,138 35,752 62,611 440 — 1,869,941 Multi-family 182,180 — 445 — — 182,625 Commercial and industrial Commercial 3,295,027 14,380 17,146 155 — 3,326,708 Leases 202,772 2,494 373 — — 205,639 Construction and land development Construction 383,677 4,241 481 — — 388,399 Land 328,278 10,289 21,087 — — 359,654 Residential real estate 284,052 2,044 13,306 — — 299,402 Consumer 32,419 233 357 — — 33,009 Total $ 8,143,813 $ 97,505 $ 155,028 $ 1,919 $ — $ 8,398,265 December 31, 2014 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Current (up to 29 days past due) $ 8,140,140 $ 95,091 $ 129,787 $ 1,764 $ — $ 8,366,782 Past due 30 - 59 days 2,771 198 4,718 155 — 7,842 Past due 60 - 89 days 385 37 6,445 — — 6,867 Past due 90 days or more 517 2,179 14,078 — — 16,774 Total $ 8,143,813 $ 97,505 $ 155,028 $ 1,919 $ — $ 8,398,265
Recorded Investment in Loans Classified as Impaired	The table below reflects the recorded investment in loans classified as impaired: December 31, 2015 2014 (in thousands) Impaired loans with a specific valuation allowance under ASC 310 (1) $ 24,287 $ 124,928 Impaired loans without a specific valuation allowance under ASC 310 (2) 104,587 41,822 Total impaired loans $ 128,874 $ 166,750 Valuation allowance related to impaired loans (3) $ (4,658 ) $ (10,765 ) (1) Includes TDR loans of $3.0 million and $103.3 million at December 31, 2015 and 2014 , respectively. (2) Includes TDR loans of $85.9 million and $35.0 million at December 31, 2015 and 2014 , respectively. (3) Includes valuation allowance related to TDR loans of $0.3 million and $8.9 million at December 31, 2015 and 2014 , respectively. The following table presents the average investment in impaired loans and income recognized on impaired loans: Year Ended December 31, 2015 2014 2013 (in thousands) Average balance on impaired loans $ 150,151 $ 169,758 $ 182,670 Interest income recognized on impaired loans 4,794 5,494 6,235 Interest recognized on non-accrual loans, cash basis 1,634 2,536 1,916
Impaired Loans by Loan Class	The following table presents impaired loans by class: December 31, 2015 2014 (in thousands) Commercial real estate Owner occupied $ 23,153 $ 44,893 Non-owner occupied 41,081 66,324 Multi-family — — Commercial and industrial Commercial 26,513 13,749 Leases 2,896 373 Construction and land development Construction — — Land 18,322 21,748 Residential real estate 16,575 19,300 Consumer 334 363 Total $ 128,874 $ 166,750
Average Investment in Impaired Loans by Loan Class	The following table presents average investment in impaired loans by loan class: Year Ended December 31, 2015 2014 2013 (in thousands) Commercial real estate Owner occupied $ 34,912 $ 37,048 $ 49,452 Non-owner occupied 56,360 68,821 56,110 Multi-family — — 89 Commercial and industrial Commercial 17,534 16,168 15,023 Leases 2,948 410 727 Construction and land development Construction — — — Land 19,561 21,580 27,326 Residential real estate 18,453 25,223 33,339 Consumer 383 508 604 Total $ 150,151 $ 169,758 $ 182,670
Interest Income on Impaired Loans by Loan Class	The following table presents interest income on impaired loans by class: Year Ended December 31, 2015 2014 2013 (in thousands) Commercial real estate Owner occupied $ 1,575 $ 1,550 $ 1,726 Non-owner occupied 1,560 1,484 2,043 Multi-family — 1 — Commercial and industrial Commercial 288 745 1,087 Leases — — — Construction and land development Construction — — — Land 785 1,021 1,288 Residential real estate 579 646 62 Consumer 7 47 29 Total $ 4,794 $ 5,494 $ 6,235
Tabular Disclosure of Nonperforming Assets	The following table summarizes nonperforming assets: December 31, 2015 2014 (in thousands) Non-accrual loans (1) $ 48,381 $ 67,659 Loans past due 90 days or more on accrual status 3,028 5,132 Troubled debt restructured loans (2) 70,707 84,720 Total nonperforming loans 122,116 157,511 Other assets acquired through foreclosure, net 43,942 57,150 Total nonperforming assets $ 166,058 $ 214,661 (1) Includes non-accrual TDR loans of $18.2 million and $53.6 million at December 31, 2015 and 2014 , respectively. (2) Includes accruing TDR loans only.
Accretable Yield Table	Changes in the accretable yield for loans acquired with deteriorated credit quality in the Centennial, Western Liberty, and Bridge acquisitions are as follows: Year Ended December 31, 2015 2014 2013 (in thousands) Balance, at beginning of period $ 19,156 $ 28,164 $ 7,072 Additions due to acquisition of Bridge 857 — — Measurement period adjustments 38 — 22,318 Reclassifications from non-accretable to accretable yield (1) 1,747 6,052 9,817 Accretion to interest income (3,996 ) (7,185 ) (7,182 ) Reversal of fair value adjustments upon disposition of loans (1,877 ) (7,875 ) (3,861 ) Balance, at end of period $ 15,925 $ 19,156 $ 28,164 (1) The primary drivers of reclassification from non-accretable to accretable yield resulted from changes in estimated cash flows.
Allowances for Credit Losses	The following table summarizes the changes in the allowance for credit losses by portfolio type: Year Ended December 31, Construction and Land Development Commercial Real Estate Residential Real Estate Commercial and Industrial Consumer Total (in thousands) 2015 Beginning Balance $ 18,558 $ 28,783 $ 7,456 $ 54,566 $ 853 $ 110,216 Charge-offs — — 820 5,550 127 6,497 Recoveries (1,872 ) (4,139 ) (2,181 ) (3,754 ) (203 ) (12,149 ) Provision (1,454 ) (9,762 ) (3,539 ) 18,411 (456 ) 3,200 Ending balance $ 18,976 $ 23,160 $ 5,278 $ 71,181 $ 473 $ 119,068 2014 Beginning Balance $ 14,519 $ 32,064 $ 11,640 $ 39,657 $ 2,170 $ 100,050 Charge-offs 87 964 1,728 4,370 513 7,662 Recoveries (2,160 ) (3,859 ) (1,896 ) (4,728 ) (459 ) (13,102 ) Provision 1,966 (6,176 ) (4,352 ) 14,551 (1,263 ) 4,726 Ending balance $ 18,558 $ 28,783 $ 7,456 $ 54,566 $ 853 $ 110,216 2013 Beginning Balance $ 10,554 $ 34,982 $ 15,237 $ 32,860 $ 1,794 $ 95,427 Charge-offs 1,538 8,648 5,922 4,000 1,371 21,479 Recoveries (2,060 ) (2,758 ) (2,097 ) (5,037 ) (930 ) (12,882 ) Provision 3,443 2,972 228 5,760 817 13,220 Ending balance $ 14,519 $ 32,064 $ 11,640 $ 39,657 $ 2,170 $ 100,050 The following table presents impairment method information related to loans and allowance for credit losses by loan portfolio segment: Commercial Real Estate-Owner Occupied Commercial Real Estate-Non-Owner Occupied Commercial and Industrial Residential Real Estate Construction and Land Development Commercial Leases Consumer Total Loans (in thousands) Loans as of December 31, 2015: Recorded Investment: Impaired loans with an allowance recorded $ 2,778 $ 2,344 $ 18,230 $ 914 $ — $ — $ 21 $ 24,287 Impaired loans with no allowance recorded 20,375 38,737 8,283 15,661 18,322 2,896 313 104,587 Total loans individually evaluated for impairment 23,153 41,081 26,513 16,575 18,322 2,896 334 128,874 Loans collectively evaluated for impairment 2,044,934 2,180,250 5,085,299 303,372 1,115,117 145,597 26,571 10,901,140 Loans acquired with deteriorated credit quality 15,198 62,205 2,445 2,992 — — — 82,840 Total recorded investment $ 2,083,285 $ 2,283,536 $ 5,114,257 $ 322,939 $ 1,133,439 $ 148,493 $ 26,905 $ 11,112,854 Unpaid Principal Balance Impaired loans with an allowance recorded $ 2,778 $ 2,344 $ 19,233 $ 969 $ — $ — $ 21 $ 25,345 Impaired loans with no allowance recorded 63,709 61,692 71,773 44,142 82,800 5,229 3,923 333,268 Total loans individually evaluated for impairment 66,487 64,036 91,006 45,111 82,800 5,229 3,944 358,613 Loans collectively evaluated for impairment 2,044,934 2,180,250 5,085,299 303,372 1,115,117 145,597 26,571 10,901,140 Loans acquired with deteriorated credit quality 20,227 88,181 7,820 3,536 — — — 119,764 Total unpaid principal balance $ 2,131,648 $ 2,332,467 $ 5,184,125 $ 352,019 $ 1,197,917 $ 150,826 $ 30,515 $ 11,379,517 Related Allowance for Credit Losses Impaired loans with an allowance recorded $ 858 $ 11 $ 3,518 $ 270 $ — $ — $ 1 $ 4,658 Impaired loans with no allowance recorded — — — — — — — — Total loans individually evaluated for impairment 858 11 3,518 270 — — 1 4,658 Loans collectively evaluated for impairment 10,953 11,302 65,806 5,008 18,976 1,857 472 114,374 Loans acquired with deteriorated credit quality — 36 — — — — — 36 Total allowance for credit losses $ 11,811 $ 11,349 $ 69,324 $ 5,278 $ 18,976 $ 1,857 $ 473 $ 119,068 Commercial Real Estate-Owner Occupied Commercial Real Estate-Non-Owner Occupied Commercial and Industrial Residential Real Estate Construction and Land Development Commercial Leases Consumer Total Loans (in thousands) Loans as of December 31, 2014: Recorded Investment: Impaired loans with an allowance recorded $ 28,024 $ 44,937 $ 11,399 $ 19,300 $ 21,052 $ 41 $ 175 $ 124,928 Impaired loans with no allowance recorded 16,869 21,387 2,350 — 696 332 188 41,822 Total loans individually evaluated for impairment 44,893 66,324 13,749 19,300 21,748 373 363 166,750 Loans collectively evaluated for impairment 1,670,083 1,910,420 3,312,629 277,692 726,305 205,266 32,646 8,135,041 Loans acquired with deteriorated credit quality 17,912 75,822 330 2,410 — — — 96,474 Total recorded investment $ 1,732,888 $ 2,052,566 $ 3,326,708 $ 299,402 $ 748,053 $ 205,639 $ 33,009 $ 8,398,265 Unpaid Principal Balance Impaired loans with an allowance recorded $ 31,292 $ 45,853 $ 11,829 $ 24,420 $ 21,169 $ 41 $ 187 $ 134,791 Impaired loans with no allowance recorded 17,010 21,550 4,104 — 885 483 188 44,220 Total loans individually evaluated for impairment 48,302 67,403 15,933 24,420 22,054 524 375 179,011 Loans collectively evaluated for impairment 1,670,083 1,910,420 3,312,629 277,692 726,305 205,266 32,646 8,135,041 Loans acquired with deteriorated credit quality 24,273 108,935 1,150 3,439 — — — 137,797 Total unpaid principal balance $ 1,742,658 $ 2,086,758 $ 3,329,712 $ 305,551 $ 748,359 $ 205,790 $ 33,021 $ 8,451,849 Related Allowance for Credit Losses Impaired loans with an allowance recorded $ 2,082 $ 2,537 $ 1,926 $ 1,052 $ 3,112 $ 39 $ 17 $ 10,765 Impaired loans with no allowance recorded — — — — — — — — Total loans individually evaluated for impairment 2,082 2,537 1,926 1,052 3,112 39 17 10,765 Loans collectively evaluated for impairment 10,198 13,734 49,809 6,404 15,446 2,761 836 99,188 Loans acquired with deteriorated credit quality 174 58 31 — — — — 263 Total allowance for credit losses $ 12,454 $ 16,329 $ 51,766 $ 7,456 $ 18,558 $ 2,800 $ 853 $ 110,216
Troubled Debt Restructured Loans by Loan Class	The following table presents information on the financial effects of TDR loans by class for the periods presented: Year Ended December 31, 2015 Number of Loans Pre-Modification Outstanding Recorded Investment Forgiven Principal Balance Lost Interest Income Post-Modification Outstanding Recorded Investment Waived Fees and Other Expenses (dollars in thousands) Commercial real estate Owner occupied — $ — $ — $ — $ — $ — Non-owner occupied 1 193 — — 193 — Multi-family — — — — — — Commercial and industrial Commercial 1 256 — — 256 — Leases — — — — — — Construction and land development Construction — — — — — — Land — — — — — — Residential real estate 1 81 — 3 78 4 Consumer — — — — — — Total 3 $ 530 $ — $ 3 $ 527 $ 4 Year Ended December 31, 2014 Number of Loans Pre-Modification Outstanding Recorded Investment Forgiven Principal Balance Lost Interest Income Post-Modification Outstanding Recorded Investment Waived Fees and Other Expenses (dollars in thousands) Commercial real estate Owner occupied 6 $ 14,646 $ 378 $ 257 $ 14,011 $ 33 Non-owner occupied 5 16,976 — 60 16,916 15 Multi-family — — — — — — Commercial and industrial Commercial 6 2,655 — — 2,655 4 Leases — — — — — — Construction and land development Construction — — — — — — Land 2 2,687 — 47 2,640 — Residential real estate 5 1,966 447 70 1,449 15 Consumer — — — — — — Total 24 $ 38,930 $ 825 $ 434 $ 37,671 $ 67 Year Ended December 31, 2013 Number of Loans Pre-Modification Outstanding Recorded Investment Forgiven Principal Balance Lost Interest Income Post-Modification Outstanding Recorded Investment Waived Fees and Other Expenses (dollars in thousands) Commercial real estate Owner occupied 8 $ 3,681 $ — $ 54 $ 3,627 $ 28 Non-owner occupied 5 10,735 1,030 63 9,642 14 Multi-family — — — — — — Commercial and industrial Commercial 13 4,809 — 19 4,790 11 Leases — — — — — — Construction and land development Construction — — — — — — Land 2 286 — — 286 1 Residential real estate 13 5,434 267 887 4,280 24 Consumer 2 74 — 5 69 3 Total 43 $ 25,019 $ 1,297 $ 1,028 $ 22,694 $ 81
Troubled Debt Restructured Loans by Class for Which There was a Payment Default	The following table presents TDR loans by class for which there was a payment default during the period: Year Ended December 31, 2015 2014 2013 Number of Loans Recorded Investment Number of Loans Recorded Investment Number of Loans Recorded Investment (dollars in thousands) Commercial real estate Owner occupied — $ — 2 $ 395 3 $ 2,506 Non-owner occupied — — 2 984 3 1,490 Multi-family — — — — — — Commercial and industrial Commercial — — 3 369 3 1,089 Leases — — — — — — Construction and land development Construction 1 137 — — — — Land — — — — 2 330 Residential real estate 3 1,047 1 202 4 955 Consumer — — — — — — Total 4 $ 1,184 8 $ 1,950 15 $ 6,370

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment [Table Text Block]	December 31, 2015 2014 (in thousands) Bank premises $ 83,431 $ 82,494 Land and improvements 33,971 33,971 Furniture, fixtures, and equipment 40,025 51,320 Leasehold improvements 18,958 18,160 Construction in progress 1,999 848 Total 178,384 186,793 Accumulated depreciation and amortization (59,849 ) (72,975 ) Premises and equipment, net $ 118,535 $ 113,818
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	(in thousands) 2016 $ 8,547 2017 7,999 2018 7,536 2019 6,628 2020 4,986 Thereafter 8,879 Total future minimum rental payments $ 44,575

Other Assets Acquired Through36

Other Assets Acquired Through Foreclosure (Tables)	12 Months Ended
	Dec. 31, 2015
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Changes in Other Assets Acquired Through Foreclosure	The following table represents the changes in other assets acquired through foreclosure: Year Ended December 31, 2015 Gross Balance Valuation Allowance Net Balance (in thousands) Balance, beginning of period $ 71,421 $ (14,271 ) $ 57,150 Additions from acquisition of Bridge 1,407 — 1,407 Transfers to other assets acquired through foreclosure, net 28,566 — 28,566 Proceeds from sale of other real estate owned and repossessed assets, net (51,038 ) 5,411 (45,627 ) Valuation adjustments, net — (182 ) (182 ) Gains, net (1) 2,628 — 2,628 Balance, end of period $ 52,984 $ (9,042 ) $ 43,942 2014 Balance, beginning of period $ 88,421 $ (21,702 ) $ 66,719 Transfers to other assets acquired through foreclosure, net 13,777 — 13,777 Proceeds from sale of other real estate owned and repossessed assets, net (33,643 ) 7,725 (25,918 ) Valuation adjustments, net — (294 ) (294 ) Gains, net (1) 2,866 — 2,866 Balance, end of period $ 71,421 $ (14,271 ) $ 57,150 2013 Balance, beginning of period $ 113,474 $ (36,227 ) $ 77,247 Additions from acquisition of Centennial 5,622 — 5,622 Transfers to other assets acquired through foreclosure, net 24,911 — 24,911 Proceeds from sale of other real estate owned and repossessed assets, net (61,510 ) 18,268 (43,242 ) Valuation adjustments, net — (3,743 ) (3,743 ) Gains, net (1) 5,924 — 5,924 Balance, end of period $ 88,421 $ (21,702 ) $ 66,719 (1) Includes net gains related to initial transfers to other assets of $0.9 million , $0.1 million , and $0.9 million during the years ended December 31, 2015 , 2014 , and 2013 respectively, pursuant to accounting guidance.

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2015
Deposit [Abstract]
Schedule Of Deposits Table [Text Block]	The table below summarizes deposits by type: December 31, 2015 2014 (in thousands) Non-interest-bearing demand $ 4,093,976 $ 2,288,048 Interest-bearing demand 1,028,073 854,935 Savings and money market 5,296,921 3,869,699 Certificate of deposit ($250,000 or more) 1,569,525 1,339,238 Other time deposits 42,129 579,123 Total deposits $ 12,030,624 $ 8,931,043
Scheduled Maturities Of Time Deposits Table [Text Block]	The summary of the contractual maturities for all time deposits as of December 31, 2015 is as follows: December 31, 2015 (in thousands) 2016 $ 1,507,050 2017 88,184 2018 9,633 2019 3,552 2020 3,235 Total $ 1,611,654

Accumulated Other Comprehensi38

Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Summary of Changes in Accumulated Other Comprehensive Income	The following table summarizes the changes in accumulated other comprehensive income (loss) by component, net of tax, for the periods indicated: Unrealized holding gains (losses) on AFS Unrealized holding gains (losses) on SERP Unrealized holding gains (losses) on junior subordinated debt Impairment loss on securities Unrealized gain on cash flow hedge Total (in thousands) Balance, December 31, 2012 $ 8,065 $ — $ — $ 144 $ 17 $ 8,226 Other comprehensive income before reclassifications (30,503 ) — — — (17 ) (30,520 ) Amounts reclassified from accumulated other comprehensive income 748 — — — — 748 Net current-period other comprehensive (loss) (29,755 ) — — — (17 ) (29,772 ) Balance, December 31, 2013 $ (21,690 ) $ — $ — $ 144 $ — $ (21,546 ) Transfer of HTM securities to AFS 8,976 — — — — 8,976 Other comprehensive income before reclassifications 29,683 — — — — 29,683 Amounts reclassified from accumulated other comprehensive income (474 ) — — — — (474 ) Net current-period other comprehensive income 38,185 — — — — 38,185 Balance, December 31, 2014 $ 16,495 $ — $ — $ 144 $ — $ 16,639 Balance, January 1, 2015 (1) 16,495 — 16,309 144 — 32,948 Transfer of HTM securities to AFS — — — — — — Other comprehensive income before reclassifications (6,117 ) 90 (4,276 ) — — (10,303 ) Amounts reclassified from accumulated other comprehensive income (385 ) — — — — (385 ) Net current-period other comprehensive (loss) income (6,502 ) 90 (4,276 ) — — (10,688 ) Balance, December 31, 2015 $ 9,993 $ 90 $ 12,033 $ 144 $ — $ 22,260
Schedule of Reclassifications Out of Accumulated Other Comprehensive Income	The following table presents reclassifications out of accumulated other comprehensive income: Year Ended December 31, Income Statement Classification 2015 2014 2013 (in thousands) Gain (loss) on sales of investment securities, net $ 615 $ 757 $ (1,195 ) Income tax (expense) benefit (230 ) (283 ) 447 Net of tax $ 385 $ 474 $ (748 )

Other Borrowings (Tables)

Other Borrowings (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Company's Borrowings	The following table summarizes the Company’s borrowings as of December 31, 2015 and 2014 : December 31, 2015 2014 (in thousands) Short-Term: Revolving line of credit $ — $ 25,000 FHLB advances 150,000 96,987 Other short-term debt — 58,182 Total short-term borrowings $ 150,000 $ 180,169 Long-Term: FHLB advances $ — $ 210,094 Total long-term borrowings $ — $ 210,094

Qualifying Debt Junior Subordin

Qualifying Debt Junior Subordinated Debt Table (Tables)	12 Months Ended
	Dec. 31, 2015
Junior Subordinated Debt Table [Abstract]
Schedule of Subordinated Borrowing [Table Text Block]	December 31, Name of Trust Maturity 2015 2014 At fair value (in thousands) BankWest Nevada Capital Trust II 2033 $ 15,464 $ 15,464 Intermountain First Statutory Trust I 2034 10,310 10,310 First Independent Statutory Trust I 2035 7,217 7,217 WAL Trust No. 1 2036 20,619 20,619 WAL Statutory Trust No. 2 2037 5,155 5,155 WAL Statutory Trust No. 3 2037 7,732 7,732 Total contractual balance 66,497 66,497 FVO on junior subordinated debt (19,569 ) (26,060 ) Junior subordinated debt, at fair value $ 46,928 $ 40,437 At amortized cost Bridge Capital Holdings Trust I 2035 $ 12,372 $ — Bridge Capital Holdings Trust II 2036 5,155 — Total contractual balance 17,527 — Purchase accounting adjustment, net of accretion (1) (6,085 ) — Junior subordinated debt, at amortized cost $ 11,442 $ — Total junior subordinated debt $ 58,370 $ 40,437

Stockholders' Equity Schedule o

Stockholders' Equity Schedule of Share-based Compensation Arrangements by Share-based Payment Award (Tables)	12 Months Ended
	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]	A summary of option activity during the year ended December 31, 2015 is presented below: December 31, 2015 Shares Weighted Average Exercise Price (per share) Weighted Average Remaining Contractual Term (in years) Aggregate (in thousands, except exercise price and contractual terms) Outstanding options, beginning of period 217 $ 9.70 Granted — — Issued in acquisition of Bridge 213 22.02 Exercised (182 ) 10.62 Forfeited or expired (24 ) 23.89 Options outstanding, end of period 224 $ 19.15 6.41 $ 3,738 Options exercisable, end of period 94 $ 11.72 3.67 $ 2,278 Options expected to vest, end of period 97 $ 24.49 8.38 $ 1,691
Schedule of Unvested Restricted Stock Units Roll Forward [Table Text Block]	A summary of the status of the Company’s unvested shares of restricted stock, including those issued in connection with the Bridge acquisition, and changes during the years then ended is presented below: December 31, 2015 2014 Shares Weighted Average Grant Date Fair Value Shares Weighted Average Grant Date Fair Value (in thousands, except per share amounts) Balance, beginning of period 1,050 $ 16.19 1,204 $ 9.71 Granted 509 27.55 508 23.90 Issued in acquisition of Bridge 546 14.70 — — Vested (528 ) 13.02 (566 ) 9.57 Forfeited (85 ) 21.63 (96 ) 15.05 Balance, end of period 1,492 $ 20.46 1,050 $ 16.19
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	Bridge's stock options had an original vesting period of four years and a contractual term of ten years. Stock option replacement awards were valued using the Black-Scholes option valuation model, using the following weighted average assumptions. June 30, 2015 Dividend yield — % Volatility 33.96 % Risk-free interest rate 2.11 % Expected life in years 7.66 Weighted average fair value of assumed options $ 19.06

Derivatives and Hedging (Tables

Derivatives and Hedging (Tables)	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position	The fair value of derivative contracts, after taking into account the effects of master netting agreements, is included in other assets or other liabilities in the Consolidated Balance Sheets, as indicated in the following table: December 31, 2015 December 31, 2014 December 31, 2013 Fair Value Fair Value Fair Value Notional Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities (in thousands) Derivatives designated as hedging instruments: Fair value hedges Interest rate swaps $ 800,478 $ 3,569 $ 64,785 $ 647,703 $ 7 $ 57,820 $ 294,997 $ 2,386 $ 788 Total 800,478 3,569 64,785 647,703 7 57,820 294,997 2,386 788 Netting adjustments (1) — — — — — — — 384 384 Net derivatives in the balance sheet $ 800,478 $ 3,569 $ 64,785 $ 647,703 $ 7 $ 57,820 $ 294,997 $ 2,002 $ 404 (1) Netting adjustments represent the amounts recorded to convert our derivative balances from a gross basis to a net basis in accordance with the applicable accounting guidance.
Gain (Loss) on Derivative Instruments	The following table summarizes the pre-tax net gains (losses) on fair value hedges for the years ended December 31, 2015 , 2014 , and 2013 which are recorded in unrealized (losses) gains on assets and liabilities measured at fair value, net in the income statement. Year Ended December 31, 2015 2014 2013 (in thousands) Hedge of Fixed Rate Loans (a) Loss on "pay fixed" swap $ (6,965 ) $ (60,377 ) $ 3,308 Gain on receive fixed rate loans 7,044 60,208 (3,317 ) Net ineffectiveness $ 79 $ (169 ) $ (9 ) Hedge of Fixed Rate Subordinated Debt (a) Gain on "receive fixed" swap $ 3,569 $ — $ — Loss on subordinated debt (3,569 ) — — Net ineffectiveness $ — $ — $ —
Largest Exposure To Individual Counterparty	The following table summarizes our largest exposure to an individual counterparty at the dates indicated: December 31, 2015 2014 2013 (in thousands) Largest gross exposure (derivative asset) to an individual counterparty $ 3,569 $ 7 $ 2,378 Collateral posted by this counterparty 4,680 — 2,002 Derivative liability with this counterparty — — 346 Collateral pledged to this counterparty 1,340 — — Net exposure after netting adjustments and collateral $ 229 $ 7 $ —

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table presents the calculation of basic and diluted EPS: Year Ended December 31, 2015 2014 2013 (in thousands, except per share amounts) Weighted average shares - basic 94,570 86,693 85,682 Dilutive effect of stock awards 649 813 859 Weighted average shares - diluted 95,219 87,506 86,541 Net income available to common stockholders $ 193,494 $ 146,564 $ 113,555 Earnings per share - basic 2.05 1.69 1.33 Earnings per share - diluted 2.03 1.67 1.31

Income Taxes Provision Current

Income Taxes Provision Current & Deferred Table (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Expense Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	Year Ended December 31, 2015 2014 2013 (in thousands) Current $ 61,040 $ 55,572 $ 43,547 Deferred 3,254 (7,182 ) (13,717 ) Total tax provision $ 64,294 $ 48,390 $ 29,830

Income Taxes Reconciliation bet

Income Taxes Reconciliation between Statutory Federal Income Tax Rate and Company's Effective Tax Rate (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	Year Ended December 31, 2015 2014 2013 (in thousands) Income tax at statutory rate $ 90,489 $ 69,125 $ 50,979 Increase (decrease) resulting from: State income taxes, net of federal benefits 5,783 4,904 3,016 Bank owned life insurance (1,365 ) (1,578 ) (1,683 ) Tax-exempt income (20,226 ) (15,006 ) (7,308 ) Deferred tax asset valuation allowance (2,290 ) (2,104 ) (2,391 ) Bargain purchase gain — — (3,775 ) Low income housing tax credits (5,223 ) (3,872 ) (2,105 ) Tax benefit related to Western Liberty acquisition — — (3,738 ) Other, net (2,874 ) (3,079 ) (3,165 ) Total tax provision $ 64,294 $ 48,390 $ 29,830

Income Taxes Cumulative Tax Eff

Income Taxes Cumulative Tax Effects of Primary Difference (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	December 31, 2015 2014 (in thousands) Deferred tax assets: Allowance for credit losses $ 47,431 $ 42,038 Fair market value adjustment related to acquired loans 13,930 8,250 Stock-based compensation 12,069 4,749 Net operating loss carryovers 9,255 8,453 Tax credit carryovers 9,052 9,617 Startup costs and other amortization 4,771 5,113 Allowance for other assets acquired through foreclosure, net 4,280 7,343 Section 382 limited NUBILs 3,284 3,657 Other 13,686 8,188 Total gross deferred tax assets 117,758 97,408 Deferred tax asset valuation allowance — (2,290 ) Total deferred tax assets 117,758 95,118 Deferred tax liabilities: Unrealized gain on debt instruments measured at fair value (7,537 ) — Deferred loan costs (7,400 ) (6,041 ) Unrealized gain on AFS securities (6,353 ) (9,949 ) Core deposit intangible (6,093 ) (1,006 ) Premises and equipment (2,039 ) (4,049 ) Unrealized gains on financial instruments measured at fair value (1,000 ) (9,798 ) Other (984 ) (1,589 ) Total deferred tax liabilities (31,406 ) (32,432 ) Deferred tax assets, net $ 86,352 $ 62,686

Income Taxes Gross Activity of

Income Taxes Gross Activity of Unrecognized Tax Benefits Related to Uncertain Tax Positions (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Contingency [Line Items]
Summary of Income Tax Contingencies [Table Text Block]	December 31, 2015 2014 (in thousands) Beginning balance $ — $ — Gross Increases Tax positions in prior periods 1,038 — Current period tax positions — — Gross decreases Tax positions in prior periods — — Settlements — — Lapse of statute of limitations — — Ending balance $ 1,038 $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Summary of Contractual Amounts for Unfunded Commitments and Letters of Credit	A summary of the contractual amounts for unfunded commitments and letters of credit are as follows: December 31, 2015 2014 (in thousands) Commitments to extend credit, including unsecured loan commitments of $341,374 at December 31, 2015 and $232,863 at December 31, 2014 $ 3,624,578 $ 2,164,523 Credit card commitments and financial guarantees 57,966 42,038 Standby letters of credit, including unsecured letters of credit of $4,257 at December 31, 2015 and $5,166 at December 31, 2014 50,659 49,556 Total $ 3,733,203 $ 2,256,117
Contractual Obligation, Fiscal Year Maturity Schedule [Table Text Block]	Amount of Commitment Expiration per Period Total Amounts Committed Less Than 1 Year 1-3 Years 3-5 Years After 5 Years (in thousands) Commitments to extend credit $ 3,624,578 $ 1,588,558 $ 1,401,293 $ 267,284 $ 367,443 Credit card commitments and financial guarantees 57,966 57,966 — — — Standby letters of credit 50,659 42,749 5,749 2,161 — Total $ 3,733,203 $ 1,689,273 $ 1,407,042 $ 269,445 $ 367,443

Fair Value Accounting (Tables)

Fair Value Accounting (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Gains and Losses from Fair Value Changes Included in Consolidated Statement of Operations	For the years ended December 31, 2015 , 2014 , and 2013 securities gains and losses from fair value changes were as follows: Changes in Fair Values for Items Measured at Fair Value Unrealized Gain/(Loss) on Assets and Liabilities Measured at Fair Value, Net Interest Income on Securities Interest Expense on Junior Subordinated Debt Total Changes Included in Current-Period Earnings Total Changes Included in OCI (in thousands) Year Ended December 31, 2015 Securities measured at fair value $ (32 ) $ 2 $ — $ (30 ) $ — Junior subordinated debt (6,491 ) — (2,151 ) (2,151 ) (4,276 ) Total $ (6,523 ) $ 2 $ (2,151 ) $ (2,181 ) $ (4,276 ) Year Ended December 31, 2014 Securities measured at fair value $ (41 ) $ 7 $ — $ (34 ) $ — Junior subordinated debt 1,421 — (1,754 ) (333 ) — Total $ 1,380 $ 7 $ (1,754 ) $ (367 ) $ — Year Ended December 31, 2013 Securities measured at fair value $ (260 ) $ 6 $ — $ (254 ) $ — Junior subordinated debt (5,640 ) — (1,823 ) (7,463 ) — Total $ (5,900 ) $ 6 $ (1,823 ) $ (7,717 ) $ —
Fair Value of Assets and Liabilities	The fair value of assets and liabilities measured at fair value on a recurring basis was determined using the following inputs as of the periods presented: Fair Value Measurements at the End of the Reporting Period Using: Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Fair Value (in thousands) December 31, 2015 Assets: Measured at fair value Residential MBS issued by GSEs $ — $ 1,481 $ — $ 1,481 Available-for-sale Collateralized debt obligations $ — $ — $ 10,060 $ 10,060 Commercial MBS issued by GSEs — 19,114 — 19,114 Corporate debt securities — 13,251 — 13,251 CRA investments 34,685 — — 34,685 Municipal obligations — 334,830 — 334,830 Preferred stock 111,236 — — 111,236 Private label commercial MBS — 4,691 — 4,691 Private label residential MBS — 257,128 — 257,128 Residential MBS issued by GSEs — 1,170,221 — 1,170,221 Trust preferred securities — 24,314 — 24,314 U.S. treasury securities 2,993 — — 2,993 Total AFS securities $ 148,914 $ 1,823,549 $ 10,060 $ 1,982,523 Loans - HFS $ — $ 23,809 $ — $ 23,809 Derivative assets (1) — 3,569 — 3,569 Liabilities: Junior subordinated debt (2) $ — $ — $ 46,928 $ 46,928 Derivative liabilities (1) — 64,785 — 64,785 (1) Derivative assets and liabilities relate to interest rate swaps, see " Note 13. Derivatives and Hedging Activities ." In addition, the carrying value of loans includes a net positive value of $64,184 and the net carrying value of subordinated debt includes a net negative value of $3,569 as of December 31, 2015 , which relates to the effective portion of the hedges put in place to mitigate against fluctuations in interest rates. (2) Includes only the portion of junior subordinated debt that is recorded at fair value at each reporting period pursuant to the election of FVO treatment. Fair Value Measurements at the End of the Reporting Period Using: Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value (in thousands) December 31, 2014 Assets: Measured at fair value Residential MBS issued by GSEs $ — $ 1,858 $ — $ 1,858 Available-for-sale Collateralized debt obligations $ — $ — $ 11,445 $ 11,445 Commercial MBS issued by GSEs — 2,147 — 2,147 Corporate debt securities — 52,489 — 52,489 CRA investments 24,332 — — 24,332 Municipal obligations — 299,037 — 299,037 Mutual funds 37,702 — — 37,702 Preferred stock 82,612 — — 82,612 Private label commercial MBS — 5,149 — 5,149 Private label residential MBS — 70,243 — 70,243 Residential MBS issued by GSEs — 891,189 — 891,189 Trust preferred securities — 25,546 — 25,546 U.S. government sponsored agency securities — 18,346 — 18,346 Total AFS securities $ 144,646 $ 1,364,146 $ 11,445 $ 1,520,237 Derivative assets (1) $ — $ 7 $ — $ 7 Liabilities: Junior subordinated debt $ — $ — $ 40,437 $ 40,437 Derivative liabilities (1) — 57,820 — 57,820 (1) Derivative assets and liabilities relate to interest rate swaps, see " Note 13. Derivatives and Hedging Activities ." In addition, the carrying value of loans includes a positive value of $57,140 as of December 31, 2014 , which relates to the effective portion of the hedges put in place to mitigate against fluctuations in interest rates.
Change in Level 3 Liabilities Measured at Fair Value on Recurring Basis	For the years ended December 31, 2015 , 2014 , and 2013 , the change in Level 3 assets and liabilities measured at fair value on a recurring basis was as follows: Junior Subordinated Debt Year Ended December 31, 2015 2014 2013 (in thousands) Beginning balance $ (40,437 ) $ (41,858 ) $ (36,218 ) Transfers into Level 3 — — — Total gains (losses) for the period Included in earnings (1) — 1,421 (5,640 ) Included in other comprehensive income (2) $ (6,491 ) $ — $ — Ending balance $ (46,928 ) $ (40,437 ) $ (41,858 ) (1) Total gains (losses) for the period are included in the non-interest income line, Unrealized gains (losses) on assets and liabilities measured at fair value, net. (2) Due to the Company's election to early adopt an element of ASU 2016-01, changes in the fair value of junior subordinated debt are presented as part of OCI rather than earnings effective January 1, 2015. Accordingly, total losses for 2015 are included in the other comprehensive income line, Unrealized gain (loss) on junior subordinated debt, which is net of tax. The above amount represents the gross loss from changes in fair value of junior subordinated debt. CDO Securities Year Ended December 31, 2015 2014 2013 (in thousands) Beginning balance $ 11,445 $ — $ — Transfers into Level 3 — 6,243 — Total gains (losses) for the period Included in other comprehensive income (3) (1,385 ) 5,202 — Ending balance $ 10,060 $ 11,445 $ — (3) Total gains (losses) for the period are included in the other comprehensive income line, Unrealized gain (loss) on AFS securities. For Level 3 liabilities measured at fair value on a recurring basis as of December 31, 2015 and 2014 , the significant unobservable inputs used in the fair value measurements were as follows: December 31, 2015 Valuation Technique Significant Unobservable Inputs (in thousands) Junior subordinated debt $ 46,928 Discounted cash flow Implied credit rating of the Company CDO securities 10,060 S&P Model Pricing indications from comparable securities December 31, 2014 Valuation Technique Significant Unobservable Inputs (in thousands) Junior subordinated debt $ 40,437 Discounted cash flow Adjusted Corporate Bond over Treasury Index with comparable credit spread CDO securities 11,445 S&P Model Pricing indications from comparable securities
Assets Measured at Fair Value on Nonrecurring Basis	The following table presents such assets carried on the balance sheet by caption and by level within the ASC 825 hierarchy: Fair Value Measurements at the End of the Reporting Period Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Active Markets for Similar Assets (Level 2) Unobservable Inputs (Level 3) (in thousands) As of December 31, 2015: Impaired loans with specific valuation allowance $ 19,629 $ — $ — $ 19,629 Impaired loans without specific valuation allowance (1) 66,754 — — 66,754 Other assets acquired through foreclosure 43,942 — — 43,942 As of December 31, 2014: Impaired loans with specific valuation allowance $ 114,163 $ — $ — $ 114,163 Impaired loans without specific valuation allowance (1) 38,019 — — 38,019 Other assets acquired through foreclosure 57,150 — — 57,150 (1) Excludes loan balances with charge-offs of $37.8 million and $3.8 million as of December 31, 2015 and 2014 , respectively.
Estimated Fair Value of Financial Instruments	The estimated fair value of the Company’s financial instruments is as follows: December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (in thousands) Financial assets: Investment securities: AFS $ 1,982,523 $ 148,914 $ 1,823,549 $ 10,060 $ 1,982,523 Trading 1,481 — 1,481 — 1,481 Derivative assets 3,569 — 3,569 — 3,569 Loans, net 11,017,595 — 10,766,826 86,383 10,853,209 Accrued interest receivable 54,445 — 54,445 — 54,445 Financial liabilities: Deposits $ 12,030,624 $ — $ 12,034,199 $ — $ 12,034,199 Customer repurchases 38,155 — 38,155 — 38,155 FHLB advances 150,000 — 150,000 — 150,000 Qualifying debt 210,328 — — 207,437 207,437 Derivative liabilities 64,785 — 64,785 — 64,785 Accrued interest payable 13,626 — 13,626 — 13,626 December 31, 2014 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (in thousands) Financial assets: Investment securities: AFS $ 1,520,237 $ 144,646 $ 1,364,146 $ 11,445 $ 1,520,237 Trading 1,858 — 1,858 — 1,858 Derivative assets 7 — 7 — 7 Loans, net 8,288,049 — 7,984,692 152,182 8,136,874 Accrued interest receivable 36,705 — 36,705 — 36,705 Financial liabilities: Deposits $ 8,931,043 $ — $ 8,935,566 $ — $ 8,935,566 Customer repurchases 54,899 — 54,899 — 54,899 FHLB advances 307,081 — 307,081 — 307,081 Other borrowed funds 83,182 — 25,000 61,074 86,074 Qualifying debt 40,437 — — 40,437 40,437 Derivative liabilities 57,820 — 57,820 — 57,820 Accrued interest payable 9,890 — 9,890 — 9,890

Regulatory Capital Requiremen50

Regulatory Capital Requirements (Tables)	12 Months Ended
	Dec. 31, 2015
Banking and Thrift [Abstract]
Summary of Actual Capital Amount and Ratio	The actual capital amounts and ratios for the Company and the Bank are presented in the following tables as of the periods indicated: Total Capital Tier 1 Capital Risk-Weighted Assets Tangible Average Assets Total Capital Ratio Tier 1 Capital Ratio Tier 1 Leverage Ratio Common Equity (dollars in thousands) Basel III December 31, 2015 WAL $ 1,603,472 $ 1,341,011 $ 13,193,563 $ 13,683,148 12.2 % 10.2 % 9.8 % 9.7 % WAB 1,485,070 1,213,304 13,073,394 13,561,251 11.4 9.3 9.0 9.3 Well-capitalized ratios 10.0 8.0 5.0 6.5 Minimum capital ratios 8.0 6.0 4.0 4.5 Basel I December 31, 2014 WAL $ 1,119,618 $ 1,007,278 $ 9,555,390 $ 10,367,575 11.7 % 10.5 % 9.7 % — WAB 1,057,253 945,687 9,435,459 10,232,297 11.2 10.0 9.2 — Well-capitalized ratios 10.0 6.0 5.0 — Minimum capital ratios 8.0 4.0 4.0 —

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets (Tables) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Amortization Schedule [Abstract]
Schedule of Finite-Lived Intangible Assets [Table Text Block]	The following is a summary of the Company's acquired intangible assets: December 31, 2015 December 31, 2014 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount (in thousands) Subject to amortization: Core deposit intangibles $ 40,804 $ 25,438 $ 15,366 $ 26,157 $ 23,468 $ 2,689 December 31, 2015 December 31, 2014 Gross Carrying Amount Impairment Net Carrying Amount Gross Carrying Amount Impairment Net Carrying Amount Not subject to amortization Trade name $ 350 $ — $ 350 $ — $ — $ —
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	Below is a summary of future estimated aggregate amortization expense: Year Ended December 31, (in thousands) 2016 $ 2,788 2017 2,074 2018 1,594 2019 1,547 2020 1,494 Thereafter 5,869 Total $ 15,366
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	$ 2,788
Finite-Lived Intangible Assets, Amortization Expense, Year Two	2,074
Finite-Lived Intangible Assets, Amortization Expense, Year Three	1,594
Finite-Lived Intangible Assets, Amortization Expense, Year Four	1,547
Finite-Lived Intangible Assets, Amortization Expense, Year Five	1,494
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	5,869
Other intangible assets, net	$ 15,716	$ 2,689

Segments (Tables)

Segments (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Operating Segment Information	The following is a summary of selected operating segment information for the years ended December 31, 2015 and 2014 . Arizona Nevada Southern California Northern California Central Business Lines Corporate & Other Consolidated Company At December 31, 2015 (dollars in millions) Assets: Cash, cash equivalents, and investment securities $ 2.3 $ 9.5 $ 2.4 $ 2.4 $ — $ 2,250.3 $ 2,266.9 Loans, net of deferred loan fees and costs 2,811.7 1,737.2 1,761.9 1,188.4 3,597.9 39.6 11,136.7 Less: allowance for credit losses (30.1 ) (18.6 ) (18.8 ) (12.7 ) (38.5 ) (0.4 ) (119.1 ) Total loans 2,781.6 1,718.6 1,743.1 1,175.7 3,559.4 39.2 11,017.6 Other assets acquired through foreclosure, net 8.4 20.8 — 0.3 — 14.4 43.9 Goodwill and other intangible assets, net — 24.8 — 158.2 122.4 — 305.4 Other assets 43.9 62.3 15.7 16.1 28.4 474.9 641.3 Total assets $ 2,836.2 $ 1,836.0 $ 1,761.2 $ 1,352.7 $ 3,710.2 $ 2,778.8 $ 14,275.1 Liabilities: Deposits $ 2,880.7 $ 3,382.8 $ 1,902.5 $ 1,541.1 $ 2,134.4 $ 189.1 $ 12,030.6 Borrowings and qualifying debt — — — — — 360.3 360.3 Other liabilities 12.2 29.0 7.8 11.2 105.1 127.4 292.7 Total liabilities 2,892.9 3,411.8 1,910.3 1,552.3 2,239.5 676.8 12,683.6 Allocated equity: 309.2 244.4 191.3 293.2 428.6 124.8 1,591.5 Total liabilities and stockholders' equity $ 3,202.1 $ 3,656.2 $ 2,101.6 $ 1,845.5 $ 2,668.1 $ 801.6 $ 14,275.1 Excess funds provided (used) 365.9 1,820.2 340.4 492.8 (1,042.1 ) (1,977.2 ) — Arizona Nevada Southern California Northern California Central Business Lines Corporate & Other Consolidated Company At December 31, 2014 (dollars in millions) Assets: Cash, cash equivalents, and investment securities $ 2.3 $ 5.0 $ 2.2 $ 0.3 $ — $ 1,702.4 $ 1,712.2 Loans, net of deferred loan fees and costs 2,341.9 1,668.7 1,553.1 198.6 2,590.0 46.0 8,398.3 Less: allowance for credit losses (30.7 ) (21.9 ) (17.9 ) (5.1 ) (34.0 ) (0.6 ) (110.2 ) Total loans 2,311.2 1,646.8 1,535.2 193.5 2,556.0 45.4 8,288.1 Other assets acquired through foreclosure, net 15.5 21.0 — — — 20.6 57.1 Goodwill and other intangible assets, net — 25.9 — — — — 25.9 Other assets 34.8 64.2 6.2 15.3 22.9 373.8 517.2 Total assets $ 2,363.8 $ 1,762.9 $ 1,543.6 $ 209.1 $ 2,578.9 $ 2,142.2 $ 10,600.5 Liabilities: Deposits $ 2,178.0 $ 3,230.6 $ 1,744.5 $ 584.0 $ 946.6 $ 247.3 $ 8,931.0 Borrowings and qualifying debt — — — — — 430.7 430.7 Other liabilities 17.4 40.8 8.9 0.2 72.4 98.2 237.9 Total liabilities 2,195.4 3,271.4 1,753.4 584.2 1,019.0 776.2 9,599.6 Allocated equity: 250.8 209.0 70.9 126.8 232.9 110.5 1,000.9 Total liabilities and stockholders' equity $ 2,446.2 $ 3,480.4 $ 1,824.3 $ 711.0 $ 1,251.9 $ 886.7 $ 10,600.5 Excess funds provided (used) 82.4 1,717.5 280.7 501.9 (1,327.0 ) (1,255.5 ) — Arizona Nevada Southern California Northern California Central Business Lines Corporate & Other Consolidated Company Year Ended December 31, 2015: (in thousands) Net interest income (expense) $ 129,914 $ 122,082 $ 94,585 $ 56,698 $ 124,222 $ (34,925 ) $ 492,576 Provision for (recovery of) credit losses 3,099 (6,887 ) 152 3,038 3,917 (119 ) 3,200 Net interest income (expense) after provision for credit losses 126,815 128,969 94,433 53,660 120,305 (34,806 ) 489,376 Non-interest income 4,204 9,202 2,697 5,161 4,110 4,394 29,768 Non-interest expense (59,917 ) (59,553 ) (47,549 ) (30,161 ) (45,831 ) (17,595 ) (260,606 ) Income (loss) from continuing operations before income taxes 71,102 78,618 49,581 28,660 78,584 (48,007 ) 258,538 Income tax expense (benefit) 27,893 27,516 20,849 12,051 29,469 (53,484 ) 64,294 Net income $ 43,209 $ 51,102 $ 28,732 $ 16,609 $ 49,115 $ 5,477 $ 194,244 Arizona Nevada Southern California Northern California Central Business Lines Corporate & Other Consolidated Company Year Ended December 31, 2014: (in thousands) Net interest income (expense) $ 112,128 $ 117,508 $ 91,090 $ 9,133 $ 71,010 $ (15,976 ) $ 384,893 Provision for (recovery of) credit losses 2,083 (7,542 ) (1,638 ) — 11,365 458 4,726 Net interest income (expense) after provision for credit losses 110,045 125,050 92,728 9,133 59,645 (16,434 ) 380,167 Non-interest income 3,586 8,944 3,917 184 1,742 6,278 24,651 Non-interest expense (54,859 ) (59,683 ) (49,764 ) (3,857 ) (27,804 ) (11,352 ) (207,319 ) Income (loss) from continuing operations before income taxes 58,772 74,311 46,881 5,460 33,583 (21,508 ) 197,499 Income tax expense (benefit) 23,053 26,009 19,711 2,296 12,594 (35,273 ) 48,390 Income from continuing operations 35,719 48,302 27,170 3,164 20,989 13,765 149,109 Loss from discontinued operations, net — — — — — (1,158 ) (1,158 ) Net income $ 35,719 $ 48,302 $ 27,170 $ 3,164 $ 20,989 $ 12,607 $ 147,951

Employee Benefit Plan (Tables)

Employee Benefit Plan (Tables)	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Schedule of Net Funded Status [Table Text Block]	The following table reflects the accumulated benefit obligation and funded status of the SERP from the June 30, 2015 acquisition date through December 31, 2015 . Six Months Ended December 31, 2015 (in thousands) Change in benefit obligation Benefit obligation at acquisition $ 7,122 Service cost 334 Interest cost 202 Actuarial (gains)/losses (147 ) Expected benefits paid (67 ) Projected benefit obligation at end of year $ 7,444 Unfunded projected/accumulated benefit obligation (7,444 ) Additional liability $ — Weighted average assumptions to determine benefit obligation Discount rate 5.75 % Rate of compensation increase 4.00 %
Schedule of Net Benefit Costs [Table Text Block]	The components of net periodic benefit cost recognized from the acquisition date through December 31, 2015 and the amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit cost during 2016 are as follows: 2016 Six Months Ended December 31, 2015 (in thousands) Components of net periodic benefit cost Service cost $ 596 $ 334 Interest cost 426 202 Amortization of prior service cost 96 60 Amortization of actuarial (gains)/losses (96 ) (18 ) Net periodic benefit cost $ 1,022 $ 578 Other comprehensive income (cost) $ — $ 42

Related Parties (Tables)

Related Parties (Tables)	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Schedule of Related Party Transactions [Table Text Block]	The following table summarizes the aggregate activity in such loans for the periods indicated: Year Ended December 31, 2015 2014 (in thousands) Balance, beginning $ 70,570 $ 30,783 New loans 10,678 35,341 Advances 18,614 23,559 Repayments and other (25,481 ) (19,113 ) Balance, ending $ 74,381 $ 70,570

Parent Company (Tables)

Parent Company (Tables)	12 Months Ended
	Dec. 31, 2015
Parent Company Financial Information [Abstract]
Condensed Balance Sheet [Table Text Block]	Condensed Balance Sheets December 31, 2015 2014 (in thousands) ASSETS: Cash and cash equivalents $ 7,627 $ 11,855 Money market investments 122 451 Investment securities - AFS 50,507 51,335 Investment in bank subsidiaries 1,522,245 987,882 Investment in non-bank subsidiaries 2,424 9,827 Loans, net of deferred loan fees and costs and allowance for credit losses 35,635 39,221 Other assets acquired through foreclosure, net 14,471 16,318 Other assets 19,378 9,912 Total assets $ 1,652,409 $ 1,126,801 LIABILITIES AND STOCKHOLDERS' EQUITY: Other borrowings $ — $ 83,182 Qualifying debt 58,370 40,437 Accrued interest and other liabilities 2,537 2,254 Total liabilities 60,907 125,873 Total stockholders’ equity 1,591,502 1,000,928 Total liabilities and stockholders’ equity $ 1,652,409 $ 1,126,801
Schedule Of Condensed Income Statement And Comprehensive Income Table [Text Block]	Condensed Income Statements Year Ended December 31, 2015 2014 2013 (in thousands) Income: Dividends from subsidiaries $ 140,900 $ 67,515 $ 71,529 Interest income 4,593 4,381 2,847 Non-interest income 586 1,235 3,995 Total income 146,079 73,131 78,371 Expense: Interest expense 6,671 8,776 10,833 Non-interest expense 11,397 10,348 32,001 Total expense 18,068 19,124 42,834 Income before income taxes and equity in undistributed earnings of subsidiaries 128,011 54,007 35,537 Income tax benefit 5,876 5,388 21,426 Income before equity in undistributed earnings of subsidiaries 133,887 59,395 56,963 Equity in undistributed earnings of subsidiaries 60,357 88,556 58,002 Net income 194,244 147,951 114,965 Dividends on preferred stock 750 1,387 1,410 Net income available to common stockholders $ 193,494 $ 146,564 $ 113,555
Condensed Cash Flow Statement [Table Text Block]	Condensed Statements of Cash Flows Year Ended December 31, 2015 2014 2013 (in thousands) Cash flows from operating activities: Net income $ 194,244 $ 147,951 $ 114,965 Adjustments to reconcile net income to net cash provided by operating activities: Equity in net undistributed earnings of subsidiaries (60,357 ) (88,556 ) (58,002 ) Excess tax benefit of stock-based compensation (1,945 ) (4,194 ) (1,552 ) Junior subordinated debt change in fair value — (1,421 ) 5,640 Loss on extinguishment of debt — 502 1,387 Other operating activities, net (4,734 ) (20,040 ) (4,011 ) Net cash provided by operating activities 127,208 34,242 58,427 Cash flows from investing activities: Purchases of securities — (23,431 ) (2,044 ) Principal pay downs, calls, maturities, and sales proceeds of securities, net 2,358 8,376 6,767 Proceeds from sale of other repossessed assets, net 4,138 9,610 9,844 Capital contributions to subsidiaries — — (40,000 ) Loans purchases, fundings, and principal collections, net 3,704 3,286 (35,979 ) Sale (purchase) of money market investments, net 330 2,181 (1,968 ) Sale (purchase) of premises, equipment, and other assets, net — 617 (481 ) Net cash and cash equivalents (used) in acquisition (1) (19,440 ) — — Net cash provided by (used in) investing activities (8,910 ) 639 (63,861 ) Cash flows from financing activities: Proceeds from other borrowings, net — 22,000 3,000 Excess tax benefit of stock-based compensation 1,945 4,194 1,552 Repayments on other borrowings (83,444 ) (6,501 ) (10,887 ) Proceeds from issuance of common stock 28,288 13,746 — Proceeds from exercise of stock options 1,935 8,294 4,595 Redemption of preferred stock (70,500 ) (70,500 ) — Cash dividends paid on preferred stock (750 ) (1,387 ) (1,410 ) Net cash used in financing activities (122,526 ) (30,154 ) (3,150 ) Net increase (decrease) in cash and cash equivalents (4,228 ) 4,727 (8,584 ) Cash and cash equivalents at beginning of year 11,855 7,128 15,712 Cash and cash equivalents at end of year $ 7,627 $ 11,855 $ 7,128 Supplemental disclosure: Cash paid during the year for: Interest $ 4,235 $ 9,067 $ 11,091 Income taxes 54,590 32,238 19,105 Non-cash investing and financing activity: Change in unrealized gain on AFS securities, net of tax 1,199 2,031 2,450 Change in unrealized (loss) on TRUPS securities, net of tax (4,276 ) — — Loan contributions to subsidiaries 183 2,663 — (1) Cash acquired, less cash consideration paid of $36.5 million , resulted in a net $19.4 million use of cash and cash equivalents in the acquisition.

Quarterly Financial Data (Table

Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data Disclosure [Abstract]
Condensed Financial Statements [Table Text Block]	23. QUARTERLY FINANCIAL DATA (UNAUDITED) Year Ended December 31, 2015 Fourth Quarter Third Quarter Second Quarter First Quarter (in thousands, except share amounts) Interest income $ 151,331 $ 146,233 $ 116,618 $ 110,962 Interest expense 7,988 8,826 7,900 7,854 Net interest income 143,343 137,407 108,718 103,108 Provision for credit losses 2,500 — — 700 Net interest income after provision for credit losses 140,843 137,407 108,718 102,408 Non-interest income 9,479 8,502 5,545 6,242 Non-interest expense (72,448 ) (72,916 ) (61,209 ) (54,033 ) Income from continuing operations before provision for income taxes 77,874 72,993 53,054 54,617 Income tax expense 19,348 17,133 13,579 14,234 Net income 58,526 55,860 39,475 40,383 Dividends on preferred stock 151 176 247 176 Net income available to common stockholders $ 58,375 $ 55,684 $ 39,228 $ 40,207 Earnings per share: Basic $ 0.58 $ 0.55 $ 0.44 $ 0.46 Diluted $ 0.57 $ 0.55 $ 0.44 $ 0.45 (1) Due to the Company's election to early adopt an element of ASU 2016-01, changes in the fair value of junior subordinated debt are presented as part of OCI rather than earnings effective January 1, 2015. Accordingly, prior period 2015 amounts have been adjusted. Year Ended December 31, 2014 Fourth Quarter Third Quarter Second Quarter First Quarter (in thousands, except per share amounts) Interest income $ 110,151 $ 105,554 $ 101,973 $ 98,701 Interest expense 8,006 7,481 8,075 7,924 Net interest income 102,145 98,073 93,898 90,777 Provision for credit losses 300 419 507 3,500 Net interest income after provision for credit losses 101,845 97,654 93,391 87,277 Non-interest income 8,417 6,073 5,599 4,562 Non-interest expense (55,742 ) (49,859 ) (52,242 ) (49,476 ) Income from continuing operations before provision for income taxes 54,520 53,868 46,748 42,363 Income tax expense 14,111 12,949 10,706 10,624 Income from continuing operations 40,409 40,919 36,042 31,739 Loss from discontinued operations, net of tax — — (504 ) (654 ) Net income 40,409 40,919 35,538 31,085 Dividends on preferred stock 329 353 352 353 Net income available to common stockholders $ 40,080 $ 40,566 $ 35,186 $ 30,732 Earnings per share: Basic $ 0.46 $ 0.47 $ 0.41 $ 0.35 Diluted $ 0.46 $ 0.46 $ 0.40 $ 0.35

Summary of Significant Accoun57

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015USD ($)Subsidiary	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Significant Of Accounting Policies [Line Items]
Life Insurance, Corporate or Bank Owned, Amount | $	$ 361,700,000	$ 321,900,000
Proceeds from Issuance of Subordinated Long-term Debt | $	$ 150,000,000	$ 0	$ 0
Number Of Wholly Owned Subsidiaries Non Bank Subsidiaries | Subsidiary	1
Number of wholly-owned subsidiaries | Subsidiary	10
Number Of Unconsolidated Subsidiaries | Subsidiary	8
Maximum period of internal loss allowance calculation model	10 years
Debt Issuance Cost | $	$ 1,800,000

Mergers, Acquisitions and Dis58

Mergers, Acquisitions and Dispositions - Summary of Operating Results of Discontinued Operations (Detail) $ / shares in Units, $ in Thousands	Jun. 30, 2015USD ($)$ / shares	Dec. 31, 2014USD ($)	Sep. 30, 2014USD ($)	Jun. 30, 2014USD ($)	Mar. 31, 2014USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net loss		$ 0	$ 0	$ (504)	$ (654)	$ 0	$ (1,158)	$ (861)
Acquisition / restructure expense						8,836	198	5,752
Assets		10,600,498				14,275,089	10,600,498
Deposits		8,931,043				12,030,624	8,931,043
Cash Acquired from Acquisition	$ 342,427					342,427	0	21,204
Business Combination, Acquired Receivables, Fair Value	1,439,930
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust		40,437				58,370	40,437
PartnersFirst [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Affinity card revenue							(358)	3,345
Non-interest expenses							(1,369)	(4,855)
Loss before income taxes							(1,727)	(1,510)
Income tax benefit							(569)	(649)
Net loss							(1,158)	$ (861)
Bridge Capital Holdings [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits	1,742,031
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Repossessed Assets	1,407
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	420,354
Business Combination, Consideration Transferred, Liabilities Incurred	10,676
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	$ 378,966
Business Acquisition Share Exchange Ratio	0.8145
Business Acquisition Cash Consideration Per Share | $ / shares	$ 2.39
Payments to Acquire Businesses, Gross	$ 36,539
Acquisition / restructure expense						6,814
Business Combination, Acquired Receivables, Fair Value	1,439,930
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust		0				17,527	0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities	61,299
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Restricted Stock Investment	7,015
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Bank Owned Life Insurance	17,385
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Investment in Low Income Housing Tax Credits	5,354
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Junior Subordinated Debt	$ 11,287	$ 0				$ 11,442	$ 0

Mergers, Acquisitions and Dis59

Mergers, Acquisitions and Dispositions Business Combination, Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Acquisition / restructure expense	$ 8,836	$ 198	$ 5,752
Bridge Capital Holdings [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Acquisition / restructure expense	6,814
Business Acquisition, Pro Forma Interest Income	560,292	495,235
Business Acquisition, Pro Forma Non-Interest Income	37,073	38,768
Business Acquisition, Pro Forma Net Income (Loss)	$ 205,099	$ 164,165
Business Acquisition, Pro Forma Earnings Per Share, Basic	$ 1.90	$ 1.64
Business Acquisition, Pro Forma Earnings Per Share, Diluted	$ 1.87	$ 1.62

Mergers, Acquisitions and Dis60

Mergers, Acquisitions and Dispositions Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Cash Payment for Vested Stock Options	$ 6,200
Business Combination, Acquisition Related Costs		$ 900
Business Combination, Fair Market Value Adjustment on Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	6,200	(6,085)	$ 0
Business Combination, Acquired Receivables, Fair Value	1,439,930
Interest Rate and Credit Marks on Acquired Loans		40,500	27,100
Non-cash liabilities acquired in acquisition		1,764,996	0	$ 421,987
Cash Acquired from Acquisition	342,427	$ 342,427	0	$ 21,204
Business Combination, Provisional Information, Initial Accounting Incomplete, Nature of Adjustments		6,786
Goodwill		$ 289,638	$ 23,224
Defined Benefit Pension Plan, Liabilities	7,100
Common Stock, Shares, Issued		103,087,044	88,691,249
Bridge Capital Holdings [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	378,966
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities	61,299
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Restricted Stock Investment	7,015
Business Combination, Acquired Receivables, Fair Value	1,439,930
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	1,519
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	14,997
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent	18,287
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets	19,993
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	1,966,152
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other	11,678
Non-cash liabilities acquired in acquisition	1,764,996
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	201,156
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	420,354
Business Combination, Consideration Transferred, Liabilities Incurred	10,676
Payments to Acquire Businesses, Gross	36,539
Business Combination, Consideration Transferred	467,569
Goodwill		$ 266,413
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Repossessed Assets	1,407
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Bank Owned Life Insurance	17,385
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Investment in Low Income Housing Tax Credits	5,354
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits	1,742,031
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Junior Subordinated Debt	$ 11,287	$ 11,442	$ 0
Common Stock, Shares, Issued	12,451,240	12,451,240
Commercial and industrial [Member]
Business Acquisition [Line Items]
Business Combination, Acquired Receivables, Fair Value	$ 1,084,104
Acquired Non-Purchased Credit Impaired Loans [Member]
Business Acquisition [Line Items]
Business Combination, Acquired Receivables, Fair Value	1,429,076
Interest Rate and Credit Marks on Acquired Loans	26,000
Acquired Non-Purchased Credit Impaired Loans [Member] | Commercial and industrial [Member]
Business Acquisition [Line Items]
Business Combination, Acquired Receivables, Fair Value	1,076,742
Receivables Acquired with Deteriorated Credit Quality [Member]
Business Acquisition [Line Items]
Business Combination, Acquired Receivables, Fair Value	10,854
Interest Rate and Credit Marks on Acquired Loans	5,700
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial and industrial [Member]
Business Acquisition [Line Items]
Business Combination, Acquired Receivables, Fair Value	$ 7,362

Investment Securities - Carryin

Investment Securities - Carrying Amounts and Fair Values of Investment Securities (Detail) - USD ($)		Dec. 31, 2015		Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost		$ 1,966,034,000		$ 1,493,648,000
Securities available-for-sale, Gross Unrealized Gains		34,907,000		40,480,000
Securities available-for-sale, Gross Unrealized (Losses)		(18,418,000)		(13,891,000)
Securities available for sale Total, Estimated Fair Value		1,982,523,000		1,520,237,000
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost				18,701,000
Securities available-for-sale, Gross Unrealized Gains				0
Securities available-for-sale, Gross Unrealized (Losses)				(355,000)
Securities available for sale Total, Estimated Fair Value				18,346,000
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost		2,996,000
Securities available-for-sale, Gross Unrealized Gains		0
Securities available-for-sale, Gross Unrealized (Losses)		(3,000)
Securities available for sale Total, Estimated Fair Value		2,993,000
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost		12,769,000		52,773,000
Securities available-for-sale, Gross Unrealized Gains		482,000		717,000
Securities available-for-sale, Gross Unrealized (Losses)		0		(1,001,000)
Securities available for sale Total, Estimated Fair Value		13,251,000		52,489,000
Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost		320,087,000		285,398,000
Securities available-for-sale, Gross Unrealized Gains		14,743,000		13,688,000
Securities available-for-sale, Gross Unrealized (Losses)		0		(49,000)
Securities available for sale Total, Estimated Fair Value		334,830,000		299,037,000
Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost		108,417,000		83,192,000
Securities available-for-sale, Gross Unrealized Gains		4,286,000		2,099,000
Securities available-for-sale, Gross Unrealized (Losses)		(1,467,000)		(2,679,000)
Securities available for sale Total, Estimated Fair Value		111,236,000		82,612,000
Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost				37,449,000
Securities available-for-sale, Gross Unrealized Gains				500,000
Securities available-for-sale, Gross Unrealized (Losses)				(247,000)
Securities available for sale Total, Estimated Fair Value				37,702,000
Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost		1,169,631,000		881,734,000
Securities available-for-sale, Gross Unrealized Gains		5,254,000		11,440,000
Securities available-for-sale, Gross Unrealized (Losses)		(4,664,000)		(1,985,000)
Securities available for sale Total, Estimated Fair Value		1,170,221,000		891,189,000
Securities measured at fair value		1,481,000		1,858,000
Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost		19,147,000		2,047,000
Securities available-for-sale, Gross Unrealized Gains		72,000		100,000
Securities available-for-sale, Gross Unrealized (Losses)		(105,000)		0
Securities available for sale Total, Estimated Fair Value		19,114,000		2,147,000
Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost		261,530,000		70,985,000
Securities available-for-sale, Gross Unrealized Gains		5,000		379,000
Securities available-for-sale, Gross Unrealized (Losses)		(4,407,000)		(1,121,000)
Securities available for sale Total, Estimated Fair Value		257,128,000		70,243,000
Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost		4,685,000		5,017,000
Securities available-for-sale, Gross Unrealized Gains		6,000		132,000
Securities available-for-sale, Gross Unrealized (Losses)		0		0
Securities available for sale Total, Estimated Fair Value		4,691,000		5,149,000
Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost		32,000,000		32,000,000
Securities available-for-sale, Gross Unrealized Gains		0		0
Securities available-for-sale, Gross Unrealized (Losses)		(7,686,000)		(6,454,000)
Securities available for sale Total, Estimated Fair Value		24,314,000		25,546,000
CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost		34,722,000		24,302,000
Securities available-for-sale, Gross Unrealized Gains		0		30,000
Securities available-for-sale, Gross Unrealized (Losses)		(37,000)		0
Securities available for sale Total, Estimated Fair Value		34,685,000		24,332,000
Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost		50,000		50,000
Securities available-for-sale, Gross Unrealized Gains		10,059,000		11,395,000
Securities available-for-sale, Gross Unrealized (Losses)		(49,000)		0
Securities available for sale Total, Estimated Fair Value		10,060,000		11,445,000
AAA [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		248,245,000	[1]	73,261,000	[2]
AAA [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				0
AAA [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0
AAA [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0
AAA [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		7,949,000		8,168,000
AAA [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
AAA [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	[3]			0
AAA [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Securities measured at fair value		0		0
AAA [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
AAA [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		235,605,000		59,944,000
AAA [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		4,691,000		5,149,000
AAA [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
AAA [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
AAA [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
AAA [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				0
Split-rated AAA/AA Plus [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		1,192,328,000	[1]	911,682,000	[2]
Split-rated AAA/AA Plus [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				18,346,000
Split-rated AAA/AA Plus [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		2,993,000
Split-rated AAA/AA Plus [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0
Split-rated AAA/AA Plus [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Split-rated AAA/AA Plus [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Split-rated AAA/AA Plus [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	[3]			0
Split-rated AAA/AA Plus [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		1,170,221,000		891,189,000
Securities measured at fair value		1,481,000		1,858,000
Split-rated AAA/AA Plus [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		19,114,000		2,147,000
Split-rated AAA/AA Plus [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Split-rated AAA/AA Plus [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Split-rated AAA/AA Plus [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Split-rated AAA/AA Plus [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Split-rated AAA/AA Plus [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Split-rated AAA/AA Plus [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				0
AA Plus to AA- [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		183,221,000	[1]	141,083,000	[2]
AA Plus to AA- [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				0
AA Plus to AA- [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0
AA Plus to AA- [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		2,721,000
AA Plus to AA- [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		180,460,000		138,256,000
AA Plus to AA- [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
AA Plus to AA- [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	[3]			0
AA Plus to AA- [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Securities measured at fair value		0		0
AA Plus to AA- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
AA Plus to AA- [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		40,000		68,000
AA Plus to AA- [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
AA Plus to AA- [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
AA Plus to AA- [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
AA Plus to AA- [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
AA Plus to AA- [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				2,759,000
A Plus to A- [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		139,785,000	[1]	155,164,000	[2]
A Plus to A- [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				0
A Plus to A- [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0
A Plus to A- [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		5,489,000
A Plus to A- [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		131,110,000		146,155,000
A Plus to A- [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
A Plus to A- [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	[3]			0
A Plus to A- [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Securities measured at fair value		0		0
A Plus to A- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
A Plus to A- [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		3,186,000		3,439,000
A Plus to A- [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
A Plus to A- [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
A Plus to A- [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
A Plus to A- [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
A Plus to A- [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				5,570,000
BBB Plus to BBB- [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		117,303,000	[1]	171,851,000	[2]
BBB Plus to BBB- [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				0
BBB Plus to BBB- [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0
BBB Plus to BBB- [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		5,041,000
BBB Plus to BBB- [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		6,243,000		6,263,000
BBB Plus to BBB- [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		79,955,000		54,585,000
BBB Plus to BBB- [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	[3]			37,702,000
BBB Plus to BBB- [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Securities measured at fair value		0		0
BBB Plus to BBB- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
BBB Plus to BBB- [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		1,750,000		3,595,000
BBB Plus to BBB- [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
BBB Plus to BBB- [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		24,314,000		25,546,000
BBB Plus to BBB- [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
BBB Plus to BBB- [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
BBB Plus to BBB- [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				44,160,000
BB Plus and below [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		36,600,000	[1]	32,469,000	[2]
BB Plus and below [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				0
BB Plus and below [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0
BB Plus and below [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0
BB Plus and below [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		180,000		195,000
BB Plus and below [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		23,655,000		17,632,000
BB Plus and below [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	[3]			0
BB Plus and below [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Securities measured at fair value		0		0
BB Plus and below [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
BB Plus and below [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		2,705,000		3,197,000
BB Plus and below [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
BB Plus and below [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
BB Plus and below [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
BB Plus and below [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		10,060,000		11,445,000
BB Plus and below [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				0
Corporate Credit Quality Indicator Unrated [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		65,041,000	[1]	34,727,000	[2]
Corporate Credit Quality Indicator Unrated [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				0
Corporate Credit Quality Indicator Unrated [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0
Corporate Credit Quality Indicator Unrated [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0
Corporate Credit Quality Indicator Unrated [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		8,888,000		0
Corporate Credit Quality Indicator Unrated [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		7,626,000		10,395,000
Corporate Credit Quality Indicator Unrated [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	[3]			0
Corporate Credit Quality Indicator Unrated [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Securities measured at fair value		0		0
Corporate Credit Quality Indicator Unrated [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Corporate Credit Quality Indicator Unrated [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		13,842,000		0
Corporate Credit Quality Indicator Unrated [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Corporate Credit Quality Indicator Unrated [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Corporate Credit Quality Indicator Unrated [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		34,685,000		24,332,000
Corporate Credit Quality Indicator Unrated [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		0		0
Corporate Credit Quality Indicator Unrated [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				0
Rated Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		1,982,523,000	[1]	1,520,237,000	[2]
Rated Securities [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				18,346,000
Rated Securities [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		2,993,000
Rated Securities [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		13,251,000
Rated Securities [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		334,830,000		299,037,000
Rated Securities [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		111,236,000		82,612,000
Rated Securities [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	[3]			37,702,000
Rated Securities [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		1,170,221,000		891,189,000
Securities measured at fair value		1,481,000		1,858,000
Rated Securities [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		19,114,000		2,147,000
Rated Securities [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		257,128,000		70,243,000
Rated Securities [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		4,691,000		5,149,000
Rated Securities [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		24,314,000		25,546,000
Rated Securities [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		34,685,000		24,332,000
Rated Securities [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value		$ 10,060,000		11,445,000
Rated Securities [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value				$ 52,489,000
[1]	The Company uses the average credit rating of the combination of S&P, Moody’s, and Fitch, where ratings differ
[2]	The Company uses the average credit rating of the combination of S&P, Moody’s, and Fitch, where ratings differ.
[3]	At least 80% of mutual funds are investment grade corporate debt securities.

Investment Securities - Additio

Investment Securities - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Sep. 30, 2014USD ($)	Dec. 31, 2015USD ($)positions	Dec. 31, 2014USD ($)positions
Investment Identifier [Line Items]
Amount of impairment losses reclassified out of accumulated other comprehensive income into earnings	$ 0	$ 0
Total number of securities in an unrealized loss position | positions		146	109
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 18,418,000	$ 13,891,000
Securities with carrying amounts were pledged		$ 830,700,000	$ 755,500,000

Investment Securities - Unreali

Investment Securities - Unrealized Losses and Fair Value of Investment Securities in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	$ 7,870	$ 1,002
Available-for-sale securities, Less Than Twelve Months, Fair Value	817,564	122,799
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	10,548	12,889
Available-for-sale securities, Twelve Months or Longer, Fair Value	107,785	229,480
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	18,418	13,891
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	925,349	352,279
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses		0
Available-for-sale securities, Less Than Twelve Months, Fair Value		0
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses		355
Available-for-sale securities, Twelve Months or Longer, Fair Value		18,346
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total		355
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total		18,346
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses		139
Available-for-sale securities, Less Than Twelve Months, Fair Value		9,860
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses		862
Available-for-sale securities, Twelve Months or Longer, Fair Value		29,139
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total		1,001
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total		38,999
Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	377	232
Available-for-sale securities, Less Than Twelve Months, Fair Value	10,542	13,811
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	1,090	2,447
Available-for-sale securities, Twelve Months or Longer, Fair Value	14,761	28,109
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	1,467	2,679
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	25,303	41,920
Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses		247
Available-for-sale securities, Less Than Twelve Months, Fair Value		25,855
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses		0
Available-for-sale securities, Twelve Months or Longer, Fair Value		0
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total		247
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total		25,855
Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	3,566	227
Available-for-sale securities, Less Than Twelve Months, Fair Value	536,515	49,217
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	1,098	1,758
Available-for-sale securities, Twelve Months or Longer, Fair Value	38,338	97,296
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	4,664	1,985
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	574,853	146,513
Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses		0
Available-for-sale securities, Less Than Twelve Months, Fair Value		0
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses		49
Available-for-sale securities, Twelve Months or Longer, Fair Value		4,430
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total		49
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total		4,430
Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	3,733	157
Available-for-sale securities, Less Than Twelve Months, Fair Value	226,720	24,056
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	674	964
Available-for-sale securities, Twelve Months or Longer, Fair Value	30,372	26,614
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	4,407	1,121
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	257,092	50,670
Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	0	0
Available-for-sale securities, Less Than Twelve Months, Fair Value	0	0
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	7,686	6,454
Available-for-sale securities, Twelve Months or Longer, Fair Value	24,314	25,546
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	7,686	6,454
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	24,314	$ 25,546
CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	37
Available-for-sale securities, Less Than Twelve Months, Fair Value	24,729
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	0
Available-for-sale securities, Twelve Months or Longer, Fair Value	0
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	37
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	24,729
Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	49
Available-for-sale securities, Less Than Twelve Months, Fair Value	1
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	0
Available-for-sale securities, Twelve Months or Longer, Fair Value	0
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	49
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	1
Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	105
Available-for-sale securities, Less Than Twelve Months, Fair Value	17,051
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	0
Available-for-sale securities, Twelve Months or Longer, Fair Value	0
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	105
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	17,051
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	3
Available-for-sale securities, Less Than Twelve Months, Fair Value	2,006
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	0
Available-for-sale securities, Twelve Months or Longer, Fair Value	0
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	3
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 2,006

Investment Securities - Amortiz

Investment Securities - Amortized Cost and Fair Value of Investment Securities by Contractual Maturities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Due in one year or less, Amortized Cost	$ 62,852
Securities available for sale, After one year through five years, Amortized Cost	77,273
Securities available for sale, After five years through ten years, Amortized Cost	68,935
Securities available for sale, After ten years, Amortized Cost	301,981
Securities available for sale, Mortgage backed securities, Amortized Cost	1,454,993
Securities available for sale Total, Amortized Cost	1,966,034	$ 1,493,648
Securities available for sale, Due in one year or less, Estimated Fair Value	63,114
Securities available for sale, After one year through five years, Estimated Fair Value	81,090
Securities available for sale, After five years through ten years, Estimated Fair Value	72,283
Securities available for sale, After ten years, Estimated Fair Value	314,882
Securities available for sale, Mortgage backed securities, Estimated Fair Value	1,451,154
Securities available for sale Total, Estimated Fair Value	$ 1,982,523	$ 1,520,237

Investment Securities - Investm

Investment Securities - Investment Securities by Credit Rating Type (Detail) - USD ($)		Dec. 31, 2015		Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		$ 1,982,523,000		$ 1,520,237,000
Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		334,830,000		299,037,000
Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		1,170,221,000		891,189,000
Securities measured at fair value		1,481,000		1,858,000
Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		19,114,000		2,147,000
Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		257,128,000		70,243,000
Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		4,691,000		5,149,000
Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014				37,702,000
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014				18,346,000
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		2,993,000
Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		111,236,000		82,612,000
Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		24,314,000		25,546,000
Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		10,060,000		11,445,000
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		13,251,000		52,489,000
CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		34,685,000		24,332,000
Rated Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		1,982,523,000	[1]	1,520,237,000	[2]
Rated Securities [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		334,830,000		299,037,000
Rated Securities [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		1,170,221,000		891,189,000
Securities measured at fair value		1,481,000		1,858,000
Rated Securities [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		19,114,000		2,147,000
Rated Securities [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		257,128,000		70,243,000
Rated Securities [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		4,691,000		5,149,000
Rated Securities [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	[3]			37,702,000
Rated Securities [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014				18,346,000
Rated Securities [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		2,993,000
Rated Securities [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		111,236,000		82,612,000
Rated Securities [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		24,314,000		25,546,000
Rated Securities [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		10,060,000		11,445,000
Rated Securities [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		13,251,000
Rated Securities [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		34,685,000		24,332,000
AAA [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		248,245,000	[1]	73,261,000	[2]
AAA [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		7,949,000		8,168,000
AAA [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Securities measured at fair value		0		0
AAA [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
AAA [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		235,605,000		59,944,000
AAA [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		4,691,000		5,149,000
AAA [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	[3]			0
AAA [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014				0
AAA [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0
AAA [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
AAA [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
AAA [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
AAA [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0
AAA [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Split-rated AAA/AA Plus [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		1,192,328,000	[1]	911,682,000	[2]
Split-rated AAA/AA Plus [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Split-rated AAA/AA Plus [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		1,170,221,000		891,189,000
Securities measured at fair value		1,481,000		1,858,000
Split-rated AAA/AA Plus [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		19,114,000		2,147,000
Split-rated AAA/AA Plus [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Split-rated AAA/AA Plus [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Split-rated AAA/AA Plus [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	[3]			0
Split-rated AAA/AA Plus [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014				18,346,000
Split-rated AAA/AA Plus [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		2,993,000
Split-rated AAA/AA Plus [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Split-rated AAA/AA Plus [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Split-rated AAA/AA Plus [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Split-rated AAA/AA Plus [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0
Split-rated AAA/AA Plus [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
AA Plus to AA- [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		183,221,000	[1]	141,083,000	[2]
AA Plus to AA- [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		180,460,000		138,256,000
AA Plus to AA- [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Securities measured at fair value		0		0
AA Plus to AA- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
AA Plus to AA- [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		40,000		68,000
AA Plus to AA- [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
AA Plus to AA- [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	[3]			0
AA Plus to AA- [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014				0
AA Plus to AA- [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0
AA Plus to AA- [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
AA Plus to AA- [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
AA Plus to AA- [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
AA Plus to AA- [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		2,721,000
AA Plus to AA- [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
A Plus to A- [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		139,785,000	[1]	155,164,000	[2]
A Plus to A- [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		131,110,000		146,155,000
A Plus to A- [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Securities measured at fair value		0		0
A Plus to A- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
A Plus to A- [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		3,186,000		3,439,000
A Plus to A- [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
A Plus to A- [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	[3]			0
A Plus to A- [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014				0
A Plus to A- [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0
A Plus to A- [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
A Plus to A- [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
A Plus to A- [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
A Plus to A- [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		5,489,000
A Plus to A- [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
BBB Plus to BBB- [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		117,303,000	[1]	171,851,000	[2]
BBB Plus to BBB- [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		6,243,000		6,263,000
BBB Plus to BBB- [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Securities measured at fair value		0		0
BBB Plus to BBB- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
BBB Plus to BBB- [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		1,750,000		3,595,000
BBB Plus to BBB- [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
BBB Plus to BBB- [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	[3]			37,702,000
BBB Plus to BBB- [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014				0
BBB Plus to BBB- [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0
BBB Plus to BBB- [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		79,955,000		54,585,000
BBB Plus to BBB- [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		24,314,000		25,546,000
BBB Plus to BBB- [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
BBB Plus to BBB- [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		5,041,000
BBB Plus to BBB- [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
BB Plus and below [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		36,600,000	[1]	32,469,000	[2]
BB Plus and below [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		180,000		195,000
BB Plus and below [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Securities measured at fair value		0		0
BB Plus and below [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
BB Plus and below [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		2,705,000		3,197,000
BB Plus and below [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
BB Plus and below [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	[3]			0
BB Plus and below [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014				0
BB Plus and below [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0
BB Plus and below [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		23,655,000		17,632,000
BB Plus and below [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
BB Plus and below [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		10,060,000		11,445,000
BB Plus and below [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0
BB Plus and below [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Corporate Credit Quality Indicator Unrated [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		65,041,000	[1]	34,727,000	[2]
Corporate Credit Quality Indicator Unrated [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		8,888,000		0
Corporate Credit Quality Indicator Unrated [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Securities measured at fair value		0		0
Corporate Credit Quality Indicator Unrated [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Corporate Credit Quality Indicator Unrated [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		13,842,000		0
Corporate Credit Quality Indicator Unrated [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Corporate Credit Quality Indicator Unrated [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	[3]			0
Corporate Credit Quality Indicator Unrated [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014				0
Corporate Credit Quality Indicator Unrated [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0
Corporate Credit Quality Indicator Unrated [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		7,626,000		10,395,000
Corporate Credit Quality Indicator Unrated [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Corporate Credit Quality Indicator Unrated [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0		0
Corporate Credit Quality Indicator Unrated [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		0
Corporate Credit Quality Indicator Unrated [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		$ 34,685,000		$ 24,332,000
[1]	The Company uses the average credit rating of the combination of S&P, Moody’s, and Fitch, where ratings differ
[2]	The Company uses the average credit rating of the combination of S&P, Moody’s, and Fitch, where ratings differ.
[3]	At least 80% of mutual funds are investment grade corporate debt securities.

Investment Securities - Inves66

Investment Securities - Investment Securities by Credit Rating Type Parenthetical (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	$ 1,982,523	$ 1,520,237
Minimum percentage of investment grade mutual funds		80.00%
CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	$ 34,685	$ 24,332

Investment Securities - Gross G

Investment Securities - Gross Gains and (Losses) on Sales of Investments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Gross gains	$ 1,144	$ 1,118	$ 1,569
Gross (losses)	(529)	(361)	(2,764)
Net (losses) gains	$ 615	$ 757	$ (1,195)

Loans, Leases and Allowance f68

Loans, Leases and Allowance for Credit Losses - Schedule of Held for Investment Loan Portfolio Composition of Loans, Leases and Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Interest Rate and Credit Marks on Acquired Loans	$ 40,500	$ 27,100
Trade and Loans Receivables Held-for-sale, Net, Not Part of Disposal Group	23,809	0
Net deferred loan fees and costs	(19,200)	(12,500)
Loans, net of deferred loan fees and costs	11,112,854	8,398,265
Allowance for credit losses	(119,068)	(110,216)
Loans, net	10,993,786	8,288,049
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	5,114,257	3,326,708
Commercial Real Estate Non Owner Occupied Multi Family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	2,283,536	2,052,566
Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	2,083,285	1,732,888
Allowance for credit losses	(11,811)	(12,454)
Construction and land development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	1,133,439	748,053
Allowance for credit losses	(18,976)	(18,558)
Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	322,939	299,402
Allowance for credit losses	(5,278)	(7,456)
Leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	148,493	205,639
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	26,905	33,009
Allowance for credit losses	$ (473)	$ (853)

Loans, Leases and Allowance f69

Loans, Leases and Allowance for Credit Losses - Contractual Aging of Loan Portfolio by Class of Loans Including Loans Held for Sale and Excluding Deferred Fees/Costs (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 11,046,589	$ 8,366,782
Total Past Due	66,265	31,483
Total	11,112,854	8,398,265
Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,078,968	1,730,164
Total Past Due	4,317	2,724
Total	2,083,285	1,732,888
Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,099,274	1,855,454
Total Past Due	5,303	14,487
Total	2,104,577	1,869,941
Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	178,959	182,180
Total Past Due	0	445
Total	178,959	182,625
Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	5,066,197	3,324,132
Total Past Due	48,060	2,576
Total	5,114,257	3,326,708
Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	145,905	205,639
Total Past Due	2,588	0
Total	148,493	205,639
Construction and land development [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	694,527	388,399
Total Past Due	0	0
Total	694,527	388,399
Construction and land development [Member] | Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	438,495	356,209
Total Past Due	417	3,445
Total	438,912	359,654
Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	317,677	292,065
Total Past Due	5,262	7,337
Total	322,939	299,402
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	26,587	32,540
Total Past Due	318	469
Total	26,905	33,009
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	30,184	7,842
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	445	1,406
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,481	2,389
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	26,358	1,523
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	888	2,347
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	12	177
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	14,736	6,867
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	362	180
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	3,361
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	445
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	14,124	15
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	2,640
Financing Receivables, 60 to 89 Days Past Due [Member] | Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	159	205
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	91	21
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	21,345	16,774
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,510	1,138
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,822	8,737
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	7,578	1,038
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,588	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	417	805
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	4,215	4,785
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 215	$ 271

Loans, Leases and Allowance f70

Loans, Leases and Allowance for Credit Losses - Summary of Recorded Investment in Nonaccrual Loans and Loans Past Due 90 Days Still Accruing Interest by Loan Class (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		$ 11,046,589	$ 8,366,782
Total Past Due		66,265	31,483
Total Non-accrual	[1]	48,381	67,659
Loans past due 90 days or more and still accruing		3,028	5,132
Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		19,590	50,893
Total Past Due		28,791	16,766
Total Non-accrual			67,659
Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		2,078,968	1,730,164
Total Past Due		4,317	2,724
Loans past due 90 days or more and still accruing		339	1,138
Commercial real estate [Member] | Owner occupied [Member] | Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		749	13,630
Total Past Due		3,253	0
Total Non-accrual		4,002	13,630
Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		2,099,274	1,855,454
Total Past Due		5,303	14,487
Loans past due 90 days or more and still accruing		0	2,171
Commercial real estate [Member] | Non-owner occupied [Member] | Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		11,851	30,226
Total Past Due		2,822	8,601
Total Non-accrual		14,673	38,827
Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		178,959	182,180
Total Past Due		0	445
Loans past due 90 days or more and still accruing		0	0
Commercial real estate [Member] | Multi-family [Member] | Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		0	0
Total Past Due		0	0
Total Non-accrual		0	0
Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		5,066,197	3,324,132
Total Past Due		48,060	2,576
Loans past due 90 days or more and still accruing		2,671	703
Commercial and industrial [Member] | Commercial [Member] | Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		3,263	2,621
Total Past Due		15,026	496
Total Non-accrual		18,289	3,117
Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		145,905	205,639
Total Past Due		2,588	0
Loans past due 90 days or more and still accruing		0	0
Commercial and industrial [Member] | Leases [Member] | Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		0	373
Total Past Due		2,588	0
Total Non-accrual		2,588	373
Construction and land development [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		694,527	388,399
Total Past Due		0	0
Loans past due 90 days or more and still accruing		0	0
Construction and land development [Member] | Construction [Member] | Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		0	0
Total Past Due		0	0
Total Non-accrual		0	0
Construction and land development [Member] | Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		438,495	356,209
Total Past Due		417	3,445
Loans past due 90 days or more and still accruing		0	805
Construction and land development [Member] | Land [Member] | Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		1,892	2,686
Total Past Due		417	2,640
Total Non-accrual		2,309	5,326
Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		317,677	292,065
Total Past Due		5,262	7,337
Loans past due 90 days or more and still accruing		0	232
Residential real estate [Member] | Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		1,835	1,332
Total Past Due		4,489	4,841
Total Non-accrual		6,324	6,173
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		26,587	32,540
Total Past Due		318	469
Loans past due 90 days or more and still accruing		18	83
Consumer [Member] | Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		0	25
Total Past Due		196	188
Total Non-accrual		$ 196	$ 213
[1]	Includes non-accrual TDR loans of $18.2 million and $53.6 million at December 31, 2015 and 2014, respectively.

Loans, Leases and Allowance f71

Loans, Leases and Allowance for Credit Losses - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Leases [Line Items]
Receivable with Imputed Interest, Discount		$ (8,200)	$ (7,500)
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	48,381	67,659
Impaired Financing Receivable, Average Recorded Investment		150,151	169,758	$ 182,670
Aggregate carrying amount of impaired loans	[2]	24,287	124,928
Reduction in interest income due to nonaccrual loans		2,500	3,800	5,400
Loans And Loans Receivable Purchases		137,200	166,400
Financing Receivable, Significant Sales		102,200
Impaired loans with no allowance recorded	[3]	104,587	41,822
Impaired loans with an allowance recorded	[4]	4,658	10,765
Loans and Leases Receivable, Gain (Loss) on Sales, Net		500
Troubled Debt Restructured Loans [Member]
Leases [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status		18,200	53,600
Impaired Financing Receivable, Average Recorded Investment		113,900	126,600	$ 141,800
Aggregate carrying amount of impaired loans		3,000	103,300
Loan commitments outstanding		100	1,200
Impaired loans with no allowance recorded		85,900	35,000
Impaired loans with an allowance recorded		300	8,900
Construction and land development [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans		0	21,052
Loans And Loans Receivable Purchases		100
Impaired loans with no allowance recorded		18,322	696
Impaired loans with an allowance recorded		0	3,112
Commercial real estate [Member]
Leases [Line Items]
Loans And Loans Receivable Purchases		13,200
Residential real estate [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans		914	19,300
Impaired loans with no allowance recorded		15,661	0
Impaired loans with an allowance recorded		270	1,052
Commercial and industrial [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans		18,230	11,399
Loans And Loans Receivable Purchases		117,100
Impaired loans with no allowance recorded		8,283	2,350
Impaired loans with an allowance recorded		3,518	1,926
Consumer [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans		21	175
Impaired loans with no allowance recorded		313	188
Impaired loans with an allowance recorded		1	$ 17
Leases [Member]
Leases [Line Items]
Loans And Loans Receivable Purchases		$ 6,800
[1]	Includes non-accrual TDR loans of $18.2 million and $53.6 million at December 31, 2015 and 2014, respectively.
[2]	Includes TDR loans of $3.0 million and $103.3 million at December 31, 2015 and 2014, respectively.
[3]	Includes TDR loans of $85.9 million and $35.0 million at December 31, 2015 and 2014, respectively.
[4]	Includes valuation allowance related to TDR loans of $0.3 million and $8.9 million at December 31, 2015 and 2014, respectively.

Loans, Leases and Allowance f72

Loans, Leases and Allowance for Credit Losses - Loans by Risk Rating (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	$ 11,112,854,000	$ 8,398,265,000
Current	11,046,589,000	8,366,782,000
Financing Receivable, Recorded Investment, Past Due	66,265,000	31,483,000
Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	322,939,000	299,402,000
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	26,905,000	33,009,000
Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	2,083,285,000	1,732,888,000
Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	2,104,577,000	1,869,941,000
Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	178,959,000	182,625,000
Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	5,114,257,000	3,326,708,000
Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	148,493,000	205,639,000
Construction and land development [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	694,527,000	388,399,000
Construction and land development [Member] | Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	438,912,000	359,654,000
Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	10,805,542,000	8,143,813,000
Current	10,799,558,000	8,140,140,000
Pass [Member] | Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	310,067,000	284,052,000
Pass [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	26,438,000	32,419,000
Pass [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	2,032,932,000	1,664,270,000
Pass [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	2,054,428,000	1,771,138,000
Pass [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	178,959,000	182,180,000
Pass [Member] | Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	4,962,930,000	3,295,027,000
Pass [Member] | Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	140,531,000	202,772,000
Pass [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	678,438,000	383,677,000
Pass [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	420,819,000	328,278,000
Watch [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	141,588,000	97,505,000
Current	140,932,000	95,091,000
Watch [Member] | Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	776,000	2,044,000
Watch [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	209,000	233,000
Watch [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	28,422,000	28,072,000
Watch [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	14,867,000	35,752,000
Watch [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Watch [Member] | Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	76,283,000	14,380,000
Watch [Member] | Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	4,580,000	2,494,000
Watch [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	16,089,000	4,241,000
Watch [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	362,000	10,289,000
Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	161,269,000	155,028,000
Current	104,232,000	129,787,000
Substandard [Member] | Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	12,096,000	13,306,000
Substandard [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	258,000	357,000
Substandard [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	20,814,000	39,222,000
Substandard [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	35,282,000	62,611,000
Substandard [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	445,000
Substandard [Member] | Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	74,294,000	17,146,000
Substandard [Member] | Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	794,000	373,000
Substandard [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	481,000
Substandard [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	17,731,000	21,087,000
Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	4,455,000	1,919,000
Current	1,867,000	1,764,000
Doubtful [Member] | Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Doubtful [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Doubtful [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	1,117,000	1,324,000
Doubtful [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	440,000
Doubtful [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Doubtful [Member] | Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	750,000	155,000
Doubtful [Member] | Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	2,588,000	0
Doubtful [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Doubtful [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Loss [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Current	0	0
Loss [Member] | Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Loss [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Loss [Member] | Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Loss [Member] | Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Loss [Member] | Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Loss [Member] | Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Loss [Member] | Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Loss [Member] | Construction and land development [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Loss [Member] | Construction and land development [Member] | Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0	0
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	30,184,000	7,842,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,907,000	2,771,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Watch [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	271,000	198,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	28,006,000	4,718,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	155,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Loss [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	14,736,000	6,867,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	4,077,000	385,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Watch [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	385,000	37,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	10,274,000	6,445,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Loss [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	21,345,000	16,774,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	517,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Watch [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	2,179,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	18,757,000	14,078,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	2,588,000	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Loss [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 0	$ 0

Loans, Leases and Allowance f73

Loans, Leases and Allowance for Credit Losses - Recorded Investment in Loans Classified as Impaired (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Impaired loans with an allowance recorded	[1]	$ 24,287	$ 124,928
Impaired loans with no allowance recorded	[2]	104,587	41,822
Total impaired loans		128,874	166,750
Valuation allowance related to impaired loans	[3]	$ (4,658)	$ (10,765)
[1]	Includes TDR loans of $3.0 million and $103.3 million at December 31, 2015 and 2014, respectively.
[2]	Includes TDR loans of $85.9 million and $35.0 million at December 31, 2015 and 2014, respectively.
[3]	Includes valuation allowance related to TDR loans of $0.3 million and $8.9 million at December 31, 2015 and 2014, respectively.

Loans, Leases and Allowance f74

Loans, Leases and Allowance for Credit Losses - Impaired Loans by Loan Class (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	$ 128,874	$ 166,750
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	16,575	19,300
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	334	363
Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	23,153	44,893
Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	41,081	66,324
Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	0	0
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	26,513	13,749
Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	26,513	13,749
Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	2,896	373
Construction and land development [Member] | Construction [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	0	0
Construction and land development [Member] | Land [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	$ 18,322	$ 21,748

Loans, Leases and Allowance f75

Loans, Leases and Allowance for Credit Losses - Schedule of Average Investment in Impaired Loans and Income Recognized on Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Receivables [Abstract]
Impaired Financing Receivable, Average Recorded Investment	$ 150,151	$ 169,758	$ 182,670
Interest income recognized on impaired loans	4,794	5,494	6,235
Interest recognized on nonaccrual loans, cash basis	$ 1,634	$ 2,536	$ 1,916

Loans, Leases and Allowance f76

Loans, Leases and Allowance for Credit Losses - Average Investment in Impaired Loans by Loan Class (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	$ 150,151	$ 169,758	$ 182,670
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	18,453	25,223	33,339
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	383	508	604
Troubled Debt Restructured Loans [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	113,900	126,600	141,800
Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	34,912	37,048	49,452
Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	56,360	68,821	56,110
Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	0	0	89
Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	17,534	16,168	15,023
Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	2,948	410	727
Construction and land development [Member] | Construction [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	0	0	0
Construction and land development [Member] | Land [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	$ 19,561	$ 21,580	$ 27,326

Loans, Leases and Allowance f77

Loans, Leases and Allowance for Credit Losses - Interest Income on Impaired Loans by Loan Class (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	$ 4,794	$ 5,494	$ 6,235
Owner occupied [Member] | Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	1,575	1,550	1,726
Non-owner occupied [Member] | Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	1,560	1,484	2,043
Multi-family [Member] | Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	0	1	0
Commercial [Member] | Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	288	745	1,087
Leases [Member] | Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	0	0	0
Construction [Member] | Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	0	0	0
Land [Member] | Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	785	1,021	1,288
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	579	646	62
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	$ 7	$ 47	$ 29

Loans, Leases and Allowance f78

Loans, Leases and Allowance for Credit Losses - Tabular Disclosure of Nonperforming Assets (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	$ 48,381	$ 67,659
Loans past due 90 days or more on accrual status		3,028	5,132
Troubled debt restructured loans	[2]	70,707	84,720
Total nonperforming loans		122,116	157,511
Other assets acquired through foreclosure, net		43,942	57,150	$ 66,719	$ 77,247
Total nonperforming assets		166,058	214,661
Troubled Debt Restructured Loans [Member]
Financing Receivable, Recorded Investment, Nonaccrual Status		$ 18,200	$ 53,600
[1]	Includes non-accrual TDR loans of $18.2 million and $53.6 million at December 31, 2015 and 2014, respectively.
[2]	Includes accruing TDR loans only.

Loans, Leases and Allowance f79

Loans, Leases and Allowance for Credit Losses - Changes in Accretable Discount for Loans Purchased with Credit Quality Deterioration (Detail) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Additions			$ 857	$ 0	$ 0
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets		$ 7,000
Balance at beginning of period			19,156	28,164	7,072
Reclassifications from non-accretable to accretable yield (1)	[1]		1,747	6,052	9,817
Accretion to interest income			(3,996)	(7,185)	(7,182)
Reversal of fair value adjustments upon disposition of loans			(1,877)	(7,875)	(3,861)
Balance at end of period			15,925	19,156	28,164
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets			$ 38	$ 0	$ 22,318
[1]	The primary drivers of reclassification from non-accretable to accretable yield resulted from changes in estimated cash flows.

Loans, Leases and Allowance f80

Loans, Leases and Allowance for Credit Losses - Allowances for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation Allowance [Line Items]
Beginning Balance				$ 110,216				$ 100,050	$ 110,216	$ 100,050	$ 95,427
Charge-offs									6,497	7,662	21,479
Recoveries									(12,149)	(13,102)	(12,882)
Provision for credit losses	$ 2,500	$ 0	$ 0	700	$ 300	$ 419	$ 507	3,500	3,200	4,726	13,220
Ending balance	119,068				110,216				119,068	110,216	100,050
Construction and land development [Member]
Valuation Allowance [Line Items]
Beginning Balance				18,558				14,519	18,558	14,519	10,554
Charge-offs									0	87	1,538
Recoveries									(1,872)	(2,160)	(2,060)
Provision for credit losses									(1,454)	1,966	3,443
Ending balance	18,976				18,558				18,976	18,558	14,519
Commercial real estate [Member]
Valuation Allowance [Line Items]
Beginning Balance				28,783				32,064	28,783	32,064	34,982
Charge-offs									0	964	8,648
Recoveries									(4,139)	(3,859)	(2,758)
Provision for credit losses									(9,762)	(6,176)	2,972
Ending balance	23,160				28,783				23,160	28,783	32,064
Residential real estate [Member]
Valuation Allowance [Line Items]
Beginning Balance				7,456				11,640	7,456	11,640	15,237
Charge-offs									820	1,728	5,922
Recoveries									(2,181)	(1,896)	(2,097)
Provision for credit losses									(3,539)	(4,352)	228
Ending balance	5,278				7,456				5,278	7,456	11,640
Commercial and industrial [Member]
Valuation Allowance [Line Items]
Beginning Balance				54,566				39,657	54,566	39,657	32,860
Charge-offs									5,550	4,370	4,000
Recoveries									(3,754)	(4,728)	(5,037)
Provision for credit losses									18,411	14,551	5,760
Ending balance	71,181				54,566				71,181	54,566	39,657
Consumer [Member]
Valuation Allowance [Line Items]
Beginning Balance				$ 853				$ 2,170	853	2,170	1,794
Charge-offs									127	513	1,371
Recoveries									(203)	(459)	(930)
Provision for credit losses									(456)	(1,263)	817
Ending balance	$ 473				$ 853				$ 473	$ 853	$ 2,170

Loans, Leases and Allowance f81

Loans, Leases and Allowance for Credit Losses - Summary of Impairment Method Information Related to Loans and Allowance for Credit Losses (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	[1]	$ 24,287	$ 124,928
Impaired loans with no allowance recorded	[2]	104,587	41,822
Total loans individually evaluated for impairment		128,874	166,750
Loans collectively evaluated for impairment		10,901,140	8,135,041
Impaired Financing Receivable, Recorded Investment		128,874	166,750
Total recorded investment		11,112,854	8,398,265
Impaired loans with an allowance recorded		25,345	134,791
Impaired loans with no allowance recorded		333,268	44,220
Total loans individually evaluated for impairment		358,613	179,011
Loans collectively evaluated for impairment		10,901,140	8,135,041
Total unpaid principal balance		11,379,517	8,451,849
Impaired loans with an allowance recorded	[3]	4,658	10,765
Impaired loans with no allowance recorded		0	0
Total loans individually evaluated for impairment		4,658	10,765
Loans collectively evaluated for impairment		114,374	99,188
Total loans held for investment		119,068	110,216
Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded		2,778	28,024
Impaired loans with no allowance recorded		20,375	16,869
Total loans individually evaluated for impairment		23,153	44,893
Loans collectively evaluated for impairment		2,044,934	1,670,083
Total recorded investment		2,083,285	1,732,888
Impaired loans with an allowance recorded		2,778	31,292
Impaired loans with no allowance recorded		63,709	17,010
Total loans individually evaluated for impairment		66,487	48,302
Loans collectively evaluated for impairment		2,044,934	1,670,083
Total unpaid principal balance		2,131,648	1,742,658
Impaired loans with an allowance recorded		858	2,082
Impaired loans with no allowance recorded		0	0
Total loans individually evaluated for impairment		858	2,082
Loans collectively evaluated for impairment		10,953	10,198
Total loans held for investment		11,811	12,454
Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded		2,344	44,937
Impaired loans with no allowance recorded		38,737	21,387
Total loans individually evaluated for impairment		41,081	66,324
Loans collectively evaluated for impairment		2,180,250	1,910,420
Total recorded investment		2,283,536	2,052,566
Impaired loans with an allowance recorded		2,344	45,853
Impaired loans with no allowance recorded		61,692	21,550
Total loans individually evaluated for impairment		64,036	67,403
Loans collectively evaluated for impairment		2,180,250	1,910,420
Total unpaid principal balance		2,332,467	2,086,758
Impaired loans with an allowance recorded		11	2,537
Impaired loans with no allowance recorded		0	0
Total loans individually evaluated for impairment		11	2,537
Loans collectively evaluated for impairment		11,302	13,734
Total loans held for investment		11,349	16,329
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded		18,230	11,399
Impaired loans with no allowance recorded		8,283	2,350
Total loans individually evaluated for impairment		26,513	13,749
Loans collectively evaluated for impairment		5,085,299	3,312,629
Total recorded investment		5,114,257	3,326,708
Impaired loans with an allowance recorded		19,233	11,829
Impaired loans with no allowance recorded		71,773	4,104
Total loans individually evaluated for impairment		91,006	15,933
Loans collectively evaluated for impairment		5,085,299	3,312,629
Total unpaid principal balance		5,184,125	3,329,712
Impaired loans with an allowance recorded		3,518	1,926
Impaired loans with no allowance recorded		0	0
Total loans individually evaluated for impairment		3,518	1,926
Loans collectively evaluated for impairment		65,806	49,809
Total loans held for investment		69,324	51,766
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded		914	19,300
Impaired loans with no allowance recorded		15,661	0
Total loans individually evaluated for impairment		16,575	19,300
Loans collectively evaluated for impairment		303,372	277,692
Total recorded investment		322,939	299,402
Impaired loans with an allowance recorded		969	24,420
Impaired loans with no allowance recorded		44,142	0
Total loans individually evaluated for impairment		45,111	24,420
Loans collectively evaluated for impairment		303,372	277,692
Total unpaid principal balance		352,019	305,551
Impaired loans with an allowance recorded		270	1,052
Impaired loans with no allowance recorded		0	0
Total loans individually evaluated for impairment		270	1,052
Loans collectively evaluated for impairment		5,008	6,404
Total loans held for investment		5,278	7,456
Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded		0	21,052
Impaired loans with no allowance recorded		18,322	696
Total loans individually evaluated for impairment		18,322	21,748
Loans collectively evaluated for impairment		1,115,117	726,305
Total recorded investment		1,133,439	748,053
Impaired loans with an allowance recorded		0	21,169
Impaired loans with no allowance recorded		82,800	885
Total loans individually evaluated for impairment		82,800	22,054
Loans collectively evaluated for impairment		1,115,117	726,305
Total unpaid principal balance		1,197,917	748,359
Impaired loans with an allowance recorded		0	3,112
Impaired loans with no allowance recorded		0	0
Total loans individually evaluated for impairment		0	3,112
Loans collectively evaluated for impairment		18,976	15,446
Total loans held for investment		18,976	18,558
Commercial leases [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded		0	41
Impaired loans with no allowance recorded		2,896	332
Total loans individually evaluated for impairment		2,896	373
Loans collectively evaluated for impairment		145,597	205,266
Total recorded investment		148,493	205,639
Impaired loans with an allowance recorded		0	41
Impaired loans with no allowance recorded		5,229	483
Total loans individually evaluated for impairment		5,229	524
Loans collectively evaluated for impairment		145,597	205,266
Total unpaid principal balance		150,826	205,790
Impaired loans with an allowance recorded		0	39
Impaired loans with no allowance recorded		0	0
Total loans individually evaluated for impairment		0	39
Loans collectively evaluated for impairment		1,857	2,761
Total loans held for investment		1,857	2,800
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded		21	175
Impaired loans with no allowance recorded		313	188
Total loans individually evaluated for impairment		334	363
Loans collectively evaluated for impairment		26,571	32,646
Total recorded investment		26,905	33,009
Impaired loans with an allowance recorded		21	187
Impaired loans with no allowance recorded		3,923	188
Total loans individually evaluated for impairment		3,944	375
Loans collectively evaluated for impairment		26,571	32,646
Total unpaid principal balance		30,515	33,021
Impaired loans with an allowance recorded		1	17
Impaired loans with no allowance recorded		0	0
Total loans individually evaluated for impairment		1	17
Loans collectively evaluated for impairment		472	836
Total loans held for investment		473	853
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Impaired [Line Items]
Loans acquired with deteriorated credit quality		119,764	137,797
Impaired loans with an allowance recorded		36	263
Receivables Acquired with Deteriorated Credit Quality [Member] | Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		15,198	17,912
Loans acquired with deteriorated credit quality		20,227	24,273
Impaired loans with an allowance recorded		0	174
Receivables Acquired with Deteriorated Credit Quality [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		82,840	96,474
Receivables Acquired with Deteriorated Credit Quality [Member] | Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		62,205	75,822
Loans acquired with deteriorated credit quality		88,181	108,935
Impaired loans with an allowance recorded		36	58
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		2,445	330
Loans acquired with deteriorated credit quality		7,820	1,150
Impaired loans with an allowance recorded		0	31
Receivables Acquired with Deteriorated Credit Quality [Member] | Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		2,992	2,410
Loans acquired with deteriorated credit quality		3,536	3,439
Impaired loans with an allowance recorded		0	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		0	0
Loans acquired with deteriorated credit quality		0	0
Impaired loans with an allowance recorded		0	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial leases [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		0	0
Loans acquired with deteriorated credit quality		0	0
Impaired loans with an allowance recorded		0	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		0	0
Loans acquired with deteriorated credit quality		0	0
Impaired loans with an allowance recorded		$ 0	$ 0
[1]	Includes TDR loans of $3.0 million and $103.3 million at December 31, 2015 and 2014, respectively.
[2]	Includes TDR loans of $85.9 million and $35.0 million at December 31, 2015 and 2014, respectively.
[3]	Includes valuation allowance related to TDR loans of $0.3 million and $8.9 million at December 31, 2015 and 2014, respectively.

Loans, Leases and Allowance f82

Loans, Leases and Allowance for Credit Losses - Troubled Debt Restructured Loans by Loan Class (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)SecurityLoan	Dec. 31, 2014USD ($)SecurityLoan	Dec. 31, 2013USD ($)SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	3	24	43
Pre-Modification Outstanding Recorded Investment	$ 530	$ 38,930	$ 25,019
Forgiven Principal Balance	0	825	1,297
Lost Interest Income	3	434	1,028
Post-Modification Outstanding Recorded Investment	527	37,671	22,694
Waived Fees and Other Expenses	$ 4	$ 67	$ 81
Residential real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	1	5	13
Pre-Modification Outstanding Recorded Investment	$ 81	$ 1,966	$ 5,434
Forgiven Principal Balance	0	447	267
Lost Interest Income	3	70	887
Post-Modification Outstanding Recorded Investment	78	1,449	4,280
Waived Fees and Other Expenses	$ 4	$ 15	$ 24
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	0	2
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 74
Forgiven Principal Balance	0	0	0
Lost Interest Income	0	0	5
Post-Modification Outstanding Recorded Investment	0	0	69
Waived Fees and Other Expenses	$ 0	$ 0	$ 3
Owner occupied [Member] | Commercial real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	6	8
Pre-Modification Outstanding Recorded Investment	$ 0	$ 14,646	$ 3,681
Forgiven Principal Balance	0	378	0
Lost Interest Income	0	257	54
Post-Modification Outstanding Recorded Investment	0	14,011	3,627
Waived Fees and Other Expenses	$ 0	$ 33	$ 28
Non-owner occupied [Member] | Commercial real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	1	5	5
Pre-Modification Outstanding Recorded Investment	$ 193	$ 16,976	$ 10,735
Forgiven Principal Balance	0	0	1,030
Lost Interest Income	0	60	63
Post-Modification Outstanding Recorded Investment	193	16,916	9,642
Waived Fees and Other Expenses	$ 0	$ 15	$ 14
Multi-family [Member] | Commercial real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0
Forgiven Principal Balance	0	0	0
Lost Interest Income	0	0	0
Post-Modification Outstanding Recorded Investment	0	0	0
Waived Fees and Other Expenses	$ 0	$ 0	$ 0
Commercial [Member] | Commercial and industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	1	6	13
Pre-Modification Outstanding Recorded Investment	$ 256	$ 2,655	$ 4,809
Forgiven Principal Balance	0	0	0
Lost Interest Income	0	0	19
Post-Modification Outstanding Recorded Investment	256	2,655	4,790
Waived Fees and Other Expenses	$ 0	$ 4	$ 11
Leases [Member] | Commercial and industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0
Forgiven Principal Balance	0	0	0
Lost Interest Income	0	0	0
Post-Modification Outstanding Recorded Investment	0	0	0
Waived Fees and Other Expenses	$ 0	$ 0	$ 0
Construction [Member] | Construction and land development [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0
Forgiven Principal Balance	0	0	0
Lost Interest Income	0	0	0
Post-Modification Outstanding Recorded Investment	0	0	0
Waived Fees and Other Expenses	$ 0	$ 0	$ 0
Land [Member] | Construction and land development [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	2	2
Pre-Modification Outstanding Recorded Investment	$ 0	$ 2,687	$ 286
Forgiven Principal Balance	0	0	0
Lost Interest Income	0	47	0
Post-Modification Outstanding Recorded Investment	0	2,640	286
Waived Fees and Other Expenses	$ 0	$ 0	$ 1

Loans, Leases and Allowance f83

Loans, Leases and Allowance for Credit Losses - Troubled Debt Restructured Loans by Class for Which There was Payment Default (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)SecurityLoan	Dec. 31, 2014USD ($)SecurityLoan	Dec. 31, 2013USD ($)SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	4	8	15
Recorded Investment | $	$ 1,184	$ 1,950	$ 6,370
Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	0	0
Recorded Investment | $	$ 0	$ 0	$ 0
Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	2	3
Recorded Investment | $	$ 0	$ 984	$ 1,490
Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	2	3
Recorded Investment | $	$ 0	$ 395	$ 2,506
Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	0	0
Recorded Investment | $	$ 0	$ 0	$ 0
Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	3	3
Recorded Investment | $	$ 0	$ 369	$ 1,089
Construction and land development [Member] | Land [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	0	2
Recorded Investment | $	$ 0	$ 0	$ 330
Construction and land development [Member] | Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	1	0	0
Recorded Investment | $	$ 137	$ 0	$ 0
Residential real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	3	1	4
Recorded Investment | $	$ 1,047	$ 202	$ 955
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	0	0	0
Recorded Investment | $	$ 0	$ 0	$ 0

Loans, Leases and Allowance f84

Loans, Leases and Allowance for Credit Losses - Summary of Aggregate Activity in Loans (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Finance Receivable Transferred To Held For Sale [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	$ 48,381	$ 67,659
Impaired Financing Receivable, Average Recorded Investment		150,151	169,758	$ 182,670
Impaired loans with an allowance recorded	[2]	24,287	124,928
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans		2,500	3,800	5,400
Impaired loans with no allowance recorded	[3]	104,587	41,822
Impaired loans with an allowance recorded	[4]	4,658	10,765
Loans And Loans Receivable Purchases		137,200	166,400
Financing Receivable, Significant Sales		102,200
Loans and Leases Receivable, Gain (Loss) on Sales, Net		500
Troubled Debt Restructured Loans [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Loan commitments outstanding		100	1,200
Financing Receivable, Recorded Investment, Nonaccrual Status		18,200	53,600
Impaired Financing Receivable, Average Recorded Investment		113,900	126,600	$ 141,800
Impaired loans with an allowance recorded		3,000	103,300
Impaired loans with no allowance recorded		85,900	35,000
Impaired loans with an allowance recorded		300	8,900
Commercial and industrial [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Impaired loans with an allowance recorded		18,230	11,399
Impaired loans with no allowance recorded		8,283	2,350
Impaired loans with an allowance recorded		3,518	1,926
Loans And Loans Receivable Purchases		117,100
Commercial real estate [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Loans And Loans Receivable Purchases		13,200
Commercial leases [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Impaired loans with an allowance recorded		0	41
Impaired loans with no allowance recorded		2,896	332
Impaired loans with an allowance recorded		0	39
Leases [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Loans And Loans Receivable Purchases		6,800
Construction and land development [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Impaired loans with an allowance recorded		0	21,052
Impaired loans with no allowance recorded		18,322	696
Impaired loans with an allowance recorded		0	$ 3,112
Loans And Loans Receivable Purchases		$ 100
[1]	Includes non-accrual TDR loans of $18.2 million and $53.6 million at December 31, 2015 and 2014, respectively.
[2]	Includes TDR loans of $3.0 million and $103.3 million at December 31, 2015 and 2014, respectively.
[3]	Includes TDR loans of $85.9 million and $35.0 million at December 31, 2015 and 2014, respectively.
[4]	Includes valuation allowance related to TDR loans of $0.3 million and $8.9 million at December 31, 2015 and 2014, respectively.

Loans, Leases and Allowance f85

Loans, Leases and Allowance for Credit Losses Acquired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2015
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets	$ 7,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					$ 1,724,971
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					1,634,602
Business Combination, Acquired Receivables, Fair Value					1,439,930
Receivables Acquired with Deteriorated Credit Quality [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets		$ 38	$ 0	$ 22,318
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					23,535
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					13,724
Business Combination, Acquired Receivables, Fair Value					10,854
Acquired Non-Purchased Credit Impaired Loans [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					1,701,436
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					1,620,878
Business Combination, Acquired Receivables, Fair Value					1,429,076
Commercial and industrial [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					1,243,736
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					1,196,142
Business Combination, Acquired Receivables, Fair Value					1,084,104
Commercial and industrial [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					17,899
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					10,066
Business Combination, Acquired Receivables, Fair Value					7,362
Commercial and industrial [Member] | Acquired Non-Purchased Credit Impaired Loans [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					1,225,837
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					1,186,076
Business Combination, Acquired Receivables, Fair Value					1,076,742
Residential real estate [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					29,508
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					28,717
Business Combination, Acquired Receivables, Fair Value					25,098
Residential real estate [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					2,509
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					2,088
Business Combination, Acquired Receivables, Fair Value					2,075
Residential real estate [Member] | Acquired Non-Purchased Credit Impaired Loans [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					26,999
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					26,629
Business Combination, Acquired Receivables, Fair Value					23,023
Consumer [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					987
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					989
Business Combination, Acquired Receivables, Fair Value					925
Consumer [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					0
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					0
Business Combination, Acquired Receivables, Fair Value					0
Consumer [Member] | Acquired Non-Purchased Credit Impaired Loans [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					987
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					989
Business Combination, Acquired Receivables, Fair Value					925
Commercial real estate [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					343,889
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					306,514
Business Combination, Acquired Receivables, Fair Value					230,723
Commercial real estate [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					3,127
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					1,570
Business Combination, Acquired Receivables, Fair Value					1,417
Commercial real estate [Member] | Acquired Non-Purchased Credit Impaired Loans [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					340,762
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					304,944
Business Combination, Acquired Receivables, Fair Value					229,306
Construction and land development [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					106,851
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					102,240
Business Combination, Acquired Receivables, Fair Value					99,080
Construction and land development [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					0
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					0
Business Combination, Acquired Receivables, Fair Value					0
Construction and land development [Member] | Acquired Non-Purchased Credit Impaired Loans [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					106,851
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition					102,240
Business Combination, Acquired Receivables, Fair Value					$ 99,080

Premises and Equipment (Details

Premises and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Abstract]
Operating Leases, Rent Expense, Net	$ 8,100	$ 6,200	$ 6,900
Buildings and Improvements, Gross	83,431	82,494
Operating Leases, Future Minimum Payments Due, Next Twelve Months	8,547
Operating Leases, Future Minimum Payments, Due in Two Years	7,999
Operating Leases, Future Minimum Payments, Due in Three Years	7,536
Operating Leases, Future Minimum Payments, Due in Four Years	6,628
Operating Leases, Future Minimum Payments, Due in Five Years	4,986
Operating Leases, Future Minimum Payments, Due Thereafter	8,879
Operating Leases, Future Minimum Payments Due	44,575
Land and Land Improvements	33,971	33,971
Furniture Fixtures And Equipment Gross	40,025	51,320
Leasehold Improvements, Gross	18,958	18,160
Construction in Progress, Gross	1,999	848
Property, Plant and Equipment, Gross	178,384	186,793
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(59,849)	(72,975)
Premises and equipment, net	118,535	113,818
Depreciation, Nonproduction	$ 7,700	$ 6,000	$ 6,000

Other Assets Acquired through87

Other Assets Acquired through Foreclosure - Changes in Other Assets Acquired through Foreclosure (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)Property	Dec. 31, 2014USD ($)Property	Dec. 31, 2013USD ($)
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Other Assets Acquired through Foreclosure Additions Due to Business Acquisition	$ 1,407		$ 5,622
Gains Losses On Transfers To Other Real Estate And Foreclosed Assets	$ 851	$ 100	900
Number of Real Estate Properties | Property	39	67
Balance, beginning of the period, Gross Balance	$ 71,421	$ 88,421	113,474
Transfers to other assets acquired through foreclosure, net, Gross Balance	28,566	13,777	24,911
Proceeds from sale of other real estate owned and repossessed assets, net, Gross Balance	(51,038)	(33,643)	(61,510)
Gains (losses), net, Gross Balance	2,628	2,866	5,924
Balance, end of period, Gross Balance	52,984	71,421	88,421
Balance, beginning of the period, Valuation Allowance	(14,271)	(21,702)	(36,227)
Proceeds from sale of other real estate owned and repossessed assets, net, Valuation Allowance	5,411	7,725	18,268
Valuation adjustments, net, Valuation Allowance	(182)	(294)	(3,743)
Balance, end of period, Valuation Allowance	(9,042)	(14,271)	(21,702)
Balance, beginning of the period, Net Balance	57,150	66,719	77,247
Transfers to other assets acquired through foreclosure, net, Net Balance	28,566	13,777	24,911
Proceeds from sale of other real estate owned and repossessed assets, net, Net Balance	(45,627)	(25,918)	(43,242)
Valuation adjustments of other repossessed assets, net	(182)	(294)	(3,743)
Gains (losses), net, Net Balance	2,628	2,866	5,924
Balance, end of period, Net Balance	$ 43,942	$ 57,150	$ 66,719

Other Assets Acquired through88

Other Assets Acquired through Foreclosure - Changes in Other Assets Acquired through Foreclosure Parenthetical (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)Property	Dec. 31, 2014USD ($)Property	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Other Assets Acquired through Foreclosure Additions Due to Business Acquisition	$ 1,407		$ 5,622
Transfers to other assets acquired through foreclosure, net	28,566	$ 13,777	24,911
Proceeds from sale of other real estate owned and repossessed assets, net, Gross Balance	(51,038)	(33,643)	(61,510)
Proceeds from Sale of Foreclosed Assets	(45,627)	(25,918)	(43,242)
Gains (losses), net, Gross Balance	2,628	2,866	5,924
Real Estate Owned, Valuation Allowance	(9,042)	(14,271)	(21,702)	$ (36,227)
Proceeds from sale of other real estate owned and repossessed assets, net, Valuation Allowance	5,411	7,725	18,268
Repossessed Assets	43,942	57,150	66,719	77,247
Foreclosed Assets Gross	52,984	71,421	88,421	$ 113,474
Valuation adjustments, net, Valuation Allowance	(182)	(294)	(3,743)
Valuation adjustments of other repossessed assets, net	(182)	(294)	(3,743)
Gains Losses On Transfers To Other Real Estate And Foreclosed Assets	$ 851	$ 100	$ 900
Number of Real Estate Properties | Property	39	67

Deposits (Details)

Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deposit [Abstract]
Certificates of Deposit, CDARS	$ 517,500	$ 700,700
Non-interest-bearing demand	4,093,976	2,288,048
Time Deposit Maturities, Next Twelve Months	1,507,050
Time Deposit Maturities, Year Two	88,184
Time Deposit Maturities, Year Three	9,633
Time Deposit Maturities, Year Four	3,552
Time Deposit Maturities, Year Five	3,235
Time Deposits	1,611,654
Interest Bearing Deposit Demand	1,028,073	854,935
Deposits, Savings Deposits	5,296,921	3,869,699
Time Deposits, $250,000 or more	1,569,525	1,339,238
Time Deposits, Less than $250,000	42,129	579,123
Deposits	12,030,624	8,931,043
Deposits, ICS	714,400	481,200
Deposits, Wholesale	184,200	257,000
Brokered Deposits, Regulatory	$ 365,600	$ 202,400

Accumulated Other Comprehensi90

Accumulated Other Comprehensive Income - Summary of Changes in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 01, 2015	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Comprehensive Income (Loss), after Adoption of New Accounting Principle				$ 32,948
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax			$ (17)		$ 17
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	$ 0	$ 0	(17)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	90	0	0
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	0	8,976	0
Beginning balance	16,639	(21,546)	8,226
Other comprehensive income before reclassifications	(10,303)	29,683	(30,520)
Amounts reclassified from accumulated other comprehensive income	(385)	(474)	748
Net other comprehensive (loss) income	(10,688)	38,185	(29,772)
Ending balance	22,260	16,639	(21,546)
Unrealized holding gains (losses) on AFS
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Comprehensive Income (Loss), after Adoption of New Accounting Principle				16,495
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	0	8,976
Beginning balance	16,495	(21,690)	8,065
Other comprehensive income before reclassifications	(6,117)	29,683	(30,503)
Amounts reclassified from accumulated other comprehensive income	(385)	(474)	748
Net other comprehensive (loss) income	(6,502)	38,185	(29,755)
Ending balance	9,993	16,495	(21,690)
Supplemental Employee Retirement Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Comprehensive Income (Loss), after Adoption of New Accounting Principle				0
Beginning balance	0
Other comprehensive income before reclassifications	90
Amounts reclassified from accumulated other comprehensive income	0
Net other comprehensive (loss) income	90
Ending balance	90	0
Financial Liability Instruments, Fair Value Option [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income before reclassifications	(4,276)
Net other comprehensive (loss) income	(4,276)
Fair Value, Measurements, Recurring [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Comprehensive Income (Loss), after Adoption of New Accounting Principle				16,309
Ending balance	12,033
Impairment loss on securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Comprehensive Income (Loss), after Adoption of New Accounting Principle				$ 144
Beginning balance	144	144	144
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income	0	0
Net other comprehensive (loss) income	0	0
Ending balance	$ 144	$ 144	$ 144

Other Borrowings - Company's Bo

Other Borrowings - Company's Borrowings (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Short Term
Revolving line of credit	$ 0	$ 25,000
FHLB advances	150,000	96,987
Other Long-term Debt, Current	0	58,182
Short-term Debt	150,000	180,169
Long Term
Long-term Debt	0	210,094
FHLB [Member]
Long Term
Long-term Debt	$ 0	$ 210,094

Accumulated Other Comprehensi92

Accumulated Other Comprehensive Income - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income	$ (230)	$ (283)
Amount reclassified from accumulated other comprehensive income	385	474	$ (748)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income	385	474	(748)
Realized Gain Loss On Sale Of Investment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized gains on sales of investment securities	615	757	(1,195)
Income Tax Expense [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income	$ (230)	$ (283)	$ 447

Other Borrowings - Additional I

Other Borrowings - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt [Line Items]
Line of Credit Facility, Interest Rate at Period End		1.75%
Weighted average interest rate of FHLB and FRB Short-term advances	0.36%	1.24%
Other Long-term Debt, Current	$ 0	$ 58,182
Long-term Debt, Weighted Average Interest Rate		1.06%
Revolving line of credit	0	$ 25,000
Repayments of Debt	200,000
Gains (Losses) on Extinguishment of Debt	(81)	(502)	$ (1,387)
FHLB advances	150,000	96,987
Fed Funds With Other Institutions [Member]
Debt [Line Items]
Revolving line of credit	0	0
Secured borrowing credit line	100,000
FRB [Member]
Debt [Line Items]
Additional available credit with the entity	1,210,000	1,150,000
Other Credit Facilities [Member]
Debt [Line Items]
Secured borrowing credit line	70,000
Secured Credit Facility [Member]
Debt [Line Items]
Secured borrowing credit line	25,000
Unsecured Credit Facility [Member]
Debt [Line Items]
Secured borrowing credit line	45,000
FHLB [Member]
Debt [Line Items]
Additional available credit with the entity	1,540,000	935,000
Long-term Debt	$ 0	$ 210,094

Qualifying Debt (Details)

Qualifying Debt (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Qualifying Debt [Abstract]
Proceeds from Issuance of Subordinated Long-term Debt	$ 150,000,000	$ 0	$ 0

Qualifying Debt Subordinated De

Qualifying Debt Subordinated Debt Details (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Subordinated Debt Details [Abstract]
Proceeds from Issuance of Subordinated Long-term Debt	$ 150,000,000	$ 0	$ 0
Debt Issuance Cost	1,800,000
Subordinated Debt	$ 152,000,000

Qualifying Debt Junior Subord96

Qualifying Debt Junior Subordinated Debt (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2015
Debt Instrument [Line Items]
Subordinated Debt Obligations, Fair Value Disclosure	$ 46,928	$ 40,437
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	58,370	40,437
Business Combination, Fair Market Value Adjustment on Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	(6,085)	0		$ 6,200
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(6,523)	$ 1,380	$ (5,900)
Long-term Debt, Weighted Average Interest Rate		1.06%
Bridge Capital Trust I [Member]
Debt Instrument [Line Items]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	12,372	$ 0
Bridge Capital Trust II [Member]
Debt Instrument [Line Items]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	$ 5,155	$ 0
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate	2.95%	2.73%
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Subordinated Debt Obligations, Fair Value Disclosure	$ 46,928	$ 40,437
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	66,497	66,497
Unrealized gain or loss on junior subordinated debt [Line Items]	(19,569)	(26,060)
Junior Subordinated Debt [Member] | BankWest Nevada Capital Trust II [Member]
Debt Instrument [Line Items]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	15,464	15,464
Junior Subordinated Debt [Member] | Intermountain First Statutory Trust I [Member]
Debt Instrument [Line Items]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	10,310	10,310
Junior Subordinated Debt [Member] | First Independent Capital Trust I [Member]
Debt Instrument [Line Items]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	7,217	7,217
Junior Subordinated Debt [Member] | WAL Trust No. 1 [Member]
Debt Instrument [Line Items]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	20,619	20,619
Junior Subordinated Debt [Member] | WAL Statutory Trust No. 2 [Member]
Debt Instrument [Line Items]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	5,155	5,155
Junior Subordinated Debt [Member] | WAL Statutory Trust No. 3 [Member]
Debt Instrument [Line Items]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	7,732	7,732
Bridge Capital Holdings [Member]
Debt Instrument [Line Items]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	17,527	0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Junior Subordinated Debt	11,442	0		$ 11,287
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ (6,491)	$ 1,421	$ (5,640)

Qualifying Debt Supplemental Sc

Qualifying Debt Supplemental Schedule - Adoption of ASU 2016-01 (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
New Accounting Pronouncement, Early Adoption [Line Items]
Retained earnings	$ 22,260				$ 16,639				$ 22,260	$ 16,639	$ (21,546)	$ 8,226
Accumulated other comprehensive income	262,638				85,453				262,638	85,453
Non-interest income	9,479	$ 8,502	$ 5,545	$ 6,242	8,417	$ 6,073	$ 5,599	$ 4,562	29,768	24,651	22,197
Income Tax Expense (Benefit)	19,348	17,133	13,579	14,234	14,111	12,949	10,706	10,624	64,294	48,390	29,830
Net income (loss)	58,526	55,860	39,475	40,383	40,409	40,919	35,538	31,085	194,244	147,951	114,965
Net income available to common shareholders	$ 58,375	$ 55,684	$ 39,228	$ 40,207	$ 40,080	$ 40,566	$ 35,186	$ 30,732	$ 193,494	$ 146,564	$ 113,555
Earnings Per Share, Basic	$ 0.58	$ 0.55	$ 0.44	$ 0.46	$ 0.46	$ 0.47	$ 0.41	$ 0.35	$ 2.05	$ 1.69	$ 1.33
Earnings Per Share, Diluted	$ 0.57	$ 0.55	$ 0.44	$ 0.45	$ 0.46	$ 0.46	$ 0.40	$ 0.35	$ 2.03	$ 1.67	$ 1.31
Accounting Standards Update 2016-01 [Member] | Scenario, Previously Reported [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Retained earnings		$ 20,643	$ 15,348	$ 23,423
Accumulated other comprehensive income		218,897	159,939	125,467
Non-interest income		13,826	(2,191)	5,933
Income Tax Expense (Benefit)		19,183	10,599	14,118
Net income (loss)		59,134	34,719	40,190
Net income available to common shareholders		$ 58,958	$ 34,472	$ 40,014
Earnings Per Share, Basic		$ 590	$ 390	$ 460
Earnings Per Share, Diluted		$ 580	$ 390	$ 450
Accounting Standards Update 2016-01 [Member] | Scenario, Adjustment [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Retained earnings		$ 35,276	$ 26,707	$ 39,538
Accumulated other comprehensive income		204,264	148,580	109,352
Non-interest income		8,502	5,545	6,242
Income Tax Expense (Benefit)		17,133	13,579	14,234
Net income (loss)		55,860	39,475	40,383
Net income available to common shareholders		$ 55,684	$ 39,228	$ 40,207
Earnings Per Share, Basic		$ 0.55	$ 0.44	$ 0.46
Earnings Per Share, Diluted		$ 0.55	$ 0.44	$ 0.45

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)		Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 18, 2015	Dec. 30, 2014	Sep. 27, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Value, Issued					$ 0	$ 0	$ 70,500,000				$ 141,000,000
Preferred Stock, Shares Issued					70,500	70,500	141,000			141,000,000	141,000,000
Preferred Stock, Par or Stated Value Per Share					$ 0.0001	$ 0.0001	$ 0.0001				$ 0.0001
Preferred Stock, Liquidation Preference Per Share					$ 1,000	$ 1,000	$ 1,000		$ 1,000		$ 1,000
Preferred Stock, Shares Outstanding						70,500	70,500
Preferred Stock, Redemption Amount							$ 70,700,000		$ 70,700,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options					$ 18,500,000	$ 18,500,000
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term						2 years 2 months 9 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value						$ 3,600,000	$ 7,100,000	$ 2,800,000
Common Stock, Shares, Issued					103,087,044	103,087,044	88,691,249
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period						509,000	508,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number					1,492,000	1,492,000	1,050,000	1,204,000
Weighted Average Selling Price Per Share						$ 38.13
Proceeds from Issuance of Common Stock, Gross						$ 29,000,000
Stock Issued During Period, Value, New Issues						28,288,000	$ 13,746,000
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Offering Cost from Issuance of Common Stock						$ 700,000	$ 500,000
Stock Issued During Period, Shares, New Issues				760,376		760,000	548,122
Weighted Average Selling Price Per Share							$ 25.96
Stock Issued During Period, Value, New Issues							$ 14,200,000
Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Shares Outstanding						71,000	70,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period			285,000			308,400
Allocated Share-based Compensation Expense						$ 4,800,000	$ 3,600,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense						$ 9,300,000	$ 6,800,000
Bridge Capital Holdings [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Business Acquisition Share Exchange Ratio		0.8145
Business Acquisition Cash Consideration Per Share		$ 2.39
Equity Award Conversion Ratio		0.905
Business Combination, Consideration Transferred, Liabilities Incurred		$ 10,676,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options		$ 2,400,000
Common Stock, Shares, Issued		12,451,240			12,451,240	12,451,240
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period						546,000	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Share-based Liabilities Paid		213,091
Stock Issued During Period, Value, New Issues	[1]					$ 431,031,000
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable		$ 420,354,000
Payments to Acquire Businesses, Gross		$ 36,539,000
Bridge Capital Holdings [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, New Issues						12,997,000
Stock Issued During Period, Value, New Issues	[1]					$ 1,000
Bridge Capital Holdings [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate		0.00%
Business Combination, Consideration Transferred, Liabilities Incurred		$ 1,713,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options		$ 4,100,000
Allocated Share-based Compensation Expense					$ 500,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate		33.96%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate		2.11%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term		7 years 7 months 28 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 19.06
Bridge Capital Holdings [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Business Combination, Consideration Transferred, Liabilities Incurred		$ 8,963,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options		17,000,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options		$ 8,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		546,151
Allocated Share-based Compensation Expense					$ 1,700,000
[1]	Includes value of certain share-based awards replaced in connection with the acquisition.

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Unvested Shares of Restricted Stock and Changes (Detail) - USD ($) $ / shares in Units, $ in Millions	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period					509,000	508,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value					$ 27.55	$ 23.90
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number				1,492,000	1,492,000	1,050,000	1,204,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value				$ 20.46	$ 20.46	$ 16.19	$ 9.71
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period					(528,000)	(566,000)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value					$ 13.02	$ 9.57
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period					(85,000)	(96,000)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value					$ 21.63	$ 15.05
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value					$ 12,600,000	$ 12,200,000	$ 6,700,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value					$ 14.6	$ 13.3	$ 6.8
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Aggregate Intrinsic Value					12.6
Allocated Share-based Compensation Expense					$ 9.3	6.8
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		285,000			308,400
Allocated Share-based Compensation Expense					$ 4.8	3.6
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number				414,650	414,650
Executive Officer [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period					52,200
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Aggregate Intrinsic Value					$ 1.4
Allocated Share-based Compensation Expense					$ 0.5	$ 0	$ 0
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, New Issues			760,376		760,000	548,122
Bridge Capital Holdings [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period					546,000	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value					$ 14.70	$ 0
Bridge Capital Holdings [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	546,151
Allocated Share-based Compensation Expense				$ 1.7
Bridge Capital Holdings [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, New Issues					12,997,000

Stockholders' Equity Share-Base

Stockholders' Equity Share-Based Compensation - Stock Options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number		224	224	217
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price		$ 19.15	$ 19.15	$ 9.70
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term			6 years 4 months 28 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value		$ 3,738	$ 3,738
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			$ 27.55	$ 23.90
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures			0
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price			$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(182)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price			$ 10.62
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period			(24)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price			$ 23.89
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number		94	94
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price		$ 11.72	$ 11.72
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term			3 years 8 months 1 day
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value		$ 2,278	$ 2,278
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number		97	97
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price		$ 24.49	$ 24.49
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term			8 years 4 months 17 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value		$ 1,691	$ 1,691
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense			$ 9,300	$ 6,800
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			$ 12,600,000	$ 12,200,000	$ 6,700,000
Bridge Capital Holdings [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			$ 14.70	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures			213
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price			$ 22.02
Bridge Capital Holdings [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		1,700
Bridge Capital Holdings [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		$ 500
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	33.96%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	2.11%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	7 years 7 months 28 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 19.06

Derivatives and Hedging Fair Va

Derivatives and Hedging Fair Value of Derivative Contracts (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Notional Amount		$ 800,478	$ 647,703	$ 294,997
Derivative Asset, Fair Value		3,569	7	2,386
Derivative Liability, Fair Value		64,785	57,820	788
Notional Amount, Netting Adjustments	[1]	0	0	0
Derivative Netting Adjustments	[1]	0	0	384
Positive NPVs		3,569	7	2,002
Negative NPVs		64,785	57,820	404
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Amount		800,478	647,703	294,997
Derivative Asset, Fair Value		3,569	7	2,386
Derivative Liability, Fair Value		$ 64,785	$ 57,820	$ 788
[1]	Netting adjustments represent the amounts recorded to convert our derivative balances from a gross basis to a net basis in accordance with the applicable accounting guidance.

Derivatives and Hedging Pre-Tax

Derivatives and Hedging Pre-Tax Net Gains (Losses) on Fair Value Hedges (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Net Hedge Ineffectiveness Gain (Loss)	$ 79	$ (169)	$ (9)
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain (Loss) on Derivatives	(6,965)	(60,377)	3,308
Increase (Decrease) to Basis of Hedged Assets	7,044	60,208	(3,317)
Subordinated Debt [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Net Hedge Ineffectiveness Gain (Loss)	0	0	0
Subordinated Debt [Member] | Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain (Loss) on Derivatives	3,569	0	0
Increase (Decrease) to Basis of Hedged Assets	$ (3,569)	$ 0	$ 0

Derivatives and Hedging Largest

Derivatives and Hedging Largest Exposure to Individual Counterparty (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Largest gross exposure (positive derivative NPV) to an individual counterparty	$ 3,569	$ 7	$ 2,002
Largest individual counterparty [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Largest gross exposure (positive derivative NPV) to an individual counterparty	3,569	7	2,378
Collateral posted by this counterparty	4,680	0	2,002
Negative derivative NPV with this counterparty	0	0	346
Collateral pledged to this counterparty	1,340	0	0
Net exposure after netting adjustments and collateral	$ 229	$ 7	$ 0

Derivatives and Hedging Additio

Derivatives and Hedging Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Largest gross exposure (positive derivative NPV) to an individual counterparty	$ 3,569	$ 7	$ 2,002
Negative NPVs	64,785	57,820	404
Collateral netted against derivative liabilities	61,700	57,800	300
Over collateralization net position	15,500	$ 14,200	$ 12,400
Additional collateral held in securities	$ 77,200

Earnings per Share (Details)

Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Anti-dilutive stock options outstanding that were not included in computation of diluted earnings per common share									0	1,500	163,300
Basic									94,570,000	86,693,000	85,682,000
Dilutive Effect Of Stock Options Restricted Stock And Equity Settled Awards									649,000	813,000	859,000
Diluted									95,219,000	87,506,000	86,541,000
Net income available to common shareholders	$ 58,375	$ 55,684	$ 39,228	$ 40,207	$ 40,080	$ 40,566	$ 35,186	$ 30,732	$ 193,494	$ 146,564	$ 113,555
Earnings (loss) per share - basic	$ 0.58	$ 0.55	$ 0.44	$ 0.46	$ 0.46	$ 0.47	$ 0.41	$ 0.35	$ 2.05	$ 1.69	$ 1.33
Earnings (loss) per share - diluted	$ 0.57	$ 0.55	$ 0.44	$ 0.45	$ 0.46	$ 0.46	$ 0.40	$ 0.35	$ 2.03	$ 1.67	$ 1.31

Income Taxes Provision for Inco

Income Taxes Provision for Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Current Income Tax Expense (Benefit)									$ 61,040	$ 55,572	$ 43,547
Deferred Income Tax Expense (Benefit)									3,254	(7,182)	(13,717)
Income Tax Expense (Benefit)	$ 19,348	$ 17,133	$ 13,579	$ 14,234	$ 14,111	$ 12,949	$ 10,706	$ 10,624	$ 64,294	$ 48,390	$ 29,830

Income Taxes Reconciliation 107

Income Taxes Reconciliation between Statutory Federal Income Tax and Company's Effective Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount									$ 90,489	$ 69,125	$ 50,979
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount									5,783	4,904	3,016
Increase Decrease In Bank Owned Life Insurance									(1,365)	(1,578)	(1,683)
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount									(20,226)	(15,006)	(7,308)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount									(2,290)	(2,104)	(2,391)
Income Tax Reconciliation Bargain Purchase Gain On Acquisition									0	0	(3,775)
Income Tax Reconciliation Low Income Housing And Other Tax Credits									(5,223)	(3,872)	(2,105)
Income Tax Reconciliation Tax Benefit Related to Acquisition									0	0	(3,738)
Income Tax Reconciliation Tax On Earnings Other Than Statutory Tax Rate									(2,874)	(3,079)	(3,165)
Income Tax Expense (Benefit)	$ 19,348	$ 17,133	$ 13,579	$ 14,234	$ 14,111	$ 12,949	$ 10,706	$ 10,624	$ 64,294	$ 48,390	$ 29,830
Effective Income Tax Rate Reconciliation, Percent									24.87%	24.50%	20.48%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation, Percent	24.87%	24.50%	20.48%
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 700	$ 0
Decreased deferred tax assets net	23,700
Recognized net deferred tax asset	86,352	62,686
Operating Loss Carryforwards, Valuation Allowance	0	1,800
IRC Section 382 Limitation, Valuation Allowance	0	500
Western Liberty Bancorp [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward Annual Limitations on Deductions From Taxable Income	1,800
Centennial Bank [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward Annual Limitations on Deductions From Taxable Income	1,600
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	$ 9,300	$ 8,500

Income Taxes Income Taxes - Cum

Income Taxes Income Taxes - Cumulative Tax Effects of Primary Differences (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Provision for Loan Losses	$ 47,431	$ 42,038
Deferred Tax Assets Fair Market Value Adjustment Related to Acquired Loans	13,930	8,250
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	12,069	4,749
Deferred Tax Assets, Tax Credit Carryforwards	9,052	9,617
Deferred Tax Assets Start Up Costs and Other Amortization	4,771	5,113
Deferred Tax Assets Other Real Estate Owned Write Down	4,280	7,343
Deferred Tax Assets Net Unrealized Built In Losses	3,284	3,657
Deferred Tax Assets, Other	13,686	8,188
Deferred Tax Assets, Gross	117,758	97,408
Deferred Tax Assets, Valuation Allowance	0	(2,290)
IRC Section 382 Limitation, Valuation Allowance	0	500
Deferred Tax Assets, Net of Valuation Allowance	117,758	95,118
Deferred Tax Liabilities, Unrealized Gains on Debt Instruments Measured at Fair Value	7,537	0
Deferred Tax Liabilities, Unrealized Gains on Trading Securities	(1,000)	(9,798)
Deferred Tax Liabilities, Deferred Expense, Deferred Financing Costs	(7,400)	(6,041)
Deferred Tax Liabilities Unrealized Gains On Available For Sale Securities	(6,353)	(9,949)
Deferred Tax Liabilities, Core Deposit Intangible	(6,093)	(1,006)
Deferred Tax Liabilities, Property, Plant and Equipment	(2,039)	(4,049)
Deferred Tax Liabilities, Other	(984)	(1,589)
Deferred Tax Liabilities, Gross	(31,406)	(32,432)
Deferred tax assets, net	$ 86,352	$ 62,686

Income Taxes - Low Income Housi

Income Taxes - Low Income Housing Tax Credit (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Investment in Low Income Housing Tax Credit		$ 152.7	$ 126.6
Unfunded Low Income Housing Tax Credit Obligations		61.2	51.4
Amortization of Low Income Housing Tax Credits	$ 3	$ 14.4	$ 10.6	$ 5.9

Income Taxes Gross Activity 111

Income Taxes Gross Activity of Unrecognized Tax Benefits Related to Uncertain Tax Positions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 700	$ 0
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	1,038
Unrecognized Tax Benefits	$ 1,038

Income Taxes Additional Informa

Income Taxes Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Investment in Low Income Housing Tax Credit		$ 152,700,000	$ 126,600,000
Unrecognized Tax Benefits, Income Tax Penalties Expense		0.1
Unrecognized Tax Benefits, Income Tax Penalties Accrued		0.1
Unrecognized Tax Benefits, Interest on Income Taxes Accrued		0.1
Unfunded Low Income Housing Tax Credit Obligations		61,200,000	51,400,000
Amortization of Low Income Housing Tax Credits	$ 3,000,000	$ 14,400,000	$ 10,600,000	$ 5,900,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Loss Contingencies [Line Items]
Letters of credit expiration period	1 year
Percentage of first liens initial loan to value ratio		75.00%
Percent of commercial real estate loans owner occupied		48.00%	46.00%
Operating Leases, Rent Expense, Net		$ 8.1	$ 6.2	$ 6.9
Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Credit Concentration Risk [Member]
Loss Contingencies [Line Items]
Percent of commercial real estate related loans		49.00%	54.00%
Unfunded Loan Commitment [Member]
Loss Contingencies [Line Items]
Loss Contingency Accrual		$ 3.3	$ 2.1

Commitments and Contingencie114

Commitments and Contingencies - Summary of Contractual Amounts for Unfunded Commitments and Letters of Credit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Commitments [Line Items]
Total amount	$ 3,733,203	$ 2,256,117
Operating Leases, Rent Expense, Net	$ 8,100	$ 6,200	$ 6,900
Percent of commercial real estate loans owner occupied	48.00%	46.00%
Unfunded Loan Commitment [Member]
Other Commitments [Line Items]
Loss Contingency Accrual	$ 3,300	$ 2,100
Standby letters of credit [Member]
Other Commitments [Line Items]
Total amount	50,659	49,556
Unsecured Letters Of Credit	4,257	5,166
Credit card guarantees [Member]
Other Commitments [Line Items]
Total amount	57,966	42,038
Commitments to extend credit [Member]
Other Commitments [Line Items]
Total amount	3,624,578	2,164,523
Unsecured Loan Commitments	$ 341,374	$ 232,863

Commitments and Contingencie115

Commitments and Contingencies - Contractual Commitments for Lines and Letters of Credit by Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Total Amount Committed	$ 3,733,203	$ 2,256,117
Other Commitment, Due in Next Twelve Months	1,689,273
Other Commitment, Due in Second and Third Year	1,407,042
Other Commitment, Due in Fourth and Fifth Year	269,445
Other Commitment, Due after Fifth Year	367,443
Commitments to extend credit [Member]
Loss Contingencies [Line Items]
Total Amount Committed	3,624,578	2,164,523
Other Commitment, Due in Next Twelve Months	1,588,558
Other Commitment, Due in Second and Third Year	1,401,293
Other Commitment, Due in Fourth and Fifth Year	267,284
Other Commitment, Due after Fifth Year	367,443
Credit card guarantees [Member]
Loss Contingencies [Line Items]
Total Amount Committed	57,966	42,038
Other Commitment, Due in Next Twelve Months	57,966
Other Commitment, Due in Second and Third Year	0
Other Commitment, Due in Fourth and Fifth Year	0
Other Commitment, Due after Fifth Year	0
Standby letters of credit [Member]
Loss Contingencies [Line Items]
Total Amount Committed	50,659	$ 49,556
Other Commitment, Due in Next Twelve Months	42,749
Other Commitment, Due in Second and Third Year	5,749
Other Commitment, Due in Fourth and Fifth Year	2,161
Other Commitment, Due after Fifth Year	$ 0

Commitments and Contingencies C

Commitments and Contingencies Concentration of Lending Activities (Details)	Dec. 31, 2015	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Percent of commercial real estate loans owner occupied	48.00%	46.00%

Fair Value Accounting - Gains a

Fair Value Accounting - Gains and Losses from Fair Value Changes Included in Consolidated Statement of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ (6,523)	$ 1,380	$ (5,900)
Interest Income on Securities	2	7	6
Interest Expense on Junior Subordinated Debt	(2,151)	(1,754)	(1,823)
Total Changes Included in Current-Period Earnings	(2,181)	(367)	(7,717)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	(4,276)
Securities measured at fair value [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(32)	(41)	(260)
Interest Income on Securities	2	7	6
Interest Expense on Junior Subordinated Debt	0	0	0
Total Changes Included in Current-Period Earnings	(30)	(34)	(254)
Junior Subordinated Debt [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(6,491)	1,421	(5,640)
Interest Income on Securities	0	0	0
Interest Expense on Junior Subordinated Debt	(2,151)	(1,754)	(1,823)
Total Changes Included in Current-Period Earnings	(2,151)	$ (333)	$ (7,463)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	$ (4,276)

Fair Value Accounting - Fair Va

Fair Value Accounting - Fair Value of Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$ 1,982,523		$ 1,520,237
Derivative Liability	64,785		57,820		$ 404
Derivative Asset	3,569		7		$ 2,002
Subordinated Debt Obligations, Fair Value Disclosure	46,928		40,437
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,982,523		1,520,237
Loans Held-for-sale, Fair Value Disclosure	23,809
Derivative Liability	64,785	[1]	57,820	[2]
Derivative Asset	3,569	[1]	7	[2]
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	148,914		144,646
Loans Held-for-sale, Fair Value Disclosure	0
Derivative Liability	0	[1]	0	[2]
Derivative Asset	0	[1]	0	[2]
Subordinated Debt Obligations, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,823,549		1,364,146
Loans Held-for-sale, Fair Value Disclosure	23,809
Derivative Liability	64,785	[1]	57,820	[2]
Derivative Asset	3,569	[1]	7	[2]
Subordinated Debt Obligations, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	10,060		11,445
Loans Held-for-sale, Fair Value Disclosure	0
Derivative Liability	0	[1]	0	[2]
Derivative Asset	0	[1]	0	[2]
Subordinated Debt Obligations, Fair Value Disclosure	46,928		40,437
Fair Value, Measurements, Recurring [Member] | Residential mortgage-backed securities issued by GSEs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities measured at fair value	1,481		1,858
Securities available for sale	1,170,221		891,189
Fair Value, Measurements, Recurring [Member] | Residential mortgage-backed securities issued by GSEs | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities measured at fair value	0		0
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Residential mortgage-backed securities issued by GSEs | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities measured at fair value	1,481		1,858
Securities available for sale	1,170,221		891,189
Fair Value, Measurements, Recurring [Member] | Residential mortgage-backed securities issued by GSEs | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities measured at fair value	0		0
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Private label residential mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	257,128		70,243
Fair Value, Measurements, Recurring [Member] | Private label residential mortgage-backed securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Private label residential mortgage-backed securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	257,128		70,243
Fair Value, Measurements, Recurring [Member] | Private label residential mortgage-backed securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	19,114		2,147
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	19,114		2,147
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	13,251		52,489
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	13,251		52,489
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Municipal obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	334,830		299,037
Fair Value, Measurements, Recurring [Member] | Municipal obligations [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Municipal obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	334,830		299,037
Fair Value, Measurements, Recurring [Member] | Municipal obligations [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	111,236		82,612
Fair Value, Measurements, Recurring [Member] | Preferred Stock [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	111,236		82,612
Fair Value, Measurements, Recurring [Member] | Preferred Stock [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Preferred Stock [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale			37,702
Fair Value, Measurements, Recurring [Member] | Mutual funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale			37,702
Fair Value, Measurements, Recurring [Member] | Mutual funds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale			0
Fair Value, Measurements, Recurring [Member] | Mutual funds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale			0
Fair Value, Measurements, Recurring [Member] | CRA investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	34,685
Fair Value, Measurements, Recurring [Member] | CRA investments [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	34,685		24,332
Fair Value, Measurements, Recurring [Member] | CRA investments [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | CRA investments [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	10,060		11,445
Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	10,060		11,445
Fair Value, Measurements, Recurring [Member] | Trust preferred securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	24,314		25,546
Fair Value, Measurements, Recurring [Member] | Trust preferred securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Trust preferred securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	24,314		25,546
Fair Value, Measurements, Recurring [Member] | Trust preferred securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Private label commercial mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	4,691		5,149
Fair Value, Measurements, Recurring [Member] | Private label commercial mortgage-backed securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | Private label commercial mortgage-backed securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	4,691		5,149
Fair Value, Measurements, Recurring [Member] | Private label commercial mortgage-backed securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0		0
Fair Value, Measurements, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale			18,346
Fair Value, Measurements, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale			0
Fair Value, Measurements, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale			18,346
Fair Value, Measurements, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale			$ 0
Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,993
Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,993
Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0
Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$ 0
[1]	Derivative assets and liabilities relate to interest rate swaps, see "Note 13. Derivatives and Hedging Activities." In addition, the carrying value of loans includes a net positive value of $64,184 and the net carrying value of subordinated debt includes a net negative value of $3,569 as of December 31, 2015, which relates to the effective portion of the hedges put in place to mitigate against fluctuations in interest rates.
[2]	Derivative assets and liabilities relate to interest rate swaps, see "Note 13. Derivatives and Hedging Activities." In addition, the carrying value of loans includes a positive value of $57,140 as of December 31, 2014, which relates to the effective portion of the hedges put in place to mitigate against fluctuations in interest rates.

Fair Value Accounting - Change

Fair Value Accounting - Change in Level 3 Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		$ (1,385)	$ 5,202	$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0	(6,243)	0
Other assets acquired through foreclosure, net		43,942	57,150	66,719	$ 77,247
Change in unrealized gains (losses) for the twelve month period included in earnings (or changes in net assets) for the period ended December 31, 2012		(6,523)	1,380	(5,900)
Junior subordinated debt		46,928	40,437
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		1,982,523	1,520,237
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets acquired through foreclosure, net		43,900
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		1,982,523	1,520,237
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt		46,928	40,437
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		$ 10,060	$ 11,445
Available-for-sale Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique		S&P Model	S&P Model
Junior subordinated debt, Significant Unobservable Inputs		Pricing indications from comparable securities	Pricing indications from comparable securities
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014		$ 10,060	$ 11,445
Available-for-sale Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		(10,060)	(11,445)	0	$ 0
Junior Subordinated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in unrealized gains (losses) for the twelve month period included in earnings (or changes in net assets) for the period ended December 31, 2012		$ (6,491)	$ 1,421	(5,640)
Junior Subordinated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Input Value		5.674%	6.242%
Junior Subordinated Debt [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt		$ 46,928	$ 40,437
Junior subordinated debt, Valuation Technique		Discounted cash flow	Discounted cash flow
Junior subordinated debt, Significant Unobservable Inputs		Implied credit rating of the Company	Adjusted Corporate Bond over Treasury Index with comparable credit spread
Junior Subordinated Debt [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance		$ (40,437)	$ (41,858)	(36,218)
Included in earnings (or changes in net assets)	[1]	0	1,421	(5,640)
Closing balance		(46,928)	(40,437)	(41,858)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		$ 0	$ 0	$ 0
[1]	CDO Securities Year Ended December 31, 2015 2014 2013 (in thousands)Beginning balance $11,445 $— $—Transfers into Level 3 — 6,243 —Total gains (losses) for the period Included in other comprehensive income (3) (1,385) 5,202 —Ending balance $10,060 $11,445 $—

Fair Value Accounting - Assets

Fair Value Accounting - Assets Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded	[1]	$ 24,287	$ 124,928
Impaired loans without specific valuation allowance	[2]	104,587	41,822
Other assets acquired through foreclosure		43,900	57,100
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded		24,300	124,900
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded		19,629	114,163
Impaired loans without specific valuation allowance	[3]	66,754	38,019
Other assets acquired through foreclosure		43,942	57,150
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded		0	0
Impaired loans without specific valuation allowance	[3]	0	0
Other assets acquired through foreclosure		0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded		0	0
Impaired loans without specific valuation allowance	[3]	0	0
Other assets acquired through foreclosure		0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded		19,629	114,163
Impaired loans without specific valuation allowance	[3]	66,754	38,019
Other assets acquired through foreclosure		$ 43,942	$ 57,150
[1]	Includes TDR loans of $3.0 million and $103.3 million at December 31, 2015 and 2014, respectively.
[2]	Includes TDR loans of $85.9 million and $35.0 million at December 31, 2015 and 2014, respectively.
[3]	Certain assets are measured at fair value on a nonrecurring basis. That is, the assets are not measured at fair value on an ongoing basis, but are subject to fair value adjustments in certain circumstances (for example, when there is evidence of impairment). The following table presents such assets carried on the balance sheet by caption and by level within the ASC 825 hierarchy: Fair Value Measurements at the End of the Reporting Period Using Total Quoted Prices in Active Markets for Identical Assets(Level 1) Active Markets for Similar Assets(Level 2) Unobservable Inputs(Level 3) (in thousands)As of December 31, 2015: Impaired loans with specific valuation allowance $19,629 $— $— $19,629Impaired loans without specific valuation allowance (1) 66,754 — — 66,754Other assets acquired through foreclosure 43,942 — — 43,942As of December 31, 2014: Impaired loans with specific valuation allowance $114,163 $— $— $114,163Impaired loans without specific valuation allowance (1) 38,019 — — 38,019Other assets acquired through foreclosure 57,150 — — 57,150(1)Excludes loan balances with charge-offs of $37.8 million and $3.8 million as of December 31, 2015 and 2014, respectively.

Fair Value Accounting - Estimat

Fair Value Accounting - Estimated Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Financial assets
Securities available for sale	$ 1,982,523		$ 1,520,237
Securities measured at fair value	1,481		1,858
Derivative Asset	3,569		7		$ 2,002
Loans, net	10,993,786		8,288,049
Financial liabilities
Deposits	12,030,624		8,931,043
Customer repurchases	38,155		54,899
FHLB and FRB advances	150,000		96,987
Junior subordinated debt	46,928		40,437
Derivative Liability	64,785		57,820		$ 404
Fair Value, Measurements, Recurring [Member]
Financial assets
Securities available for sale	1,982,523		1,520,237
Derivative Asset	3,569	[1]	7	[2]
Financial liabilities
Derivative Liability	64,785	[1]	57,820	[2]
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Financial assets
Securities available for sale	148,914		144,646
Derivative Asset	0	[1]	0	[2]
Financial liabilities
Junior subordinated debt	0		0
Derivative Liability	0	[1]	0	[2]
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Financial assets
Securities available for sale	1,823,549		1,364,146
Derivative Asset	3,569	[1]	7	[2]
Financial liabilities
Junior subordinated debt	0		0
Derivative Liability	64,785	[1]	57,820	[2]
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Financial assets
Securities available for sale	10,060		11,445
Derivative Asset	0	[1]	0	[2]
Financial liabilities
Junior subordinated debt	46,928		40,437
Derivative Liability	0	[1]	0	[2]
Fair Value, Measurements, Recurring [Member] | Carrying Amount [Member]
Financial assets
Securities available for sale	1,982,523		1,520,237
Securities measured at fair value	1,481		1,858
Derivative Asset	3,569		7
Loans, net	11,017,595		8,288,049
Accrued Investment Income Receivable	54,445		36,705
Financial liabilities
Deposits	12,030,624		8,931,043
Customer repurchases	38,155		54,899
Federal Home Loan Bank Borrowings, Fair Value Disclosure	150,000		307,081
Other borrowed funds			83,182
Junior subordinated debt	210,328		40,437
Derivative Liability	64,785		57,820
Interest Payable, Current	13,626		9,890
Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Financial assets
Securities available for sale	1,982,523		1,520,237
Securities measured at fair value	1,481		1,858
Derivative Asset	3,569		7
Loans, net	10,853,209		8,136,874
Accrued Investment Income Receivable	54,445		36,705
Financial liabilities
Deposits	12,034,199		8,935,566
Customer repurchases	38,155		54,899
Federal Home Loan Bank Borrowings, Fair Value Disclosure	150,000		307,081
Other borrowed funds			86,074
Junior subordinated debt	207,437		40,437
Derivative Liability	64,785		57,820
Interest Payable, Current	13,626		9,890
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Level 1 [Member]
Financial assets
Securities available for sale	148,914		144,646
Securities measured at fair value	0		0
Derivative Asset	0		0
Loans, net	0		0
Accrued Investment Income Receivable	0		0
Financial liabilities
Deposits	0		0
Customer repurchases	0		0
Federal Home Loan Bank Borrowings, Fair Value Disclosure	0		0
Other borrowed funds			0
Junior subordinated debt	0		0
Derivative Liability	0		0
Interest Payable, Current	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Level 2 [Member]
Financial assets
Securities available for sale	1,823,549		1,364,146
Securities measured at fair value	1,481		1,858
Derivative Asset	3,569		7
Loans, net	10,766,826		7,984,692
Accrued Investment Income Receivable	54,445		36,705
Financial liabilities
Deposits	12,034,199		8,935,566
Customer repurchases	38,155		54,899
Federal Home Loan Bank Borrowings, Fair Value Disclosure	150,000		307,081
Other borrowed funds			25,000
Junior subordinated debt	0		0
Derivative Liability	64,785		57,820
Interest Payable, Current	13,626		9,890
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Level 3 [Member]
Financial assets
Securities available for sale	10,060		11,445
Securities measured at fair value	0		0
Derivative Asset	0		0
Loans, net	86,383		152,182
Accrued Investment Income Receivable	0		0
Financial liabilities
Deposits	0		0
Customer repurchases	0		0
Federal Home Loan Bank Borrowings, Fair Value Disclosure	0		0
Other borrowed funds			61,074
Junior subordinated debt	207,437		40,437
Derivative Liability	0		0
Interest Payable, Current	$ 0		$ 0
[1]	Derivative assets and liabilities relate to interest rate swaps, see "Note 13. Derivatives and Hedging Activities." In addition, the carrying value of loans includes a net positive value of $64,184 and the net carrying value of subordinated debt includes a net negative value of $3,569 as of December 31, 2015, which relates to the effective portion of the hedges put in place to mitigate against fluctuations in interest rates.
[2]	Derivative assets and liabilities relate to interest rate swaps, see "Note 13. Derivatives and Hedging Activities." In addition, the carrying value of loans includes a positive value of $57,140 as of December 31, 2014, which relates to the effective portion of the hedges put in place to mitigate against fluctuations in interest rates.

Fair Value Accounting - Additio

Fair Value Accounting - Additional Information (Detail) - USD ($) $ in Thousands, shares in Millions		3 Months Ended	12 Months Ended
		Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate carrying amount of impaired loans	[1]		$ 24,287	$ 124,928
Impaired loans with an allowance recorded	[2]		(4,658)	(10,765)
Repossessed Assets			43,942	57,150	$ 66,719	$ 77,247
Other assets acquired through foreclosure			43,900	57,100
Collateralized debt obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities contained credit losses		0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate carrying amount of impaired loans			24,300	124,900
Impaired loans with an allowance recorded			$ (4,700)	$ (10,800)
Junior Subordinated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Input Value			5.674%	6.242%
Period of basis point spread			5.06%	5.99%
Percentage of LIBOR			0.613%	0.256%
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate carrying amount of impaired loans			$ 19,629	$ 114,163
Repossessed Assets			43,900
Other assets acquired through foreclosure			43,942	57,150
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate carrying amount of impaired loans			19,629	114,163
Other assets acquired through foreclosure			$ 43,942	$ 57,150
[1]	Includes TDR loans of $3.0 million and $103.3 million at December 31, 2015 and 2014, respectively.
[2]	Includes valuation allowance related to TDR loans of $0.3 million and $8.9 million at December 31, 2015 and 2014, respectively.

Regulatory Capital Requireme123

Regulatory Capital Requirements - Summary of Actual Capital Amount and Ratio (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	6.00%
Tier 1 Capital Ratio	6.00%	4.00%
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
Common Equity Tier One Required To Be Well Capitalized	6.50%
Tier 1 Leverage Ratio	4.00%	4.00%
Common Equity Tier One Required For Capital Adequacy	4.50%
Consolidated Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital	$ 1,603,472	$ 1,119,618
Tier 1 Capital	1,341,011	1,007,278
Risk-Weighted Assets	13,193,563	9,555,390
Tangible Average Assets	$ 13,683,148	$ 10,367,575
Capital to Risk Weighted Assets	12.20%	11.70%
Tier One Risk Based Capital to Risk Weighted Assets	10.20%	10.50%
Tier One Leverage Capital to Average Assets	9.80%	9.70%
Common Equity Tier One Risk-Based Capital Ratio	9.70%
Western Alliance Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital	$ 1,485,070	$ 1,057,253
Tier 1 Capital	1,213,304	945,687
Risk-Weighted Assets	13,073,394	9,435,459
Tangible Average Assets	$ 13,561,251	$ 10,232,297
Capital to Risk Weighted Assets	11.40%	11.20%
Tier One Risk Based Capital to Risk Weighted Assets	9.30%	10.00%
Tier One Leverage Capital to Average Assets	9.00%	9.20%
Common Equity Tier One Risk-Based Capital Ratio	9.30%

Goodwill and Other Intangibl124

Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 289,638	$ 23,224
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	8 years 8 months 12 days
Finite-Lived Trade Names, Gross	$ 350	0
Trade Name, Impaired, Accumulated Impairment Loss	0	0
Indefinite-Lived Trade Names	350	0
Finite-Lived Intangible Assets, Net	15,366
Intangible amortization	1,970	1,461	$ 2,388
Nevada [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	23,224
Northern California [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	149,602
Central Business Lines [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	116,811
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	40,804	26,157
Finite-Lived Intangible Assets, Accumulated Amortization	25,438	23,468
Finite-Lived Intangible Assets, Net	$ 15,366	$ 2,689

Segments - Operating Segment In

Segments - Operating Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Statistics [Line Items]
Assets	$ 14,275,089				$ 10,600,498				$ 14,275,089	$ 10,600,498
Cash, Cash Equivalents and Investment Securities	2,266,900				1,712,200				2,266,900	1,712,200
Loans, net of deferred loan fees and costs	11,112,854				8,398,265				11,112,854	8,398,265
Loans, net of deferred loan fees and costs	11,136,663								11,136,663
Less: Allowance for credit losses	(119,068)				(110,216)				(119,068)	(110,216)
Loans, net	10,993,786				8,288,049				10,993,786	8,288,049
Total loans held for investment	11,017,600								11,017,600
Intangible Assets, Net (Including Goodwill)	305,400				25,900				305,400	25,900
Other Assets Segment	641,300				517,200				641,300	517,200
Deposits	12,030,624				8,931,043				12,030,624	8,931,043
Stockholders' equity	1,591,502				1,000,928				1,591,502	1,000,928	$ 855,498	$ 759,421
Net interest income	143,343	$ 137,407	$ 108,718	$ 103,108	102,145	$ 98,073	$ 93,898	$ 90,777	492,576	384,893	332,895
Provision for Loan, Lease, and Other Losses	2,500	0	0	700	300	419	507	3,500	3,200	4,726	13,220
Net interest income (loss) after provision for credit losses	140,843	137,407	108,718	102,408	101,845	97,654	93,391	87,277	489,376	380,167	319,675
Non-interest income	9,479	8,502	5,545	6,242	8,417	6,073	5,599	4,562	29,768	24,651	22,197
Non-interest expense	(72,448)	(72,916)	(61,209)	(54,033)	(55,742)	(49,859)	(52,242)	(49,476)	(260,606)	(207,319)	(196,216)
Income from continuing operations before income taxes	77,874	72,993	53,054	54,617	54,520	53,868	46,748	42,363	258,538	197,499	145,656
Income tax expense (benefit)	19,348	17,133	13,579	14,234	14,111	12,949	10,706	10,624	64,294	48,390	29,830
Income from continuing operations					40,409	40,919	36,042	31,739	194,244	149,109	115,826
Loss from discontinued operations, net					0	0	(504)	(654)	0	(1,158)	(861)
Net income (loss)	58,526	$ 55,860	$ 39,475	$ 40,383	40,409	$ 40,919	$ 35,538	$ 31,085	194,244	147,951	$ 114,965
Other Repossessed Assets	43,900				57,100				43,900	57,100
Other Liabilities Segment	292,700				237,900				292,700	237,900
Liabilities	12,683,587				9,599,570				12,683,587	9,599,570
Liabilities and Equity	14,275,089				10,600,498				14,275,089	10,600,498
Excess Funds Provided (Used) Segment Basis	0				0				0	0
Other borrowings	360,328				430,700				360,328	430,700
Reportable Geographical Components [Member] | ARIZONA
Operating Statistics [Line Items]
Assets	2,836,200				2,363,800				2,836,200	2,363,800
Cash, Cash Equivalents and Investment Securities	2,300				2,300				2,300	2,300
Loans, net of deferred loan fees and costs					2,341,900					2,341,900
Loans, net of deferred loan fees and costs	2,811,700								2,811,700
Less: Allowance for credit losses	(30,100)				(30,700)				(30,100)	(30,700)
Loans, net					2,311,200					2,311,200
Total loans held for investment	2,781,600								2,781,600
Intangible Assets, Net (Including Goodwill)	0				0				0	0
Other Assets Segment	43,900				34,800				43,900	34,800
Deposits	2,880,700				2,178,000				2,880,700	2,178,000
Stockholders' equity	309,200				250,800				309,200	250,800
Net interest income									129,914	112,128
Provision for Loan, Lease, and Other Losses									3,099	2,083
Net interest income (loss) after provision for credit losses									126,815	110,045
Non-interest income									4,204	3,586
Non-interest expense									(59,917)	(54,859)
Income from continuing operations before income taxes									71,102	58,772
Income tax expense (benefit)									27,893	23,053
Income from continuing operations										35,719
Loss from discontinued operations, net										0
Net income (loss)									43,209	35,719
Other Repossessed Assets	8,400				15,500				8,400	15,500
Other Liabilities Segment	12,200				17,400				12,200	17,400
Liabilities	2,892,900				2,195,400				2,892,900	2,195,400
Liabilities and Equity	3,202,100				2,446,200				3,202,100	2,446,200
Excess Funds Provided (Used) Segment Basis	365,900				82,400				365,900	82,400
Other borrowings	0				0				0	0
Reportable Geographical Components [Member] | NEVADA
Operating Statistics [Line Items]
Assets	1,836,000				1,762,900				1,836,000	1,762,900
Cash, Cash Equivalents and Investment Securities	9,500				5,000				9,500	5,000
Loans, net of deferred loan fees and costs					1,668,700					1,668,700
Loans, net of deferred loan fees and costs	1,737,200								1,737,200
Less: Allowance for credit losses	(18,600)				(21,900)				(18,600)	(21,900)
Loans, net					1,646,800					1,646,800
Total loans held for investment	1,718,600								1,718,600
Intangible Assets, Net (Including Goodwill)	24,800				25,900				24,800	25,900
Other Assets Segment	62,300				64,200				62,300	64,200
Deposits	3,382,800				3,230,600				3,382,800	3,230,600
Stockholders' equity	244,400				209,000				244,400	209,000
Net interest income									122,082	117,508
Provision for Loan, Lease, and Other Losses									(6,887)	(7,542)
Net interest income (loss) after provision for credit losses									128,969	125,050
Non-interest income									9,202	8,944
Non-interest expense									(59,553)	(59,683)
Income from continuing operations before income taxes									78,618	74,311
Income tax expense (benefit)									27,516	26,009
Income from continuing operations										48,302
Loss from discontinued operations, net										0
Net income (loss)									51,102	48,302
Other Repossessed Assets	20,800				21,000				20,800	21,000
Other Liabilities Segment	29,000				40,800				29,000	40,800
Liabilities	3,411,800				3,271,400				3,411,800	3,271,400
Liabilities and Equity	3,656,200				3,480,400				3,656,200	3,480,400
Excess Funds Provided (Used) Segment Basis	1,820,200				1,717,500				1,820,200	1,717,500
Other borrowings	0				0				0	0
Reportable Geographical Components [Member] | CALIFORNIA
Operating Statistics [Line Items]
Assets	1,761,200				1,543,600				1,761,200	1,543,600
Cash, Cash Equivalents and Investment Securities	2,400				2,200				2,400	2,200
Loans, net of deferred loan fees and costs					1,553,100					1,553,100
Loans, net of deferred loan fees and costs	1,761,900								1,761,900
Less: Allowance for credit losses	(18,800)				(17,900)				(18,800)	(17,900)
Loans, net					1,535,200					1,535,200
Total loans held for investment	1,743,100								1,743,100
Intangible Assets, Net (Including Goodwill)	0				0				0	0
Other Assets Segment	15,700				6,200				15,700	6,200
Deposits	1,902,500				1,744,500				1,902,500	1,744,500
Stockholders' equity	191,300				70,900				191,300	70,900
Net interest income									94,585	91,090
Provision for Loan, Lease, and Other Losses									152	(1,638)
Net interest income (loss) after provision for credit losses									94,433	92,728
Non-interest income									2,697	3,917
Non-interest expense									(47,549)	(49,764)
Income from continuing operations before income taxes									49,581	46,881
Income tax expense (benefit)									20,849	19,711
Income from continuing operations										27,170
Loss from discontinued operations, net										0
Net income (loss)									28,732	27,170
Other Repossessed Assets	0				0				0	0
Other Liabilities Segment	7,800				8,900				7,800	8,900
Liabilities	1,910,300				1,753,400				1,910,300	1,753,400
Liabilities and Equity	2,101,600				1,824,300				2,101,600	1,824,300
Excess Funds Provided (Used) Segment Basis	340,400				280,700				340,400	280,700
Other borrowings	0				0				0	0
Reportable Geographical Components [Member] | Northern California [Member]
Operating Statistics [Line Items]
Assets					209,100					209,100
Cash, Cash Equivalents and Investment Securities					300					300
Loans, net of deferred loan fees and costs					198,600					198,600
Less: Allowance for credit losses					(5,100)					(5,100)
Loans, net					193,500					193,500
Intangible Assets, Net (Including Goodwill)					0					0
Other Assets Segment					15,300					15,300
Deposits					584,000					584,000
Stockholders' equity					126,800					126,800
Net interest income									56,698	9,133
Provision for Loan, Lease, and Other Losses									3,038	0
Net interest income (loss) after provision for credit losses									53,660	9,133
Non-interest income									5,161	184
Non-interest expense									(30,161)	(3,857)
Income from continuing operations before income taxes									28,660	5,460
Income tax expense (benefit)									12,051	2,296
Income from continuing operations										3,164
Loss from discontinued operations, net										0
Net income (loss)									16,609	3,164
Other Repossessed Assets					0					0
Other Liabilities Segment					200					200
Liabilities					584,200					584,200
Liabilities and Equity					711,000					711,000
Excess Funds Provided (Used) Segment Basis					501,900					501,900
Other borrowings					0					0
Operating Segments [Member] | Central Business Lines
Operating Statistics [Line Items]
Assets	3,710,200				2,578,900				3,710,200	2,578,900
Cash, Cash Equivalents and Investment Securities	0				0				0	0
Loans, net of deferred loan fees and costs					2,590,000					2,590,000
Loans, net of deferred loan fees and costs	3,597,900								3,597,900
Less: Allowance for credit losses	(38,500)				(34,000)				(38,500)	(34,000)
Loans, net					2,556,000					2,556,000
Total loans held for investment	3,559,400								3,559,400
Intangible Assets, Net (Including Goodwill)	122,400				0				122,400	0
Other Assets Segment	28,400				22,900				28,400	22,900
Deposits	2,134,400				946,600				2,134,400	946,600
Stockholders' equity	428,600				232,900				428,600	232,900
Net interest income									124,222	71,010
Provision for Loan, Lease, and Other Losses									3,917	11,365
Net interest income (loss) after provision for credit losses									120,305	59,645
Non-interest income									4,110	1,742
Non-interest expense									(45,831)	(27,804)
Income from continuing operations before income taxes									78,584	33,583
Income tax expense (benefit)									29,469	12,594
Income from continuing operations										20,989
Loss from discontinued operations, net										0
Net income (loss)									49,115	20,989
Other Repossessed Assets	0				0				0	0
Other Liabilities Segment	105,100				72,400				105,100	72,400
Liabilities	2,239,500				1,019,000				2,239,500	1,019,000
Liabilities and Equity	2,668,100				1,251,900				2,668,100	1,251,900
Excess Funds Provided (Used) Segment Basis	(1,042,100)				(1,327,000)				(1,042,100)	(1,327,000)
Other borrowings	0				0				0	0
Operating Segments [Member] | Northern California [Member]
Operating Statistics [Line Items]
Assets	1,352,700								1,352,700
Cash, Cash Equivalents and Investment Securities	2,400								2,400
Loans, net of deferred loan fees and costs	1,188,400								1,188,400
Less: Allowance for credit losses	(12,700)								(12,700)
Total loans held for investment	1,175,700								1,175,700
Intangible Assets, Net (Including Goodwill)	158,200								158,200
Other Assets Segment	16,100								16,100
Deposits	1,541,100								1,541,100
Stockholders' equity	293,200								293,200
Other Repossessed Assets	300								300
Other Liabilities Segment	11,200								11,200
Liabilities	1,552,300								1,552,300
Liabilities and Equity	1,845,500								1,845,500
Excess Funds Provided (Used) Segment Basis	492,800								492,800
Other borrowings	0								0
Corporate & Other
Operating Statistics [Line Items]
Assets	2,778,800				2,142,200				2,778,800	2,142,200
Cash, Cash Equivalents and Investment Securities	2,250,300				1,702,400				2,250,300	1,702,400
Loans, net of deferred loan fees and costs					46,000					46,000
Loans, net of deferred loan fees and costs	39,600								39,600
Less: Allowance for credit losses	(400)				(600)				(400)	(600)
Loans, net					45,400					45,400
Total loans held for investment	39,200								39,200
Intangible Assets, Net (Including Goodwill)	0				0				0	0
Other Assets Segment	474,900				373,800				474,900	373,800
Deposits	189,100				247,300				189,100	247,300
Stockholders' equity	124,800				110,500				124,800	110,500
Net interest income									(34,925)	(15,976)
Provision for Loan, Lease, and Other Losses									(119)	458
Net interest income (loss) after provision for credit losses									(34,806)	(16,434)
Non-interest income									4,394	6,278
Non-interest expense									(17,595)	(11,352)
Income from continuing operations before income taxes									(48,007)	(21,508)
Income tax expense (benefit)									(53,484)	(35,273)
Income from continuing operations										13,765
Loss from discontinued operations, net										(1,158)
Net income (loss)									5,477	12,607
Other Repossessed Assets	14,400				20,600				14,400	20,600
Other Liabilities Segment	127,400				98,200				127,400	98,200
Liabilities	676,800				776,200				676,800	776,200
Liabilities and Equity	801,600				886,700				801,600	886,700
Excess Funds Provided (Used) Segment Basis	(1,977,200)				(1,255,500)				(1,977,200)	(1,255,500)
Other borrowings	$ 360,300				$ 430,700				$ 360,300	$ 430,700

Segments - Additional Informati

Segments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015Subsidiary
Segment Reporting Information [Line Items]
Number of wholly-owned subsidiaries	10

Employee Benefit Plan (Details)

Employee Benefit Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan Initial Percentage Of Discretionary Deferred Compensation	6.00%
Defined Benefit Plan, Contributions by Employer	$ 2,200,000	$ 1,700,000	$ 1,700,000
Defined Contribution Plan Percentage Of Discretionary Deferred Compensation	50.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount	$ 18,000
Defined Contribution Plan Age Of Participants	50 years
Restoration Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Benefit Plan, Contributions by Employer	$ 68,000	$ 77,000	$ 64,000
Minimum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan Initial Percentage Of Discretionary Deferred Compensation	1.00%
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	100.00%

Employee Benefit Plan Accumulat

Employee Benefit Plan Accumulated Benefit Obligation and Funded Status of SERP (Details) - USD ($) $ in Thousands	6 Months Ended
	Dec. 31, 2015	Jun. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Defined Benefit Plan, Benefit Obligation	$ 7,444	$ 7,122
Defined Benefit Plan, Service Cost	334
Defined Benefit Plan, Interest Cost	202
Defined Benefit Plan, Actuarial Gain (Loss)	(147)
Defined Benefit Plan, Benefits Paid	(67)
Defined Benefit Plan, Accumulated Benefit Obligation	$ (7,444)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	5.80%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	4.00%

Employee Benefit Plan Net Perio

Employee Benefit Plan Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2016
Defined Contribution Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	$ 334
Defined Benefit Plan, Interest Cost	202
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	60
Defined Benefit Plan, Amortization of Gains (Losses)	(18)
Defined Benefit Plan, Net Periodic Benefit Cost	578
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax, Portion Attributable to Parent	$ 42
Scenario, Forecast [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost		$ 596
Defined Benefit Plan, Interest Cost		426
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		96
Defined Benefit Plan, Amortization of Gains (Losses)		(96)
Defined Benefit Plan, Net Periodic Benefit Cost		1,022
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax, Portion Attributable to Parent		$ 0

Related Parties (Details)

Related Parties (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Loans and Leases Receivable, Related Parties	$ 74,381	$ 70,570	$ 30,783
Origination of Notes Receivable from Related Parties	10,678	35,341
Loans and Leases Receivable Advances, Related Parties	18,614	23,559
Loans and Leases Receivable Repayments, Related Parties	(25,481)	(19,113)
Related Party Deposit Liabilities	76,000	47,700
Interest Expense, Related Party	100
Related Party Transaction, Expenses from Transactions with Related Party	1,000	2,000
Interest Income, Related Party	2,700	1,900
Loan and Leases Receivable, Commitment Outstanding, Related Parties	$ 164,500	$ 151,800

Parent Company Parent Company B

Parent Company Parent Company Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 224,640	$ 164,396	$ 305,514	$ 204,625
Money Market Funds, at Carrying Value	122	451
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	1,982,523	1,520,237
Loans, net of deferred loan fees and costs	11,112,854	8,398,265
Repossessed Assets	43,942	57,150	66,719	77,247
Other assets	273,976	198,696
Assets	14,275,089	10,600,498
Other borrowings	150,000	390,263
Liabilities	12,683,587	9,599,570
Stockholders' equity	1,591,502	1,000,928	855,498	759,421
Liabilities and Equity	14,275,089	10,600,498
Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and Cash Equivalents, at Carrying Value	7,627	11,855	$ 7,128	$ 15,712
Money Market Funds, at Carrying Value	122	451
Investment securities - AFS, at fair value; amortized cost of $1,966,034 at December 31, 2015 and $1,493,648 at December 31, 2014	50,507	51,335
Investments in and Advance to Bank Subsidiaries	1,522,245	987,882
Investments in and Advance to Non Bank Subsidiaries	2,424	9,827
Loans, net of deferred loan fees and costs	35,635	39,221
Repossessed Assets	14,471	16,318
Other assets	19,378	9,912
Assets	1,652,409	1,126,801
Other borrowings	0	83,182
Accrued Liabilities and Other Liabilities	2,537	2,254
Junior Subordinated Notes	58,370	40,437
Liabilities	60,907	125,873
Stockholders' equity	1,591,502	1,000,928
Liabilities and Equity	$ 1,652,409	$ 1,126,801

Parent Company Parent Company C

Parent Company Parent Company Condensed Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Income Tax Expense (Benefit)	$ 19,348	$ 17,133	$ 13,579	$ 14,234	$ 14,111	$ 12,949	$ 10,706	$ 10,624	$ 64,294	$ 48,390	$ 29,830
Net income (loss)	58,526	55,860	39,475	40,383	40,409	40,919	35,538	31,085	194,244	147,951	114,965
Preferred Stock Dividends and Other Adjustments	151	176	247	176	329	353	352	353	750	1,387	1,410
Net income available to common shareholders	58,375	55,684	39,228	40,207	40,080	40,566	35,186	30,732	193,494	146,564	113,555
Non-interest income	9,479	8,502	5,545	6,242	8,417	6,073	5,599	4,562	29,768	24,651	22,197
Interest Expense	7,988	8,826	7,900	7,854	8,006	7,481	8,075	7,924	32,568	31,486	29,760
Noninterest Expense	72,448	72,916	61,209	54,033	55,742	49,859	52,242	49,476	260,606	207,319	196,216
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	$ 77,874	$ 72,993	$ 53,054	$ 54,617	$ 54,520	$ 53,868	$ 46,748	$ 42,363	258,538	197,499	145,656
Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Investment Income, Dividend									140,900	67,515	71,529
Income Tax Expense (Benefit)									5,876	5,388	21,426
Income Before Equity in Undistributed Earnings of Subsidiaries									133,887	59,395	56,963
Income (Loss) from Subsidiaries, Net of Tax									60,357	88,556	58,002
Net income (loss)									194,244	147,951	114,965
Preferred Stock Dividends and Other Adjustments									750	1,387	1,410
Net income available to common shareholders									193,494	146,564	113,555
Interest Income, Other									4,593	4,381	2,847
Non-interest income									586	1,235	3,995
Revenues									146,079	73,131	78,371
Interest Expense									6,671	8,776	10,833
Noninterest Expense									11,397	10,348	32,001
Operating Expenses									18,068	19,124	42,834
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									$ 128,011	$ 54,007	$ 35,537

Parent Company Parent Compan133

Parent Company Parent Company Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ 58,526	$ 55,860	$ 39,475	$ 40,383	$ 40,409	$ 40,919	$ 35,538	$ 31,085	$ 194,244	$ 147,951	$ 114,965
Excess tax benefit of stock-based compensation									(5,874)	(4,194)	(1,552)
Gains (Losses) on Extinguishment of Debt									(81)	(502)	(1,387)
Net Cash Provided by (Used in) Operating Activities									212,812	163,289	165,049
Principal pay downs and maturities									347	1,144	1,881
Proceeds from Sale (Payments to Purchase) Investment In Money Market									330	2,181	(1,968)
Net Cash Provided by (Used in) Investing Activities									(1,366,443)	(1,386,013)	(1,173,342)
Excess tax benefit of stock-based compensation									5,874	4,194	1,552
Proceeds from Issuance of Common Stock									28,288	13,746	0
Proceeds from exercise of common stock options									1,935	8,294	4,595
Net Cash Provided by (Used in) Financing Activities									1,213,875	1,081,606	1,109,182
Cash and Cash Equivalents, Period Increase (Decrease)									60,244	(141,118)	100,889
Cash and Cash Equivalents, at Carrying Value	224,640				164,396				224,640	164,396	305,514	$ 204,625
Interest									28,831	26,516	28,613
Income taxes									54,590	35,556	19,105
Change in unrealized gain on AFS securities, net of tax									(6,502)	29,209	0
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Subordinated Debt									(4,276)	0	0
Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									194,244	147,951	114,965
Income (Loss) from Subsidiaries, Net of Tax									(60,357)	(88,556)	(58,002)
Excess tax benefit of stock-based compensation									(1,945)	(4,194)	(1,552)
Change in Unrealized Gains Losses on Trust Preferred Securities									0	(1,421)	5,640
Gains (Losses) on Extinguishment of Debt									0	502	1,387
Other Operating Activities, Cash Flow Statement									(4,734)	(20,040)	(4,011)
Net Cash Provided by (Used in) Operating Activities									127,208	34,242	58,427
Payments to Acquire Marketable Securities									0	(23,431)	(2,044)
Principal pay downs and maturities									2,358	8,376	6,767
Proceeds From Sale Of Other Repossessed Assets Net									4,138	9,610	9,844
Payments to Acquire Interest in Subsidiaries and Affiliates									0	0	(40,000)
Loan fundings and principal collections, net									3,704	3,286	(35,979)
Proceeds from Sale (Payments to Purchase) Investment In Money Market									330	2,181	(1,968)
Payments to Acquire Productive Assets									0	617	(481)
Proceeds from Divestiture of Businesses									(19,440)	0	0
Net Cash Provided by (Used in) Investing Activities									(8,910)	639	(63,861)
Proceeds from Other Debt									0	22,000	3,000
Excess tax benefit of stock-based compensation									1,945	4,194	1,552
Repayments of Other Debt									(83,444)	(6,501)	(10,887)
Proceeds from Issuance of Common Stock									28,288	13,746	0
Proceeds from exercise of common stock options									1,935	8,294	4,595
Payments for Repurchase of Preferred Stock and Preference Stock									(70,500)	(70,500)	0
Payments of Dividends									(750)	(1,387)	(1,410)
Net Cash Provided by (Used in) Financing Activities									(122,526)	(30,154)	(3,150)
Cash and Cash Equivalents, Period Increase (Decrease)									(4,228)	4,727	(8,584)
Cash and Cash Equivalents, at Carrying Value	$ 7,627				$ 11,855				7,627	11,855	7,128	$ 15,712
Interest									4,235	9,067	11,091
Income taxes									54,590	32,238	19,105
Change in unrealized gain on AFS securities, net of tax									1,199	2,031	2,450
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Subordinated Debt									$ (4,276)	$ 0	$ 0

Quarterly Financial Data (Detai

Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Data Disclosure [Abstract]
Interest and Dividend Income, Operating	$ 151,331	$ 146,233	$ 116,618	$ 110,962	$ 110,151	$ 105,554	$ 101,973	$ 98,701	$ 525,144	$ 416,379	$ 362,655
Interest Expense	7,988	8,826	7,900	7,854	8,006	7,481	8,075	7,924	32,568	31,486	29,760
Interest Income (Expense), Net	143,343	137,407	108,718	103,108	102,145	98,073	93,898	90,777	492,576	384,893	332,895
Provision for Loan, Lease, and Other Losses	2,500	0	0	700	300	419	507	3,500	3,200	4,726	13,220
Interest Income (Expense), after Provision for Loan Loss	140,843	137,407	108,718	102,408	101,845	97,654	93,391	87,277	489,376	380,167	319,675
Non-interest income	9,479	8,502	5,545	6,242	8,417	6,073	5,599	4,562	29,768	24,651	22,197
Non-interest expense	(72,448)	(72,916)	(61,209)	(54,033)	(55,742)	(49,859)	(52,242)	(49,476)	(260,606)	(207,319)	(196,216)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	77,874	72,993	53,054	54,617	54,520	53,868	46,748	42,363	258,538	197,499	145,656
Income Tax Expense (Benefit)	19,348	17,133	13,579	14,234	14,111	12,949	10,706	10,624	64,294	48,390	29,830
Income (Loss) from Continuing Operations Attributable to Parent					40,409	40,919	36,042	31,739	194,244	149,109	115,826
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent					0	0	(504)	(654)	0	(1,158)	(861)
Net income (loss)	58,526	55,860	39,475	40,383	40,409	40,919	35,538	31,085	194,244	147,951	114,965
Preferred Stock Dividends and Other Adjustments	151	176	247	176	329	353	352	353	750	1,387	1,410
Net income available to common shareholders	$ 58,375	$ 55,684	$ 39,228	$ 40,207	$ 40,080	$ 40,566	$ 35,186	$ 30,732	$ 193,494	$ 146,564	$ 113,555
Earnings Per Share, Basic	$ 0.58	$ 0.55	$ 0.44	$ 0.46	$ 0.46	$ 0.47	$ 0.41	$ 0.35	$ 2.05	$ 1.69	$ 1.33
Earnings Per Share, Diluted	$ 0.57	$ 0.55	$ 0.44	$ 0.45	$ 0.46	$ 0.46	$ 0.40	$ 0.35	$ 2.03	$ 1.67	$ 1.31