Pacwest Bancorp (PACW) 10-K 1 Mar 18 2017 Q4 Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 23, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	PACWEST BANCORP
Entity Central Index Key	1,102,112
Document Period End Date	Dec. 31, 2017
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q4
Amendment Flag	false
Entity Common Stock, Shares Outstanding		125,777,985
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 5,663,703,829

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
ASSETS:
Cash and due from banks	$ 233,215	$ 337,965
Interest-earning deposits in financial institutions	165,222	81,705
Total cash and cash equivalents	398,437	419,670
Securities available-for-sale, at fair value	3,774,431	3,223,830
Federal Home Loan Bank stock, at cost	20,790	21,870
Total investment securities	3,795,221	3,245,700
Loans held for sale, at lower of cost or fair value	481,100	0
Gross loans and leases held for investment	17,032,221	15,520,537
Deferred fees, net	(59,478)	(64,583)
Allowance for loan and lease losses	(139,456)	(157,238)
Total loans and leases held for investment, net	16,833,287	15,298,716
Equipment leased to others under operating leases	284,631	229,905
Premises and equipment, net	31,852	38,594
Foreclosed assets, net	1,329	12,976
Deferred tax asset, net	0	94,112
Goodwill	2,548,670	2,173,949
Core deposit and customer relationship intangibles, net	79,626	36,366
Other assets	540,723	319,779
Total assets	24,994,876	21,869,767
LIABILITIES:
Noninterest-bearing deposits	8,508,044	6,659,016
Interest-bearing deposits	10,357,492	9,211,595
Total deposits	18,865,536	15,870,611
Borrowings	467,342	905,812
Subordinated debentures	462,437	440,744
Accrued interest payable and other liabilities	221,963	173,545
Total liabilities	20,017,278	17,390,712
Commitments and contingencies
STOCKHOLDERS' EQUITY:
Preferred stock ($0.01 par value; 5,000,000 shares authorized; none issued and outstanding)	0	0
Common stock ($0.01 par value, 200,000,000 shares authorized at December 31, 2017 and 2016; 130,491,108 and 122,803,029 shares issued, respectively, includes 1,436,120 and 1,476,132 shares of unvested restricted stock, respectively)	1,305	1,228
Additional paid-in capital	4,287,487	4,162,132
Retained earnings	723,471	366,073
Treasury stock, at cost (1,708,230 and 1,519,360 shares at December 31, 2017 and 2016)	(65,836)	(56,360)
Accumulated other comprehensive income, net	31,171	5,982
Total stockholders' equity	4,977,598	4,479,055
Total liabilities and stockholders' equity	$ 24,994,876	$ 21,869,767

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred Stock, Shares Authorized	$ 0.01	$ 0.01
Preferred Stock, Value, Outstanding	5,000,000	5,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common Stock, Shares, Issued, Acquisitions		122,803,029
Equity Instruments Other than Options, Nonvested, Number	1,436,120	1,476,132
Treasury Stock, Shares		1,519,360

Consolidated Statements of Earn

Consolidated Statements of Earnings - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income:
Loans and leases	$ 952,771	$ 924,294	$ 819,094
Investment securities	98,202	90,557	64,368
Deposits in financial institutions	1,543	1,061	476
Total interest income	1,052,516	1,015,912	883,938
Interest expense:
Deposits	45,694	31,512	41,503
Borrowings	3,638	2,259	554
Subordinated debentures	23,613	20,850	18,535
Total interest expense	72,945	54,621	60,592
Net interest income	979,571	961,291	823,346
Provision for credit losses	57,752	65,729	45,481
Net interest income after provision for credit losses	921,819	895,562	777,865
Noninterest income:
Service charges on deposit accounts	15,307	14,534	11,688
Other commissions and fees	41,422	47,126	31,586
Leased equipment income	37,700	33,919	24,023
Gain on sale of loans and leases	6,197	909	373
(Loss) gain on sale of securities	(541)	9,485	3,744
FDIC loss sharing expense, net	0	(8,917)	(18,246)
Other income	28,488	15,419	31,142
Total noninterest income	128,573	112,475	84,310
Noninterest expense:
Compensation	266,567	251,913	203,914
Occupancy	48,863	48,911	44,144
Data processing	26,575	24,356	18,617
Other professional services	17,353	16,478	13,760
Insurance and assessments	19,733	18,364	16,996
Intangible asset amortization	14,240	16,517	9,410
Leased equipment depreciation	20,767	20,899	13,603
Foreclosed assets expense (income), net	1,702	1,881	(668)
Acquisition, integration and reorganization costs	19,735	200	21,247
Loan expense	13,832	9,371	6,064
Other expense	46,294	41,211	34,952
Total noninterest expense	495,661	450,101	382,039
Earnings before income taxes	554,731	557,936	480,136
Income tax expense	(196,913)	(205,770)	(180,517)
Net earnings	$ 357,818	$ 352,166	$ 299,619
Earnings Per Share, Basic (usd per share)	$ 2.91	$ 2.90	$ 2.79
Diluted income per share (usd per share)	2.91	2.90	2.79
Dividends declared per share (usd per share)	$ 2	$ 2	$ 2

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net earnings		$ 357,818	$ 352,166	$ 299,619
arising during the year		42,190	(27,392)	6,490
arising during the year		(17,481)	11,148	(2,869)
Unrealized net holding gains (losses) on securities available-for-sale, net of tax		24,709	(16,244)	3,621
Reclassification adjustment for net losses (gains) included in net earnings (1)	[1]	541	(9,485)	(3,744)
Income tax (benefit) expense related to reclassification adjustment		(61)	3,883	1,571
net of tax		480	(5,602)	(2,173)
Other comprehensive income (loss), net of tax		25,189	(21,846)	1,448
Comprehensive income		$ 383,007	$ 330,320	$ 301,067
[1]	Entire amount recognized in "(Loss) gain on sale of securities" on the Consolidated Statements of Earnings.

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity - USD ($)		Total	Common Stock [Member]	Shares Of Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Shares, Outstanding at Dec. 31, 2014			103,022,017
Total stockholders' equity at Dec. 31, 2014		$ 3,506,230,000	$ 1,042,000		$ 3,807,167,000	$ (285,712,000)	$ (42,647,000)	$ 26,380,000
Net Income		299,619,000				299,619,000
available-for-sale, net of tax		1,448,000						1,448,000
Stock Issued During Period, Shares, Acquisitions			18,135,845
Issuance of common stock for merger with CapitalSource Inc.		797,433,000	$ 181,000		797,252,000	0	0	0
Restricted stock awarded and earned stock compensation, net of shares forfeited, shares			435,387
net of shares forfeited		15,630,000	$ 5,000		15,625,000
Restricted stock surrendered, shares			(180,822)
Stock Repurchase Program		(8,400,000)					(8,400,000)
Dividend reinvestment, shares			1,300
Dividend reinvestment		58,000			58,000
restricted stock		841,000			841,000
Cash dividends paid		(215,168,000)			(215,168,000)
Total stockholders' equity at Dec. 31, 2015		4,397,691,000	$ 1,228,000		4,405,775,000	13,907,000	(51,047,000)	27,828,000
Shares, Outstanding at Dec. 31, 2015			121,413,727
Net Income		352,166,000				352,166,000
available-for-sale, net of tax		(21,846,000)						(21,846,000)
Restricted stock awarded and earned stock compensation, net of shares forfeited, shares			664,135
net of shares forfeited		$ 23,319,000	$ 7,000		23,312,000
Restricted stock surrendered, shares			(141,358)	(652,835)
Stock Repurchase Program, Number of Shares Authorized to be Repurchased		(7,000)
Stock Repurchase Program		$ (5,313,000)					(5,313,000)
Common Stock Repurchased Under Stock Repurchase Program, Amount Repurchased		(27,931,000)			(27,924,000)		0
restricted stock		4,406,000			4,406,000
Cash dividends paid		(243,437,000)			(243,437,000)
Total stockholders' equity at Dec. 31, 2016		4,479,055,000	$ 1,228,000		4,162,132,000	366,073,000	(56,360,000)	5,982,000
Shares, Outstanding at Dec. 31, 2016			121,283,669
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	[1]	291,000			711,000	(420,000)
Net Income		357,818,000				357,818,000
available-for-sale, net of tax		25,189,000						25,189,000
Stock Issued During Period, Shares, Acquisitions			9,298,451
Issuance of common stock for merger with CapitalSource Inc.		446,233,000	$ 93,000		446,140,000	0	0	0
Restricted stock awarded and earned stock compensation, net of shares forfeited, shares			470,855
net of shares forfeited		$ 25,568,000	$ 5,000		25,563,000
Restricted stock surrendered, shares			(188,870)	(2,081,227)
Stock Repurchase Program, Number of Shares Authorized to be Repurchased		(21,000)
Stock Repurchase Program		$ (9,476,000)					(9,476,000)
Common Stock Repurchased Under Stock Repurchase Program, Amount Repurchased		(99,677,000)			(99,656,000)		0
Cash dividends paid		(247,403,000)			(247,403,000)
Total stockholders' equity at Dec. 31, 2017		$ 4,977,598,000	$ 1,305,000		$ 4,287,487,000	723,471,000	$ (65,836,000)	$ 31,171,000
Shares, Outstanding at Dec. 31, 2017			128,782,878
Cumulative Effect of New Accounting Principle in Period of Adoption						$ (420,000)
[1]	Impact due to adoption on January 1, 2017 of ASU 2016-09, "Improvements to Employee Share-Based Payment Accounting."

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net earnings	$ 357,818	$ 352,166	$ 299,619
Depreciation and amortization	32,029	32,884	24,885
Accretion (Amortization) of Discounts and Premiums, Investments	41,450	39,797	19,675
Intangible asset amortization	14,240	16,517	9,410
Provision for credit losses	57,752	65,729	45,481
Gain on sale of foreclosed assets, net	(871)	(837)	(2,967)
Provision for losses on foreclosed assets	2,138	2,576	5,228
Gain on sale of loans and leases, net	(6,197)	(909)	(373)
(Gain) loss on sale of premises and equipment	(386)	78	(28)
Loss (gain) on sale of securities, net	541	(9,485)	(3,744)
Gain (Loss) on Sale of Insurance Block	(1,050)	(539)	0
Unrealized gain on derivatives and foreign currencies, net	(429)	(202)	(160)
Earned stock compensation	25,568	23,319	15,630
Gain (Loss) on Sale of Capital Leases, Net	0	720	0
Decrease in deferred income taxes, net	76,860	53,556	149,664
Tax effect included in stockholders' equity of restricted stock vesting	0	(4,406)	(841)
(Increase) decrease in other assets	(118,477)	6,441	48,172
Increase (decrease) in accrued interest payable and other liabilities	2,982	3,702	(15,773)
Net cash provided by operating activities	483,968	581,107	593,878
Cash flows from investing activities:
Cash acquired in acquisitions, net of cash consideration paid	160,318	0	260,936
Proceeds (Net Cash Used) From Branch Sale	0	(178,792)	0
Net increase in loans and leases	(1,303,752)	(1,257,734)	(1,105,925)
Proceeds from sales of loans and leases	1,322,456	121,053	31,993
Proceeds from maturities and paydowns of securities available-for-sale	435,925	250,170	144,847
Proceeds from sales of securities available-for-sale	759,300	393,509	1,035,926
Purchases of securities available-for-sale	(1,298,105)	(375,261)	(992,680)
Net redemptions (purchases) of Federal Home Loan Bank stock	12,982	(2,160)	23,686
Proceeds from sales of foreclosed assets	12,345	8,186	32,812
Purchases of premises and equipment, net	(7,919)	(8,183)	(8,929)
Proceeds from sales of premises and equipment	10,309	24	146
Proceeds from Sale and Collection of Lease Receivables	0	138,955	0
Proceeds from Life Insurance Policy	2,478	3,238	0
Net increase in equipment leased to others under operating leases	(73,596)	(51,557)	(65,309)
Net cash provided by (used in) investing activities	32,741	(958,552)	(642,497)
Cash flows from financing activities:
Net increase in noninterest-bearing deposits	343,663	490,997	685,742
Net decrease in interest-bearing deposits	(63,700)	(104,021)	(569,706)
Net (decrease) increase in borrowings	(461,349)	285,928	238,512
Common stock repurchased and restricted stock surrendered	(109,153)	(33,244)	(8,400)
Tax effect of restricted stock vesting included in stockholders' equity	0	4,406	841
Cash dividends paid, net	(247,403)	(243,437)	(215,110)
Net cash (used in) provided by financing activities	(537,942)	400,629	131,879
Net (decrease) increase in cash and cash equivalents	(21,233)	23,184	83,260
Cash and cash equivalents, beginning of year	419,670	396,486	313,226
Cash and cash equivalents, end of year	398,437	419,670	396,486
Supplemental disclosures of cash flow information:
Cash paid for interest	69,477	54,389	65,868
Cash paid for income taxes	208,066	133,897	16,602
Real Estate Owned, Transfer to Real Estate Owned	580	781
Loans transferred to foreclosed assets		781	13,472
Transfer of Portfolio Loans and Leases to Held-for-sale	481,100	0	0
Partnership interest transferred to equipment leased to others under operating leases	0	0	20,833
Common stock issued in acquisitions	$ 446,233	$ 0	$ 797,433

Organization

Organization	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations and Summary of Significant Accounting Policies	NOTE 1. NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES PacWest Bancorp, a Delaware corporation, is a bank holding company registered under the BHCA, with our corporate headquarters located in Beverly Hills, California. Our principal business is to serve as the holding company for our wholly-owned subsidiary, Pacific Western Bank. References to "Pacific Western" or the "Bank" refer to Pacific Western Bank together with its wholly-owned subsidiaries. References to "we," "us," or the "Company" refer to PacWest Bancorp together with its subsidiaries on a consolidated basis. When we refer to "PacWest" or to the "holding company," we are referring to PacWest Bancorp, the parent company, on a stand-alone basis. We are focused on relationship-based business banking to small, middle-market, and venture-backed businesses nationwide. The Bank offers a broad range of loan and lease and deposit products and services through 76 full-service branches located throughout the State of California, one branch located in Durham, North Carolina, and loan production offices located in cities across the country. We provide commercial banking services, including real estate, construction, and commercial loans, and comprehensive deposit and treasury management services to small and middle-market businesses. We offer additional products and services through our CapitalSource and Square 1 Bank divisions. Our CapitalSource Division provides asset-based, real estate, equipment, and cash flow loans and treasury management services to established middle market businesses on a national basis. Our Square 1 Bank Division offers a comprehensive suite of financial services focused on entrepreneurial businesses and their venture capital and private equity investors, with offices located in key innovation hubs across the United States. In addition, we provide investment advisory and asset management services to select clients through Square 1 Asset Management, Inc., a wholly-owned subsidiary of the Bank and a SEC-registered investment adviser. We generate our revenue primarily from interest received on loans and leases and, to a lesser extent, from interest received on investment securities, and fees received in connection with deposit services, extending credit and other services offered, including treasury management and investment management services. Our major operating expenses are the interest paid by the Bank on deposits and borrowings, compensation and general operating expenses. We completed 29 acquisitions from May 1, 2000 through December 31, 2017 , including the acquisitions of CUB on October 20, 2017 and Square 1 on October 6, 2015 . Our acquisitions were accounted for using the acquisition method of accounting and, accordingly, the operating results of the acquired entities were included in the consolidated financial statements from their respective acquisition dates. See Note 3. Acquisitions for more information about the CUB and Square 1 acquisitions. In the fourth quarter of 2017, we sold $1.5 billion of cash flow loans and exited our CapitalSource Division origination operations related to general, technology, and healthcare cash flow loans. As of December 31, 2017, $1.0 billion of the loans sold had settled while $481.1 million were classified as held for sale. The sales of the loans held for sale at December 31, 2017 settled in the first quarter of 2018. (a) Accounting Standards Adopted in 2017 Effective January 1, 2017, the Company adopted ASU 2016-09, " Improvements to Employee Share-Based Accounting ." ASU 2016-09 changed aspects of the accounting for share-based payment award transactions, including: (1) accounting for income taxes; (2) classification of excess tax benefits on the statement of cash flows; (3) forfeitures; (4) minimum statutory tax withholding requirements; and (5) classification of employee taxes paid on the statement of cash flows when an employer withholds shares for tax-withholding purposes. The recognition of excess tax benefits and tax deficiencies in the income statement was adopted prospectively. Income tax benefits of $1.5 million were recognized during the year ended December 31, 2017 as a result of the adoption of ASU 2016-09. We expect the requirements of ASU 2016-09 to result in fluctuations in our effective tax rate from period to period based upon the timing of share-based award vestings. In connection with the adoption of ASU 2016-09, we elected to recognize forfeitures on stock-based compensation awards when they occur, instead of estimating forfeitures at the grant date of the awards and throughout the vesting period. The modified retrospective application of this change in accounting principle resulted in a cumulative adjustment charge to retained earnings of $420,000 , net of income taxes. We elected to present the classification of excess tax benefits on the statement of cash flows using a prospective transition method and the prior period has not been adjusted. Effective July 1, 2017, the Company early-adopted ASU 2017-08, " Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities ." ASU 2017-08 requires certain premiums on callable debt securities to be amortized to the earliest call date. The amortization period for discounts on callable debt securities was not impacted. The adoption of this ASU had no material impact on the Company's consolidated financial position, results of operations, or cash flows. (b) Basis of Presentation The accounting and reporting policies of the Company are in accordance with U.S. generally accepted accounting principles, which we may refer to as U.S. GAAP. In the opinion of management, all significant intercompany accounts and transactions have been eliminated and adjustments, consisting solely of normal recurring accruals and considered necessary for the fair presentation of financial statements have been included. (c) Use of Estimates We have made a number of estimates and assumptions relating to the reporting of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period to prepare these consolidated financial statements in conformity with U.S. GAAP. Actual results could differ from those estimates. Material estimates subject to change in the near term include, among other items, the allowance for credit losses, the carrying value of intangible assets, the fair value estimates of assets acquired and liabilities assumed in acquisitions and the realization of deferred tax assets/liabilities. These estimates may be adjusted as more current information becomes available, and any adjustment may be significant. As described in Note 3. Acquisitions below, we completed the CUB acquisition on October 20, 2017 and the Square 1 acquisition on October 6, 2015 . The acquired assets and liabilities in each of these acquisitions were measured at their estimated fair values. Management made significant estimates and exercised significant judgment in estimating such fair values and accounting for the acquired assets and assumed liabilities in each of these transactions. (d) Reclassifications Certain prior period amounts have been reclassified to conform to the current period’s presentation format. On the consolidated statements of earnings a new line is presented for "Loan expense," as that category exceeded the disclosure materiality threshold in 2017, which previously had been included as part of "Other expense." Included in loan expense are legal fees and other costs related to servicing our loans. Prior to 2017, time deposits disclosures were presented as: (1) under $100,000 , and (2) $100,000 or more. We are now using the current FDIC insurance limit of $250,000 and presenting the categories as: (1) $250,000 and under, and (2) over $250,000 . (e) Cash and Cash Equivalents For purposes of the consolidated statements of cash flows, cash and cash equivalents consist of: (1) cash and due from banks, and (2) interest‑earning deposits in financial institutions. Interest‑earning deposits in financial institutions represent mostly cash held at the FRBSF, the majority of which is immediately available. (f) Investment Securities We determine the classification of securities at the time of purchase. If we have the intent and the ability at the time of purchase to hold securities until maturity, they are classified as held‑to‑maturity. Investment securities held‑to‑maturity are stated at amortized cost. Securities to be held for indefinite periods of time, but not necessarily to be held‑to‑maturity or on a long‑term basis, are classified as available‑for‑sale and carried at estimated fair value, with unrealized gains or losses reported as a separate component of stockholders’ equity in accumulated other comprehensive income, net of applicable income taxes. Securities available‑for‑sale include securities that management intends to use as part of its asset/liability management strategy and that may be sold in response to changes in interest rates, prepayment risk, and other related factors. Securities are individually evaluated for appropriate classification when acquired. As a result, similar types of securities may be classified differently depending on factors existing at the time of purchase. The carrying values of all securities are adjusted for amortization of premiums and accretion of discounts using the interest method. Premiums on callable securities are amortized to the earliest call date. Realized gains or losses on the sale of securities, if any, are determined using the amortized cost of the specific securities sold. Declines in the fair value of debt securities classified as available-for-sale are reviewed to determine whether the impairment is other-than-temporary. This review considers a number of factors, including the severity of the decline in fair value, current market conditions, historical performance of the security, risk ratings and the length of time the security has been in an unrealized loss position. If we do not expect to recover the entire amortized cost basis of the security, then an other-than-temporary impairment is considered to have occurred. The cost basis of the security is written down to its estimated fair value and the amount of the write‑down is recognized through a charge to earnings. Investments in FHLB stock are carried at cost and evaluated regularly for impairment. FHLB stock is expected to be redeemed at par and is a required investment based on measurements of the Bank’s assets and/or borrowing levels. (g) Loans and Leases Originated loans. Loans are originated by the Company with the intent to hold them for investment and are stated at the principal amount outstanding, net of unearned income. Unearned income includes deferred unamortized nonrefundable loan fees and direct loan origination costs. Net deferred fees or costs are recognized as an adjustment to interest income over the contractual life of the loans using the effective interest method or taken into income when the related loans are paid off or sold. The amortization of loan fees or costs is discontinued when a loan is placed on nonaccrual status. Interest income is recorded on an accrual basis in accordance with the terms of the respective loan. Purchased loans. Purchased loans are stated at the principal amount outstanding, net of unearned discounts or unamortized premiums. All loans acquired in our acquisitions are initially measured and recorded at their fair value on the acquisition date. A component of the initial fair value measurement is an estimate of the credit losses over the life of the purchased loans. Purchased loans are also evaluated for impairment as of the acquisition date and are accounted for as “acquired non‑impaired” or “purchased credit impaired” loans. Acquired non‑impaired loans. Acquired non‑impaired loans are those loans for which there was no evidence of credit deterioration at their acquisition date and it was probable that we would be able to collect all contractually required payments. Acquired non‑impaired loans, together with originated loans, are referred to as Non‑PCI loans. Purchase discounts or premiums on acquired non‑impaired loans are recognized as an adjustment to interest income over the contractual life of such loans using the effective interest method or taken into income when the related loans are paid off or sold. Purchased credit impaired loans. PCI loans are accounted for in accordance with ASC Subtopic 310‑30, “ Loans and Debt Securities Acquired with Deteriorated Credit Quality.” A purchased loan is deemed to be credit impaired when there is evidence of credit deterioration since its origination and it is probable at the acquisition date that collection of all contractually required payments is unlikely. We apply PCI loan accounting when we acquire loans deemed to be impaired, and as a general policy election when we acquire a portfolio of loans in a distressed bank acquisition. For PCI loans, at the time of acquisition we (i) calculated the contractual amount and timing of undiscounted principal and interest payments (the “undiscounted contractual cash flows”) and (ii) estimated the amount and timing of undiscounted expected principal and interest payments (the “undiscounted expected cash flows”). The difference between the undiscounted contractual cash flows and the undiscounted expected cash flows is the nonaccretable difference. The nonaccretable difference represents an estimate of the loss exposure of principal and interest related to the PCI loan portfolios; such amount is subject to change over time based on the performance of such loans. The carrying value of PCI loans is reduced by payments received, both principal and interest, and increased by the portion of the accretable yield recognized as interest income. The excess of the undiscounted expected cash flows at acquisition over the initial fair value of acquired impaired loans is referred to as the “accretable yield” and is recorded as interest income over the estimated life of the loans using the effective yield method if the timing and amount of the future cash flows is reasonably estimable. PCI loans that are contractually past due are still considered to be accruing and performing as long as there is an expectation that the estimated cash flows will be received. If the timing and amount of cash flows is uncertain, then recognition of interest income will be suspended. All cash payments received will be recognized as a reduction of the recorded investment until satisfied. Cash payments received in excess of the recorded investment will be recorded as interest income on a cash basis. As part of the fair value process and the subsequent accounting, the Company aggregates PCI loans into pools having common credit risk characteristics such as type and risk rating. Increases in expected cash flows over those previously estimated increase the accretable yield and are recognized as interest income prospectively. Decreases in the amount and changes in the timing of expected cash flows compared to those previously estimated decrease the accretable yield and usually result in a provision for loan losses and the establishment of an allowance for loan losses. As the accretable yield increases or decreases from changes in cash flow expectations, the offset is a decrease or increase to the nonaccretable difference. The accretable yield is measured at each financial reporting date based on information then currently available and represents the difference between the remaining undiscounted expected cash flows and the current carrying value of the loans. Leases. We provide equipment financing to our customers through a variety of lease arrangements. For direct financing leases, lease receivables are recorded on the balance sheet but the leased property is not, although we generally retain legal title to the leased property until the end of each lease. Direct financing leases are stated at the net amount of minimum lease payments receivable, plus any unguaranteed residual value, less the amount of unearned income and net acquisition discount at the reporting date. Direct lease origination costs are amortized using the effective interest method over the life of the leases. Leases acquired in an acquisition are initially measured and recorded at their fair value on the acquisition date. Purchase discount or premium on acquired leases is recognized as an adjustment to interest income over the contractual life of the leases using the effective interest method or taken into income when the related leases are paid off. Direct financing leases are subject to our allowance for loans and leases. We also have operating leases where we purchase equipment which is then leased to our customers. We receive periodic rental income payments, which are recorded as "Noninterest income" in the consolidated statements of earnings, and the equipment remains on our balance sheet and is depreciated according to our fixed asset accounting policy. Loans and leases held for sale. As part of our management of the loans and leases held in our portfolio, on occasion we will transfer loans from held for investment to held for sale. Upon transfer, any associated allowance for loan and lease loss is charged off and the carrying value of the loan is adjusted to the lower of cost or estimated fair value. The net deferred fees and costs associated with loans held for sale are deferred (not accreted or amortized to interest income) until the related loans are sold. Gains or losses on the sale of these loans are recorded as "Noninterest income" in the consolidated statements of earnings. Delinquent or past due loans and leases. Loans and leases are considered delinquent when principal or interest payments are past due 30 days or more; delinquent loans may remain on accrual status between 30 days and 89 days past due. Nonaccrual loans and leases. When we discontinue the accrual of interest on a loan or lease it is designated as nonaccrual. We discontinue the accrual of interest on a loan generally when principal or interest payments are past due 90 days or when, in the opinion of management, there is a reasonable doubt as to collectability in the normal course of business. Loans with interest or principal past due 90 days may be accruing if the loans are concluded to be well-secured and in the process of collection; however, these loans are still reported as nonperforming loans. When loans are placed on nonaccrual status, all interest previously accrued but not collected is reversed against current period interest income. Income on nonaccrual loans is subsequently recognized only to the extent that cash is received and the loan’s principal balance is deemed collectable. Loans are restored to accrual status when the loans become both well‑secured and are in the process of collection. Leases are designated as nonaccrual leases when the recognition of interest has been discontinued. The recognition of interest on leases is generally discontinued when a lessee’s payments are past due 90 days or when, in the opinion of management, there is a reasonable doubt as to collectability. Leases with payments past due 90 days may be accruing if the leases are concluded to be well-secured and in the process of collection; however, these leases are still reported as nonperforming leases. Interest on nonaccrual leases is subsequently recognized only to the extent that cash is received and the lease balance is deemed collectable. Leases are restored to accrual status when the leases become both well-secured and are in the process of collection. Impaired loans and leases. A loan or lease is considered impaired when it is probable that we will be unable to collect all amounts due according to the contractual terms of the loan or lease agreement. Impaired loans and leases include loans and leases on nonaccrual status and performing troubled debt restructured loans. Income from impaired loans is recognized on an accrual basis unless the loan is on nonaccrual status. Income from loans on nonaccrual status is recognized to the extent cash is received and when the loan’s principal balance is deemed collectable. We measure impairment of a loan or lease by using the estimated fair value of the collateral, less estimated costs to sell and other applicable costs, if the loan or lease is collateral‑dependent and the present value of the expected future cash flows discounted at the loan’s or lease’s effective interest rate if the loan or lease is not collateral‑dependent. The impairment amount on a collateral‑dependent loan or lease is charged‑off, and the impairment amount on a loan that is not collateral‑dependent is generally recorded as a specific reserve. Troubled debt restructurings. A loan is classified as a troubled debt restructuring when we grant a concession to a borrower experiencing financial difficulties that we otherwise would not consider under our normal lending policies. These concessions may include a reduction of the interest rate, principal or accrued interest, extension of the maturity date or other actions intended to minimize potential losses. All modifications of criticized loans are evaluated to determine whether such modifications are troubled debt restructurings as outlined under ASC Subtopic 310‑40, “Troubled Debt Restructurings by Creditors.” Loans restructured with an interest rate equal to or greater than that of a new loan with comparable market risk at the time the loan is modified may be excluded from certain restructured loan disclosures in years subsequent to the restructuring if the loans are in compliance with their modified terms. A loan that has been placed on nonaccrual status that is subsequently restructured will usually remain on nonaccrual status until the borrower is able to demonstrate repayment performance in compliance with the restructured terms for a sustained period of time, typically for six months. A restructured loan may return to accrual status sooner based on other significant events or circumstances. A loan that has not been placed on nonaccrual status may be restructured and such loan may remain on accrual status after such restructuring. In these circumstances, the borrower has made payments before and after the restructuring. Generally, this restructuring involves maturity extensions, a reduction in the loan interest rate and/or a change to interest‑only payments for a period of time. The restructured loan is considered impaired despite the accrual status and a specific reserve is calculated based on the present value of expected cash flows discounted at the loan’s original effective interest rate or based on the fair value of the collateral if the loan is collateral-dependent. (h) Allowances for Credit Losses Allowance for credit losses on Non‑PCI loans and leases held for investment. The allowance for credit losses on Non-PCI loans and leases held for investment is the combination of the allowance for loan and lease losses and the reserve for unfunded loan commitments. The allowance for loan and lease losses is reported as a reduction of outstanding loan and lease balances and the reserve for unfunded loan commitments is included within "Accrued interest payable and other liabilities" on the consolidated balance sheets. The following discussion is for Non-PCI loans and leases and the related allowance for credit losses. Refer to "— Allowance for loan losses on PCI loans held for investment " for the allowance policy on PCI loans. For loans and leases acquired and measured at fair value and deemed non-impaired on the acquisition date, our allowance methodology measures deterioration in credit quality or other inherent risks related to these acquired assets that may occur after the acquisition date. The allowance for credit losses is maintained at a level deemed appropriate by management to adequately provide for known and inherent risks in the loan and lease portfolio and other extensions of credit at the balance sheet date. The allowance is based upon our review of the credit quality of the loan and lease portfolio, which includes loan and lease payment trends, borrowers' compliance with loan agreements, borrowers' current and budgeted financial performance, collateral valuation trends, and current economic factors and external conditions that may affect our borrowers' ability to make payments to us in accordance with their contractual loan agreements. Loans and leases that are deemed to be uncollectable are charged off and deducted from the allowance. The provision for loan and lease losses and recoveries on loans and leases previously charged off are added to the allowance. The allowance for loan and lease losses has a general reserve component for loans and leases with no credit impairment and a specific reserve component for loans and leases determined to be impaired. A loan or lease is considered impaired when it is probable that we will be unable to collect all amounts due according to the original contractual terms of the agreement. We assess our loans and leases for impairment on an ongoing basis using certain criteria such as payment performance, borrower reported financial results and budgets, and other external factors when appropriate. We measure impairment of a loan or lease based upon the fair value of the underlying collateral if the loan or lease is collateral-dependent or the present value of cash flows, discounted at the effective interest rate, if the loan or lease is not collateral-dependent. To the extent a loan or lease balance exceeds the estimated collectable value, a specific reserve or charge-off is recorded depending upon either the certainty of the estimate of loss or the fair value of the loan's collateral if the loan is collateral-dependent. Smaller balance loans (under $250,000 ), with a few exceptions for certain loan types, are generally not individually assessed for impairment but are evaluated collectively. Our allowance methodology for the general reserve component includes both quantitative and qualitative loss factors which are applied to the population of unimpaired loans and leases to estimate our general reserves. The quantitative loss factors are the average charge-offs experienced over a prescribed historical look-back period on loans and leases pooled both by loan or lease type and credit risk rating; loans with more adverse credit risk ratings or higher historical loss experience have higher quantitative loss factors. The qualitative loss factors consider, among other things, current economic trends and forecasts, current collateral values and performance trends, and the loan portfolio's current composition and credit performance trends. The quantitative estimation of the allowance for credit losses at December 31, 2017 considered actual historical loan and lease charge-off experience over a 31 -quarter look-back period starting with the first quarter of 2010. This look-back period is inclusive of the average timeframe over which charge-offs typically occur following loan or lease origination. The estimation of the allowance for credit losses at December 31, 2016 considered actual historical loan and lease charge-off experience over a 27 -quarter look-back period starting with the first quarter of 2010. The increase in the historical look-back period to a 31 -quarter look-back period at December 31, 2017 from 27 quarters at December 31, 2016 allows the look-back period to capture sufficient loss observations and is relevant to the current portfolio; in a good economic cycle with less frequent loss events, management believes a longer look-back period is more appropriate to reflect the level of incurred losses over an entire economic cycle. When estimating the general reserve component for the various pools of similar loan types, the loss factors applied to the loan pools consider the current credit risk ratings, giving greater weight to loans with more adverse credit risk ratings. We recognize that the determination of the allowance for credit losses is sensitive to the assigned credit risk ratings and inherent loss rates at any given point in time. To ensure the accuracy of our credit risk ratings, an independent credit review function assesses the appropriateness of the credit risk ratings assigned to loans on a regular basis. The qualitative criteria we consider when establishing the loss factors include the following: • current economic trends and forecasts; • current collateral values, performance trends, and overall outlook in the markets where we lend; • legal and regulatory matters that could impact our borrowers’ ability to repay our loans and leases; • loan and lease portfolio composition and any loan concentrations; • current lending policies and the effects of any new policies or policy amendments; • loan and lease production volume and mix; • loan and lease portfolio credit performance trends; • results of our independent credit review; and • changes in management related to credit administration functions. We estimate the reserve for unfunded commitments using the same loss factors as used for the allowance for loan and lease losses. The reserve for unfunded commitments is computed using expected future usage of the unfunded commitments based on historical usage of unfunded commitments for the various loan types. The allowance for credit losses is directly correlated to the credit risk ratings of our loans. To ensure the accuracy of our credit risk ratings, an independent credit review function assesses the appropriateness of the credit risk ratings assigned to loans on a regular basis. The credit risk ratings assigned to every loan and lease are either “pass,” “special mention,” “substandard,” or “doubtful” and defined as follows: • Pass : Loans and leases classified as "pass" are not adversely classified and collection and repayment in full are expected. • Special Mention : Loans and leases classified as "special mention" have a potential weakness that requires management's attention. If not addressed, these potential weaknesses may result in further deterioration in the borrower's ability to repay the loan or lease. • Substandard : Loans and leases classified as "substandard" have a well-defined weakness or weaknesses that jeopardize the collection of the debt. They are characterized by the possibility that we will sustain some loss if the weaknesses are not corrected. • Doubtful : Loans and leases classified as "doubtful" have all the weaknesses of those classified as "substandard," with the additional trait that the weaknesses make collection or repayment in full highly questionable and improbable. In addition, we may refer to the loans and leases with assigned credit risk ratings of "substandard" and "doubtful" together as "classified" loans and leases. For further information on classified loans and leases, see Note 6. Loans and Leases. Management believes the allowance for credit losses is appropriate for the known and inherent risks in our Non-PCI loan and lease portfolio and the credit risk ratings and inherent loss rates currently assigned are appropriate. It is possible that others, given the same information, may at any point in time reach different conclusions that could result in a significant impact to the Company's financial statements. In addition, current credit risk ratings are subject to change as we continue to monitor our loans and leases. To the extent we experience, for example, increased levels of borrower loan defaults, borrowers' noncompliance with our loan agreements, adverse changes in collateral values, or negative changes in economic and business conditions that adversely affect our borrowers, our classified loans and leases may increase. Higher levels of classified loans and leases generally result in increased provisions for credit losses and an increased allowance for credit losses. Although we have established an allowance for credit losses that we consider appropriate, there can be no assurance that the established allowance will be sufficient to absorb future losses. Our federal and state banking regulators, as an integral part of their examination process, periodically review the Company’s allowance for credit losses. Our regulators may require the Company to recognize additions to the allowance based on their judgments related to information available to them at the time of their examinations. Allowance for loan losses on PCI loans held for investment. We measure t

Restricted Cash Balances

Restricted Cash Balances	12 Months Ended
	Dec. 31, 2017
Restricted Cash Balances [Abstract]
Restricted Cash Balances	NOTE 2. RESTRICTED CASH BALANCES The Company is required to maintain reserve balances with the FRBSF. Such reserve requirements are based on a percentage of deposit liabilities and may be satisfied by cash on hand. The average reserves required to be held at the FRBSF for the years ended December 31, 2017 and 2016 were $77.6 million and $67.7 million , respectively.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions	NOTE 3. ACQUISITIONS The following assets acquired and liabilities assumed of the acquired entities are presented at estimated fair value as of their respective acquisition dates: Acquisition and Date Acquired CU Bancorp Square 1 Financial, Inc. October 20, 2017 October 6, 2015 (In thousands) Assets Acquired: Cash and due from banks $ 51,857 $ 24,867 Interest‑earning deposits in financial institutions 332,799 236,069 Securities available‑for‑sale 446,980 2,193,538 FHLB stock 11,902 2,787 Loans and leases 2,075,890 1,553,720 Premises and equipment 2,981 1,927 Goodwill 374,721 446,069 Core deposit and customer relationship intangibles 57,500 45,426 Other assets 103,498 106,757 Total assets acquired $ 3,458,128 $ 4,611,160 Liabilities Assumed: Noninterest‑bearing deposits $ 1,510,285 $ 2,549,000 Interest‑bearing deposits 1,209,597 1,240,635 Borrowings 22,879 — Subordinated debentures 12,372 — Accrued interest payable and other liabilities 32,424 24,092 Total liabilities assumed $ 2,787,557 $ 3,813,727 Total consideration paid $ 670,571 $ 797,433 Summary of consideration: Cash paid $ 224,338 $ — PacWest common stock issued 446,233 797,433 Total $ 670,571 $ 797,433 CU Bancorp Acquisition On October 20, 2017 , we completed the acquisition of CUB. As part of the acquisition, CU Bank, a wholly-owned subsidiary of CUB, was merged with and into PacWest's wholly-owned banking subsidiary, Pacific Western Bank. Under the terms of the Agreement and Plan of Merger, each CUB common share, except dissenting shares, and each restricted stock award was converted into the right to receive 0.5308 of a share of PacWest common stock and $12.00 in cash, and each outstanding CUB stock option was settled in cash pursuant to terms of the Agreement and Plan of Merger. PacWest issued an aggregate of approximately 9.3 million shares of PacWest common stock and paid $224.3 million in cash to CUB common shareholders and equity award holders. Based on the closing price of PacWest’s common stock on October 20, 2017 of $47.99 per share, the aggregate consideration paid to CUB common shareholders and equity awards holders was $670.6 million . Former holders of CUB common stock as a group received shares of PacWest common stock in the acquisition constituting approximately 7% of the outstanding shares of PacWest common stock immediately after the acquisition. CU Bank was a commercial bank headquartered in Los Angeles, California. We completed the acquisition to, among other things, enhance our Southern California community bank franchise by adding a $2.1 billion loan portfolio and $2.7 billion of core deposits. The CUB acquisition has been accounted for under the acquisition method of accounting. We acquired $3.5 billion of assets and assumed $2.8 billion of liabilities upon closing of the acquisition. The assets and liabilities, both tangible and intangible, were recorded at their estimated fair values as of the acquisition date. We made significant estimates and exercised significant judgment in estimating fair values and accounting for such acquired assets and liabilities. Such fair values are preliminary estimates and are subject to adjustment for up to one year after the acquisition date or when additional information relative to the closing date fair values becomes available and such information is considered final, whichever is earlier. The fair value of the acquired net tax assets, once the final tax returns have been filed, may change. The application of the acquisition method of accounting resulted in goodwill of $374.7 million . All of the recognized goodwill is non-deductible fo r tax purposes. Square 1 Financial, Inc. Acquisition We acquired Square 1 on October 6, 2015 . As part of the acquisition, Square 1 Bank, a wholly-owned subsidiary of Square 1, merged with and into Pacific Western. At closing, we formed the Square 1 Ban k Division of Pacific Western to focus on providing a comprehensive suite of financial services to entrepreneurial businesses and their venture capital and private equity investors nationwide. When we refer to "Square 1," we are referring to the company acquired on October 6, 2015, and when we refer to the "Square 1 Bank Division," we are referring to a division of Pacif ic Western. We completed this acquisition to increase our core deposits, expand our nationwide lending platform, and increase our presence in the technology and life-sciences credit markets. The Square 1 acquisition has been accounted for under the acquisition method of accounting. We acquired $4.6 billion of assets and assumed $3.8 billion of liabilities upon closing of the acquisition. The assets and liabilities, both tangible and intangible, were recorded at their estimated fair values as of the acquisition date. We made significant estimates and exercised significant judgment in estimating fair values and accounting for such acquired assets and liabilities. The application of the acquisition method of accounting resulted in goodwill of $446.1 million . All of the recognized goodwill is non-deductible for tax purposes.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	NOTE 4. GOODWILL AND OTHER INTANGIBLE ASSETS The following table presents the changes in the carrying amount of goodwill for the years indicated: Goodwill (In thousands) Balance, December 31, 2014 $ 1,720,479 Adjustment to acquired CapitalSource Inc. tax assets 7,901 Addition from the Square 1 acquisition 447,911 Balance, December 31, 2015 2,176,291 Adjustment to acquired Square 1 tax assets (1,842 ) Reduction due to sale of PWEF leasing unit (500 ) Balance, December 31, 2016 2,173,949 Addition from the CUB acquisition 374,721 Balance, December 31, 2017 $ 2,548,670 Goodwill adjustments include: (1) the 2016 finalization of the fair value of the tax assets acquired in the Square 1 acquisition, (2) the 2016 reduction of goodwill in connection with the sale of the PWEF leasing unit, and (3) the 2015 finalization of the fair value of the tax assets acquired in the CapitalSource merger. The finalization of the day one fair value of the acquired Square 1 tax assets was due to completion of the 2015 tax returns. Through the sale of the PWEF leasing unit on March 31, 2016, $0.5 million of goodwill was allocated to this business group; as such, a goodwill reduction was included in the $0.7 million loss on sale of the PWEF leasing unit and included in "Other income" in the consolidated statements of earnings. We perform our annual goodwill impairment testing in the fourth quarter. In the fourth quarter of 2017, we evaluated the carrying value of our goodwill and determined that it was not impaired. Our other intangible assets with definite lives are CDI and CRI. CDI and CRI are amortized over their respective estimated useful lives and reviewed for impairment at least quarterly. The amortization expense represents the estimated decline in the value of the underlying deposits or loan and lease customers acquired. The weighted average amortization period remaining for all of our CDI and CRI as of December 31, 2017 is 5.0 years. The estimated aggregate amortization expense related to these intangible assets for each of the next five years is $24.4 million for 2018 , $19.6 million for 2019 , $15.3 million for 2020 , $11.7 million for 2021 and $7.9 million for 2022 . The following table presents the changes in CDI and CRI and the related accumulated amortization for the years indicated: Year Ended December 31, 2017 2016 2015 (In thousands) Gross Amount of CDI and CRI: Balance, beginning of year $ 64,187 $ 95,524 $ 53,090 Additions due to acquisitions 57,500 — 45,426 Fully amortized portion (2,190 ) (29,637 ) (2,992 ) Reduction due to sale of PWEF leasing unit — (1,700 ) — Balance, end of year 119,497 64,187 95,524 Accumulated Amortization: Balance, beginning of year (27,821 ) (42,304 ) (35,886 ) Amortization (14,240 ) (16,517 ) (9,410 ) Fully amortized portion 2,190 29,637 2,992 Reduction due to sale of PWEF leasing unit — 1,363 — Balance, end of year (39,871 ) (27,821 ) (42,304 ) Net CDI and CRI, end of year $ 79,626 $ 36,366 $ 53,220

Investment Securities

Investment Securities	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Investment	NOTE 5. INVESTMENT SECURITIES Securities Available-for-Sale The following table presents amortized cost, gross unrealized gains and losses, and fair values of securities available-for-sale as of the dates indicated: December 31, 2017 December 31, 2016 Gross Gross Gross Gross Amortized Unrealized Unrealized Fair Amortized Unrealized Unrealized Fair Security Type Cost Gains Losses Value Cost Gains Losses Value (In thousands) Residential MBS and CMOs: Agency MBS $ 243,375 $ 3,743 $ (844 ) $ 246,274 $ 499,185 $ 6,222 $ (2,964 ) $ 502,443 Agency CMOs 277,638 968 (2,897 ) 275,709 145,258 1,528 (497 ) 146,289 Private label CMOs 122,816 3,813 (642 ) 125,987 122,707 4,199 (1,437 ) 125,469 Municipal securities 1,627,707 53,700 (1,339 ) 1,680,068 1,447,064 15,406 (6,011 ) 1,456,459 Agency commercial MBS 1,169,969 2,758 (8,758 ) 1,163,969 555,552 1,798 (9,658 ) 547,692 Corporate debt securities 17,000 2,295 — 19,295 47,100 680 (271 ) 47,509 Collateralized loan obligations 6,960 55 — 7,015 155,440 1,685 (238 ) 156,887 SBA securities 160,214 695 (575 ) 160,334 179,085 510 (750 ) 178,845 Asset-backed and other securities 95,846 938 (1,004 ) 95,780 62,264 358 (385 ) 62,237 Total $ 3,721,525 $ 68,965 $ (16,059 ) $ 3,774,431 $ 3,213,655 $ 32,386 $ (22,211 ) $ 3,223,830 See Note 12. Fair Value Measurements for information on fair value measurements and methodology. As of December 31, 2017 , securities available‑for‑sale with a fair value of $449.2 million were pledged as collateral for borrowings, public deposits and other purposes as required by various statutes and agreements. Realized Gains and Losses on Securities Available-for-Sale Realized gains or losses in the consolidated statements of earnings resulting from the sale of securities are calculated using the specific identification method and included in (loss) gain on sale of securities. During the year ended December 31, 2017 , we sold $355.4 million of securities available-for-sale for a gross realized gain of $3.3 million and a gross realized loss of $3.8 million . We also sold $404.5 million of the $447.0 million of securities obtained in the CUB acquisition for no gain or loss as they were marked to fair value at the time of acquisition. During the year ended December 31, 2016 , we sold $384.0 million of securities available-for-sale for a gross realized gain of $11.1 million and a gross realized loss of $1.6 million . During the year ended December 31, 2015 , we sold $208.4 million of securities available-for-sale for a gross realized gain of $4.5 million and a gross realized loss of $0.7 million . We also sold $823.8 million of the $2.2 billion of securities obtained in the Square 1 acquisition for no gain or loss as they were marked to fair value at the time of acquisition. Unrealized Losses on Securities Available-for-Sale The following tables present the gross unrealized losses and fair values of securities available-for-sale that were in unrealized loss positions, for which other-than-temporary impairments have not been recognized in earnings, as of the dates indicated: December 31, 2017 Less Than 12 Months 12 Months or More Total Gross Gross Gross Fair Unrealized Fair Unrealized Fair Unrealized Security Type Value Losses Value Losses Value Losses (In thousands) Residential MBS and CMOs: Agency MBS $ 44,795 $ (311 ) $ 26,010 $ (533 ) $ 70,805 $ (844 ) Agency CMOs 163,014 (2,452 ) 20,928 (445 ) 183,942 (2,897 ) Private label CMOs 50,521 (500 ) 5,035 (142 ) 55,556 (642 ) Municipal securities 67,936 (365 ) 32,326 (974 ) 100,262 (1,339 ) Agency commercial MBS 579,373 (3,777 ) 129,060 (4,981 ) 708,433 (8,758 ) SBA securities 74,904 (575 ) — — 74,904 (575 ) Asset-backed and other securities 46,237 (948 ) 10,473 (56 ) 56,710 (1,004 ) Total $ 1,026,780 $ (8,928 ) $ 223,832 $ (7,131 ) $ 1,250,612 $ (16,059 ) December 31, 2016 Less Than 12 Months 12 Months or More Total Gross Gross Gross Fair Unrealized Fair Unrealized Fair Unrealized Security Type Value Losses Value Losses Value Losses (In thousands) Residential MBS and CMOs: Agency MBS $ 149,281 $ (1,691 ) $ 122,902 $ (1,273 ) $ 272,183 $ (2,964 ) Agency CMOs 44,111 (416 ) 25,316 (81 ) 69,427 (497 ) Private label CMOs 49,067 (906 ) 30,155 (531 ) 79,222 (1,437 ) Municipal securities 644,424 (6,011 ) — — 644,424 (6,011 ) Agency commercial MBS 349,550 (9,658 ) — — 349,550 (9,658 ) Corporate debt securities 29,829 (271 ) — — 29,829 (271 ) Collateralized loan obligations 12,450 (37 ) 39,231 (201 ) 51,681 (238 ) SBA securities 69,293 (407 ) 39,024 (343 ) 108,317 (750 ) Asset-backed and other securities 18,213 (309 ) 7,851 (76 ) 26,064 (385 ) Total $ 1,366,218 $ (19,706 ) $ 264,479 $ (2,505 ) $ 1,630,697 $ (22,211 ) We reviewed the securities that were in an unrealized loss position at December 31, 2017 and 2016 , and concluded their unrealized losses were a result of the level of market interest rates relative to the types of securities and pricing changes caused by shifting supply and demand dynamics and not a result of downgraded credit ratings or other indicators of deterioration of the underlying issuers' ability to repay. Accordingly, we determined the securities were temporarily impaired and we did not recognize such impairment in the consolidated statements of earnings. Although we periodically sell securities for portfolio management purposes, we do not foresee having to sell any temporarily impaired securities strictly for liquidity needs and believe that it is more likely than not we would not be required to sell any temporarily impaired securities before recovery of their amortized cost. Contractual Maturities of Securities Available-for-Sale The following table presents the contractual maturities of our available-for-sale securities portfolio based on amortized cost and carrying value as of the date indicated. December 31, 2017 Amortized Fair Maturity Cost Value (In thousands) Due in one year or less $ 14,398 $ 15,091 Due after one year through five years 375,559 378,522 Due after five years through ten years 1,128,639 1,130,138 Due after ten years 2,202,929 2,250,680 Total securities available-for-sale $ 3,721,525 $ 3,774,431 Mortgage-backed securities have contractual terms to maturity, but require periodic payments to reduce principal. In addition, expected maturities may differ from contractual maturities because obligors and/or issuers may have the right to call or prepay obligations with or without call or prepayment penalties. FHLB Stock In connection with outstanding FHLB advances, the Bank owned FHLB stock carried at cost of $20.8 million and $21.9 million at December 31, 2017 and 2016 . At December 31, 2017 and 2016 , the Bank was required to own FHLB stock at least equal to 2.7% of outstanding FHLB advances. During the year ended December 31, 2017 , FHLB stock decreased by $1.1 million due to $25.8 million in redemptions, offset partially by $12.8 million in purchases and $11.9 million acquired in the acquisition of CUB. We evaluated the carrying value of our FHLB stock investment at December 31, 2017 , and determined that it was not impaired. Our evaluation considered the long-term nature of the investment, the current financial and liquidity position of the FHLB, repurchase activity of excess stock by the FHLB at its carrying value, the return on the investment from recurring dividends, and our intent and ability to hold this investment for a period of time sufficient to recover our recorded investment. Interest Income on Investment Securities The following table presents the composition of our interest income on investment securities for the years indicated: Year Ended December 31, 2017 2016 2015 (In thousands) Taxable interest $ 52,981 $ 46,097 $ 35,103 Non-taxable interest 43,355 41,885 25,219 Dividend income 1,866 2,575 4,046 Total interest income on investment securities $ 98,202 $ 90,557 $ 64,368

Loans and Credit Quality

Loans and Credit Quality	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Loans and Leases	NOTE 6. LOANS AND LEASES Our loan and lease portfolio includes originated and purchased loans and leases. Originated and purchased loans and leases for which there was no evidence of credit deterioration at their acquisition date and for which it was probable that we would collect all contractually due payments, are referred to collectively as Non-PCI loans. Generally, PCI loans are purchased loans for which there was, at the acquisition date, evidence of credit deterioration since their origination and for which it was probable that collection of all contractually due payments was unlikely. Non-PCI loans are carried at the principal amount outstanding, net of deferred fees and costs, and net of purchase discounts and premiums for acquired loans. Deferred fees and costs and purchase discounts and premiums on acquired non-impaired loans are recognized as an adjustment to interest income over the contractual life of the loans primarily using the effective interest method or recognized as income when the related loans are paid off or sold. PCI loans are accounted for in accordance with ASC Subtopic 310‑30, “ Loans and Debt Securities Acquired with Deteriorated Credit Quality .” For PCI loans, at the time of acquisition, we estimate the amount and timing of undiscounted expected principal and interest payments (the "undiscounted expected cash flows"). The difference between the undiscounted expected cash flows and the estimated fair value of the acquired loans is the accretable yield. The carrying value of PCI loans is reduced by payments received, both principal and interest, and increased by the portion of the accretable yield recognized as interest income. Loans Held for Sale In the fourth quarter of 2017, we sold $1.5 billion of cash flow loans and exited our CapitalSource Division origination operations related to general, technology, and healthcare cash flow loans. As of December 31, 2017 , $1.0 billion of the loans sold had settled, while $481.1 million were classified as held for sale. The loans held for sale at December 31, 2017 settled in the first quarter of 2018. In connection with the loan sale and transfer of loans to held for sale, we recognized $2.2 million in charge-offs during the fourth quarter of 2017 to record the loans at the lower of cost or fair value. Loans and Leases Held for Investment The following table summarizes the composition of our loans and leases held for investment as of the dates indicated: December 31, 2017 December 31, 2016 Non-PCI Non-PCI Loans PCI Loans PCI and Leases Loans Total and Leases Loans Total (In thousands) Real estate mortgage $ 7,815,355 $ 53,658 $ 7,869,013 $ 5,635,675 $ 92,793 $ 5,728,468 Real estate construction and land 1,611,287 — 1,611,287 975,032 2,409 977,441 Commercial 7,137,978 4,158 7,142,136 8,426,236 12,994 8,439,230 Consumer 409,551 234 409,785 375,149 249 375,398 Total gross loans and leases held for investment 16,974,171 58,050 17,032,221 15,412,092 108,445 15,520,537 Deferred fees, net (59,464 ) (14 ) (59,478 ) (64,562 ) (21 ) (64,583 ) Total loans and leases held for investment, net of deferred fees 16,914,707 58,036 16,972,743 15,347,530 108,424 15,455,954 Allowance for loan and lease losses (133,012 ) (6,444 ) (139,456 ) (143,755 ) (13,483 ) (157,238 ) Total loans and leases held for investment, net $ 16,781,695 $ 51,592 $ 16,833,287 $ 15,203,775 $ 94,941 $ 15,298,716 Non‑PCI Loans and Leases Held for Investment The following tables present an aging analysis of our Non‑PCI loans and leases held for investment, net of deferred fees, by portfolio segment and class as of the dates indicated: December 31, 2017 30 - 89 90 or More Days Days Total Past Due Past Due Past Due Current Total (In thousands) Real estate mortgage: Commercial $ 29,070 $ 9,107 $ 38,177 $ 5,323,310 $ 5,361,487 Residential 6,999 2,022 9,021 2,428,483 2,437,504 Total real estate mortgage 36,069 11,129 47,198 7,751,793 7,798,991 Real estate construction and land: Commercial — — — 769,075 769,075 Residential 2,081 — 2,081 820,073 822,154 Total real estate construction and land 2,081 — 2,081 1,589,148 1,591,229 Commercial: Asset-based 1,512 — 1,512 3,010,188 3,011,700 Venture capital 6,533 760 7,293 2,115,418 2,122,711 Cash flow 1,334 1,586 2,920 1,320,594 1,323,514 Equipment finance 344 690 1,034 655,961 656,995 Total commercial 9,723 3,036 12,759 7,102,161 7,114,920 Consumer 562 — 562 409,005 409,567 Total (1) $ 48,435 $ 14,165 $ 62,600 $ 16,852,107 $ 16,914,707 ________________________ (1) Excludes loans held for sale carried at lower of cost or fair value. December 31, 2016 30 - 89 90 or More Days Days Total Past Due Past Due Past Due Current Total (In thousands) Real estate mortgage: Commercial $ 8,590 $ 3,303 $ 11,893 $ 4,341,740 $ 4,353,633 Residential 5,694 1,999 7,693 1,256,630 1,264,323 Total real estate mortgage 14,284 5,302 19,586 5,598,370 5,617,956 Real estate construction and land: Commercial — — — 578,838 578,838 Residential 364 — 364 383,637 384,001 Total real estate construction and land 364 — 364 962,475 962,839 Commercial: Asset-based 1,500 2 1,502 2,607,543 2,609,045 Venture capital 13,589 5,769 19,358 1,963,798 1,983,156 Cash flow 191 1,821 2,012 3,105,380 3,107,392 Equipment finance 1,417 3,051 4,468 687,499 691,967 Total commercial 16,697 10,643 27,340 8,364,220 8,391,560 Consumer 224 — 224 374,951 375,175 Total $ 31,569 $ 15,945 $ 47,514 $ 15,300,016 $ 15,347,530 It is our policy to discontinue accruing interest when principal or interest payments are past due 90 days or more unless the loan is both well secured and in the process of collection or when, in the opinion of management, there is a reasonable doubt as to the collectability of a loan or lease in the normal course of business. Interest income on nonaccrual loans is recognized only to the extent cash is received and the principal balance of the loan is deemed collectable. The amount of interest income that would have been recorded on nonaccrual loans and leases at December 31, 2017 and 2016 had such loans and leases been current in accordance with their original terms was $10.8 million and $8.0 million for 2017 and 2016 . The following table presents our nonaccrual and performing Non‑PCI loans and leases held for investment, net of deferred fees, by portfolio segment and class as of the dates indicated: December 31, 2017 (1) December 31, 2016 Nonaccrual Performing Total Nonaccrual Performing Total (In thousands) Real estate mortgage: Commercial $ 65,563 $ 5,295,924 $ 5,361,487 $ 62,454 $ 4,291,179 $ 4,353,633 Residential 3,350 2,434,154 2,437,504 6,881 1,257,442 1,264,323 Total real estate mortgage 68,913 7,730,078 7,798,991 69,335 5,548,621 5,617,956 Real estate construction and land: Commercial — 769,075 769,075 — 578,838 578,838 Residential — 822,154 822,154 364 383,637 384,001 Total real estate construction and land — 1,591,229 1,591,229 364 962,475 962,839 Commercial: Asset-based 3,174 3,008,526 3,011,700 2,118 2,606,927 2,609,045 Venture capital 29,424 2,093,287 2,122,711 11,687 1,971,469 1,983,156 Cash flow 23,315 1,300,199 1,323,514 53,908 3,053,484 3,107,392 Equipment finance 30,938 626,057 656,995 32,848 659,119 691,967 Total commercial 86,851 7,028,069 7,114,920 100,561 8,290,999 8,391,560 Consumer 20 409,547 409,567 339 374,836 375,175 Total $ 155,784 $ 16,758,923 $ 16,914,707 $ 170,599 $ 15,176,931 $ 15,347,530 ________________________ (1) Excludes loans held for sale carried at lower of cost or fair value. At December 31, 2017 , nonaccrual loans and leases totaled $155.8 million . Nonaccrual loans and leases included $14.2 million of loans and leases 90 or more days past due, $3.2 million of loans 30 to 89 days past due and $138.4 million of current loans that were placed on nonaccrual status based on management’s judgment regarding their collectability. Nonaccrual loans and leases totaled $170.6 million at December 31, 2016 , including $15.9 million of loans and leases 90 or more days past due, $3.0 million of loans 30 to 89 days past due and $151.7 million of current loans that were placed on nonaccrual status based on management’s judgment regarding their collectability. As of December 31, 2017 , our ten largest Non-PCI loan relationships on nonaccrual status had an aggregate carrying value of $120.0 million and represented 77.0% of total Non-PCI nonaccrual loans and leases. The following table presents the credit risk rating categories for Non‑PCI loans and leases held for investment by portfolio segment and class as of the dates indicated. Nonclassified loans and leases are those with a credit risk rating of either pass or special mention, while classified loans and leases are those with a credit risk rating of either substandard or doubtful. December 31, 2017 (1) December 31, 2016 Classified Nonclassified Total Classified Nonclassified Total (In thousands) Real estate mortgage: Commercial $ 93,795 $ 5,267,692 $ 5,361,487 $ 99,641 $ 4,253,992 $ 4,353,633 Residential 8,425 2,429,079 2,437,504 17,540 1,246,783 1,264,323 Total real estate mortgage 102,220 7,696,771 7,798,991 117,181 5,500,775 5,617,956 Real estate construction and land: Commercial — 769,075 769,075 409 578,429 578,838 Residential — 822,154 822,154 364 383,637 384,001 Total real estate construction and land — 1,591,229 1,591,229 773 962,066 962,839 Commercial: Asset-based 35,305 2,976,395 3,011,700 28,112 2,580,933 2,609,045 Venture capital 49,671 2,073,040 2,122,711 52,646 1,930,510 1,983,156 Cash flow 60,008 1,263,506 1,323,514 177,661 2,929,731 3,107,392 Equipment finance 30,938 626,057 656,995 32,848 659,119 691,967 Total commercial 175,922 6,938,998 7,114,920 291,267 8,100,293 8,391,560 Consumer 263 409,304 409,567 424 374,751 375,175 Total $ 278,405 $ 16,636,302 $ 16,914,707 $ 409,645 $ 14,937,885 $ 15,347,530 ________________________ (1) Excludes loans held for sale carried at lower of cost or fair value. In addition to our internal risk rating process, our federal and state banking regulators, as an integral part of their examination process, periodically review the Company’s loan risk rating classifications. Our regulators may require the Company to recognize rating downgrades based on their judgments related to information available to them at the time of their examinations. Risk rating downgrades generally result in increases in the provisions for credit losses and the allowance for credit losses. Non‑PCI nonaccrual loans and leases and performing troubled debt restructured loans are considered impaired for reporting purposes. Troubled debt restructurings are a result of rate reductions, term extensions, fee concessions and debt forgiveness or a combination thereof. At December 31, 2017 and 2016 , we had unfunded commitments related to Non-PCI troubled debt restructured loans of $4.5 million and $4.6 million . The following table presents the composition of our impaired loans and leases held for investment, net of deferred fees, by portfolio segment as of the dates indicated: December 31, 2017 (1) December 31, 2016 Performing Total Performing Total Nonaccrual Troubled Impaired Nonaccrual Troubled Impaired Loans Debt Loans Loans Debt Loans and Restructured and and Restructured and Leases Loans Leases Leases Loans Leases (In thousands) Real estate mortgage $ 68,913 $ 47,560 $ 116,473 $ 69,335 $ 54,750 $ 124,085 Real estate construction and land — 5,690 5,690 364 6,893 7,257 Commercial 86,851 3,488 90,339 100,561 3,157 103,718 Consumer 20 100 120 339 152 491 Total $ 155,784 $ 56,838 $ 212,622 $ 170,599 $ 64,952 $ 235,551 ________________________ (1) Excludes loans held for sale carried at lower of cost or fair value. The following tables present information regarding our Non‑PCI impaired loans and leases held for investment, net of deferred fees, by portfolio segment and class as of and for the years indicated: December 31, 2017 (1) December 31, 2016 Unpaid Unpaid Recorded Principal Related Recorded Principal Related Impaired Loans and Leases Investment Balance Allowance Investment Balance Allowance (In thousands) With An Allowance Recorded: Real estate mortgage: Commercial $ 15,750 $ 16,548 $ 628 $ 63,325 $ 65,031 $ 6,266 Residential 2,787 2,957 342 8,424 8,612 585 Real estate construction and land: Residential — — — 213 213 — Commercial: Asset-based 1,311 1,337 51 4,395 4,861 2,144 Venture capital 16,565 17,203 4,267 5,821 5,880 3,294 Cash flow 19,093 28,614 8,317 51,272 52,910 12,474 Equipment finance — — — 1,524 4,636 — Consumer 100 100 16 270 280 170 With No Related Allowance Recorded: Real estate mortgage: Commercial $ 93,827 $ 105,923 $ — $ 44,557 $ 51,402 $ — Residential 4,109 4,481 — 7,779 8,940 — Real estate construction and land: Commercial 5,690 5,689 — 6,680 6,680 — Residential — — — 364 366 — Commercial: Asset-based 3,519 5,559 — 664 1,652 — Venture capital 14,534 40,029 — 5,866 8,939 — Cash flow 4,378 8,270 — 2,852 5,939 — Equipment finance 30,939 50,433 — 31,324 53,319 — Consumer 20 93 — 221 292 — Total Non-PCI Loans and Leases With and Without an Allowance Recorded: Real estate mortgage $ 116,473 $ 129,909 $ 970 $ 124,085 $ 133,985 $ 6,851 Real estate construction and land 5,690 5,689 — 7,257 7,259 — Commercial 90,339 151,445 12,635 103,718 138,136 17,912 Consumer 120 193 16 491 572 170 Total $ 212,622 $ 287,236 $ 13,621 $ 235,551 $ 279,952 $ 24,933 ________________________ (1) Excludes loans held for sale carried at lower of cost or fair value. Year Ended December 31, 2017 (1) 2016 2015 Weighted Interest Weighted Interest Weighted Interest Average Income Average Income Average Income Impaired Loans and Leases Balance (1) Recognized Balance (1) Recognized Balance (1) Recognized (In thousands) With An Allowance Recorded: Real estate mortgage: Commercial $ 15,538 $ 881 $ 26,870 $ 898 $ 17,833 $ 1,130 Residential 2,787 55 6,521 255 2,143 33 Real estate construction and land: Residential — — 213 14 747 15 Commercial: Asset-based 1,236 53 3,842 134 3,204 56 Venture capital 10,228 — 1,227 — — — Cash flow 19,093 7 22,736 10 12,590 32 Equipment finance — — 508 — 8,475 — Consumer 100 8 233 — 355 15 With No Related Allowance Recorded: Real estate mortgage: Commercial $ 89,554 $ 2,648 $ 41,917 $ 1,506 $ 28,366 $ 345 Residential 3,842 59 7,254 144 4,643 41 Real estate construction and land: Commercial 5,690 306 6,680 224 7,053 240 Residential — — 364 — — — Commercial: Asset-based 1,640 49 528 18 1,746 130 Venture capital 2,860 — 2,446 — 124 — Cash flow 2,499 35 2,455 4 2,752 89 Equipment finance 30,653 — 30,767 — 30,363 — Consumer 20 — 166 9 1,363 — Total Non-PCI Loans and Leases With and Without an Allowance Recorded: Real estate mortgage $ 111,721 $ 3,643 $ 82,562 $ 2,803 $ 52,985 $ 1,549 Real estate construction and land 5,690 306 7,257 238 7,800 255 Commercial 68,209 144 64,509 166 59,254 307 Consumer 120 8 399 9 1,718 15 Total $ 185,740 $ 4,101 $ 154,727 $ 3,216 $ 121,757 $ 2,126 _________________________ (1) For the loans and leases (excluding PCI loans) reported as impaired at December 31, 2017 , 2016 and 2015 , amounts were calculated based on the period of time such loans and leases were impaired during the reported period. (2) Excludes loans held for sale carried at lower of cost or fair value. The following table presents our troubled debt restructurings of Non-PCI loans held for investment and defaulted troubled debt restructurings of Non-PCI loans held for investment by portfolio segment and class for the years indicated: Troubled Debt Restructurings Troubled Debt Restructurings That Subsequently Defaulted (1) Pre-Modification Post-Modification Outstanding Outstanding Number Recorded Recorded Number Recorded of Loans Investment Investment of Loans Investment (1) (Dollars In thousands) Year Ended December 31, 2017 Real estate mortgage: Commercial 5 $ 2,527 $ 2,463 — $ — Residential 8 1,328 489 — — Real estate construction and land: Residential 1 362 — — — Commercial: Asset-based 10 7,987 7,987 — — Venture capital 11 29,733 29,733 — — Cash flow 14 27,703 18,468 1 1 Consumer 1 97 97 — — Total 50 $ 69,737 $ 59,237 1 $ 1 (2) Year Ended December 31, 2016 Real estate mortgage: Commercial 12 $ 13,833 $ 6,099 — $ — Residential 10 7,091 6,439 2 5,000 Real estate construction and land: Commercial 1 1,245 1,245 — — Commercial: Asset-based 5 2,158 2,158 2 1,502 Cash flow 14 30,788 30,788 — — Equipment finance 7 44,196 42,572 — — Consumer 5 850 142 — — Total 54 $ 100,161 $ 89,443 4 $ 6,502 (3) Year Ended December 31, 2015 Real estate mortgage: Commercial 21 $ 43,536 $ 43,012 2 $ 2,670 Residential 18 3,128 2,961 1 155 Real estate construction and land: Commercial 8 23,881 23,881 — — Commercial: Asset-based 13 8,400 8,400 — — Cash flow 25 2,718 2,539 — — Equipment finance 10 93,868 93,868 — — Consumer 2 197 197 — — Total 97 $ 175,728 $ 174,858 3 $ 2,825 (4) _________________________ (1) The population of defaulted restructured loans for the period indicated includes only those loans restructured during the preceding 12-month period. For example, for the year ended December 31, 2017 , the population of defaulted restructured loans includes only those loans restructured after December 31, 2016 . The table excludes defaulted troubled restructurings in those classes for which the recorded investment was zero at the end of the period. (2) Represents the balance at December 31, 2017 , and is net of charge-offs of $68,000 . (3) Represents the balance at December 31, 2016 , and there were no charge-offs. (4) Represents the balance at December 31, 2015 , and is net of charge-offs of $96,900 . Allowance for Loan and Lease Losses The following tables present a summary of the activity in the allowance for loan and lease losses on Non‑PCI loans and leases held for investment by portfolio segment and PCI loans held for investment for the years indicated: Year Ended December 31, 2017 Real Estate Real Estate Construction Total Total Mortgage and Land Commercial Consumer Non-PCI PCI Total (In thousands) Allowance for Loan and Lease Losses: Balance, beginning of year $ 37,765 $ 10,045 $ 93,853 $ 2,092 $ 143,755 $ 13,483 $ 157,238 Charge-offs (2,410 ) — (70,709 ) (1,023 ) (74,142 ) (6,154 ) (80,296 ) Recoveries 1,209 429 9,415 132 11,185 363 11,548 Provision (negative provision) (1,583 ) 2,581 50,167 1,049 52,214 (1,248 ) 50,966 Balance, end of year $ 34,981 $ 13,055 $ 82,726 $ 2,250 $ 133,012 $ 6,444 $ 139,456 Ending Allowance by Impairment Methodology: Individually evaluated for impairment $ 970 $ — $ 12,635 $ 16 $ 13,621 Collectively evaluated for impairment $ 34,011 $ 13,055 $ 70,091 $ 2,234 $ 119,391 Acquired loans with deteriorated credit quality $ 6,444 Ending Loans and Leases by Impairment Methodology: Individually evaluated for impairment $ 115,319 $ 5,690 $ 89,626 $ 100 $ 210,735 Collectively evaluated for impairment $ 7,683,672 $ 1,585,539 $ 7,025,294 $ 409,467 $ 16,703,972 Acquired loans with deteriorated credit quality $ 58,036 Ending balance $ 7,798,991 $ 1,591,229 $ 7,114,920 $ 409,567 $ 16,914,707 $ 58,036 $ 16,972,743 Year Ended December 31, 2016 Real Estate Real Estate Construction Total Total Mortgage and Land Commercial Consumer Non-PCI PCI Total (In thousands) Allowance for Loan and Lease Losses: Balance, beginning of year $ 36,654 $ 7,137 $ 61,082 $ 661 $ 105,534 $ 9,577 $ 115,111 Charge-offs (2,059 ) — (32,210 ) (823 ) (35,092 ) (862 ) (35,954 ) Recoveries 4,519 673 7,794 116 13,102 39 13,141 Provision (negative provision) (1,349 ) 2,235 57,187 2,138 60,211 4,729 64,940 Balance, end of year $ 37,765 $ 10,045 $ 93,853 $ 2,092 $ 143,755 $ 13,483 $ 157,238 Ending Allowance by Impairment Methodology: Individually evaluated for impairment $ 6,851 $ — $ 17,912 $ 170 $ 24,933 Collectively evaluated for impairment $ 30,914 $ 10,045 $ 75,941 $ 1,922 $ 118,822 Acquired loans with deteriorated credit quality $ 13,483 Ending Loans and Leases by Impairment Methodology: Individually evaluated for impairment $ 123,348 $ 7,257 $ 103,431 $ 394 $ 234,430 Collectively evaluated for impairment $ 5,494,608 $ 955,582 $ 8,288,129 $ 374,781 $ 15,113,100 Acquired loans with deteriorated credit quality $ 108,424 Ending balance $ 5,617,956 $ 962,839 $ 8,391,560 $ 375,175 $ 15,347,530 $ 108,424 $ 15,455,954 Allowance for Credit Losses The Non-PCI allowance for credit losses is the combination of the Non-PCI allowance for loan and lease losses and the Non-PCI reserve for unfunded loan commitments. The Non-PCI reserve for unfunded loan commitments is included within "Accrued interest payable and other liabilities" on the consolidated balance sheets. The following tables present a summary of the activity in the Non-PCI allowance for loan and lease losses, Non-PCI reserve for unfunded loan commitments, and PCI allowance for loan losses for the years indicated: Year Ended December 31, 2017 Non-PCI Allowance for Reserve for PCI Total Loan and Unfunded Loan Allowance for Allowance for Allowance for Lease Losses Commitments Credit Losses Loan Losses Credit Losses (In thousands) Balance, beginning of period $ 143,755 $ 17,523 $ 161,278 $ 13,483 $ 174,761 Charge-offs (74,142 ) — (74,142 ) (6,154 ) (80,296 ) Recoveries 11,185 — 11,185 363 11,548 Net charge-offs (62,957 ) — (62,957 ) (5,791 ) (68,748 ) Provision (negative provision) 52,214 6,786 59,000 (1,248 ) 57,752 Fair value of acquired reserve for unfunded loan commitments — 4,326 4,326 — 4,326 Balance, end of period $ 133,012 $ 28,635 $ 161,647 $ 6,444 $ 168,091 Year Ended December 31, 2016 Non-PCI Allowance for Reserve for PCI Total Loan and Unfunded Loan Allowance for Allowance for Allowance for Lease Losses Commitments Credit Losses Loan Losses Credit Losses (In thousands) Balance, beginning of period $ 105,534 $ 16,734 $ 122,268 $ 9,577 $ 131,845 Charge-offs (35,092 ) — (35,092 ) (862 ) (35,954 ) Recoveries 13,102 — 13,102 39 13,141 Net charge-offs (21,990 ) — (21,990 ) (823 ) (22,813 ) Provision 60,211 789 61,000 4,729 65,729 Balance, end of period $ 143,755 $ 17,523 $ 161,278 $ 13,483 $ 174,761 PCI Loans Held for Investment The following table reflects the PCI loans held for investment by portfolio segment as of the dates indicated: December 31, 2017 2016 (In thousands) Real estate mortgage $ 72,399 $ 112,982 Real estate construction and land — 1,901 Commercial 7,568 19,109 Consumer 262 281 Total gross PCI loans held for investment 80,229 134,273 Discount (22,193 ) (25,849 ) Total PCI loans held for investment, net of discount 58,036 108,424 Allowance for loan losses (6,444 ) (13,483 ) Total PCI loans held for investment, net $ 51,592 $ 94,941 The following table summarizes the changes in the carrying amount of PCI loans held for investment and accretable yield on those loans for the years indicated: Carrying Accretable Amount Yield (In thousands) Balance, December 31, 2014 $ 276,792 $ (106,856 ) Addition from the Square 1 acquisition 16,455 (2,852 ) Accretion 31,857 31,857 Payments received (148,436 ) — Increase in expected cash flows, net — (7,785 ) Negative provision for credit losses 2,800 — Balance, December 31, 2015 179,468 (85,636 ) Accretion 51,907 51,907 Payments received (131,705 ) — Increase in expected cash flows, net — (22,215 ) Provision for credit losses (4,729 ) — Balance, December 31, 2016 94,941 (55,944 ) Accretion 14,739 14,739 Payments received (59,336 ) — Increase in expected cash flows, net — (4,375 ) Negative provision for credit losses 1,248 — Balance, December 31, 2017 $ 51,592 $ (45,580 ) The following table presents the credit risk rating categories for PCI loans held for investment, net of discount, by portfolio segment as of the dates indicated. Nonclassified loans are those with a credit risk rating of either pass or special mention, while classified loans are those with a credit risk rating of either substandard or doubtful. December 31, 2017 December 31, 2016 Classified Nonclassified Total Classified Nonclassified Total (In thousands) Real estate mortgage $ 11,063 $ 42,581 $ 53,644 $ 19,445 $ 73,330 $ 92,775 Real estate construction and land — — — 1,023 1,385 2,408 Commercial 4,158 — 4,158 10,943 2,049 12,992 Consumer 234 — 234 249 — 249 Total PCI loans held for investment, net of discount $ 15,455 $ 42,581 $ 58,036 $ 31,660 $ 76,764 $ 108,424 In addition to our internal risk rating process, our federal and state banking regulators, as an integral part of their examination process, periodically review the Company’s loan risk rating classifications. Our regulators may require the Company to recognize rating downgrades based on their judgments related to information available to them at the time of their examinations.

Foreclosed Assets

Foreclosed Assets	12 Months Ended
	Dec. 31, 2017
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Foreclosed Assets	NOTE 7. FORECLOSED ASSETS The following table summarizes foreclosed assets as of the dates indicated: December 31, Property Type 2017 2016 (In thousands) Construction and land development $ 219 $ 11,224 Multi‑family — 652 Single family residence 1,019 — Commercial real estate 64 — Total other real estate owned, net 1,302 11,876 Other foreclosed assets 27 1,100 Total foreclosed assets, net $ 1,329 $ 12,976 The following table presents the changes in foreclosed assets, net of the valuation allowance, for the years indicated: Year Ended December 31, Foreclosed Assets 2017 2016 2015 (In thousands) Balance, beginning of year $ 12,976 $ 22,120 $ 43,721 Transfers to foreclosed assets from loans 580 781 13,472 Other additions 1,385 — — Provision for losses (2,138 ) (2,576 ) (5,228 ) Reductions related to sales (11,474 ) (7,349 ) (29,845 ) Balance, end of year $ 1,329 $ 12,976 $ 22,120 The following table presents the changes in the foreclosed assets valuation allowance for the years indicated: Year Ended December 31, Foreclosed Assets Valuation Allowance 2017 2016 2015 (In thousands) Balance, beginning of year $ 12,696 $ 10,246 $ 12,123 Provision for losses 2,138 2,576 5,228 Reductions related to sales (14,820 ) (126 ) (7,105 ) Balance, end of year $ 14 $ 12,696 $ 10,246

Premises and Equipment, Net

Premises and Equipment, Net	12 Months Ended
	Dec. 31, 2017
Premises and Equipment, Net [Abstract]
Premises and Equipment, Net	NOTE 8. PREMISES AND EQUIPMENT, NET The following table presents the components of premises and equipment as of the dates indicated: December 31, 2017 2016 (In thousands) Land $ 1,243 $ 5,505 Buildings 8,154 14,929 Furniture, fixtures and equipment 43,250 38,806 Leasehold improvements 42,521 38,967 Premises and equipment, gross 95,168 98,207 Less: accumulated depreciation and amortization (63,316 ) (59,613 ) Premises and equipment, net $ 31,852 $ 38,594 Depreciation and amortization expense was $7.6 million , $8.2 million , and $8.1 million for the years ended December 31, 2017 , 2016 , and 2015 . We have obligations under a number of noncancelable operating leases for premises and equipment. The following table presents future minimum rental payments under noncancelable operating leases as of the date indicated: December 31, 2017 (In thousands) Estimated Lease Payments for Year Ending December 31, 2018 $ 30,574 2019 28,098 2020 25,544 2021 21,346 2022 15,494 2023 and thereafter 34,107 Total $ 155,163 Total gross rental expense for the years ended December 31, 2017 , 2016 , and 2015 , was $31.7 million , $30.0 million , and $26.2 million . Most of the leases provide that the Company pays maintenance, insurance and certain other operating expenses applicable to the leased premises in addition to the monthly rental payments. Total rental income for the years ended December 31, 2017 , 2016 , and 2015 , was $481,000 , $500,000 , and $487,000 . As of December 31, 2017 , the future minimum rental payments to be received under noncancelable subleases were $21.1 million through September 2025.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2017
Deposits [Abstract]
Deposits	NOTE 9. DEPOSITS The following table presents the components of interest‑bearing deposits as of the dates indicated: December 31, Deposit Category 2017 2016 (In thousands) Interest checking deposits $ 2,711,250 $ 1,462,305 Money market deposits 4,890,567 4,865,961 Savings deposits 690,353 711,039 Time deposits $250,000 and under 1,709,980 1,758,434 Time deposits over $250,000 355,342 413,856 Total interest-bearing deposits $ 10,357,492 $ 9,211,595 Brokered time deposits totaled $732.2 million and $405.5 million at December 31, 2017 and 2016 . Brokered non-maturity deposits totaled $0.8 billion and $1.2 billion at December 31, 2017 and 2016 . The following table summarizes the maturities of time deposits as of the date indicated: Time Deposits $250,000 Over Year of Maturity and Under $250,000 Total (In thousands) 2018 $ 1,593,877 $ 337,257 $ 1,931,134 2019 77,405 9,870 87,275 2020 16,551 3,713 20,264 2021 15,689 1,607 17,296 2022 6,325 2,895 9,220 2022 133 — 133 Total at December 31, 2017 $ 1,709,980 $ 355,342 $ 2,065,322

Borrowings and Subordinated Deb

Borrowings and Subordinated Debentures	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Borrowings and Subordinated Debentures	NOTE 10. BORROWINGS AND SUBORDINATED DEBENTURES Borrowings The following table summarizes our borrowings as of the dates indicated: December 31, 2017 December 31, 2016 Weighted Weighted Average Average Borrowing Type Amount Rate Amount Rate (Dollars in thousands) Non‑recourse debt $ 342 6.87% $ 812 6.41% FHLB secured advances 332,000 1.41% 735,000 0.59% FHLB unsecured overnight advance 135,000 1.34% 130,000 0.55% AFX borrowings — —% 40,000 0.81% Total borrowings $ 467,342 $ 905,812 The non‑recourse debt represents the payment stream of certain equipment leases sold to third parties. The debt is secured by the equipment in the leases and all interest rates are fixed. As of December 31, 2017 , this debt had a weighted average remaining maturity of 1.6 years . The Bank has established secured and unsecured lines of credit under which it may borrow funds from time to time on a term or overnight basis from the FHLB, the FRBSF, and other financial institutions. FHLB Secured Line of Credit. The Bank had secured financing capacity with the FHLB as of December 31, 2017 of $3.8 billion , collateralized by a blanket lien on $5.5 billion of certain qualifying loans. As of December 31, 2017 , the balance outstanding was $332.0 million , which consisted of a $332.0 million overnight advance. As of December 31, 2016 , the balance outstanding was $735 million , which consisted of a $435.0 million overnight advance and a $300.0 million one-month advance with a January 23, 2017 maturity date. FRBSF Secured Line of Credit. The Bank has a secured line of credit with the FRBSF. As of December 31, 2017 , the Bank had secured borrowing capacity of $1.8 billion collateralized by liens covering $2.3 billion of certain qualifying loans. As of December 31, 2017 and 2016 , there were no balances outstanding. FHLB Unsecured Line of Credit. The Bank has a $135.0 million unsecured line of credit with the FHLB for the borrowing of overnight funds, of which $135.0 million was outstanding at December 31, 2017 . As of December 31, 2016 , the balance outstanding was $130.0 million . Federal Funds Arrangements with Commercial Banks. As of December 31, 2017 , the Bank had unsecured lines of credit of $75.0 million with correspondent banks for the borrowing of overnight funds, subject to availability of funds. These lines are renewable annually and have no unused commitment fees. As of December 31, 2017 and December 31, 2016 , there were no balances outstanding. The Bank is a member of the AFX, through which it may either borrow or lend funds on an overnight or short-term basis with a group of pre-approved commercial banks. The availability of funds changes daily. As of December 31, 2017 , there was no balance outstanding. At December 31, 2016 , the balance outstanding was $40.0 million , which consisted of a $26.0 million overnight borrowing and a $14.0 million one-month borrowing with a January 20, 2017 maturity date. Subordinated Debentures The following table summarizes the terms of each issuance of subordinated debentures outstanding as of the dates indicated: December 31, 2017 December 31, 2016 Issue Maturity Rate Index Series Amount Rate Amount Rate Date Date (Quarterly Reset) (Dollars in thousands) Trust V $ 10,310 4.70 % $ 10,310 4.09 % 8/15/2003 9/17/2033 3 month LIBOR + 3.10 Trust VI 10,310 4.64 % 10,310 4.01 % 9/3/2003 9/15/2033 3 month LIBOR + 3.05 Trust CII 5,155 4.55 % 5,155 3.95 % 9/17/2003 9/17/2033 3 month LIBOR + 2.95 Trust VII 61,856 4.13 % 61,856 3.64 % 2/5/2004 4/23/2034 3 month LIBOR + 2.75 Trust CIII 20,619 3.28 % 20,619 2.65 % 8/15/2005 9/15/2035 3 month LIBOR + 1.69 Trust FCCI 16,495 3.19 % 16,495 2.56 % 1/25/2007 3/15/2037 3 month LIBOR + 1.60 Trust FCBI 10,310 3.14 % 10,310 2.51 % 9/30/2005 12/15/2035 3 month LIBOR + 1.55 Trust CS 2005-1 82,475 3.54 % 82,475 2.91 % 11/21/2005 12/15/2035 3 month LIBOR + 1.95 Trust CS 2005-2 128,866 3.33 % 128,866 2.84 % 12/14/2005 1/30/2036 3 month LIBOR + 1.95 Trust CS 2006-1 51,545 3.33 % 51,545 2.84 % 2/22/2006 4/30/2036 3 month LIBOR + 1.95 Trust CS 2006-2 51,550 3.33 % 51,550 2.84 % 9/27/2006 10/30/2036 3 month LIBOR + 1.95 Trust CS 2006-3 (1) 30,986 1.72 % 27,185 1.74 % 9/29/2006 10/30/2036 3 month EURIBOR + 2.05 Trust CS 2006-4 16,470 3.33 % 16,470 2.84 % 12/5/2006 1/30/2037 3 month LIBOR + 1.95 Trust CS 2006-5 6,650 3.33 % 6,650 2.84 % 12/19/2006 1/30/2037 3 month LIBOR + 1.95 Trust CS 2007-2 39,177 3.33 % 39,177 2.84 % 6/13/2007 7/30/2037 3 month LIBOR + 1.95 Trust I (2) 6,186 3.64 % — — % 12/10/2004 3/15/2035 3 month LIBOR + 2.05 Trust II (2) 3,093 3.34 % — — % 12/23/2005 3/15/2036 3 month LIBOR + 1.75 Trust III (2) 3,093 3.44 % — — % 6/30/2006 9/18/2036 3 month LIBOR + 1.85 Gross subordinated debentures 555,146 538,973 Unamortized discount (3) (92,709 ) (98,229 ) Net subordinated debentures $ 462,437 $ 440,744 ___________________ (1) Denomination is in Euros with a value of €25.8 million . (2) Acquired in the CUB acquisition on October 20, 2017. (3) Amount represents the fair value adjustment on trust preferred securities assumed in acquisitions. Interest payments made by the Company on subordinated debentures are considered dividend payments under FRB regulations. Bank holding companies, such as PacWest, are required to notify the FRB prior to declaring and paying a dividend to stockholders during any period in which quarterly and/or cumulative twelve‑month net earnings are insufficient to fund the dividend amount, among other requirements.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 11. COMMITMENTS AND CONTINGENCIES Lending Commitments The Company is a 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. Those instruments involve, to varying degrees, elements of credit risk in excess of the amount recognized in the consolidated balance sheets. The contract or notional amounts of those instruments reflect the extent of involvement the Company has in particular classes of financial instruments. The following table presents a summary of the financial instruments described above as of the dates indicated: December 31, 2017 2016 (In thousands) Loan commitments to extend credit $ 6,234,061 $ 4,166,703 Standby letters of credit 320,063 211,398 Total $ 6,554,124 $ 4,378,101 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. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. Standby letters of credit are conditional commitments issued by the Company to guarantee the performance of a customer to a third party. We provide standby letters of credit in conjunction with some of our lending arrangements and property lease obligations. Most guarantees expire within one year from the date of issuance. If a borrower defaults on its commitments subject to any letter of credit issued under these arrangements, we would be required to meet the borrower's financial obligation but would seek repayment of that financial obligation from the borrower. In some cases, borrowers have pledged cash or investment securities as collateral for these arrangements. In addition, we invest in low income housing project partnerships, that provide income tax credits, and small business investment companies that call for capital contributions up to an amount specified in the partnership agreements. As of December 31, 2017 and 2016 , we had commitments to contribute capital to these entities totaling $62.6 million and $26.6 million . We also had commitments to contribute up to an additional $2.5 million and $2.8 million to private equity funds at December 31, 2017 and 2016 . Legal Matters In the ordinary course of our business, we are party to various legal actions, which we believe are incidental to the operation of our business. The outcome of such legal actions and the timing of ultimate resolution are inherently difficult to predict. In the opinion of management, based upon information currently available to us, any resulting liability, in addition to amounts already accrued, would not have a material adverse effect on the Company’s financial statements or operations.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	NOTE 12. FAIR VALUE MEASUREMENTS ASC Topic 820, “ Fair Value Measurement ,” defines fair value, establishes a framework for measuring fair value including a three‑level valuation hierarchy, and expands disclosures about fair value measurements. Fair value is defined as the exchange price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date reflecting assumptions that a market participant would use when pricing an asset or liability. The hierarchy uses three levels of inputs to measure the fair value of assets and liabilities as follows: • Level 1: Quoted prices (unadjusted) for identical assets or liabilities in active markets. • Level 2: Observable inputs other than Level 1, including quoted prices for similar assets and liabilities in active markets, quoted prices in less active markets, or other observable inputs that can be corroborated by observable market data, either directly or indirectly, for substantially the full term of the financial instrument. This category generally includes municipal securities, agency residential and commercial MBS, collateralized loan obligations, agency and registered publicly rated private label CMOs, corporate debt securities, SBA securities, and asset-backed securitizations. • Level 3: Inputs to a valuation methodology that are unobservable, supported by little or no market activity, and significant to the fair value measurement. These valuation methodologies generally include pricing models, discounted cash flow models, or a determination of fair value that requires significant management judgment or estimation. This category also includes observable inputs from a pricing service not corroborated by observable market data, and includes our non-rated private label CMOs, non-rated private label asset-backed securities, and equity warrants. We use fair value to measure certain assets and liabilities on a recurring basis, primarily securities available‑for‑sale and derivatives. For assets measured at the lower of cost or fair value, the fair value measurement criteria may or may not be met during a reporting period and such measurements are therefore considered “nonrecurring” for purposes of disclosing our fair value measurements. Fair value is used on a nonrecurring basis to adjust carrying values for impaired loans and other real estate owned and also to record impairment on certain assets, such as goodwill, CDI, and other long‑lived assets. The following tables present information on the assets measured and recorded at fair value on a recurring basis as of the dates indicated: Fair Value Measurements as of December 31, 2017 Measured on a Recurring Basis Total Level 1 Level 2 Level 3 (In thousands) Securities available‑for‑sale: Residential MBS and CMOs: Agency MBS $ 246,274 $ — $ 246,274 $ — Agency CMOs 275,709 — 275,709 — Private label CMOs 125,987 — 103,113 22,874 Municipal securities 1,680,068 — 1,680,068 — Agency commercial MBS 1,163,969 — 1,163,969 — Corporate debt securities 19,295 — 19,295 — Collateralized loan obligations 7,015 — 7,015 — SBA securities 160,334 — 160,334 — Asset-backed and other securities 95,780 5,922 47,749 42,109 Total securities available-for-sale 3,774,431 5,922 3,703,526 64,983 Equity warrants 5,161 — — 5,161 Other derivative assets 1,873 — 1,873 — Total recurring assets $ 3,779,592 $ 5,922 $ 3,703,526 $ 70,144 Derivative liabilities $ 1,379 $ — $ 1,379 $ — Fair Value Measurements as of December 31, 2016 Measured on a Recurring Basis Total Level 1 Level 2 Level 3 (In thousands) Securities available‑for‑sale: Residential MBS and CMOs: Agency MBS $ 502,443 $ — $ 502,443 $ — Agency CMOs 146,289 — 146,289 — Private label CMOs 125,469 — 68,567 56,902 Municipal securities 1,456,459 — 1,456,459 — Agency commercial MBS 547,692 — 547,692 — Corporate debt securities 47,509 — 47,509 — Collateralized loan obligations 156,887 — 156,887 — SBA securities 178,845 — 178,845 — Asset-backed and other securities 62,237 2,080 51,784 8,373 Total securities available-for-sale 3,223,830 2,080 3,156,475 65,275 Equity warrants 5,497 — — 5,497 Other derivative assets 694 — 694 — Total recurring assets $ 3,230,021 $ 2,080 $ 3,157,169 $ 70,772 Derivative liabilities $ 3,285 $ — $ 3,285 $ — During the year ended December 31, 2017 , there was a $0.6 million transfer of private label CMOs from Level 2 to Level 3, a $21.2 million transfer of private label CMOs from Level 3 to Level 2, and a $1.2 million transfer from Level 3 equity warrants to Level 1 securities available-for-sale for assets measured on a recurring basis. During the year ended December 31, 2016 , there were no transfers of assets either between Level 1 and Level 2, and there was a $0.8 million transfer from Level 3 equity warrants to Level 1 securities available-for-sale for assets measured on a recurring basis. The following table presents information about the quantitative inputs and assumptions used to determine the fair values provided by our third party pricing service for our Level 3 private label CMOs and asset-backed securities available-for-sale measured at fair value on a recurring basis as of the date indicated: December 31, 2017 Private Label CMOs Asset-Backed Securities Weighted Weighted Range of Average Range of Average Unobservable Inputs Inputs Input Inputs Input Voluntary annual prepayment speeds 3.6% - 43.6% 8.6% 5% - 15% 13.8% Annual default rates 0.1% - 15.3% 2.5% 1% - 2% 1.9% Loss severity rates 4.0% - 102% 55.8% 10% - 60% 53.9% Discount rates 1.8% - 10.3% 5.3% 3.2% - 4.3% 3.6% The following table presents information about the quantitative inputs and assumptions used in the modified Black-Scholes option pricing model to determine the fair value for our Level 3 equity warrants measured at fair value on a recurring basis as of the date indicated: December 31, 2017 Equity Warrants Weighted Average Unobservable Inputs Input Volatility 16.7% Risk-free interest rate 2.1% Remaining life assumption (in years) 3.7 The following table summarizes activity for our Level 3 private label CMOs measured at fair value on a recurring basis for the years indicated: Year Ended December 31, Level 3 Private Label CMOs 2017 2016 2015 (In thousands) Balance, beginning of year $ 56,902 $ 81,241 $ 33,947 Total included in earnings 2,256 1,636 1,104 Total unrealized loss in comprehensive income (742 ) (1,648 ) (1,388 ) Sales (4,732 ) — — Transfer from Level 2 574 — — Transfers to Level 2 (21,165 ) — — Net settlements (10,219 ) (24,327 ) (3,881 ) Addition from the Square 1 acquisition — — 51,459 Balance, end of year $ 22,874 $ 56,902 $ 81,241 The following table summarizes activity for our Level 3 asset-backed securities measured at fair value on a recurring basis for the years indicated: Year Ended December 31, Level 3 Asset-Backed Securities 2017 2016 2015 (In thousands) Balance, beginning of year $ 8,373 $ 18,200 $ — Total included in earnings 367 96 — Total unrealized (loss) gain in comprehensive income (937 ) 94 — Purchases 42,910 — — Net settlements (8,604 ) (10,017 ) — Addition from the Square 1 acquisition — — 18,200 Balance, end of year $ 42,109 $ 8,373 $ 18,200 The following table summarizes activity for our Level 3 equity warrants measured at fair value on a recurring basis for the year ended December 31, 2017 and 2016 and the period from the October 6, 2015 Square 1 acquisition date to December 31, 2015: Year Ended December 31, Period Ended Level 3 Equity Warrants 2017 2016 December 31, 2015 (In thousands) Balance, beginning of year or acquisition date $ 5,497 $ 4,914 $ 5,552 Total included in earnings 2,532 1,402 530 Sales (3,093 ) (1,894 ) (1,529 ) Issuances 1,407 1,911 363 Transfers to Level 1 (securities available-for-sale) (1,182 ) (836 ) (2 ) Balance, end of year $ 5,161 $ 5,497 $ 4,914 The following tables present assets measured at fair value on a non‑recurring basis as of the dates indicated: Fair Value Measurement as of December 31, 2017 Measured on a Non‑Recurring Basis Total Level 1 Level 2 Level 3 (In thousands) Impaired Non‑PCI loans $ 61,095 $ — $ 5,143 $ 55,952 Loans held for sale 483,563 — 483,563 — Total non-recurring $ 544,658 $ — $ 488,706 $ 55,952 Fair Value Measurement as of December 31, 2016 Measured on a Non‑Recurring Basis Total Level 1 Level 2 Level 3 (In thousands) Impaired Non‑PCI loans $ 149,749 $ — $ 1,661 $ 148,088 OREO 11,224 — 11,224 — Investments carried at cost 242 — — 242 Total non-recurring $ 161,215 $ — $ 12,885 $ 148,330 The following table presents losses recognized on assets measured on a nonrecurring basis for the years indicated: Year Ended December 31, Loss on Assets Measured on a Non‑Recurring Basis 2017 2016 2015 (In thousands) Impaired Non‑PCI loans $ 20,422 $ 43,240 $ 16,097 Loans held for sale 957 — — OREO 14 2,576 4,726 Investments carried at cost — 10 17 Total net loss $ 21,393 $ 45,826 $ 20,840 The following table presents the valuation methodology and unobservable inputs for Level 3 assets measured at fair value on a nonrecurring basis as of the date indicated: December 31, 2017 Valuation Unobservable Weighted Asset Fair Value Technique Inputs Range Average (In thousands) Impaired Non-PCI loans $ 41,984 Discounted cash flows Discount rates 2.00% - 10.20% 7.43% 13,968 Third party appraisals No discounts Total non-recurring Level 3 $ 55,952 ASC Topic 825, “ Financial Instruments ,” requires disclosure of the estimated fair value of certain financial instruments and the methods and significant assumptions used to estimate such fair values. Additionally, certain financial instruments and all nonfinancial instruments are excluded from the applicable disclosure requirements. The following tables present carrying amounts and estimated fair values of certain financial instruments as of the dates indicated: December 31, 2017 Carrying Estimated Fair Value Amount Total Level 1 Level 2 Level 3 ( In thousands ) Financial Assets: Cash and due from banks $ 233,215 $ 233,215 $ 233,215 $ — $ — Interest‑earning deposits in financial institutions 165,222 165,222 165,222 — — Securities available‑for‑sale 3,774,431 3,774,431 5,922 3,703,526 64,983 Investment in FHLB stock 20,790 20,790 — 20,790 — Investments carried at cost 977 9,573 — — 9,573 Loans held for sale 481,100 483,563 — 483,563 — Loans and leases held for investment, net 16,833,287 17,023,098 — 5,143 17,017,955 Equity warrants 5,161 5,161 — — 5,161 Other derivative assets 1,873 1,873 — 1,873 — Financial Liabilities: Core deposits 15,937,012 15,937,012 — 15,937,012 — Non-core non-maturity deposits 863,202 863,202 — 863,202 — Time deposits 2,065,322 2,055,104 — 2,055,104 — Borrowings 467,342 467,343 467,000 343 — Subordinated debentures 462,437 444,383 — 444,383 — Derivative liabilities 1,379 1,379 — 1,379 — December 31, 2016 Carrying Estimated Fair Value Amount Total Level 1 Level 2 Level 3 ( In thousands ) Financial Assets: Cash and due from banks $ 337,965 $ 337,965 $ 337,965 $ — $ — Interest‑earning deposits in financial institutions 81,705 81,705 81,705 — — Securities available‑for‑sale 3,223,830 3,223,830 2,080 3,156,475 65,275 Investment in FHLB stock 21,870 21,870 — 21,870 — Investments carried at cost 1,416 3,843 — — 3,843 Loans and leases held for investment, net 15,298,716 15,494,808 — 1,661 15,493,147 Equity warrants 5,497 5,497 — — 5,497 Other derivative assets 694 694 — 694 — Financial Liabilities: Core deposits 12,523,834 12,523,834 — 12,523,834 — Non-core non-maturity deposits 1,174,487 1,174,487 — 1,174,487 — Time deposits 2,172,290 2,166,187 — 2,166,187 — Borrowings 905,812 905,838 591,000 314,838 — Subordinated debentures 440,744 424,507 — 424,507 — Derivative liabilities 3,285 3,285 — 3,285 — The following is a description of the valuation methodologies used to measure our assets recorded at fair value (under ASC Topic 820, “ Fair Value Measurement ”) and for estimating fair value for financial instruments not recorded at fair value (under ASC Topic 825). Cash and due from banks. The carrying amount is assumed to be the fair value because of the liquidity of these instruments. Interest‑earning deposits in financial institutions. The carrying amount is assumed to be the fair value given the short‑term nature of these deposits. Securities available‑for‑sale. Securities available‑for‑sale are measured and carried at fair value on a recurring basis. Unrealized gains and losses on available‑for‑sale securities are reported as a component of “Accumulated other comprehensive income” in the consolidated balance sheets. See Note 5. Investment Securities for further information on unrealized gains and losses on securities available‑for‑sale. Fair value for securities categorized as Level 1, which are publicly traded securities, are based on readily available quoted prices. In determining the fair value of the securities categorized as Level 2, we obtain a report from a nationally recognized broker‑dealer detailing the fair value of each investment security we hold as of each reporting date. The broker‑dealer uses observable market information to value our securities, with the primary source being a nationally recognized pricing service. We review the market prices provided by the broker‑dealer for our securities for reasonableness based on our understanding of the marketplace and we consider any credit issues related to the securities. As we have not made any adjustments to the market quotes provided to us and they are based on observable market data, they have been categorized as Level 2 within the fair value hierarchy. Our non-rated private label CMOs, non-rated private label asset-backed securities, and equity warrants (collectively, “the Level 3 Securities”) were categorized as Level 3 due in part to the inactive market for such securities. There is a wide range of prices quoted for our Level 3 Securities among independent third party pricing services, and this range reflects the significant judgment being exercised over the assumptions and variables that determine the pricing of such securities. We consider this subjectivity relating to our Level 3 Securities to be a significant unobservable input. Our fair value estimate was based on either 1) prices provided to us by a nationally recognized pricing service which we also use to determine the fair value of the majority of our securities portfolio, or 2) pricing estimates we obtained from brokers. We determined the reasonableness of the fair values by reviewing assumptions at the individual security level about prepayment, default expectations, estimated loss severity factors, and discount rates, all of which are not directly observable in the market. Significant changes in default expectations, loss severity factors, or discount rates, which occur all together or in isolation, would result in different fair value measurements. FHLB stock. Investments in FHLB stock are recorded at cost and measured for impairment quarterly. Ownership of FHLB stock is restricted to member banks and the securities do not have a readily determinable market value. Purchases and sales of these securities are at par value with the issuer. The fair value of investments in FHLB stock is equal to the carrying amount. Non-PCI loans and leases. As Non-PCI loans and leases are not measured at fair value, the following discussion relates to estimating the fair value disclosures under ASC Topic 825. Fair values are estimated for portfolios of loans and leases with similar financial characteristics. Loans are segregated by type and further segmented into fixed and adjustable rate interest terms by credit risk categories. The fair value estimates do not take into consideration the value of the loan portfolio in the event the loans are sold outside the parameters of normal operating activities. The fair value of performing fixed rate loans is estimating by discounting scheduled cash flows through the estimated maturity using estimated market prepayment speeds. The fair value of equipment leases is estimated by discounting scheduled lease and expected lease residual cash flows over their remaining term. The estimated market discount rates used for performing fixed rate loans and equipment leases are current market rates for instruments with similar risk and similar terms. The fair value of performing adjustable-rate loans is estimated by discounting scheduled cash flows through the next repricing date. As these loans reprice frequently at market rates and the credit risk is not considered to be greater than normal, the market value is typically close to the carrying amount of these loans. These methods and assumptions are not based on the exit price concept of fair value. Impaired Non‑PCI loans. Nonaccrual loans and performing troubled debt restructured loans are considered impaired for reporting purposes and are measured and recorded at fair value on a non‑recurring basis. Nonaccrual Non‑PCI loans with an unpaid principal balance over $250,000 and all performing troubled debt restructured loans are reviewed individually for the amount of impairment, if any. Nonaccrual Non‑PCI loans with an unpaid principal balance less than $250,000 are not individually assessed for impairment but are instead reserved for under our general reserve component. To the extent a loan is collateral dependent, we measure such impaired loan based on the estimated fair value of the underlying collateral. The fair value of each loan’s collateral is generally based on estimated market prices from an independently prepared appraisal, which is then adjusted for the cost related to liquidating such collateral; such valuation inputs result in a nonrecurring fair value measurement that is categorized as a Level 2 measurement. The Level 2 measurement is based on appraisals obtained within the last 12 months and for which a charge‑off was recognized or a change in the specific valuation allowance was made during the year ended December 31, 2017 . When adjustments are made to an appraised value to reflect various factors such as the age of the appraisal or known changes in the market or the collateral, such valuation inputs are considered unobservable and the fair value measurement is categorized as a Level 3 measurement. The impaired loans categorized as Level 3 also include unsecured loans and other secured loans whose fair values are based significantly on unobservable inputs such as the strength of a guarantor, including an SBA government guarantee, cash flows discounted at the effective loan rate, and management’s judgment. The impaired Non‑PCI loan balances shown above as measured on a non-recurring basis represent those nonaccrual and restructured loans for which impairment was recognized during the year ended December 31, 2017 . The amounts shown as net losses include the impairment recognized during the year ended December 31, 2017 , for the loan balances shown. Loans held for sale. Loans held for sale are carried at the lower of cost or fair value, with fair value adjustments recorded on a nonrecurring basis. The loans held for sale at December 31, 2017 consisted of cash flow loans, and the fair value of these loans was based on sale agreements which we entered into during the fourth quarter of 2017. Loans held for sale which are under contract for sale are considered Level 2 in the fair value hierarchy. Investments that do not have readily determinable fair values. Other investments accounted for under the cost or equity methods of accounting are carried at fair value on a nonrecurring basis to the extent that they are determined to be other-than-temporarily impaired during the period. As there is rarely an observable price or market for such investments, we determine fair value using internally developed models. Our models utilize industry valuation benchmarks, such as multiples of net revenue or EBITDA, to determine a value for the underlying enterprise. We may also reduce the value determined by the model due to illiquidity or other investee-specific characteristics which may affect the fair value. Significant decreases to these valuation benchmarks would result in significant decreases in the estimated fair values. We reduce this value by the value of debt outstanding to arrive at an estimated equity value of the enterprise. When an external event such as a purchase transaction, public offering or subsequent equity sale occurs, the pricing indicated by the external event is used to corroborate our internal valuation. Fair value measurements related to these investments are typically classified within Level 3 of the fair value hierarchy. OREO . The fair value of OREO is generally based on the lower of estimated market prices from independently prepared current appraisals or negotiated sales prices with potential buyers, less estimated costs to sell; such valuation inputs result in a fair value measurement that is categorized as a Level 2 measurement on a nonrecurring basis. As a matter of policy, appraisals are required annually and may be updated more frequently as circumstances require in the opinion of management. The Level 2 measurement for OREO is based on appraisals obtained within the last 12 months and for which a write‑down was recognized during the year ended December 31, 2017 . When a current appraised value is not available or management determines the fair value of the collateral is further impaired below the appraised value as a result of known changes in the market or the collateral and there is no observable market price, such valuation inputs result in a fair value measurement that is categorized as a Level 3 measurement. To the extent a negotiated sales price or reduced listing price represents a significant discount to an observable market price, such valuation input would result in a fair value measurement that is also considered a Level 3 measurement. The OREO losses disclosed are write‑downs based on either a recent appraisal obtained after foreclosure or an accepted purchase offer by an independent third party received after foreclosure. Deposits. Deposits are carried at historical cost. The fair values of deposits with no stated maturity, such as core deposits (defined as noninterest‑bearing demand, interest checking, money market, and savings accounts) and non-core non-maturity deposits, are equal to the amount payable on demand as of the balance sheet date and considered Level 2. The fair value of time deposits is based on the discounted value of contractual cash flows and considered Level 2. The discount rate is estimated using the rates currently offered for deposits of similar remaining maturities. No value has been separately assigned to the Company’s long‑term relationships with its deposit customers, such as a core deposit intangible. Borrowings. Borrowings include overnight FHLB advances and other fixed‑rate term borrowings. Borrowings are carried at amortized cost. The fair value of overnight FHLB advances is equal to the carrying value and considered Level 1. The fair value of fixed‑rate borrowings is calculated by discounting scheduled cash flows through the maturity dates or call dates, if applicable, using estimated market discount rates that reflect current rates offered for borrowings with similar remaining maturities and characteristics and are considered Level 2. Subordinated debentures. Subordinated debentures are carried at amortized cost. The fair value of subordinated debentures with variable rates is determined using a market discount rate on the expected cash flows and are considered Level 2. Derivative assets and liabilities. Derivatives are carried at fair value on a recurring basis and primarily relate to forward exchange contracts which we enter into to manage foreign exchange risk. Our derivatives are principally traded in over-the-counter markets where quoted market prices are not readily available. Instead, the fair value of derivatives is estimated using market observable inputs such as foreign exchange forward rates, interest rate yield curves, volatilities and basis spreads. We also consider counter-party credit risk in valuing our derivatives. We typically classify our foreign exchange derivatives in Level 2 of the fair value hierarchy. Equity Warrants. Equity warrants with net settlement terms are received in connection with extending loan commitments to certain of our customers. We estimate the fair value of equity warrants using a Black-Scholes option pricing model to approximate fair market value. For warrants of private companies, the model estimates market value for each warrant based on the most recent equity offering at the time of issuance, the warrant's exercise price, the warrant's expected life, a risk-free interest rate based on a duration-matched U.S. Treasury rate and volatility factors derived from the iShares Russell Microcap index (IWC). For warrants of publicly-traded companies, the model estimates market value for each warrant based on the underlying share price as of the evaluation date, the warrant's exercise price, the warrant's expected life, a risk-free interest rate based on a duration-matched U.S. Treasury rate and uses a company-specific volatility factor. We typically classify our equity warrant derivatives in Level 3 of the fair value hierarchy. Commitments to extend credit. The majority of our commitments to extend credit carry current market interest rates if converted to loans. Because these commitments are generally not assignable by either the borrower or us, they only have value to the borrower and us. The estimated fair value approximates the recorded deferred fee amounts and is excluded from the table above because it is not material. Limitations Fair value estimates are made at a specific point in time and are based on relevant market information and information about the financial instrument. These estimates do not reflect income taxes or any premium or discount that could result from offering for sale at one time the Company’s entire holdings of a particular financial instrument. Because no market exists for a portion of the Company’s financial instruments, fair value estimates are based on what management believes to be conservative judgments regarding expected future cash flows, current economic conditions, risk characteristics of various financial instruments, and other factors. These estimated fair values are subjective in nature and involve uncertainties and matters of significant judgment and therefore cannot be determined with precision. Changes in assumptions could significantly affect the estimates. Since the fair values have been estimated as of December 31, 2017 , the amounts that will actually be realized or paid at settlement or maturity of the instruments could be significantly different.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 13. INCOME TAXES The following table presents the components of income tax expense for the years indicated: December 31, 2017 2016 2015 (In thousands) Current Income Tax Expense: Federal $ 74,769 $ 101,530 $ 11,950 State 38,933 52,551 28,167 Total current income tax expense 113,702 154,081 40,117 Deferred Income Tax Expense (Benefit): Federal 63,463 55,857 128,436 State 19,748 (4,168 ) 11,964 Total deferred income tax expense 83,211 51,689 140,400 Total income tax expense $ 196,913 $ 205,770 $ 180,517 The following table presents a reconciliation of the recorded income tax expense to the amount of taxes computed by applying the applicable federal statutory income tax rate of 35% to earnings or loss before income taxes for the years indicated: December 31, 2017 2016 2015 (In thousands) Computed expected income tax expense at federal statutory rate $ 194,156 $ 195,278 $ 168,047 State tax expense, net of federal tax benefit 33,729 32,896 29,009 Tax‑exempt interest benefit (15,510 ) (13,992 ) (8,274 ) Increase in cash surrender value of life insurance (1,853 ) (1,544 ) (884 ) Tax credits (2,054 ) (1,439 ) (2,441 ) Nondeductible employee compensation 1,781 1,257 1,005 Nondeductible acquisition‑related expense 1,608 — 876 Change in unrecognized tax benefits 1,157 (2,268 ) (5,529 ) Valuation allowance change (13,071 ) (8,689 ) (2,917 ) Federal rate change (1,156 ) — — Other, net (1,874 ) 4,271 1,625 Recorded income tax expense $ 196,913 $ 205,770 $ 180,517 We have net operating loss carryforwards for state income tax purposes and federal tax credit carryforwards that can be utilized to offset future taxable income. Upon a change in ownership of more than 50% of our capital stock over a three-year period as measured under Section 382 of the Internal Revenue Code (“the Code”), our ability to utilize our net operating loss carryforwards and other tax attributes after the ownership change generally could be limited. The annual limit would generally equal the product of the applicable long term tax exempt rate and the value of the relevant entity’s capital stock immediately before the ownership change. We acquired Square 1 on October 6, 2015. As merger consideration, we issued approximately 18.1 million shares of common stock to the Square 1 stockholders. The issuance of these shares caused us to experience an ownership change under Section 382 of the Code. Consequently, the utilization of our net operating loss carryforwards, tax credits, and other tax attributes are subject to an annual limitation. While an annual limitation on the ability to utilize tax attributes resulted from the Square 1 transaction, our ability to utilize these tax attributes over time is not expected to be any less than that prior to the Square 1 transaction. At December 31, 2017 , we had no federal net operating loss carryforwards and approximately $1.1 billion of unused state net operating loss carryforwards available to be applied against future taxable income. The state net operating loss carryforwards will expire in varying amounts beginning in 2018 through 2037 . As of December 31, 2017 , for federal tax purposes, we had capital loss carryforwards of $33.5 million . If not used, these carryforwards will fully expire in 2021 . However, $30.5 million of the capital loss carryforwards will expire in 2018 if not used. As of December 31, 2017 , for federal tax purposes, we had foreign tax credit carryforwards of $5.7 million . The foreign tax credit carryforwards are available to offset federal taxes on future foreign source income. If not used, these carryforwards will fully expire in 2021 . The following table presents the tax effects of temporary differences that give rise to significant portions of deferred tax assets and deferred tax liabilities as of the dates indicated: December 31, 2017 2016 (In thousands) Deferred Tax Assets: Book allowance for loan losses in excess of tax specific charge-offs $ 60,349 $ 81,380 Interest on nonaccrual loans 8,519 7,485 Deferred compensation 6,174 3,148 Premises and equipment, principally due to differences in depreciation 3,789 7,395 Foreclosed assets valuation allowance 248 5,546 State tax benefit 3,781 7,187 Net operating losses 70,269 57,416 Capital loss carryforwards 14,264 17,740 Accrued liabilities 25,986 43,366 Unrealized loss from FDIC‑assisted acquisitions 4,654 7,207 Tax mark-to-market 9,207 11,793 Equity investments 7,549 15,195 Goodwill 15,641 29,996 Tax credits 5,651 16,493 Gross deferred tax assets 236,081 311,347 Valuation allowance (94,120 ) (100,920 ) Deferred tax assets, net of valuation allowance 141,961 210,427 Deferred Tax Liabilities: Core deposit and customer relationship intangibles 21,529 12,792 Deferred loan fees and costs 9,735 13,389 Unrealized gain on securities available‑for‑sale 15,107 4,118 FHLB stock 744 1,098 Subordinated debentures 24,518 37,499 Operating leases 65,286 41,785 Other 7,303 5,634 Gross deferred tax liabilities 144,222 116,315 Total net deferred tax asset (liability) $ (2,261 ) $ 94,112 Based upon our taxpaying history and estimates of taxable income over the years in which the items giving rise to the deferred tax assets are deductible, management believes it is more likely than not the Company will realize the benefits of these deductible differences. The Company had net income taxes receivable of $98.8 million at December 31, 2017 and net income taxes payable of $7.4 million at December 31, 2016 . As of December 31, 2017 and 2016 , the Company had a valuation allowance of $94.1 million and $100.9 million against DTA. Periodic reviews of the carrying amount of DTA are made to determine if a valuation allowance is necessary. A valuation allowance is required, based on available evidence, when it is more likely than not that all or a portion of a DTA will not be realized due to the inability to generate sufficient taxable income in the period and/or of the character necessary to utilize the benefit of the DTA. All available evidence, both positive and negative, that may affect the realizability of the DTA is identified and considered in determining the appropriate amount of the valuation allowance. It is more likely than not that these deferred tax assets subject to a valuation allowance will not be realized primarily due to their character and/or the expiration of the carryforward periods. Notwithstanding the increase in the valuation allowance of $6.3 million as a result of the TCJA, the reduction in the valuation allowance during 2017 was $13.1 million . The reduction was due primarily to the release of an $11.6 million valuation allowance against foreign tax credits that the Company had previously determined was more likely than not to be expired unused. Combined with the result of the TCJA, the net change in the valuation allowance in 2017 was a net decrease of $6.8 million . The TCJA, enacted on December 22, 2017, reduces the U.S. federal corporate tax rate from 35% to 21% , and, as a result, we re-measured our deferred federal tax assets and liabilities based on the rates at which they are expected to reverse in the future. The re-valuation of our deferred tax assets and liabilities is subject to further clarification of the TCJA and could result in refinements to our estimates. As a result, the actual impact to our deferred tax assets and liabilities and income tax expense due to the TCJA may vary from the amounts estimated. The following table summarizes the activity related to the Company's unrecognized tax benefits for the years indicated: Year Ended December 31, Unrecognized Tax Benefits 2017 2016 (In thousands) Balance, beginning of year $ 9,985 $ 15,155 Increase based on tax positions related to prior years 5,725 17,099 Reductions for tax positions related to prior years (767 ) (1,901 ) Reductions related to settlements (3,795 ) (19,833 ) Reductions for tax positions as a result of a lapse of the applicable statute of limitations (939 ) (535 ) Balance, end of year $ 10,209 $ 9,985 As of December 31, 2017 and 2016 , our unrecognized tax benefits that, if recognized, would affect the effective tax rate were $2.2 million and $1.1 million . Due to the potential for the resolution of federal and state examinations and the expiration of various statutes of limitations, it is reasonably possible that our gross unrecognized tax benefits may decrease within the next twelve months by as much as $1.5 million . We recognize interest and penalties related to unrecognized tax benefits as a component of income tax expense. For the year ended December 31, 2017 , we recognized $0.2 million in expense for interest expense and penalties. For the year ended December 31, 2016 , we reduced our accrual for interest expense and penalties and recognized $0.6 million in income related to these items. For the year ended December 31, 2015 , we reduced our accrual for interest expense and penalties and recognized $2.4 million in income related to these items. We had $0.5 million and $0.3 million accrued for the payment of interest and penalties as of December 31, 2017 and 2016 . We file federal and state income tax returns with the Internal Revenue Service ("IRS") and various state and local jurisdictions and generally remain subject to examinations by these tax jurisdictions for tax years 2009 through 2016 . We are currently under examination by the IRS for tax years 2011 through 2012 and certain state jurisdictions for tax years 2009 through 2015 .

Earnings per Share

Earnings per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	NOTE 14. EARNINGS PER SHARE The following table presents the computation of basic and diluted net earnings per share for the years indicated: Year Ended December 31, 2017 2016 2015 (Dollars in thousands, except per share data) Basic Earnings Per Share: Net earnings $ 357,818 $ 352,166 $ 299,619 Less: earnings allocated to unvested restricted stock (1) (4,184 ) (3,988 ) (2,892 ) Net earnings allocated to common shares $ 353,634 $ 348,178 $ 296,727 Weighted-average basic shares and unvested restricted stock outstanding 123,060 121,670 107,401 Less: weighted-average unvested restricted stock outstanding (1,447 ) (1,431 ) (1,074 ) Weighted-average basic shares outstanding 121,613 120,239 106,327 Basic earnings per share: $ 2.91 $ 2.90 $ 2.79 Diluted Earnings Per Share: Net earnings allocated to common shares $ 353,634 $ 348,178 $ 296,727 Weighted-average basic shares outstanding 121,613 120,239 106,327 Diluted earnings per share: $ 2.91 $ 2.90 $ 2.79 ________________________ (1) Represents cash dividends paid to holders of unvested restricted stock, net of forfeitures, plus undistributed earnings amounts available to holders of unvested restricted stock, if any.

Stock Based Compensation Plan

Stock Based Compensation Plan	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	NOTE 15. STOCK-BASED COMPENSATION The Company’s 2017 Stock Incentive Plan, or the 2017 Plan, permits stock-based compensation awards to officers, directors, key employees, and consultants. The 2017 Plan authorized grants of stock‑based compensation instruments to issue up to 4,000,000 shares of Company common stock. As of December 31, 2017 , there were 3,638,497 shares available for grant under the 2017 Plan. Though frozen for new issuances, certain awards issued under the 2003 Stock Incentive Plan, or the 2003 Plan, remain outstanding. Restricted Stock Restricted stock amortization totaled $24.9 million , $22.7 million and $15.0 million for the years ended December 31, 2017 , 2016 and 2015 . Such amounts are included in compensation expense on the accompanying consolidated statements of earnings. The income tax benefit recognized in the consolidated statements of earnings related to this expense was $8.9 million , $8.4 million , and $5.6 million for the years ended December 31, 2017 , 2016 and 2015 . The amount of unrecognized compensation expense related to all unvested TRSAs and PRSUs as of December 31, 2017 totaled $49.0 million . Such expense is expected to be recognized over a weighted average period of 1.5 years . The following table presents a summary of restricted stock transactions during the year ended December 31, 2017 : TRSAs PRSUs Weighted Weighted Average Average Grant Date Grant Date Number of Fair Value Number of Fair Value Shares (Per Share) Units (Per Unit) Unvested restricted stock, December 31, 2016 1,476,132 $39.83 153,715 $27.32 Granted 557,955 $50.08 85,310 $57.80 Vested (498,186 ) $40.20 — $— Forfeited (99,781 ) $42.87 — $— Unvested restricted stock, December 31, 2017 1,436,120 $43.47 239,025 $38.20 Time-Based Restricted Stock Awards At December 31, 2017 , there were 1,436,120 shares of unvested TRSAs outstanding pursuant to the Company's 2003 and 2017 Stock Incentive Plans (the "Plans"). The TRSAs generally vest over a service period of three to four years from the date of the grant or immediately upon death of an employee. For awards granted before December 11, 2014, time-based restricted common stock also vests immediately upon a change in control of the Company, as defined in the Plans. Grants issued on or after December 11, 2014, are subject to "double-trigger" vesting, meaning that, in the event of a change in control of the Company, as defined in the Plans, and in the event an employee's employment is terminated within 24 months after the change in control by the Company without Cause or by the employee for Good Reason, as defined in the Plans, such awards will vest. Compensation expense related to TRSAs is based on the fair value of the underlying stock on the award date and is recognized over the vesting period using the straight‑line method. The weighted average grant date fair value per share of TRSAs granted during 2017 , 2016 and 2015 were $ 50.08 , $36.05 and $46.18 . The vesting date fair value of TRSAs that vested during 2017 , 2016 and 2015 were $24.9 million , $14.4 million and $14.7 million . Performance-Based Restricted Stock Units At December 31, 2017 , there were 239,025 units of unvested PRSUs that have been granted. The PRSUs will vest only if performance goals with respect to certain financial metrics are met over a three-year performance period. The PRSUs are not considered issued and outstanding under the 2003 Stock Incentive Plan until they vest. PRSUs are granted and initially expensed based on a target number. The number of shares that will ultimately vest based on actual performance will range from zero to a maximum of either 150% or 200% of target. Compensation expense related to PRSUs is based on the fair value of the underlying stock on the award date and is amortized over the vesting period using the straight-line method unless it is determined that: (1) attainment of the financial metrics is less than probable, in which case a portion of the amortization is suspended, or (2) attainment of the financial metrics is improbable, in which case a portion of the previously recognized amortization is reversed and also suspended. If it is determined that attainment of a financial measure higher than target is probable, the amortization will increase up to 150% or 200% of the target amortization amount. Annual PRSU expense may vary during the three-year performance period based upon changes in management's estimate of the number of shares that may ultimately vest. In the case where the performance target for the PRSU’s is based on a market condition (such as total shareholder return), the amortization is neither reversed nor suspended if it is subsequently determined that the attainment of the performance target is less than probable or improbable. Upon a change in control, each PRSU will (i) be deemed earned at the target level with respect to all open performance periods if the change in control occurs within six months after the grant date, and (ii) be deemed earned at the actual performance level as of the date of the change in control if a change in control occurs more than six months after the grant date, and in both cases, the PRSU will cease to be subject to any further performance conditions, but will be subject to time-based service vesting following the change in control in accordance with the original performance period. The weighted average grant date fair value per share of PRSUs granted during 2017 and 2016 was $57.80 and $27.32 . There were no grants of PRSUs prior to 2016. There were no PRSUs that vested during 2017 , 2016 , and 2015 .

Benefit Plans

Benefit Plans	12 Months Ended
	Dec. 31, 2017
Benefit Plans [Abstract]
Benefits Plans	NOTE 16. BENEFIT PLANS 401(K) Plans The Company sponsors a defined contribution plan for the benefit of its employees. Participants are eligible to participate immediately as long as they are scheduled to work a minimum of 1,000 hours and are at least 18 years of age. Eligible participants may contribute up to 60% of their annual compensation, not to exceed the dollar limit imposed by the Internal Revenue Code. Employer contributions are determined annually by the Board of Directors in accordance with plan requirements and applicable tax code. Expense related to 401(k) employer matching contributions was $4.0 million , $3.7 million and $2.8 million for the years ended December 31, 2017 , 2016 , and 2015 .

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Disclosure [Abstract]
Stockholders' Equity	NOTE 17. STOCKHOLDERS' EQUITY Common Stock Repurchased The Company's common stock repurchased consisted of: (1) restricted stock surrendered as treasury shares and (2) stock purchased under the Company's Stock Repurchase Program and retired. Treasury Shares As a Delaware corporation, the Company records treasury shares for shares surrendered to the Company resulting from statutory payroll tax obligations arising from the vesting of restricted stock. During the years ended December 31, 2017 , 2016 , and 2015 , the Company purchased 188,870 treasury shares at a weighted average price of $50.17 per share, 141,358 treasury shares at a weighted average price of $37.59 per share, and 180,822 treasury shares at a weighted average price of $46.46 per share. Stock Repurchase Program The Stock Repurchase Program was initially authorized by PacWest's Board of Directors on October 17, 2016 , pursuant to which the Company could, until December 31, 2017 , purchase shares of its common stock for an aggregate purchase price not to exceed $400 million . On November 15, 2017 , PacWest's Board of Directors amended the Stock Repurchase Program to reduce the authorized purchase amount to $150 million and extend the maturity date to December 31, 2018 . On February 14, 2018 , PacWest's Board of Directors amended the Stock Repurchase Program to increase the authorized purchase amount to $350 million and extend the maturity date to February 28, 2019 . The common stock repurchases may be effected through open market purchases or in privately negotiated transactions and may utilize any derivative or similar instrument to effect share repurchase transactions (including, without limitation, accelerated share repurchase contracts, equity forward transactions, equity option transactions, equity swap transactions, cap transactions, collar transactions, floor transactions or other similar transactions or any combination of the foregoing transactions). The amount and exact timing of any repurchases will depend upon market conditions and other factors. The Stock Repurchase Program may be suspended or discontinued at any time. During the year ended December 31, 2017 , the Company repurchased 2,081,227 shares for $99.7 million at a weighted average price of $47.89 per share. During the year ended December 31, 2016 , the Company repurchased 652,835 shares for $27.9 million at a weighted average price of $42.78 per share. All shares repurchased under the Stock Repurchase Program were retired upon settlement. At December 31, 2017 , the remaining amount that could be used to repurchase shares under the Stock Repurchase Program was $112.5 million . After the amendment on February 14, 2018 , the remaining amount that could be used to repurchase shares under the Stock Repurchase Program is $350 million .

Dividend Availability and Regul

Dividend Availability and Regulatory Matters	12 Months Ended
	Dec. 31, 2017
Dividend Availability and Regulatory Matters [Abstract]
Dividend Availability and Regulatory Matters	NOTE 18. DIVIDEND AVAILABILITY AND REGULATORY MATTERS Holders of Company common stock may receive dividends declared by the Board of Directors out of funds legally available under DGCL and certain federal laws and regulations governing the banking and financial services business. Our ability to pay dividends to our stockholders is subject to the restrictions set forth in DGCL and certain covenants contained in our subordinated debentures and borrowing agreements. Notification to the FRB is also required prior to our declaring and paying dividends during any period in which our quarterly and/or cumulative twelve‑month net earnings are insufficient to fund the dividend amount, among other requirements. Should the FRB object to payment of dividends, we would not be able to make the payment until approval is received or we no longer need to provide notice under applicable regulations. It is possible, depending upon the financial condition of the Bank and other factors, that the FRB, the FDIC, or the DBO, could assert that payment of dividends or other payments is an unsafe or unsound practice. The Bank is subject to restrictions under certain federal and state laws and regulations governing banks which limit its ability to transfer funds to the holding company through intercompany loans, advances or cash dividends. Dividends paid by California state-chartered banks such as Pacific Western are regulated by the DBO and FDIC under their general supervisory authority as it relates to a bank’s capital requirements. A state-chartered bank may declare a dividend without the approval of the DBO and FDIC as long as the total dividends declared in a calendar year do not exceed either the retained earnings or the total of net earnings for three previous fiscal years less any dividend paid during such period. During 2017 , PacWest received $265 million in dividends from the Bank. Since the Bank had an accumulated deficit of $434.8 million at December 31, 2017 , for the foreseeable future dividends from the Bank to PacWest will continue to require DBO and FDIC approval. PacWest, as a bank holding company, is subject to regulation by the FRB under the BHCA. The FDICIA required that the federal regulatory agencies adopt regulations defining capital tiers for banks: well capitalized, adequately capitalized, undercapitalized, significantly undercapitalized and critically undercapitalized. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Company’s consolidated 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 the Company’s and the Bank’s 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. Quantitative measures established by regulation to ensure capital adequacy require the Company and the Bank to maintain minimum amounts and ratios of common equity Tier 1, Tier 1, and total capital to risk‑weighted assets ("total capital ratio"), and of Tier I capital to average assets, adjusted for goodwill and other non-qualifying intangible assets and other assets (“leverage ratio”). Common equity Tier 1 capital includes common stockholders’ equity less goodwill and certain other deductions (including a portion of servicing assets and the after‑tax unrealized net gains and losses on securities available‑for‑sale). Tier 1 capital includes common equity Tier 1 plus additional Tier 1 capital instruments meeting certain requirements. Total capital includes Tier 1 capital and other items such as subordinated debt and the allowance for credit losses. All three measures are stated as a percentage of risk‑weighted assets, which are measured based on their perceived credit risk and include certain off‑balance sheet exposures, such as unfunded loan commitments and letters of credit. Regulatory capital requirements limit the amount of deferred tax assets that may be included when determining the amount of regulatory capital. Deferred tax asset amounts in excess of the calculated limit are disallowed from regulatory capital. At December 31, 2017 , such disallowed amounts were $0.2 million for the Company and $0.1 million for the Bank. No assurance can be given that the regulatory capital deferred tax asset limitation will not increase in the future or that the Company or Bank will not have increased deferred tax assets that are disallowed. Banks considered to be “adequately capitalized” are required to maintain a minimum total capital ratio of 8.0% , a minimum Tier 1 capital ratio of 6.0% , a minimum common equity Tier 1 capital ratio of 4.5% , and a minimum leverage ratio of 4.0% . Banks considered to be “well capitalized” must maintain a minimum total capital ratio of 10.0% , a minimum Tier 1 capital ratio of 8.0% , a minimum common equity Tier 1 capital ratio of 6.5% , and a minimum leverage ratio of 5.0% . As of December 31, 2017 , the most recent notification date to the regulatory agencies, the Company and the Bank are each “well capitalized” under the regulatory framework for prompt corrective action. There are no conditions or events since that notification that management believes have changed the Company’s or any of the Bank’s categories. Management believes, as of December 31, 2017 , that the Company and the Bank met all capital adequacy requirements to which we are subject. Basel III, the comprehensive regulatory capital rules for U.S. banking organizations, became effective for the Company and the Bank on January 1, 2015, subject to phase-in periods for certain components and other provisions. The most significant provisions of Basel III which applied to the Company and the Bank were the phase-out of trust preferred securities from Tier 1 capital, the higher risk-weighting of high volatility and past due real estate loans, and the capital treatment of deferred tax assets and liabilities above certain thresholds. Beginning January 1, 2016, Basel III requires all banking organizations to maintain a capital conservation buffer above the minimum risk-based capital requirements in order to avoid certain limitations on capital distributions, stock repurchases and discretionary bonus payments to executive officers. The capital conservation buffer is exclusively comprised of common equity tier 1 capital, and it applies to each of the three risk-based capital ratios but not to the leverage ratio. At December 31, 2017 , the Company and Bank were in compliance with the capital conservation buffer requirement. The capital conservation buffer will increase by 0.625% each year through 2019, at which point, the common equity tier 1, tier 1 and total capital ratio minimums inclusive of the capital conservation buffer will be 7.0%, 8.5%, and 10.5%. The following table presents actual capital amounts and ratios for the Company and the Bank as of the dates indicated: Well Capitalized Minimum Excess Actual Requirement Capital Amount Ratio Amount Ratio Amount (Dollars in thousands) December 31, 2017 Tier I leverage PacWest Bancorp Consolidated $ 2,361,800 10.66% $ 1,107,900 5.00% $ 1,253,900 Pacific Western Bank $ 2,574,561 11.75% $ 1,095,656 5.00% $ 1,478,905 Common equity Tier I capital PacWest Bancorp Consolidated $ 2,361,800 10.91% $ 1,407,743 6.50% $ 954,057 Pacific Western Bank $ 2,574,561 11.91% $ 1,405,299 6.50% $ 1,169,262 Tier I capital PacWest Bancorp Consolidated $ 2,361,800 10.91% $ 1,732,607 8.00% $ 629,193 Pacific Western Bank $ 2,574,561 11.91% $ 1,729,599 8.00% $ 844,962 Total capital PacWest Bancorp Consolidated $ 2,978,643 13.75% $ 2,165,759 10.00% $ 812,884 Pacific Western Bank $ 2,742,624 12.69% $ 2,161,999 10.00% $ 580,625 December 31, 2016 Tier I leverage PacWest Bancorp Consolidated $ 2,286,203 11.91% $ 959,477 5.00% $ 1,326,726 Pacific Western Bank $ 2,184,097 11.40% $ 957,630 5.00% $ 1,226,467 Common equity Tier I capital PacWest Bancorp Consolidated $ 2,286,203 12.31% $ 1,206,960 6.50% $ 1,079,243 Pacific Western Bank $ 2,184,097 11.78% $ 1,205,541 6.50% $ 978,556 Tier I capital PacWest Bancorp Consolidated $ 2,286,203 12.31% $ 1,485,490 8.00% $ 800,713 Pacific Western Bank $ 2,184,097 11.78% $ 1,483,742 8.00% $ 700,355 Total capital PacWest Bancorp Consolidated $ 2,889,163 15.56% $ 1,856,862 10.00% $ 1,032,301 Pacific Western Bank $ 2,358,829 12.72% $ 1,854,678 10.00% $ 504,151 We issued or assumed through mergers subordinated debentures to trusts that were established by us or entities that we previously acquired, which, in turn, issued trust preferred securities. The carrying value of subordinated debentures totaled $462.4 million at December 31, 2017 . At December 31, 2017 , none of the trust preferred securities were included in the Company's Tier I capital under the phase-out limitations of Basel III, and $448.8 million was included in Tier II capital. Interest payments on subordinated debentures are considered dividend payments under the FRB regulations and subject to the same notification requirements for declaring and paying dividends on common stock.

Condensed Financial Information

Condensed Financial Information Of Parent Company	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information Of Parent Company [Abstract]
Condensed Financial Information of Parent Company Only Disclosure	NOTE 19. CONDENSED FINANCIAL INFORMATION OF PARENT COMPANY The following tables present the parent company only condensed balance sheets and the related condensed statements of earnings and condensed statements of cash flows as of and for the years indicated: Parent Company Only December 31, Condensed Balance Sheets 2017 2016 (In thousands) Assets: Cash and cash equivalents $ 185,511 $ 494,765 Investments in subsidiaries 4,869,391 4,053,711 Other assets 76,458 67,074 Total assets $ 5,131,360 $ 4,615,550 Liabilities: Subordinated debentures $ 147,233 $ 134,360 Other liabilities 6,529 2,135 Total liabilities 153,762 136,495 Stockholders’ equity 4,977,598 4,479,055 Total liabilities and stockholders’ equity $ 5,131,360 $ 4,615,550 Parent Company Only December 31, Condensed Statements of Earnings 2017 2016 2015 (In thousands) Miscellaneous income $ 3,393 $ 2,146 $ 1,458 Dividends from Bank subsidiary 265,000 259,000 214,000 Total income 268,393 261,146 215,458 Interest expense 5,519 4,816 4,279 Operating expenses 8,273 7,732 6,983 Total expenses 13,792 12,548 11,262 Earnings before income taxes and equity in undistributed earnings of subsidiaries 254,601 248,598 204,196 Income tax benefit 19,957 2,612 4,225 Earnings before equity in undistributed earnings of subsidiaries 274,558 251,210 208,421 Equity in undistributed earnings of subsidiaries 83,260 100,956 91,198 Net earnings $ 357,818 $ 352,166 $ 299,619 Parent Company Only December 31, Condensed Statements of Cash Flows 2017 2016 2015 (In thousands) Cash flows from operating activities: Net earnings $ 357,818 $ 352,166 $ 299,619 Adjustments to reconcile net earnings to net cash provided by operating activities: Change in other assets (34,274 ) 96,668 145,709 Change in liabilities 4,857 (17,311 ) 9,115 Gain on sale of securities, net (15 ) (405 ) — Earned stock compensation 25,568 23,319 14,994 Tax effect of restricted stock vesting included in stockholders’ equity — 4,406 841 Equity in undistributed earnings of subsidiaries (83,260 ) (100,956 ) (91,198 ) Net cash provided by operating activities 270,694 357,887 379,080 Cash flows from investing activities: Proceeds from sales of securities available-for-sale 426 995 — Net cash and cash equivalents (paid in) acquired in acquisitions (223,818 ) — 3,021 Net cash (used in) provided by investing activities (223,392 ) 995 3,021 Cash flows from financing activities: Common stock repurchased and restricted stock surrendered (109,153 ) (33,244 ) (8,400 ) Tax effect of restricted stock vesting included in stockholders’ equity — (4,406 ) (841 ) Increase in note receivable — — (50,000 ) Cash dividends paid, net (247,403 ) (243,437 ) (215,110 ) Net cash used in financing activities (356,556 ) (281,087 ) (274,351 ) Net (decrease) increase in cash and cash equivalents (309,254 ) 77,795 107,750 Cash and cash equivalents, beginning of year 494,765 416,970 309,220 Cash and cash equivalents, end of year $ 185,511 $ 494,765 $ 416,970 Supplemental disclosure of noncash investing and financing activities: Common stock issued for acquisitions $ 446,233 $ — $ 797,433

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	NOTE 21. SUBSEQUENT EVENTS Stock Repurchase Program On February 14, 2018 , PacWest Bancorp’s Board of Directors amended its existing stock repurchase program to increase the authorized repurchase amount to $350 million and extended the expiration date to February 28, 2019 . After the amendment on February 14, 2018 , the remaining amount that could be used to repurchase shares under the Stock Repurchase Program is $350 million . Common Stock Dividends On February 1, 2018 , the Company announced that the Board of Directors had declared a quarterly cash dividend of $0.50 per common share. The cash dividend is payable on February 28, 2018 to stockholders of record at the close of business on February 20, 2018 . We have evaluated events that have occurred subsequent to December 31, 2017 and have concluded there are no subsequent events that would require recognition in the accompanying consolidated financial statements.

Accounting Policies (Policies)

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Business Combinations and Other Purchase of Business Transactions	We are focused on relationship-based business banking to small, middle-market, and venture-backed businesses nationwide. The Bank offers a broad range of loan and lease and deposit products and services through 76 full-service branches located throughout the State of California, one branch located in Durham, North Carolina, and loan production offices located in cities across the country. We provide commercial banking services, including real estate, construction, and commercial loans, and comprehensive deposit and treasury management services to small and middle-market businesses. We offer additional products and services through our CapitalSource and Square 1 Bank divisions. Our CapitalSource Division provides asset-based, real estate, equipment, and cash flow loans and treasury management services to established middle market businesses on a national basis. Our Square 1 Bank Division offers a comprehensive suite of financial services focused on entrepreneurial businesses and their venture capital and private equity investors, with offices located in key innovation hubs across the United States. In addition, we provide investment advisory and asset management services to select clients through Square 1 Asset Management, Inc., a wholly-owned subsidiary of the Bank and a SEC-registered investment adviser. We generate our revenue primarily from interest received on loans and leases and, to a lesser extent, from interest received on investment securities, and fees received in connection with deposit services, extending credit and other services offered, including treasury management and investment management services. Our major operating expenses are the interest paid by the Bank on deposits and borrowings, compensation and general operating expenses. We completed 29 acquisitions from May 1, 2000 through December 31, 2017 , including the acquisitions of CUB on October 20, 2017 and Square 1 on October 6, 2015 . Our acquisitions were accounted for using the acquisition method of accounting and, accordingly, the operating results of the acquired entities were included in the consolidated financial statements from their respective acquisition dates. See Note 3. Acquisitions for more information about the CUB and Square 1 acquisitions.
Basis of Presentation	(b) Basis of Presentation
Use of Estimates	Use of Estimates We have made a number of estimates and assumptions relating to the reporting of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period to prepare these consolidated financial statements in conformity with U.S. GAAP. Actual results could differ from those estimates. Material estimates subject to change in the near term include, among other items, the allowance for credit losses, the carrying value of intangible assets, the fair value estimates of assets acquired and liabilities assumed in acquisitions and the realization of deferred tax assets/liabilities. These estimates may be adjusted as more current information becomes available, and any adjustment may be significant. As described in Note 3. Acquisitions below, we completed the CUB acquisition on October 20, 2017 and the Square 1 acquisition on October 6, 2015 . The acquired assets and liabilities in each of these acquisitions were measured at their estimated fair values. Management made significant estimates and exercised significant judgment in estimating such fair values and accounting for the acquired assets and assumed liabilities in each of these transactions.
Cash and Cash Equivalents	Cash and Cash Equivalents For purposes of the consolidated statements of cash flows, cash and cash equivalents consist of: (1) cash and due from banks, and (2) interest‑earning deposits in financial institutions. Interest‑earning deposits in financial institutions represent mostly cash held at the FRBSF, the majority of which is immediately available.
Investment Securities	Investment Securities We determine the classification of securities at the time of purchase. If we have the intent and the ability at the time of purchase to hold securities until maturity, they are classified as held‑to‑maturity. Investment securities held‑to‑maturity are stated at amortized cost. Securities to be held for indefinite periods of time, but not necessarily to be held‑to‑maturity or on a long‑term basis, are classified as available‑for‑sale and carried at estimated fair value, with unrealized gains or losses reported as a separate component of stockholders’ equity in accumulated other comprehensive income, net of applicable income taxes. Securities available‑for‑sale include securities that management intends to use as part of its asset/liability management strategy and that may be sold in response to changes in interest rates, prepayment risk, and other related factors. Securities are individually evaluated for appropriate classification when acquired. As a result, similar types of securities may be classified differently depending on factors existing at the time of purchase. The carrying values of all securities are adjusted for amortization of premiums and accretion of discounts using the interest method. Premiums on callable securities are amortized to the earliest call date. Realized gains or losses on the sale of securities, if any, are determined using the amortized cost of the specific securities sold. Declines in the fair value of debt securities classified as available-for-sale are reviewed to determine whether the impairment is other-than-temporary. This review considers a number of factors, including the severity of the decline in fair value, current market conditions, historical performance of the security, risk ratings and the length of time the security has been in an unrealized loss position. If we do not expect to recover the entire amortized cost basis of the security, then an other-than-temporary impairment is considered to have occurred. The cost basis of the security is written down to its estimated fair value and the amount of the write‑down is recognized through a charge to earnings. Investments in FHLB stock are carried at cost and evaluated regularly for impairment. FHLB stock is expected to be redeemed at par and is a required investment based on measurements of the Bank’s assets and/or borrowing levels.
Loans and Leases	Loans and Leases Originated loans. Loans are originated by the Company with the intent to hold them for investment and are stated at the principal amount outstanding, net of unearned income. Unearned income includes deferred unamortized nonrefundable loan fees and direct loan origination costs. Net deferred fees or costs are recognized as an adjustment to interest income over the contractual life of the loans using the effective interest method or taken into income when the related loans are paid off or sold. The amortization of loan fees or costs is discontinued when a loan is placed on nonaccrual status. Interest income is recorded on an accrual basis in accordance with the terms of the respective loan. Purchased loans. Purchased loans are stated at the principal amount outstanding, net of unearned discounts or unamortized premiums. All loans acquired in our acquisitions are initially measured and recorded at their fair value on the acquisition date. A component of the initial fair value measurement is an estimate of the credit losses over the life of the purchased loans. Purchased loans are also evaluated for impairment as of the acquisition date and are accounted for as “acquired non‑impaired” or “purchased credit impaired” loans. Acquired non‑impaired loans. Acquired non‑impaired loans are those loans for which there was no evidence of credit deterioration at their acquisition date and it was probable that we would be able to collect all contractually required payments. Acquired non‑impaired loans, together with originated loans, are referred to as Non‑PCI loans. Purchase discounts or premiums on acquired non‑impaired loans are recognized as an adjustment to interest income over the contractual life of such loans using the effective interest method or taken into income when the related loans are paid off or sold. Purchased credit impaired loans. PCI loans are accounted for in accordance with ASC Subtopic 310‑30, “ Loans and Debt Securities Acquired with Deteriorated Credit Quality.” A purchased loan is deemed to be credit impaired when there is evidence of credit deterioration since its origination and it is probable at the acquisition date that collection of all contractually required payments is unlikely. We apply PCI loan accounting when we acquire loans deemed to be impaired, and as a general policy election when we acquire a portfolio of loans in a distressed bank acquisition. For PCI loans, at the time of acquisition we (i) calculated the contractual amount and timing of undiscounted principal and interest payments (the “undiscounted contractual cash flows”) and (ii) estimated the amount and timing of undiscounted expected principal and interest payments (the “undiscounted expected cash flows”). The difference between the undiscounted contractual cash flows and the undiscounted expected cash flows is the nonaccretable difference. The nonaccretable difference represents an estimate of the loss exposure of principal and interest related to the PCI loan portfolios; such amount is subject to change over time based on the performance of such loans. The carrying value of PCI loans is reduced by payments received, both principal and interest, and increased by the portion of the accretable yield recognized as interest income. The excess of the undiscounted expected cash flows at acquisition over the initial fair value of acquired impaired loans is referred to as the “accretable yield” and is recorded as interest income over the estimated life of the loans using the effective yield method if the timing and amount of the future cash flows is reasonably estimable. PCI loans that are contractually past due are still considered to be accruing and performing as long as there is an expectation that the estimated cash flows will be received. If the timing and amount of cash flows is uncertain, then recognition of interest income will be suspended. All cash payments received will be recognized as a reduction of the recorded investment until satisfied. Cash payments received in excess of the recorded investment will be recorded as interest income on a cash basis. As part of the fair value process and the subsequent accounting, the Company aggregates PCI loans into pools having common credit risk characteristics such as type and risk rating. Increases in expected cash flows over those previously estimated increase the accretable yield and are recognized as interest income prospectively. Decreases in the amount and changes in the timing of expected cash flows compared to those previously estimated decrease the accretable yield and usually result in a provision for loan losses and the establishment of an allowance for loan losses. As the accretable yield increases or decreases from changes in cash flow expectations, the offset is a decrease or increase to the nonaccretable difference. The accretable yield is measured at each financial reporting date based on information then currently available and represents the difference between the remaining undiscounted expected cash flows and the current carrying value of the loans. Leases. We provide equipment financing to our customers through a variety of lease arrangements. For direct financing leases, lease receivables are recorded on the balance sheet but the leased property is not, although we generally retain legal title to the leased property until the end of each lease. Direct financing leases are stated at the net amount of minimum lease payments receivable, plus any unguaranteed residual value, less the amount of unearned income and net acquisition discount at the reporting date. Direct lease origination costs are amortized using the effective interest method over the life of the leases. Leases acquired in an acquisition are initially measured and recorded at their fair value on the acquisition date. Purchase discount or premium on acquired leases is recognized as an adjustment to interest income over the contractual life of the leases using the effective interest method or taken into income when the related leases are paid off. Direct financing leases are subject to our allowance for loans and leases. We also have operating leases where we purchase equipment which is then leased to our customers. We receive periodic rental income payments, which are recorded as "Noninterest income" in the consolidated statements of earnings, and the equipment remains on our balance sheet and is depreciated according to our fixed asset accounting policy. Loans and leases held for sale. As part of our management of the loans and leases held in our portfolio, on occasion we will transfer loans from held for investment to held for sale. Upon transfer, any associated allowance for loan and lease loss is charged off and the carrying value of the loan is adjusted to the lower of cost or estimated fair value. The net deferred fees and costs associated with loans held for sale are deferred (not accreted or amortized to interest income) until the related loans are sold. Gains or losses on the sale of these loans are recorded as "Noninterest income" in the consolidated statements of earnings. Delinquent or past due loans and leases. Loans and leases are considered delinquent when principal or interest payments are past due 30 days or more; delinquent loans may remain on accrual status between 30 days and 89 days past due. Nonaccrual loans and leases. When we discontinue the accrual of interest on a loan or lease it is designated as nonaccrual. We discontinue the accrual of interest on a loan generally when principal or interest payments are past due 90 days or when, in the opinion of management, there is a reasonable doubt as to collectability in the normal course of business. Loans with interest or principal past due 90 days may be accruing if the loans are concluded to be well-secured and in the process of collection; however, these loans are still reported as nonperforming loans. When loans are placed on nonaccrual status, all interest previously accrued but not collected is reversed against current period interest income. Income on nonaccrual loans is subsequently recognized only to the extent that cash is received and the loan’s principal balance is deemed collectable. Loans are restored to accrual status when the loans become both well‑secured and are in the process of collection. Leases are designated as nonaccrual leases when the recognition of interest has been discontinued. The recognition of interest on leases is generally discontinued when a lessee’s payments are past due 90 days or when, in the opinion of management, there is a reasonable doubt as to collectability. Leases with payments past due 90 days may be accruing if the leases are concluded to be well-secured and in the process of collection; however, these leases are still reported as nonperforming leases. Interest on nonaccrual leases is subsequently recognized only to the extent that cash is received and the lease balance is deemed collectable. Leases are restored to accrual status when the leases become both well-secured and are in the process of collection. Impaired loans and leases. A loan or lease is considered impaired when it is probable that we will be unable to collect all amounts due according to the contractual terms of the loan or lease agreement. Impaired loans and leases include loans and leases on nonaccrual status and performing troubled debt restructured loans. Income from impaired loans is recognized on an accrual basis unless the loan is on nonaccrual status. Income from loans on nonaccrual status is recognized to the extent cash is received and when the loan’s principal balance is deemed collectable. We measure impairment of a loan or lease by using the estimated fair value of the collateral, less estimated costs to sell and other applicable costs, if the loan or lease is collateral‑dependent and the present value of the expected future cash flows discounted at the loan’s or lease’s effective interest rate if the loan or lease is not collateral‑dependent. The impairment amount on a collateral‑dependent loan or lease is charged‑off, and the impairment amount on a loan that is not collateral‑dependent is generally recorded as a specific reserve. Troubled debt restructurings. A loan is classified as a troubled debt restructuring when we grant a concession to a borrower experiencing financial difficulties that we otherwise would not consider under our normal lending policies. These concessions may include a reduction of the interest rate, principal or accrued interest, extension of the maturity date or other actions intended to minimize potential losses. All modifications of criticized loans are evaluated to determine whether such modifications are troubled debt restructurings as outlined under ASC Subtopic 310‑40, “Troubled Debt Restructurings by Creditors.” Loans restructured with an interest rate equal to or greater than that of a new loan with comparable market risk at the time the loan is modified may be excluded from certain restructured loan disclosures in years subsequent to the restructuring if the loans are in compliance with their modified terms. A loan that has been placed on nonaccrual status that is subsequently restructured will usually remain on nonaccrual status until the borrower is able to demonstrate repayment performance in compliance with the restructured terms for a sustained period of time, typically for six months. A restructured loan may return to accrual status sooner based on other significant events or circumstances. A loan that has not been placed on nonaccrual status may be restructured and such loan may remain on accrual status after such restructuring. In these circumstances, the borrower has made payments before and after the restructuring. Generally, this restructuring involves maturity extensions, a reduction in the loan interest rate and/or a change to interest‑only payments for a period of time. The restructured loan is considered impaired despite the accrual status and a specific reserve is calculated based on the present value of expected cash flows discounted at the loan’s original effective interest rate or based on the fair value of the collateral if the loan is collateral-dependent.
Allowance for Credit Losses	Allowances for Credit Losses Allowance for credit losses on Non‑PCI loans and leases held for investment. The allowance for credit losses on Non-PCI loans and leases held for investment is the combination of the allowance for loan and lease losses and the reserve for unfunded loan commitments. The allowance for loan and lease losses is reported as a reduction of outstanding loan and lease balances and the reserve for unfunded loan commitments is included within "Accrued interest payable and other liabilities" on the consolidated balance sheets. The following discussion is for Non-PCI loans and leases and the related allowance for credit losses. Refer to "— Allowance for loan losses on PCI loans held for investment " for the allowance policy on PCI loans. For loans and leases acquired and measured at fair value and deemed non-impaired on the acquisition date, our allowance methodology measures deterioration in credit quality or other inherent risks related to these acquired assets that may occur after the acquisition date. The allowance for credit losses is maintained at a level deemed appropriate by management to adequately provide for known and inherent risks in the loan and lease portfolio and other extensions of credit at the balance sheet date. The allowance is based upon our review of the credit quality of the loan and lease portfolio, which includes loan and lease payment trends, borrowers' compliance with loan agreements, borrowers' current and budgeted financial performance, collateral valuation trends, and current economic factors and external conditions that may affect our borrowers' ability to make payments to us in accordance with their contractual loan agreements. Loans and leases that are deemed to be uncollectable are charged off and deducted from the allowance. The provision for loan and lease losses and recoveries on loans and leases previously charged off are added to the allowance. The allowance for loan and lease losses has a general reserve component for loans and leases with no credit impairment and a specific reserve component for loans and leases determined to be impaired. A loan or lease is considered impaired when it is probable that we will be unable to collect all amounts due according to the original contractual terms of the agreement. We assess our loans and leases for impairment on an ongoing basis using certain criteria such as payment performance, borrower reported financial results and budgets, and other external factors when appropriate. We measure impairment of a loan or lease based upon the fair value of the underlying collateral if the loan or lease is collateral-dependent or the present value of cash flows, discounted at the effective interest rate, if the loan or lease is not collateral-dependent. To the extent a loan or lease balance exceeds the estimated collectable value, a specific reserve or charge-off is recorded depending upon either the certainty of the estimate of loss or the fair value of the loan's collateral if the loan is collateral-dependent. Smaller balance loans (under $250,000 ), with a few exceptions for certain loan types, are generally not individually assessed for impairment but are evaluated collectively. Our allowance methodology for the general reserve component includes both quantitative and qualitative loss factors which are applied to the population of unimpaired loans and leases to estimate our general reserves. The quantitative loss factors are the average charge-offs experienced over a prescribed historical look-back period on loans and leases pooled both by loan or lease type and credit risk rating; loans with more adverse credit risk ratings or higher historical loss experience have higher quantitative loss factors. The qualitative loss factors consider, among other things, current economic trends and forecasts, current collateral values and performance trends, and the loan portfolio's current composition and credit performance trends. The quantitative estimation of the allowance for credit losses at December 31, 2017 considered actual historical loan and lease charge-off experience over a 31 -quarter look-back period starting with the first quarter of 2010. This look-back period is inclusive of the average timeframe over which charge-offs typically occur following loan or lease origination. The estimation of the allowance for credit losses at December 31, 2016 considered actual historical loan and lease charge-off experience over a 27 -quarter look-back period starting with the first quarter of 2010. The increase in the historical look-back period to a 31 -quarter look-back period at December 31, 2017 from 27 quarters at December 31, 2016 allows the look-back period to capture sufficient loss observations and is relevant to the current portfolio; in a good economic cycle with less frequent loss events, management believes a longer look-back period is more appropriate to reflect the level of incurred losses over an entire economic cycle. When estimating the general reserve component for the various pools of similar loan types, the loss factors applied to the loan pools consider the current credit risk ratings, giving greater weight to loans with more adverse credit risk ratings. We recognize that the determination of the allowance for credit losses is sensitive to the assigned credit risk ratings and inherent loss rates at any given point in time. To ensure the accuracy of our credit risk ratings, an independent credit review function assesses the appropriateness of the credit risk ratings assigned to loans on a regular basis. The qualitative criteria we consider when establishing the loss factors include the following: • current economic trends and forecasts; • current collateral values, performance trends, and overall outlook in the markets where we lend; • legal and regulatory matters that could impact our borrowers’ ability to repay our loans and leases; • loan and lease portfolio composition and any loan concentrations; • current lending policies and the effects of any new policies or policy amendments; • loan and lease production volume and mix; • loan and lease portfolio credit performance trends; • results of our independent credit review; and • changes in management related to credit administration functions. We estimate the reserve for unfunded commitments using the same loss factors as used for the allowance for loan and lease losses. The reserve for unfunded commitments is computed using expected future usage of the unfunded commitments based on historical usage of unfunded commitments for the various loan types. The allowance for credit losses is directly correlated to the credit risk ratings of our loans. To ensure the accuracy of our credit risk ratings, an independent credit review function assesses the appropriateness of the credit risk ratings assigned to loans on a regular basis. The credit risk ratings assigned to every loan and lease are either “pass,” “special mention,” “substandard,” or “doubtful” and defined as follows: • Pass : Loans and leases classified as "pass" are not adversely classified and collection and repayment in full are expected. • Special Mention : Loans and leases classified as "special mention" have a potential weakness that requires management's attention. If not addressed, these potential weaknesses may result in further deterioration in the borrower's ability to repay the loan or lease. • Substandard : Loans and leases classified as "substandard" have a well-defined weakness or weaknesses that jeopardize the collection of the debt. They are characterized by the possibility that we will sustain some loss if the weaknesses are not corrected. • Doubtful : Loans and leases classified as "doubtful" have all the weaknesses of those classified as "substandard," with the additional trait that the weaknesses make collection or repayment in full highly questionable and improbable. In addition, we may refer to the loans and leases with assigned credit risk ratings of "substandard" and "doubtful" together as "classified" loans and leases. For further information on classified loans and leases, see Note 6. Loans and Leases. Management believes the allowance for credit losses is appropriate for the known and inherent risks in our Non-PCI loan and lease portfolio and the credit risk ratings and inherent loss rates currently assigned are appropriate. It is possible that others, given the same information, may at any point in time reach different conclusions that could result in a significant impact to the Company's financial statements. In addition, current credit risk ratings are subject to change as we continue to monitor our loans and leases. To the extent we experience, for example, increased levels of borrower loan defaults, borrowers' noncompliance with our loan agreements, adverse changes in collateral values, or negative changes in economic and business conditions that adversely affect our borrowers, our classified loans and leases may increase. Higher levels of classified loans and leases generally result in increased provisions for credit losses and an increased allowance for credit losses. Although we have established an allowance for credit losses that we consider appropriate, there can be no assurance that the established allowance will be sufficient to absorb future losses. Our federal and state banking regulators, as an integral part of their examination process, periodically review the Company’s allowance for credit losses. Our regulators may require the Company to recognize additions to the allowance based on their judgments related to information available to them at the time of their examinations. Allowance for loan losses on PCI loans held for investment. We measure the allowance for loan losses for PCI loans held for investment at the end of each financial reporting period based on expected cash flows of our PCI loans. Decreases or increases in the amount and changes in the timing of expected cash flows on the PCI loans as of the financial reporting date compared to those previously estimated are recognized by recording a provision or negative provision, respectively, for loan losses on such loans. For example, generally a decrease in the expected cash flows of PCI loans would result in an additional reserve requirement and a provision for PCI loan losses would be recorded.
Land, Premises and Equipment	Land, Premises and Equipment Premises and equipment are stated at cost less accumulated depreciation and amortization. Land is not depreciated. Depreciation and amortization is charged to "Noninterest expense" in the consolidated statements of earnings using the straight‑line method over the estimated useful lives of the assets. The estimated useful lives of furniture, fixtures and equipment range from 3 to 7 years and for buildings up to 35 years. Leasehold improvements are amortized over their estimated useful lives, or the life of the lease, whichever is shorter.
Foreclosed Assets	Foreclosed Assets Foreclosed assets include OREO and repossessed non-real estate assets. Foreclosed assets are initially recorded at the estimated fair value of the property, based on current independent appraisals obtained at the time of acquisition, less estimated costs to sell, including senior obligations such as delinquent property taxes. The excess of the recorded loan balance over the estimated fair value of the property at the time of acquisition less estimated costs to sell is charged to the allowance for loan losses. Any subsequent write‑downs are charged to "Noninterest expense" in the consolidated statements of earnings and recognized through a foreclosed assets valuation allowance. Subsequent increases in the fair value of the asset less selling costs reduce the foreclosed assets valuation allowance, but not below zero, and are credited to "Noninterest expense." Gains and losses on the sale of foreclosed assets and operating expenses of such assets are included in "Noninterest expense."
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in earnings in the period that includes the enactment date. Any interest or penalties assessed by the taxing authorities is classified in the financial statements as income tax expense. Deferred tax assets and liabilities, net of valuation allowances, are grouped together and reported net on the consolidated balance sheets. On a quarterly basis, the Company evaluates its deferred tax assets to assess whether they are expected to be realized in the future. This determination is based on currently available facts and circumstances, including our current and projected future tax positions, the historical level of our taxable income, and estimates of our future taxable income. In most cases, the realization of deferred tax assets is based on our future profitability. To the extent our deferred tax assets are no longer considered more likely than not to be realized, we are required to record a valuation allowance on our deferred tax assets by charging earnings. The Company also evaluates existing valuation allowances periodically to determine if sufficient evidence exists to support an increase or reduction in the allowance.
Goodwill and Intangible Assets	Goodwill and Other Intangible Assets Goodwill and other intangible assets arise from the acquisition method of accounting for business combinations. Goodwill and other intangible assets generated from business combinations and deemed to have indefinite lives are not subject to amortization and instead are tested for impairment at least annually unless certain events occur or circumstances change. Goodwill represents the excess of the purchase price over the fair value of the net assets and other identifiable intangible assets acquired. We test for goodwill impairment annually or earlier if events or changes in circumstances indicate goodwill might possibly be impaired. Impairment exists when the carrying value of the goodwill exceeds its implied fair value. An impairment loss would be recognized in an amount equal to that excess as a charge to "Noninterest expense" in the consolidated statements of earnings. Intangible assets with estimable useful lives are amortized over such useful lives to their estimated residual values. CDI and CRI are recognized apart from goodwill at the time of acquisition based on market valuations. In preparing such valuations, variables considered included deposit servicing costs, attrition rates, and market discount rates. CDI assets are amortized to expense over their useful lives, which we have estimated to range from 7 to 10 years. CRI assets are amortized to expense over their useful lives, which we have estimated to range from 4 to 7 years. The amortization expense represents the estimated decline in the value of the underlying deposits or customer relationships acquired. Both CDI and CRI are reviewed for impairment quarterly or earlier if events or changes in circumstances indicate that their carrying values may not be recoverable. If the recoverable amount of either CDI or CRI is determined to be less than its carrying value, we would then measure the amount of impairment based on an estimate of the intangible asset’s fair value at that time. If the fair value is below the carrying value, then the intangible asset is reduced to such fair value; an impairment loss for such amount would be recognized as a charge to "Noninterest expense" in the consolidated statements of earnings.
Stock-based Compensation	Stock-Based Compensation The Company issues stock-based compensation instruments consisting of TRSAs and PRSUs. Compensation expense related to TRSAs is based on the fair value of the underlying stock on the award date and is recognized over the vesting period using the straight‑line method. Compensation expense related to PRSUs is based on the fair value of the underlying stock on the award date and is amortized over the vesting period using the straight-line method unless it is determined that: (1) attainment of the financial metrics is less than probable, in which case a portion of the amortization is suspended, or (2) attainment of the financial metrics is improbable, in which case a portion of the previously recognized amortization is reversed and also suspended. If it is determined that attainment of a financial measure higher than target is probable, the amortization will increase up to 150% or 200% of the target amortization amount. Annual PRSU expense may vary during the three -year performance period based upon changes in management's estimate of the number of shares that may ultimately vest. In the case where the performance target for the PRSU’s is based on a market condition (such as total shareholder return), the amortization is neither reversed nor suspended if it is subsequently determined that the attainment of the performance target is less than probable or improbable. Unvested TRSAs participate with common stock in any dividends declared and paid. Dividends are paid on unvested TRSAs and are charged to equity and the related tax impact is recorded to income tax expense. Dividends paid on forfeited TRSAs are charged to compensation expense.
Derivative Instruments	(n) Derivative Instruments Our derivative contracts primarily manage the foreign currency risk associated with certain assets and liabilities. As of December 31, 2017 , all of our derivatives were held for risk management purposes and none were designated as accounting hedges. The objective is to manage the uncertainty of future foreign exchange rate fluctuations. These derivatives provide for a fixed exchange rate which has the effect of reducing or eliminating changes to anticipated cash flows to be received on assets and liabilities denominated in foreign currencies as the result of changes to exchange rates. Our derivatives are recorded in other assets or other liabilities, as appropriate. The changes in fair value of our derivatives and the related interest are recognized in "Noninterest income - other" in the consolidated statements of earnings. At December 31, 2017 , our derivative contracts had a notional value of $91.1 million . Derivative instruments expose us to credit risk in the event of nonperformance by counterparties. This risk exposure consists primarily of the termination value of agreements where we are in a favorable position. We manage the credit risk associated with various derivative agreements through counterparty credit review and monitoring procedures.
Investments That Do Not Have Readily Determinable Fair Value	Investments That Do Not Have Readily Determinable Fair Values Investments in common or preferred stock that are not publicly traded are considered equity investments that do not have a readily determinable fair value. If we have the ability to significantly influence the operating and financial policies of the investee, these investments are accounted for pursuant to the equity method of accounting. This is generally presumed to exist when we own between 20% and 50% of a corporation, or when we own greater than 5% of a limited partnership or similarly structured entity. Our investment carrying values are included in other assets and our share of earnings and losses in equity method investees is included in "Noninterest income - other" on the consolidated statements of earnings. If we do not have significant influence over the investee, the cost method is used to account for the equity interest. Investments accounted for using the cost or equity method of accounting are evaluated for other-than-temporary impairment quarterly. An impairment exists when the estimated fair value for each investment is less than its carrying value. If an impairment exists, then such impairment is evaluated for whether it is considered to be temporary or other-than-temporary. In determining whether an other-than-temporary decline in value exists, management evaluates information such as budgets, business plans, and financial statements of the investee in addition to quoted market prices, if any. Factors indicative of an other-than-temporary decline in value include, but are not limited to, recurring operating losses and credit defaults. If we determine that an investment has sustained an other-than-temporary decline in its value, then the equity interest is written down to its estimated fair value as a reduction to "Noninterest income - other" and a new carrying value for the investment is established. Realized gains or losses resulting from the sale of investments are calculated using the specific identification method and are included in "Noninterest income - other."
Comprehensive Income	Comprehensive Income Comprehensive income consists of net earnings and net unrealized gains (losses) on securities available‑for‑sale, net, and is presented in the consolidated statements of comprehensive income.
Earnings Per Share	Earnings Per Share In accordance with ASC Topic 260, “ Earnings Per Share ,” all outstanding unvested share‑based payment awards that contain rights to nonforfeitable dividends are considered participating securities and are included in the two‑class method of determining basic and diluted earnings per share. All of our unvested restricted stock participates with our common stockholders in dividends. Accordingly, earnings allocated to unvested restricted stock are deducted from net earnings to determine that amount of earnings available to common stockholders. In the two‑class method, the amount of our earnings available to common stockholders is divided by the weighted average shares outstanding, excluding any unvested restricted stock, for both the basic and diluted earnings per share.
Business Combinations	Business Combinations Business combinations are accounted for under the acquisition method of accounting in accordance with ASC Topic 805, “ Business Combinations .” Under the acquisition method, the acquiring entity in a business combination recognizes 100 percent of the acquired assets and assumed liabilities, regardless of the percentage owned, 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 other identifiable assets, exceeds the purchase price, a bargain purchase gain is recognized. Assets acquired and liabilities assumed from contingencies must also be 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 statement of earnings from the date of acquisition. Acquisition‑related costs, including conversion and restructuring charges, are expensed as incurred.
Business Segments	(s) Business Segments We regularly assess our strategic plans, operations and reporting structures to identify our reportable segments. Changes to our reportable segments are expected to be infrequent. As of December 31, 2017 , 2016, and 2015, we operated as one reportable segment. The factors considered in making this determination include the nature of products and offered services, geographic regions in which we operate, the applicable regulatory environment, and the discrete financial information reviewed by our key decision makers. Through our network of banking offices nationwide, our entire operations provide relationship-based banking products, services and solutions for small to mid-sized companies, entrepreneurial businesses, venture capital and private equity investors, real estate investors, professionals and other individuals. Our products and services include commercial real estate, multi-family, commercial business, construction and land, consumer and government-guaranteed small business loans, business and personal deposit products, and treasury cash management services.
Recently issued Accounting Standards	Recently Issued Accounting Standards In May 2014, the FASB issued ASU 2014-09, " Revenue Recognition (Topic 606): Revenue from Contracts with Customers." ASU 2014-09 requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 will replace most existing revenue recognition guidance in GAAP when it becomes effective. The standard permits the use of either the retrospective or cumulative effect transition method. In August 2015, the FASB issued ASU 2015-14, "Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date," which deferred the effective date of ASU 2014-09 to annual and interim periods beginning after December 15, 2017. We have completed our assessment and implementation for adopting this new standard. We determined that substantially all of the Company's revenues, such as net interest income, are excluded from the scope of the new standard. For the noninterest income revenue streams determined to be within the scope of the new standard, we examined customer contracts to determine the appropriate accounting for those contracts under the new standard. The changes to our accounting, operations, and internal controls related to implementing the requirements of the new standard were not significant. The Company will adopt this standard effective January 1, 2018, and we have determined that there will be no cumulative effect adjustment to retained earnings as a result of adopting the new standard, nor will the standard have a material impact on our consolidated financial statements including the timing or amounts of revenue recognized. In January 2016, the FASB issued ASU 2016-01, " Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities ," which will significantly change the income statement impact of equity investments and the recognition of changes in fair value of financial liabilities when the fair value option is elected. For equity investments with readily determinable fair values, entities must measure these investments at fair value and recognize changes in fair value in net income. For equity investments without readily determinable fair values, entities have the option to either measure these investments at fair value or at cost, adjusted for changes in observable prices, minus impairment. Changes in measurement under either alternative must be recognized in net income. ASU 2016-01 will be effective for annual and interim periods beginning after December 15, 2017. Early adoption is permitted only for the provisions related to the recognition of changes in fair value of financial liabilities, which does not apply to the Company. The Company will adopt this standard effective January 1, 2018 and the standard will not have a material impact on its consolidated financial position or results of operations. In February 2016, the FASB issued ASU 2016-02, " Leases (Topic 842) ," which, among other things, requires lessees to recognize most leases on-balance sheet, which will result in an increase in their reported assets and liabilities. Lessor accounting remains substantially similar to current U.S. GAAP. ASU 2016-02 supersedes Topic 840, Leases, and is effective for annual and interim periods in fiscal years beginning after December 15, 2018. The Company will adopt the standard effective January 1, 2019. The current ASU mandates a modified retrospective transition method for all entities, however the FASB has proposed an optional transition method where the Company could elect to record a cumulative effect adjustment to retained earnings at the date of adoption. The Company has reviewed its current lessee portfolio and is assessing the impact of the new standard on its financial statements, related disclosures, systems, and internal controls. The accounting changes are expected to relate primarily to its leased branches and office space which are currently accounted for as operating leases. For information on our future minimum lease payments refer to Note 8. Premises and Equipment, Net . The Company has not yet determined the quantitative effect ASU 2016-02 will have on its consolidated financial position and results of operations. In June 2016, the FASB issued ASU 2016-13, " Measurement of Credit Losses on Financial Instruments," which significantly changes the way entities recognize credit losses and impairment of many financial assets. Currently, the credit loss and impairment model is based on incurred losses, and investments are recognized as impaired when there is no longer an assumption that future cash flows will be collected in full under the originally contracted terms. Under the new current expected credit loss ("CECL") model, the new standard requires immediate recognition of estimated credit losses expected to occur over the remaining life of the asset. The forward-looking concept of CECL to estimate future credit losses will broaden the range of data to consider including, but not limited to, past and current events and conditions along with reasonable and supportable forecasts that affect expected collectability. The new standard will also add new disclosure requirements. The Company has set up a multidisciplinary project team, developed an implementation plan, selected a software solution, completed the readiness assessment, and has started the implementation phase of the project. The Company, with the assistance of a third party adviser, has begun to work on: (1) developing a new expected loss model with supportable assumptions, (2) identifying data, reporting, and disclosure gaps, (3) assessing updates to accounting policies, and (4) documenting new processes and controls. ASU 2016-13 is effective for interim and annual periods in fiscal years beginning after December 15, 2019, with earlier adoption permitted. The Company plans to adopt this standard on January 1, 2020. Entities are required to use a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted (modified-retrospective approach). A prospective transition approach is required for debt securities for which an other-than-temporary impairment had been recognized before the adoption date. The new standard will be significant to the policies, processes, and methodology used to determine credit losses, however the Company has not yet determined the quantitative effect ASU 2016-13 will have on its consolidated financial position and results of operations. In August 2016, the FASB issued ASU 2016-15, " Classification of Certain Cash Receipts and Cash Payments," which addressed eight issues related to the statement of cash flows, including proceeds from the settlement of BOLI policies. ASU 2016-15 is effective for interim and annual periods in fiscal years beginning after December 15, 2017. Entities should apply ASU 2016-15 using a retrospective transition method to each period presented. If it is impracticable for an entity to apply ASU 2016-15 retrospectively for some of the issues, it may apply the amendments for those issues prospectively as of the earliest date practicable. ASU 2016-15 will result in some changes in classification in the consolidated statements of cash flows, which the Company does not expect will be significant, and will not have any impact on its consolidated financial position or results of operations. The Company will adopt this standard effective January 1, 2018. In January 2017, the FASB issued ASU 2017-01, " Business Combinations (Topic 805): Clarifying the Definition of a Business ," which provides a new framework for determining whether transactions should be accounted for as acquisitions of assets or businesses. ASU 2017-01 is effective for interim and annual periods in fiscal years beginning after December 15, 2017. The Company will adopt this standard on January 1, 2018 and does not expect ASU 2017-01 to have a material impact on its consolidated financial position or results of operations. In January 2017, the FASB issued ASU 2017-04, " Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment," which intends to simplify goodwill impairment testing by eliminating the second step of the analysis under which the implied fair value of goodwill is determined as if the reporting unit were being acquired in a business combination. ASU 2017-04 instead requires entities to compare the fair value of a reporting unit with its carrying amount and recognize an impairment charge for any amount by which the carrying amount exceeds the reporting unit's fair value, to the extent that the loss recognized does not exceed the amount of goodwill allocated to that reporting unit. ASU 2017-04 must be applied prospectively and is effective for the Company on January 1, 2020. Early adoption is permitted. The Company does not expect ASU 2017-04 to have a material impact on its consolidated financial position or results of operations. In May 2017, the FASB issued ASU 2017-09, " Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting ," which clarifies what constitutes a modification of a share-based payment award. ASU 2017-09 is effective for interim and annual periods in fiscal years beginning after December 15, 2017. Early adoption is permitted as of the beginning of an annual period for which financial statements (interim or annual) have not been issued or made available for issuance. The Company will adopt this standard effective January 1, 2018 and does not expect ASU 2017-09 to have a material impact on its consolidated financial position or results of operations. In February 2018, the FASB issued ASU 2018-02, " Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income ," which provides financial statement preparers with an option to reclassify stranded tax effects within accumulated other comprehensive income to retained earnings in each period in which the effect of the change in the U.S. federal corporate income tax rate in the TCJA (or portion thereof) is recorded. ASU 2018-02 is effective for interim and annual periods in fiscal years beginning after December 15, 2018. Early adoption is permitted and the proposed amendments should be applied either in the period of adoption or retrospectively to each period in which the effect of the change in the U.S. federal corporate income tax rate in the TCJA is recognized. The Company will adopt this standard effective January 1, 2018 and does not expect ASU 2018-02 to have a material impact on its consolidated financial position or results of operations. Accounting Standards Adopted in 2017 Effective January 1, 2017, the Company adopted ASU 2016-09, " Improvements to Employee Share-Based Accounting ." ASU 2016-09 changed aspects of the accounting for share-based payment award transactions, including: (1) accounting for income taxes; (2) classification of excess tax benefits on the statement of cash flows; (3) forfeitures; (4) minimum statutory tax withholding requirements; and (5) classification of employee taxes paid on the statement of cash flows when an employer withholds shares for tax-withholding purposes. The recognition of excess tax benefits and tax deficiencies in the income statement was adopted prospectively. Income tax benefits of $1.5 million were recognized during the year ended December 31, 2017 as a result of the adoption of ASU 2016-09. We expect the requirements of ASU 2016-09 to result in fluctuations in our effective tax rate from period to period based upon the timing of share-based award vestings. In connection with the adoption of ASU 2016-09, we elected to recognize forfeitures on stock-based compensation awards when they occur, instead of estimating forfeitures at the grant date of the awards and throughout the vesting period. The modified retrospective application of this change in accounting principle resulted in a cumulative adjustment charge to retained earnings of $420,000 , net of income taxes. We elected to present the classification of excess tax benefits on the statement of cash flows using a prospective transition method and the prior period has not been adjusted. Effective July 1, 2017, the Company early-adopted ASU 2017-08, " Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities ." ASU 2017-08 requires certain premiums on callable debt securities to be amortized to the earliest call date. The amortization period for discounts on callable debt securities was not impacted. The adoption of this ASU had no material impact on the Company's consolidated financial position, results of operations, or cash flows.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Schedule of Business Acquisitions, by Acquisition	The following assets acquired and liabilities assumed of the acquired entities are presented at estimated fair value as of their respective acquisition dates: Acquisition and Date Acquired CU Bancorp Square 1 Financial, Inc. October 20, 2017 October 6, 2015 (In thousands) Assets Acquired: Cash and due from banks $ 51,857 $ 24,867 Interest‑earning deposits in financial institutions 332,799 236,069 Securities available‑for‑sale 446,980 2,193,538 FHLB stock 11,902 2,787 Loans and leases 2,075,890 1,553,720 Premises and equipment 2,981 1,927 Goodwill 374,721 446,069 Core deposit and customer relationship intangibles 57,500 45,426 Other assets 103,498 106,757 Total assets acquired $ 3,458,128 $ 4,611,160 Liabilities Assumed: Noninterest‑bearing deposits $ 1,510,285 $ 2,549,000 Interest‑bearing deposits 1,209,597 1,240,635 Borrowings 22,879 — Subordinated debentures 12,372 — Accrued interest payable and other liabilities 32,424 24,092 Total liabilities assumed $ 2,787,557 $ 3,813,727 Total consideration paid $ 670,571 $ 797,433 Summary of consideration: Cash paid $ 224,338 $ — PacWest common stock issued 446,233 797,433 Total $ 670,571 $ 797,433

Goodwill and Other Intangible30

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill Disclosure	The following table presents the changes in the carrying amount of goodwill for the years indicated: Goodwill (In thousands) Balance, December 31, 2014 $ 1,720,479 Adjustment to acquired CapitalSource Inc. tax assets 7,901 Addition from the Square 1 acquisition 447,911 Balance, December 31, 2015 2,176,291 Adjustment to acquired Square 1 tax assets (1,842 ) Reduction due to sale of PWEF leasing unit (500 ) Balance, December 31, 2016 2,173,949 Addition from the CUB acquisition 374,721 Balance, December 31, 2017 $ 2,548,670
Intangible Assets Disclosure	The following table presents the changes in CDI and CRI and the related accumulated amortization for the years indicated: Year Ended December 31, 2017 2016 2015 (In thousands) Gross Amount of CDI and CRI: Balance, beginning of year $ 64,187 $ 95,524 $ 53,090 Additions due to acquisitions 57,500 — 45,426 Fully amortized portion (2,190 ) (29,637 ) (2,992 ) Reduction due to sale of PWEF leasing unit — (1,700 ) — Balance, end of year 119,497 64,187 95,524 Accumulated Amortization: Balance, beginning of year (27,821 ) (42,304 ) (35,886 ) Amortization (14,240 ) (16,517 ) (9,410 ) Fully amortized portion 2,190 29,637 2,992 Reduction due to sale of PWEF leasing unit — 1,363 — Balance, end of year (39,871 ) (27,821 ) (42,304 ) Net CDI and CRI, end of year $ 79,626 $ 36,366 $ 53,220

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities Reconciliation	The following table presents amortized cost, gross unrealized gains and losses, and fair values of securities available-for-sale as of the dates indicated: December 31, 2017 December 31, 2016 Gross Gross Gross Gross Amortized Unrealized Unrealized Fair Amortized Unrealized Unrealized Fair Security Type Cost Gains Losses Value Cost Gains Losses Value (In thousands) Residential MBS and CMOs: Agency MBS $ 243,375 $ 3,743 $ (844 ) $ 246,274 $ 499,185 $ 6,222 $ (2,964 ) $ 502,443 Agency CMOs 277,638 968 (2,897 ) 275,709 145,258 1,528 (497 ) 146,289 Private label CMOs 122,816 3,813 (642 ) 125,987 122,707 4,199 (1,437 ) 125,469 Municipal securities 1,627,707 53,700 (1,339 ) 1,680,068 1,447,064 15,406 (6,011 ) 1,456,459 Agency commercial MBS 1,169,969 2,758 (8,758 ) 1,163,969 555,552 1,798 (9,658 ) 547,692 Corporate debt securities 17,000 2,295 — 19,295 47,100 680 (271 ) 47,509 Collateralized loan obligations 6,960 55 — 7,015 155,440 1,685 (238 ) 156,887 SBA securities 160,214 695 (575 ) 160,334 179,085 510 (750 ) 178,845 Asset-backed and other securities 95,846 938 (1,004 ) 95,780 62,264 358 (385 ) 62,237 Total $ 3,721,525 $ 68,965 $ (16,059 ) $ 3,774,431 $ 3,213,655 $ 32,386 $ (22,211 ) $ 3,223,830
Unrealized losses on investment securities	Unrealized Losses on Securities Available-for-Sale The following tables present the gross unrealized losses and fair values of securities available-for-sale that were in unrealized loss positions, for which other-than-temporary impairments have not been recognized in earnings, as of the dates indicated: December 31, 2017 Less Than 12 Months 12 Months or More Total Gross Gross Gross Fair Unrealized Fair Unrealized Fair Unrealized Security Type Value Losses Value Losses Value Losses (In thousands) Residential MBS and CMOs: Agency MBS $ 44,795 $ (311 ) $ 26,010 $ (533 ) $ 70,805 $ (844 ) Agency CMOs 163,014 (2,452 ) 20,928 (445 ) 183,942 (2,897 ) Private label CMOs 50,521 (500 ) 5,035 (142 ) 55,556 (642 ) Municipal securities 67,936 (365 ) 32,326 (974 ) 100,262 (1,339 ) Agency commercial MBS 579,373 (3,777 ) 129,060 (4,981 ) 708,433 (8,758 ) SBA securities 74,904 (575 ) — — 74,904 (575 ) Asset-backed and other securities 46,237 (948 ) 10,473 (56 ) 56,710 (1,004 ) Total $ 1,026,780 $ (8,928 ) $ 223,832 $ (7,131 ) $ 1,250,612 $ (16,059 ) December 31, 2016 Less Than 12 Months 12 Months or More Total Gross Gross Gross Fair Unrealized Fair Unrealized Fair Unrealized Security Type Value Losses Value Losses Value Losses (In thousands) Residential MBS and CMOs: Agency MBS $ 149,281 $ (1,691 ) $ 122,902 $ (1,273 ) $ 272,183 $ (2,964 ) Agency CMOs 44,111 (416 ) 25,316 (81 ) 69,427 (497 ) Private label CMOs 49,067 (906 ) 30,155 (531 ) 79,222 (1,437 ) Municipal securities 644,424 (6,011 ) — — 644,424 (6,011 ) Agency commercial MBS 349,550 (9,658 ) — — 349,550 (9,658 ) Corporate debt securities 29,829 (271 ) — — 29,829 (271 ) Collateralized loan obligations 12,450 (37 ) 39,231 (201 ) 51,681 (238 ) SBA securities 69,293 (407 ) 39,024 (343 ) 108,317 (750 ) Asset-backed and other securities 18,213 (309 ) 7,851 (76 ) 26,064 (385 ) Total $ 1,366,218 $ (19,706 ) $ 264,479 $ (2,505 ) $ 1,630,697 $ (22,211 )
Investments Classified by Contractual Maturity Date	The following table presents the contractual maturities of our available-for-sale securities portfolio based on amortized cost and carrying value as of the date indicated. December 31, 2017 Amortized Fair Maturity Cost Value (In thousands) Due in one year or less $ 14,398 $ 15,091 Due after one year through five years 375,559 378,522 Due after five years through ten years 1,128,639 1,130,138 Due after ten years 2,202,929 2,250,680 Total securities available-for-sale $ 3,721,525 $ 3,774,431
Investment Income	The following table presents the composition of our interest income on investment securities for the years indicated: Year Ended December 31, 2017 2016 2015 (In thousands) Taxable interest $ 52,981 $ 46,097 $ 35,103 Non-taxable interest 43,355 41,885 25,219 Dividend income 1,866 2,575 4,046 Total interest income on investment securities $ 98,202 $ 90,557 $ 64,368

Loans and Leases (Tables)

Loans and Leases (Tables)	12 Months Ended
	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Schedule Of Composition of Loans Portfolio	The following table summarizes the composition of our loans and leases held for investment as of the dates indicated: December 31, 2017 December 31, 2016 Non-PCI Non-PCI Loans PCI Loans PCI and Leases Loans Total and Leases Loans Total (In thousands) Real estate mortgage $ 7,815,355 $ 53,658 $ 7,869,013 $ 5,635,675 $ 92,793 $ 5,728,468 Real estate construction and land 1,611,287 — 1,611,287 975,032 2,409 977,441 Commercial 7,137,978 4,158 7,142,136 8,426,236 12,994 8,439,230 Consumer 409,551 234 409,785 375,149 249 375,398 Total gross loans and leases held for investment 16,974,171 58,050 17,032,221 15,412,092 108,445 15,520,537 Deferred fees, net (59,464 ) (14 ) (59,478 ) (64,562 ) (21 ) (64,583 ) Total loans and leases held for investment, net of deferred fees 16,914,707 58,036 16,972,743 15,347,530 108,424 15,455,954 Allowance for loan and lease losses (133,012 ) (6,444 ) (139,456 ) (143,755 ) (13,483 ) (157,238 ) Total loans and leases held for investment, net $ 16,781,695 $ 51,592 $ 16,833,287 $ 15,203,775 $ 94,941 $ 15,298,716
CV of Loans Held for Investment by Class by Classified and Nonclassiified	As of December 31, 2017 , our ten largest Non-PCI loan relationships on nonaccrual status had an aggregate carrying value of $120.0 million and represented 77.0% of total Non-PCI nonaccrual loans and leases. The following table presents the credit risk rating categories for Non‑PCI loans and leases held for investment by portfolio segment and class as of the dates indicated. Nonclassified loans and leases ar
Allowance for Loan Losses	The following tables present a summary of the activity in the allowance for loan and lease losses on Non‑PCI loans and leases held for investment by portfolio segment and PCI loans held for investment for the years indicated: Year Ended December 31, 2017 Real Estate Real Estate Construction Total Total Mortgage and Land Commercial Consumer Non-PCI PCI Total (In thousands) Allowance for Loan and Lease Losses: Balance, beginning of year $ 37,765 $ 10,045 $ 93,853 $ 2,092 $ 143,755 $ 13,483 $ 157,238 Charge-offs (2,410 ) — (70,709 ) (1,023 ) (74,142 ) (6,154 ) (80,296 ) Recoveries 1,209 429 9,415 132 11,185 363 11,548 Provision (negative provision) (1,583 ) 2,581 50,167 1,049 52,214 (1,248 ) 50,966 Balance, end of year $ 34,981 $ 13,055 $ 82,726 $ 2,250 $ 133,012 $ 6,444 $ 139,456 Ending Allowance by Impairment Methodology: Individually evaluated for impairment $ 970 $ — $ 12,635 $ 16 $ 13,621 Collectively evaluated for impairment $ 34,011 $ 13,055 $ 70,091 $ 2,234 $ 119,391 Acquired loans with deteriorated credit quality $ 6,444 Ending Loans and Leases by Impairment Methodology: Individually evaluated for impairment $ 115,319 $ 5,690 $ 89,626 $ 100 $ 210,735 Collectively evaluated for impairment $ 7,683,672 $ 1,585,539 $ 7,025,294 $ 409,467 $ 16,703,972 Acquired loans with deteriorated credit quality $ 58,036 Ending balance $ 7,798,991 $ 1,591,229 $ 7,114,920 $ 409,567 $ 16,914,707 $ 58,036 $ 16,972,743 Year Ended December 31, 2016 Real Estate Real Estate Construction Total Total Mortgage and Land Commercial Consumer Non-PCI PCI Total (In thousands) Allowance for Loan and Lease Losses: Balance, beginning of year $ 36,654 $ 7,137 $ 61,082 $ 661 $ 105,534 $ 9,577 $ 115,111 Charge-offs (2,059 ) — (32,210 ) (823 ) (35,092 ) (862 ) (35,954 ) Recoveries 4,519 673 7,794 116 13,102 39 13,141 Provision (negative provision) (1,349 ) 2,235 57,187 2,138 60,211 4,729 64,940 Balance, end of year $ 37,765 $ 10,045 $ 93,853 $ 2,092 $ 143,755 $ 13,483 $ 157,238 Ending Allowance by Impairment Methodology: Individually evaluated for impairment $ 6,851 $ — $ 17,912 $ 170 $ 24,933 Collectively evaluated for impairment $ 30,914 $ 10,045 $ 75,941 $ 1,922 $ 118,822 Acquired loans with deteriorated credit quality $ 13,483 Ending Loans and Leases by Impairment Methodology: Individually evaluated for impairment $ 123,348 $ 7,257 $ 103,431 $ 394 $ 234,430 Collectively evaluated for impairment $ 5,494,608 $ 955,582 $ 8,288,129 $ 374,781 $ 15,113,100 Acquired loans with deteriorated credit quality $ 108,424 Ending balance $ 5,617,956 $ 962,839 $ 8,391,560 $ 375,175 $ 15,347,530 $ 108,424 $ 15,455,954
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period	The following table summarizes the changes in the carrying amount of PCI loans held for investment and accretable yield on those loans for the years indicated: Carrying Accretable Amount Yield (In thousands) Balance, December 31, 2014 $ 276,792 $ (106,856 ) Addition from the Square 1 acquisition 16,455 (2,852 ) Accretion 31,857 31,857 Payments received (148,436 ) — Increase in expected cash flows, net — (7,785 ) Negative provision for credit losses 2,800 — Balance, December 31, 2015 179,468 (85,636 ) Accretion 51,907 51,907 Payments received (131,705 ) — Increase in expected cash flows, net — (22,215 ) Provision for credit losses (4,729 ) — Balance, December 31, 2016 94,941 (55,944 ) Accretion 14,739 14,739 Payments received (59,336 ) — Increase in expected cash flows, net — (4,375 ) Negative provision for credit losses 1,248 — Balance, December 31, 2017 $ 51,592 $ (45,580 )
Non Purchased Credit Impaired Loans and Leases [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Delinquent loans in loan portfolio	The following tables present an aging analysis of our Non‑PCI loans and leases held for investment, net of deferred fees, by portfolio segment and class as of the dates indicated: December 31, 2017 30 - 89 90 or More Days Days Total Past Due Past Due Past Due Current Total (In thousands) Real estate mortgage: Commercial $ 29,070 $ 9,107 $ 38,177 $ 5,323,310 $ 5,361,487 Residential 6,999 2,022 9,021 2,428,483 2,437,504 Total real estate mortgage 36,069 11,129 47,198 7,751,793 7,798,991 Real estate construction and land: Commercial — — — 769,075 769,075 Residential 2,081 — 2,081 820,073 822,154 Total real estate construction and land 2,081 — 2,081 1,589,148 1,591,229 Commercial: Asset-based 1,512 — 1,512 3,010,188 3,011,700 Venture capital 6,533 760 7,293 2,115,418 2,122,711 Cash flow 1,334 1,586 2,920 1,320,594 1,323,514 Equipment finance 344 690 1,034 655,961 656,995 Total commercial 9,723 3,036 12,759 7,102,161 7,114,920 Consumer 562 — 562 409,005 409,567 Total (1) $ 48,435 $ 14,165 $ 62,600 $ 16,852,107 $ 16,914,707 ________________________ (1) Excludes loans held for sale carried at lower of cost or fair value. December 31, 2016 30 - 89 90 or More Days Days Total Past Due Past Due Past Due Current Total (In thousands) Real estate mortgage: Commercial $ 8,590 $ 3,303 $ 11,893 $ 4,341,740 $ 4,353,633 Residential 5,694 1,999 7,693 1,256,630 1,264,323 Total real estate mortgage 14,284 5,302 19,586 5,598,370 5,617,956 Real estate construction and land: Commercial — — — 578,838 578,838 Residential 364 — 364 383,637 384,001 Total real estate construction and land 364 — 364 962,475 962,839 Commercial: Asset-based 1,500 2 1,502 2,607,543 2,609,045 Venture capital 13,589 5,769 19,358 1,963,798 1,983,156 Cash flow 191 1,821 2,012 3,105,380 3,107,392 Equipment finance 1,417 3,051 4,468 687,499 691,967 Total commercial 16,697 10,643 27,340 8,364,220 8,391,560 Consumer 224 — 224 374,951 375,175 Total $ 31,569 $ 15,945 $ 47,514 $ 15,300,016 $ 15,347,530
Financing Receivable Non Accrual And Performing	The following table presents our nonaccrual and performing Non‑PCI loans and leases held for investment, net of deferred fees, by portfolio segment and class as of the dates indicated: December 31, 2017 (1) December 31, 2016 Nonaccrual Performing Total Nonaccrual Performing Total (In thousands) Real estate mortgage: Commercial $ 65,563 $ 5,295,924 $ 5,361,487 $ 62,454 $ 4,291,179 $ 4,353,633 Residential 3,350 2,434,154 2,437,504 6,881 1,257,442 1,264,323 Total real estate mortgage 68,913 7,730,078 7,798,991 69,335 5,548,621 5,617,956 Real estate construction and land: Commercial — 769,075 769,075 — 578,838 578,838 Residential — 822,154 822,154 364 383,637 384,001 Total real estate construction and land — 1,591,229 1,591,229 364 962,475 962,839 Commercial: Asset-based 3,174 3,008,526 3,011,700 2,118 2,606,927 2,609,045 Venture capital 29,424 2,093,287 2,122,711 11,687 1,971,469 1,983,156 Cash flow 23,315 1,300,199 1,323,514 53,908 3,053,484 3,107,392 Equipment finance 30,938 626,057 656,995 32,848 659,119 691,967 Total commercial 86,851 7,028,069 7,114,920 100,561 8,290,999 8,391,560 Consumer 20 409,547 409,567 339 374,836 375,175 Total $ 155,784 $ 16,758,923 $ 16,914,707 $ 170,599 $ 15,176,931 $ 15,347,530
Schedule Of Non Accrual and Performing Restructured Impaired Financing Receivables	Non‑PCI nonaccrual loans and leases and performing troubled debt restructured loans are considered impaired for reporting purposes. Troubled debt restructurings are a result of rate reductions, term extensions, fee concessions and debt forgiveness or a combination thereof. At December 31, 2017 and 2016 , we had unfunded commitments related to Non-PCI troubled debt restructured loans of $4.5 million and $4.6 million . The following table presents the composition of our impaired loans and leases held for investment, net of deferred fees, by portfolio segment as of the dates indicated: December 31, 2017 (1) December 31, 2016 Performing Total Performing Total Nonaccrual Troubled Impaired Nonaccrual Troubled Impaired Loans Debt Loans Loans Debt Loans and Restructured and and Restructured and Leases Loans Leases Leases Loans Leases (In thousands) Real estate mortgage $ 68,913 $ 47,560 $ 116,473 $ 69,335 $ 54,750 $ 124,085 Real estate construction and land — 5,690 5,690 364 6,893 7,257 Commercial 86,851 3,488 90,339 100,561 3,157 103,718 Consumer 20 100 120 339 152 491 Total $ 155,784 $ 56,838 $ 212,622 $ 170,599 $ 64,952 $ 235,551
Impaired Financing Receivables, Average Balances And Interest Income Recognized	The following tables present information regarding our Non‑PCI impaired loans and leases held for investment, net of deferred fees, by portfolio segment and class as of and for the years indicated: December 31, 2017 (1) December 31, 2016 Unpaid Unpaid Recorded Principal Related Recorded Principal Related Impaired Loans and Leases Investment Balance Allowance Investment Balance Allowance (In thousands) With An Allowance Recorded: Real estate mortgage: Commercial $ 15,750 $ 16,548 $ 628 $ 63,325 $ 65,031 $ 6,266 Residential 2,787 2,957 342 8,424 8,612 585 Real estate construction and land: Residential — — — 213 213 — Commercial: Asset-based 1,311 1,337 51 4,395 4,861 2,144 Venture capital 16,565 17,203 4,267 5,821 5,880 3,294 Cash flow 19,093 28,614 8,317 51,272 52,910 12,474 Equipment finance — — — 1,524 4,636 — Consumer 100 100 16 270 280 170 With No Related Allowance Recorded: Real estate mortgage: Commercial $ 93,827 $ 105,923 $ — $ 44,557 $ 51,402 $ — Residential 4,109 4,481 — 7,779 8,940 — Real estate construction and land: Commercial 5,690 5,689 — 6,680 6,680 — Residential — — — 364 366 — Commercial: Asset-based 3,519 5,559 — 664 1,652 — Venture capital 14,534 40,029 — 5,866 8,939 — Cash flow 4,378 8,270 — 2,852 5,939 — Equipment finance 30,939 50,433 — 31,324 53,319 — Consumer 20 93 — 221 292 — Total Non-PCI Loans and Leases With and Without an Allowance Recorded: Real estate mortgage $ 116,473 $ 129,909 $ 970 $ 124,085 $ 133,985 $ 6,851 Real estate construction and land 5,690 5,689 — 7,257 7,259 — Commercial 90,339 151,445 12,635 103,718 138,136 17,912 Consumer 120 193 16 491 572 170 Total $ 212,622 $ 287,236 $ 13,621 $ 235,551 $ 279,952 $ 24,933 ________________________ (1) Excludes loans held for sale carried at lower of cost or fair value. Year Ended December 31, 2017 (1) 2016 2015 Weighted Interest Weighted Interest Weighted Interest Average Income Average Income Average Income Impaired Loans and Leases Balance (1) Recognized Balance (1) Recognized Balance (1) Recognized (In thousands) With An Allowance Recorded: Real estate mortgage: Commercial $ 15,538 $ 881 $ 26,870 $ 898 $ 17,833 $ 1,130 Residential 2,787 55 6,521 255 2,143 33 Real estate construction and land: Residential — — 213 14 747 15 Commercial: Asset-based 1,236 53 3,842 134 3,204 56 Venture capital 10,228 — 1,227 — — — Cash flow 19,093 7 22,736 10 12,590 32 Equipment finance — — 508 — 8,475 — Consumer 100 8 233 — 355 15 With No Related Allowance Recorded: Real estate mortgage: Commercial $ 89,554 $ 2,648 $ 41,917 $ 1,506 $ 28,366 $ 345 Residential 3,842 59 7,254 144 4,643 41 Real estate construction and land: Commercial 5,690 306 6,680 224 7,053 240 Residential — — 364 — — — Commercial: Asset-based 1,640 49 528 18 1,746 130 Venture capital 2,860 — 2,446 — 124 — Cash flow 2,499 35 2,455 4 2,752 89 Equipment finance 30,653 — 30,767 — 30,363 — Consumer 20 — 166 9 1,363 — Total Non-PCI Loans and Leases With and Without an Allowance Recorded: Real estate mortgage $ 111,721 $ 3,643 $ 82,562 $ 2,803 $ 52,985 $ 1,549 Real estate construction and land 5,690 306 7,257 238 7,800 255 Commercial 68,209 144 64,509 166 59,254 307 Consumer 120 8 399 9 1,718 15 Total $ 185,740 $ 4,101 $ 154,727 $ 3,216 $ 121,757 $ 2,126 _________________________ (1) For the loans and leases (excluding PCI loans) reported as impaired at December 31, 2017 , 2016 and 2015 , amounts were calculated based on the period of time such loans and leases were impaired during the reported period.
Troubled Debt Restructurings on Financing Receivables	The following table presents our troubled debt restructurings of Non-PCI loans held for investment and defaulted troubled debt restructurings of Non-PCI loans held for investment by portfolio segment and class for the years indicated: Troubled Debt Restructurings Troubled Debt Restructurings That Subsequently Defaulted (1) Pre-Modification Post-Modification Outstanding Outstanding Number Recorded Recorded Number Recorded of Loans Investment Investment of Loans Investment (1) (Dollars In thousands) Year Ended December 31, 2017 Real estate mortgage: Commercial 5 $ 2,527 $ 2,463 — $ — Residential 8 1,328 489 — — Real estate construction and land: Residential 1 362 — — — Commercial: Asset-based 10 7,987 7,987 — — Venture capital 11 29,733 29,733 — — Cash flow 14 27,703 18,468 1 1 Consumer 1 97 97 — — Total 50 $ 69,737 $ 59,237 1 $ 1 (2) Year Ended December 31, 2016 Real estate mortgage: Commercial 12 $ 13,833 $ 6,099 — $ — Residential 10 7,091 6,439 2 5,000 Real estate construction and land: Commercial 1 1,245 1,245 — — Commercial: Asset-based 5 2,158 2,158 2 1,502 Cash flow 14 30,788 30,788 — — Equipment finance 7 44,196 42,572 — — Consumer 5 850 142 — — Total 54 $ 100,161 $ 89,443 4 $ 6,502 (3) Year Ended December 31, 2015 Real estate mortgage: Commercial 21 $ 43,536 $ 43,012 2 $ 2,670 Residential 18 3,128 2,961 1 155 Real estate construction and land: Commercial 8 23,881 23,881 — — Commercial: Asset-based 13 8,400 8,400 — — Cash flow 25 2,718 2,539 — — Equipment finance 10 93,868 93,868 — — Consumer 2 197 197 — — Total 97 $ 175,728 $ 174,858 3 $ 2,825 (4) _________________________ (1) The population of defaulted restructured loans for the period indicated includes only those loans restructured during the preceding 12-month period. For example, for the year ended December 31, 2017 , the population of defaulted restructured loans includes only those loans restructured after December 31, 2016 . The table excludes defaulted troubled restructurings in those classes for which the recorded investment was zero at the end of the period. (2) Represents the balance at December 31, 2017 , and is net of charge-offs of $68,000 . (3) Represents the balance at December 31, 2016 , and there were no charge-offs. (4) Represents the balance at December 31, 2015 , and is net of charge-offs of $96,900 .
Purchased Credit Impaired Loans and Leases [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
CV of Loans Held for Investment by Class by Classified and Nonclassiified	The following table presents the credit risk rating categories for PCI loans held for investment, net of discount, by portfolio segment as of the dates indicated. Nonclassified loans are those with a credit risk rating of either pass or special mention, while classified loans are those with a credit risk rating of either substandard or doubtful. December 31, 2017 December 31, 2016 Classified Nonclassified Total Classified Nonclassified Total (In thousands) Real estate mortgage $ 11,063 $ 42,581 $ 53,644 $ 19,445 $ 73,330 $ 92,775 Real estate construction and land — — — 1,023 1,385 2,408 Commercial 4,158 — 4,158 10,943 2,049 12,992 Consumer 234 — 234 249 — 249 Total PCI loans held for investment, net of discount $ 15,455 $ 42,581 $ 58,036 $ 31,660 $ 76,764 $ 108,424
Schedule of Accounts, Notes, Loans and Financing Receivable	The following table reflects the PCI loans held for investment by portfolio segment as of the dates indicated: December 31, 2017 2016 (In thousands) Real estate mortgage $ 72,399 $ 112,982 Real estate construction and land — 1,901 Commercial 7,568 19,109 Consumer 262 281 Total gross PCI loans held for investment 80,229 134,273 Discount (22,193 ) (25,849 ) Total PCI loans held for investment, net of discount 58,036 108,424 Allowance for loan losses (6,444 ) (13,483 ) Total PCI loans held for investment, net $ 51,592 $ 94,941

Foreclosed Assets Foreclosed As

Foreclosed Assets Foreclosed Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Other Real Estate and Foreclosed Assets	The following table summarizes foreclosed assets as of the dates indicated: December 31, Property Type 2017 2016 (In thousands) Construction and land development $ 219 $ 11,224 Multi‑family — 652 Single family residence 1,019 — Commercial real estate 64 — Total other real estate owned, net 1,302 11,876 Other foreclosed assets 27 1,100 Total foreclosed assets, net $ 1,329 $ 12,976
Other Foreclosed Assets Rollforward	The following table presents the changes in foreclosed assets, net of the valuation allowance, for the years indicated: Year Ended December 31, Foreclosed Assets 2017 2016 2015 (In thousands) Balance, beginning of year $ 12,976 $ 22,120 $ 43,721 Transfers to foreclosed assets from loans 580 781 13,472 Other additions 1,385 — — Provision for losses (2,138 ) (2,576 ) (5,228 ) Reductions related to sales (11,474 ) (7,349 ) (29,845 ) Balance, end of year $ 1,329 $ 12,976 $ 22,120
Foreclosed Assets Valuation Allowance Rollforward	The following table presents the changes in the foreclosed assets valuation allowance for the years indicated: Year Ended December 31, Foreclosed Assets Valuation Allowance 2017 2016 2015 (In thousands) Balance, beginning of year $ 12,696 $ 10,246 $ 12,123 Provision for losses 2,138 2,576 5,228 Reductions related to sales (14,820 ) (126 ) (7,105 ) Balance, end of year $ 14 $ 12,696 $ 10,246

Premises and Equipment, Net Pre

Premises and Equipment, Net Premises and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2017
Premises and Equipment, Net [Abstract]
Property, Plant and Equipment	The following table presents the components of premises and equipment as of the dates indicated: December 31, 2017 2016 (In thousands) Land $ 1,243 $ 5,505 Buildings 8,154 14,929 Furniture, fixtures and equipment 43,250 38,806 Leasehold improvements 42,521 38,967 Premises and equipment, gross 95,168 98,207 Less: accumulated depreciation and amortization (63,316 ) (59,613 ) Premises and equipment, net $ 31,852 $ 38,594
Schedule of Future Minimum Rental Payments for Operating Leases	We have obligations under a number of noncancelable operating leases for premises and equipment. The following table presents future minimum rental payments under noncancelable operating leases as of the date indicated: December 31, 2017 (In thousands) Estimated Lease Payments for Year Ending December 31, 2018 $ 30,574 2019 28,098 2020 25,544 2021 21,346 2022 15,494 2023 and thereafter 34,107 Total $ 155,163

Deposits Deposits (Tables)

Deposits Deposits (Tables)	12 Months Ended
	Dec. 31, 2017
Deposits [Abstract]
Summary of Interest Bearing Deposits	The following table presents the components of interest‑bearing deposits as of the dates indicated: December 31, Deposit Category 2017 2016 (In thousands) Interest checking deposits $ 2,711,250 $ 1,462,305 Money market deposits 4,890,567 4,865,961 Savings deposits 690,353 711,039 Time deposits $250,000 and under 1,709,980 1,758,434 Time deposits over $250,000 355,342 413,856 Total interest-bearing deposits $ 10,357,492 $ 9,211,595
Schedule of Maturities Of Time Deposits	The following table summarizes the maturities of time deposits as of the date indicated: Time Deposits $250,000 Over Year of Maturity and Under $250,000 Total (In thousands) 2018 $ 1,593,877 $ 337,257 $ 1,931,134 2019 77,405 9,870 87,275 2020 16,551 3,713 20,264 2021 15,689 1,607 17,296 2022 6,325 2,895 9,220 2022 133 — 133 Total at December 31, 2017 $ 1,709,980 $ 355,342 $ 2,065,322

Borrowings and Subordinated D36

Borrowings and Subordinated Debentures (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Debt	The following table summarizes our borrowings as of the dates indicated: December 31, 2017 December 31, 2016 Weighted Weighted Average Average Borrowing Type Amount Rate Amount Rate (Dollars in thousands) Non‑recourse debt $ 342 6.87% $ 812 6.41% FHLB secured advances 332,000 1.41% 735,000 0.59% FHLB unsecured overnight advance 135,000 1.34% 130,000 0.55% AFX borrowings — —% 40,000 0.81% Total borrowings $ 467,342 $ 905,812
Borrowings Subordinated Debentures And Brokered Deposits Disclosure	The following table summarizes the terms of each issuance of subordinated debentures outstanding as of the dates indicated: December 31, 2017 December 31, 2016 Issue Maturity Rate Index Series Amount Rate Amount Rate Date Date (Quarterly Reset) (Dollars in thousands) Trust V $ 10,310 4.70 % $ 10,310 4.09 % 8/15/2003 9/17/2033 3 month LIBOR + 3.10 Trust VI 10,310 4.64 % 10,310 4.01 % 9/3/2003 9/15/2033 3 month LIBOR + 3.05 Trust CII 5,155 4.55 % 5,155 3.95 % 9/17/2003 9/17/2033 3 month LIBOR + 2.95 Trust VII 61,856 4.13 % 61,856 3.64 % 2/5/2004 4/23/2034 3 month LIBOR + 2.75 Trust CIII 20,619 3.28 % 20,619 2.65 % 8/15/2005 9/15/2035 3 month LIBOR + 1.69 Trust FCCI 16,495 3.19 % 16,495 2.56 % 1/25/2007 3/15/2037 3 month LIBOR + 1.60 Trust FCBI 10,310 3.14 % 10,310 2.51 % 9/30/2005 12/15/2035 3 month LIBOR + 1.55 Trust CS 2005-1 82,475 3.54 % 82,475 2.91 % 11/21/2005 12/15/2035 3 month LIBOR + 1.95 Trust CS 2005-2 128,866 3.33 % 128,866 2.84 % 12/14/2005 1/30/2036 3 month LIBOR + 1.95 Trust CS 2006-1 51,545 3.33 % 51,545 2.84 % 2/22/2006 4/30/2036 3 month LIBOR + 1.95 Trust CS 2006-2 51,550 3.33 % 51,550 2.84 % 9/27/2006 10/30/2036 3 month LIBOR + 1.95 Trust CS 2006-3 (1) 30,986 1.72 % 27,185 1.74 % 9/29/2006 10/30/2036 3 month EURIBOR + 2.05 Trust CS 2006-4 16,470 3.33 % 16,470 2.84 % 12/5/2006 1/30/2037 3 month LIBOR + 1.95 Trust CS 2006-5 6,650 3.33 % 6,650 2.84 % 12/19/2006 1/30/2037 3 month LIBOR + 1.95 Trust CS 2007-2 39,177 3.33 % 39,177 2.84 % 6/13/2007 7/30/2037 3 month LIBOR + 1.95 Trust I (2) 6,186 3.64 % — — % 12/10/2004 3/15/2035 3 month LIBOR + 2.05 Trust II (2) 3,093 3.34 % — — % 12/23/2005 3/15/2036 3 month LIBOR + 1.75 Trust III (2) 3,093 3.44 % — — % 6/30/2006 9/18/2036 3 month LIBOR + 1.85 Gross subordinated debentures 555,146 538,973 Unamortized discount (3) (92,709 ) (98,229 ) Net subordinated debentures $ 462,437 $ 440,744 ___________________ (1) Denomination is in Euros with a value of €25.8 million . (2) Acquired in the CUB acquisition on October 20, 2017. (3) Amount represents the fair value adjustment on trust preferred securities assumed in acquisitions.

Commitments and Contingencies D

Commitments and Contingencies Disclosure (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments Disclosure	The following table presents a summary of the financial instruments described above as of the dates indicated: December 31, 2017 2016 (In thousands) Loan commitments to extend credit $ 6,234,061 $ 4,166,703 Standby letters of credit 320,063 211,398 Total $ 6,554,124 $ 4,378,101

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Assets and Liabilities Carried at Fair Value on Recurring Basis	The following tables present information on the assets measured and recorded at fair value on a recurring basis as of the dates indicated: Fair Value Measurements as of December 31, 2017 Measured on a Recurring Basis Total Level 1 Level 2 Level 3 (In thousands) Securities available‑for‑sale: Residential MBS and CMOs: Agency MBS $ 246,274 $ — $ 246,274 $ — Agency CMOs 275,709 — 275,709 — Private label CMOs 125,987 — 103,113 22,874 Municipal securities 1,680,068 — 1,680,068 — Agency commercial MBS 1,163,969 — 1,163,969 — Corporate debt securities 19,295 — 19,295 — Collateralized loan obligations 7,015 — 7,015 — SBA securities 160,334 — 160,334 — Asset-backed and other securities 95,780 5,922 47,749 42,109 Total securities available-for-sale 3,774,431 5,922 3,703,526 64,983 Equity warrants 5,161 — — 5,161 Other derivative assets 1,873 — 1,873 — Total recurring assets $ 3,779,592 $ 5,922 $ 3,703,526 $ 70,144 Derivative liabilities $ 1,379 $ — $ 1,379 $ — Fair Value Measurements as of December 31, 2016 Measured on a Recurring Basis Total Level 1 Level 2 Level 3 (In thousands) Securities available‑for‑sale: Residential MBS and CMOs: Agency MBS $ 502,443 $ — $ 502,443 $ — Agency CMOs 146,289 — 146,289 — Private label CMOs 125,469 — 68,567 56,902 Municipal securities 1,456,459 — 1,456,459 — Agency commercial MBS 547,692 — 547,692 — Corporate debt securities 47,509 — 47,509 — Collateralized loan obligations 156,887 — 156,887 — SBA securities 178,845 — 178,845 — Asset-backed and other securities 62,237 2,080 51,784 8,373 Total securities available-for-sale 3,223,830 2,080 3,156,475 65,275 Equity warrants 5,497 — — 5,497 Other derivative assets 694 — 694 — Total recurring assets $ 3,230,021 $ 2,080 $ 3,157,169 $ 70,772 Derivative liabilities $ 3,285 $ — $ 3,285 $ —
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques	The following table presents information about the quantitative inputs and assumptions used to determine the fair values provided by our third party pricing service for our Level 3 private label CMOs and asset-backed securities available-for-sale measured at fair value on a recurring basis as of the date indicated: December 31, 2017 Private Label CMOs Asset-Backed Securities Weighted Weighted Range of Average Range of Average Unobservable Inputs Inputs Input Inputs Input Voluntary annual prepayment speeds 3.6% - 43.6% 8.6% 5% - 15% 13.8% Annual default rates 0.1% - 15.3% 2.5% 1% - 2% 1.9% Loss severity rates 4.0% - 102% 55.8% 10% - 60% 53.9% Discount rates 1.8% - 10.3% 5.3% 3.2% - 4.3% 3.6% The following table presents information about the quantitative inputs and assumptions used in the modified Black-Scholes option pricing model to determine the fair value for our Level 3 equity warrants measured at fair value on a recurring basis as of the date indicated: December 31, 2017 Equity Warrants Weighted Average Unobservable Inputs Input Volatility 16.7% Risk-free interest rate 2.1% Remaining life assumption (in years) 3.7
Fair Value, Assets Measured on Recurring Basis, Significant Unobservable Inputs (Level 3) Reconciliation	The following table summarizes activity for our Level 3 private label CMOs measured at fair value on a recurring basis for the years indicated: Year Ended December 31, Level 3 Private Label CMOs 2017 2016 2015 (In thousands) Balance, beginning of year $ 56,902 $ 81,241 $ 33,947 Total included in earnings 2,256 1,636 1,104 Total unrealized loss in comprehensive income (742 ) (1,648 ) (1,388 ) Sales (4,732 ) — — Transfer from Level 2 574 — — Transfers to Level 2 (21,165 ) — — Net settlements (10,219 ) (24,327 ) (3,881 ) Addition from the Square 1 acquisition — — 51,459 Balance, end of year $ 22,874 $ 56,902 $ 81,241
Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block]	The following table summarizes activity for our Level 3 equity warrants measured at fair value on a recurring basis for the year ended December 31, 2017 and 2016 and the period from the October 6, 2015 Square 1 acquisition date to December 31, 2015: Year Ended December 31, Period Ended Level 3 Equity Warrants 2017 2016 December 31, 2015 (In thousands) Balance, beginning of year or acquisition date $ 5,497 $ 4,914 $ 5,552 Total included in earnings 2,532 1,402 530 Sales (3,093 ) (1,894 ) (1,529 ) Issuances 1,407 1,911 363 Transfers to Level 1 (securities available-for-sale) (1,182 ) (836 ) (2 ) Balance, end of year $ 5,161 $ 5,497 $ 4,914
Assets carried at fair value on a nonrecurring basis	The following tables present assets measured at fair value on a non‑recurring basis as of the dates indicated: Fair Value Measurement as of December 31, 2017 Measured on a Non‑Recurring Basis Total Level 1 Level 2 Level 3 (In thousands) Impaired Non‑PCI loans $ 61,095 $ — $ 5,143 $ 55,952 Loans held for sale 483,563 — 483,563 — Total non-recurring $ 544,658 $ — $ 488,706 $ 55,952 Fair Value Measurement as of December 31, 2016 Measured on a Non‑Recurring Basis Total Level 1 Level 2 Level 3 (In thousands) Impaired Non‑PCI loans $ 149,749 $ — $ 1,661 $ 148,088 OREO 11,224 — 11,224 — Investments carried at cost 242 — — 242 Total non-recurring $ 161,215 $ — $ 12,885 $ 148,330
Net Losses (Gains) on Nonrecurring Assets [Table Text Block]	The following table presents losses recognized on assets measured on a nonrecurring basis for the years indicated: Year Ended December 31, Loss on Assets Measured on a Non‑Recurring Basis 2017 2016 2015 (In thousands) Impaired Non‑PCI loans $ 20,422 $ 43,240 $ 16,097 Loans held for sale 957 — — OREO 14 2,576 4,726 Investments carried at cost — 10 17 Total net loss $ 21,393 $ 45,826 $ 20,840
Fair Value Inputs, Assets, Quantitative Information	The following table presents the valuation methodology and unobservable inputs for Level 3 assets measured at fair value on a nonrecurring basis as of the date indicated: December 31, 2017 Valuation Unobservable Weighted Asset Fair Value Technique Inputs Range Average (In thousands) Impaired Non-PCI loans $ 41,984 Discounted cash flows Discount rates 2.00% - 10.20% 7.43% 13,968 Third party appraisals No discounts Total non-recurring Level 3 $ 55,952
Fair Value, by Balance Sheet Grouping	December 31, 2017 Carrying Estimated Fair Value Amount Total Level 1 Level 2 Level 3 ( In thousands ) Financial Assets: Cash and due from banks $ 233,215 $ 233,215 $ 233,215 $ — $ — Interest‑earning deposits in financial institutions 165,222 165,222 165,222 — — Securities available‑for‑sale 3,774,431 3,774,431 5,922 3,703,526 64,983 Investment in FHLB stock 20,790 20,790 — 20,790 — Investments carried at cost 977 9,573 — — 9,573 Loans held for sale 481,100 483,563 — 483,563 — Loans and leases held for investment, net 16,833,287 17,023,098 — 5,143 17,017,955 Equity warrants 5,161 5,161 — — 5,161 Other derivative assets 1,873 1,873 — 1,873 — Financial Liabilities: Core deposits 15,937,012 15,937,012 — 15,937,012 — Non-core non-maturity deposits 863,202 863,202 — 863,202 — Time deposits 2,065,322 2,055,104 — 2,055,104 — Borrowings 467,342 467,343 467,000 343 — Subordinated debentures 462,437 444,383 — 444,383 — Derivative liabilities 1,379 1,379 — 1,379 — December 31, 2016 Carrying Estimated Fair Value Amount Total Level 1 Level 2 Level 3 ( In thousands ) Financial Assets: Cash and due from banks $ 337,965 $ 337,965 $ 337,965 $ — $ — Interest‑earning deposits in financial institutions 81,705 81,705 81,705 — — Securities available‑for‑sale 3,223,830 3,223,830 2,080 3,156,475 65,275 Investment in FHLB stock 21,870 21,870 — 21,870 — Investments carried at cost 1,416 3,843 — — 3,843 Loans and leases held for investment, net 15,298,716 15,494,808 — 1,661 15,493,147 Equity warrants 5,497 5,497 — — 5,497 Other derivative assets 694 694 — 694 — Financial Liabilities: Core deposits 12,523,834 12,523,834 — 12,523,834 — Non-core non-maturity deposits 1,174,487 1,174,487 — 1,174,487 — Time deposits 2,172,290 2,166,187 — 2,166,187 — Borrowings 905,812 905,838 591,000 314,838 — Subordinated debentures 440,744 424,507 — 424,507 — Derivative liabilities 3,285 3,285 — 3,285 —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	The following table presents the components of income tax expense for the years indicated: December 31, 2017 2016 2015 (In thousands) Current Income Tax Expense: Federal $ 74,769 $ 101,530 $ 11,950 State 38,933 52,551 28,167 Total current income tax expense 113,702 154,081 40,117 Deferred Income Tax Expense (Benefit): Federal 63,463 55,857 128,436 State 19,748 (4,168 ) 11,964 Total deferred income tax expense 83,211 51,689 140,400 Total income tax expense $ 196,913 $ 205,770 $ 180,517
Schedule of Effective Income Tax Rate Reconciliation	The following table presents a reconciliation of the recorded income tax expense to the amount of taxes computed by applying the applicable federal statutory income tax rate of 35% to earnings or loss before income taxes for the years indicated: December 31, 2017 2016 2015 (In thousands) Computed expected income tax expense at federal statutory rate $ 194,156 $ 195,278 $ 168,047 State tax expense, net of federal tax benefit 33,729 32,896 29,009 Tax‑exempt interest benefit (15,510 ) (13,992 ) (8,274 ) Increase in cash surrender value of life insurance (1,853 ) (1,544 ) (884 ) Tax credits (2,054 ) (1,439 ) (2,441 ) Nondeductible employee compensation 1,781 1,257 1,005 Nondeductible acquisition‑related expense 1,608 — 876 Change in unrecognized tax benefits 1,157 (2,268 ) (5,529 ) Valuation allowance change (13,071 ) (8,689 ) (2,917 ) Federal rate change (1,156 ) — — Other, net (1,874 ) 4,271 1,625 Recorded income tax expense $ 196,913 $ 205,770 $ 180,517
Schedule of Deferred Tax Assets and Liabilities	The following table presents the tax effects of temporary differences that give rise to significant portions of deferred tax assets and deferred tax liabilities as of the dates indicated: December 31, 2017 2016 (In thousands) Deferred Tax Assets: Book allowance for loan losses in excess of tax specific charge-offs $ 60,349 $ 81,380 Interest on nonaccrual loans 8,519 7,485 Deferred compensation 6,174 3,148 Premises and equipment, principally due to differences in depreciation 3,789 7,395 Foreclosed assets valuation allowance 248 5,546 State tax benefit 3,781 7,187 Net operating losses 70,269 57,416 Capital loss carryforwards 14,264 17,740 Accrued liabilities 25,986 43,366 Unrealized loss from FDIC‑assisted acquisitions 4,654 7,207 Tax mark-to-market 9,207 11,793 Equity investments 7,549 15,195 Goodwill 15,641 29,996 Tax credits 5,651 16,493 Gross deferred tax assets 236,081 311,347 Valuation allowance (94,120 ) (100,920 ) Deferred tax assets, net of valuation allowance 141,961 210,427 Deferred Tax Liabilities: Core deposit and customer relationship intangibles 21,529 12,792 Deferred loan fees and costs 9,735 13,389 Unrealized gain on securities available‑for‑sale 15,107 4,118 FHLB stock 744 1,098 Subordinated debentures 24,518 37,499 Operating leases 65,286 41,785 Other 7,303 5,634 Gross deferred tax liabilities 144,222 116,315 Total net deferred tax asset (liability) $ (2,261 ) $ 94,112
Schedule of Unrecognized Tax Benefits Roll Forward	e

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Income Per Share	The following table presents the computation of basic and diluted net earnings per share for the years indicated: Year Ended December 31, 2017 2016 2015 (Dollars in thousands, except per share data) Basic Earnings Per Share: Net earnings $ 357,818 $ 352,166 $ 299,619 Less: earnings allocated to unvested restricted stock (1) (4,184 ) (3,988 ) (2,892 ) Net earnings allocated to common shares $ 353,634 $ 348,178 $ 296,727 Weighted-average basic shares and unvested restricted stock outstanding 123,060 121,670 107,401 Less: weighted-average unvested restricted stock outstanding (1,447 ) (1,431 ) (1,074 ) Weighted-average basic shares outstanding 121,613 120,239 106,327 Basic earnings per share: $ 2.91 $ 2.90 $ 2.79 Diluted Earnings Per Share: Net earnings allocated to common shares $ 353,634 $ 348,178 $ 296,727 Weighted-average basic shares outstanding 121,613 120,239 106,327 Diluted earnings per share: $ 2.91 $ 2.90 $ 2.79 ________________________ (1) Represents cash dividends paid to holders of unvested restricted stock, net of forfeitures, plus undistributed earnings amounts available to holders of unvested restricted stock, if any.

Stock Based Compensation Plan S

Stock Based Compensation Plan Stock-based Compensation Plan (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]	The following table presents a summary of restricted stock transactions during the year ended December 31, 2017 : TRSAs PRSUs Weighted Weighted Average Average Grant Date Grant Date Number of Fair Value Number of Fair Value Shares (Per Share) Units (Per Unit) Unvested restricted stock, December 31, 2016 1,476,132 $39.83 153,715 $27.32 Granted 557,955 $50.08 85,310 $57.80 Vested (498,186 ) $40.20 — $— Forfeited (99,781 ) $42.87 — $— Unvested restricted stock, December 31, 2017 1,436,120 $43.47 239,025 $38.20

Dividend Availability and Reg42

Dividend Availability and Regulatory Matters Dividend Availability and Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2017
Dividend Availability and Regulatory Matters [Abstract]
Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations	The following table presents actual capital amounts and ratios for the Company and the Bank as of the dates indicated: Well Capitalized Minimum Excess Actual Requirement Capital Amount Ratio Amount Ratio Amount (Dollars in thousands) December 31, 2017 Tier I leverage PacWest Bancorp Consolidated $ 2,361,800 10.66% $ 1,107,900 5.00% $ 1,253,900 Pacific Western Bank $ 2,574,561 11.75% $ 1,095,656 5.00% $ 1,478,905 Common equity Tier I capital PacWest Bancorp Consolidated $ 2,361,800 10.91% $ 1,407,743 6.50% $ 954,057 Pacific Western Bank $ 2,574,561 11.91% $ 1,405,299 6.50% $ 1,169,262 Tier I capital PacWest Bancorp Consolidated $ 2,361,800 10.91% $ 1,732,607 8.00% $ 629,193 Pacific Western Bank $ 2,574,561 11.91% $ 1,729,599 8.00% $ 844,962 Total capital PacWest Bancorp Consolidated $ 2,978,643 13.75% $ 2,165,759 10.00% $ 812,884 Pacific Western Bank $ 2,742,624 12.69% $ 2,161,999 10.00% $ 580,625 December 31, 2016 Tier I leverage PacWest Bancorp Consolidated $ 2,286,203 11.91% $ 959,477 5.00% $ 1,326,726 Pacific Western Bank $ 2,184,097 11.40% $ 957,630 5.00% $ 1,226,467 Common equity Tier I capital PacWest Bancorp Consolidated $ 2,286,203 12.31% $ 1,206,960 6.50% $ 1,079,243 Pacific Western Bank $ 2,184,097 11.78% $ 1,205,541 6.50% $ 978,556 Tier I capital PacWest Bancorp Consolidated $ 2,286,203 12.31% $ 1,485,490 8.00% $ 800,713 Pacific Western Bank $ 2,184,097 11.78% $ 1,483,742 8.00% $ 700,355 Total capital PacWest Bancorp Consolidated $ 2,889,163 15.56% $ 1,856,862 10.00% $ 1,032,301 Pacific Western Bank $ 2,358,829 12.72% $ 1,854,678 10.00% $ 504,151

Condensed Financial Informati43

Condensed Financial Information Of Parent Company Parent Company Information (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information Of Parent Company [Abstract]
Condensed Balance Sheet	Parent Company Only December 31, Condensed Balance Sheets 2017 2016 (In thousands) Assets: Cash and cash equivalents $ 185,511 $ 494,765 Investments in subsidiaries 4,869,391 4,053,711 Other assets 76,458 67,074 Total assets $ 5,131,360 $ 4,615,550 Liabilities: Subordinated debentures $ 147,233 $ 134,360 Other liabilities 6,529 2,135 Total liabilities 153,762 136,495 Stockholders’ equity 4,977,598 4,479,055 Total liabilities and stockholders’ equity $ 5,131,360 $ 4,615,550
Condensed Income Statement	Parent Company Only December 31, Condensed Statements of Earnings 2017 2016 2015 (In thousands) Miscellaneous income $ 3,393 $ 2,146 $ 1,458 Dividends from Bank subsidiary 265,000 259,000 214,000 Total income 268,393 261,146 215,458 Interest expense 5,519 4,816 4,279 Operating expenses 8,273 7,732 6,983 Total expenses 13,792 12,548 11,262 Earnings before income taxes and equity in undistributed earnings of subsidiaries 254,601 248,598 204,196 Income tax benefit 19,957 2,612 4,225 Earnings before equity in undistributed earnings of subsidiaries 274,558 251,210 208,421 Equity in undistributed earnings of subsidiaries 83,260 100,956 91,198 Net earnings $ 357,818 $ 352,166 $ 299,619
Condensed Cash Flow Statement	Parent Company Only December 31, Condensed Statements of Cash Flows 2017 2016 2015 (In thousands) Cash flows from operating activities: Net earnings $ 357,818 $ 352,166 $ 299,619 Adjustments to reconcile net earnings to net cash provided by operating activities: Change in other assets (34,274 ) 96,668 145,709 Change in liabilities 4,857 (17,311 ) 9,115 Gain on sale of securities, net (15 ) (405 ) — Earned stock compensation 25,568 23,319 14,994 Tax effect of restricted stock vesting included in stockholders’ equity — 4,406 841 Equity in undistributed earnings of subsidiaries (83,260 ) (100,956 ) (91,198 ) Net cash provided by operating activities 270,694 357,887 379,080 Cash flows from investing activities: Proceeds from sales of securities available-for-sale 426 995 — Net cash and cash equivalents (paid in) acquired in acquisitions (223,818 ) — 3,021 Net cash (used in) provided by investing activities (223,392 ) 995 3,021 Cash flows from financing activities: Common stock repurchased and restricted stock surrendered (109,153 ) (33,244 ) (8,400 ) Tax effect of restricted stock vesting included in stockholders’ equity — (4,406 ) (841 ) Increase in note receivable — — (50,000 ) Cash dividends paid, net (247,403 ) (243,437 ) (215,110 ) Net cash used in financing activities (356,556 ) (281,087 ) (274,351 ) Net (decrease) increase in cash and cash equivalents (309,254 ) 77,795 107,750 Cash and cash equivalents, beginning of year 494,765 416,970 309,220 Cash and cash equivalents, end of year $ 185,511 $ 494,765 $ 416,970 Supplemental disclosure of noncash investing and financing activities: Common stock issued for acquisitions $ 446,233 $ — $ 797,433

Selected Quarterly Financial Da

Selected Quarterly Financial Data Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following tables set forth our unaudited quarterly results for the periods indicated: Three Months Ended December 31, September 30, June 30, March 31, 2017 2017 2017 2017 (Dollars in thousands, except per share data) Interest income $ 284,597 $ 260,966 $ 259,544 $ 247,409 Interest expense (21,641 ) (19,276 ) (17,071 ) (14,957 ) Net interest income 262,956 241,690 242,473 232,452 Provision for credit losses (6,406 ) (15,119 ) (11,499 ) (24,728 ) (Loss) gain on sale of securities (3,329 ) 1,236 1,651 (99 ) Other noninterest income 30,124 30,146 33,631 35,213 Total noninterest income 26,795 31,382 35,282 35,114 Foreclosed assets income (expense), net 475 (2,191 ) 157 (143 ) Acquisition, integration and reorganization costs (16,085 ) (1,450 ) (1,700 ) (500 ) Other noninterest expense (127,258 ) (114,901 ) (116,164 ) (115,901 ) Total noninterest expense (142,868 ) (118,542 ) (117,707 ) (116,544 ) Earnings before income taxes 140,477 139,411 148,549 126,294 Income tax expense (56,440 ) (37,945 ) (54,902 ) (47,626 ) Net earnings $ 84,037 $ 101,466 $ 93,647 $ 78,668 Basic and diluted earnings per share $ 0.66 $ 0.84 $ 0.77 $ 0.65 Three Months Ended December 31, September 30, June 30, March 31, 2016 2016 2016 2016 (Dollars in thousands, except per share data) Interest income $ 261,773 $ 247,855 $ 247,054 $ 259,230 Interest expense (13,468 ) (13,220 ) (13,297 ) (14,636 ) Net interest income 248,305 234,635 233,757 244,594 Provision for credit losses (23,215 ) (8,471 ) (13,903 ) (20,140 ) Gain on sale of securities 515 382 478 8,110 FDIC loss sharing expense, net — — (6,502 ) (2,415 ) Other noninterest income 28,380 26,538 28,145 28,844 Total noninterest income 28,895 26,920 22,121 34,539 Foreclosed assets (expense) income, net (2,693 ) 248 3 561 Acquisition, integration and reorganization costs — — — (200 ) Other noninterest expense (115,929 ) (110,958 ) (110,084 ) (111,049 ) Total noninterest expense (118,622 ) (110,710 ) (110,081 ) (110,688 ) Earnings before income taxes 135,363 142,374 131,894 148,305 Income tax expense (49,716 ) (48,479 ) (49,726 ) (57,849 ) Net earnings $ 85,647 $ 93,895 $ 82,168 $ 90,456 Basic and diluted earnings per share $ 0.71 $ 0.77 $ 0.68 $ 0.74

Organization (Details)

Organization (Details)	12 Months Ended
	Dec. 31, 2017USD ($)reportable_segmentacquisitionbank_branch	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Number of Businesses Acquired | acquisition	29
Loans Receivable Held-for-sale, Amount	$ 1,500,000,000
Transfer of Portfolio Loans and Leases to Held-for-sale	481,100,000	$ 0	$ 0
Loans held for sale, at lower of cost or fair value	481,100,000	0
Proceeds from Sale and Collection of Lease Receivables	0	$ 138,955,000	$ 0
New Accounting Pronouncement Or Change In Accounting Principle Effect Of Change of Income Taxes	$ 1,500,000
Allowance For Credit Losses, Look-back Period for Estimation	31	27
Fair Value Hedges, Net	$ 0
Derivative, Notional Amount	$ 91,100,000
Number of Reportable Segments | reportable_segment	1
FDIC Insurance Limits	$ 250,000
Core Deposits [Member] | Minimum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 years
Core Deposits [Member] | Maximum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	10 years
Customer Relationships [Member] | Minimum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	4 years
Customer Relationships [Member] | Maximum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 years
Furniture and Fixtures [Member] | Minimum [Member]
Business Acquisition [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Furniture and Fixtures [Member] | Maximum [Member]
Business Acquisition [Line Items]
Property, Plant and Equipment, Useful Life	7 years
Building [Member]
Business Acquisition [Line Items]
Property, Plant and Equipment, Useful Life	35 years
Equity Securities [Member] | Equity Method Investments [Member] | Minimum [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage	20.00%
Equity Securities [Member] | Equity Method Investments [Member] | Maximum [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Limited Partner [Member] | Equity Method Investments [Member] | Minimum [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage	5.00%
Loans Under $250,000
Business Acquisition [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	$ 250,000
CALIFORNIA
Business Acquisition [Line Items]
Retail Branch Locations | bank_branch	76
NORTH CAROLINA
Business Acquisition [Line Items]
Retail Branch Locations | bank_branch	1
Expired Policies [Member]
Business Acquisition [Line Items]
Time Deposits, Less than $100,000	$ 100,000
Time Deposits, $100,000 or More	100,000
New Policies [Member]
Business Acquisition [Line Items]
Time Deposits, Less Than $250,000	250,000
Time Deposits, $250,000 or More	250,000
Retained Earnings [Member]
Business Acquisition [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	(420,000)
Cash Flow [Member]
Business Acquisition [Line Items]
Proceeds from Sale of Loans Held-for-sale	$ 1,000,000,000
Performance Shares [Member]
Business Acquisition [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Performance Period	3 years
Share-based Compensation Award, Tranche One [Member] | Maximum [Member]
Business Acquisition [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	150.00%
Share-based Compensation Award, Tranche Two [Member] | Maximum [Member]
Business Acquisition [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	200.00%

Restricted Cash (Details)

Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Restricted Cash Balances [Abstract]
Restricted Cash and Cash Equivalents	$ 77.6	$ 67.7

Acquisition (Details)

Acquisition (Details) - USD ($) $ in Thousands	Oct. 20, 2017	Oct. 06, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Equipment leased to others under operating leases			$ 284,631	$ 229,905
Goodwill			$ 2,548,670	$ 2,173,949	$ 2,176,291	$ 1,720,479
Square 1 Financial, Inc. [Member]
Business Acquisition [Line Items]
Cash and due from banks		$ 24,867
Interest‑earning deposits in financial institutions		236,069
Securities available‑for‑sale		2,193,538
FHLB stock		2,787
Loans and leases		1,553,720
Premises and equipment		1,927
Goodwill		446,069
Core deposit and customer relationship intangibles		45,426
Other assets		106,757
Total assets acquired		4,611,160
Noninterest‑bearing deposits		2,549,000
Interest‑bearing deposits		1,240,635
Borrowings		0
Subordinated debentures		0
Accrued interest payable and other liabilities		24,092
Total liabilities assumed		3,813,727
Cash paid		0
PacWest common stock issued		797,433
Total consideration paid		$ 797,433
CU Bancorp [Member]
Business Acquisition [Line Items]
Cash and due from banks	$ 51,857
Interest‑earning deposits in financial institutions	332,799
Securities available‑for‑sale	446,980
FHLB stock	11,902
Loans and leases	2,075,890
Premises and equipment	2,981
Goodwill	374,721
Core deposit and customer relationship intangibles	57,500
Other assets	103,498
Total assets acquired	3,458,128
Noninterest‑bearing deposits	1,510,285
Interest‑bearing deposits	1,209,597
Borrowings	22,879
Subordinated debentures	12,372
Accrued interest payable and other liabilities	32,424
Total liabilities assumed	2,787,557
Cash paid	224,338
PacWest common stock issued	446,233
Total consideration paid	$ 670,571

Acquisitions (Details Textual)

Acquisitions (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	Oct. 20, 2017	Oct. 06, 2015	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Common Stock, Par or Stated Value Per Share			$ 0.01				$ 0.01				$ 0.01	$ 0.01
Goodwill			$ 2,548,670				$ 2,173,949				$ 2,548,670	$ 2,173,949	$ 2,176,291	$ 1,720,479
Acquisition, integration and reorganization costs			$ 127,258	$ 114,901	$ 116,164	$ 115,901	$ 115,929	$ 110,958	$ 110,084	$ 111,049	$ 19,735	$ 200	$ 21,247
Business Acquisition, Percentage of Voting Interests Acquired	7.00%
CU Bancorp [Member]
Business Acquisition [Line Items]
Business Acquisition Shares Receivable By Stockholders Of Acquiree Ratio	0.5308
Business Acquisition, Share Price	$ 12
Cash paid	$ 224,338
Common Stock, Par or Stated Value Per Share	$ 47.99
Assets acquired	$ 3,458,128
Liabilities assumed	2,787,557
Goodwill	374,721
Business Combination, Consideration Transferred	670,571
Loans and leases	2,075,890
Square 1 Financial, Inc. [Member]
Business Acquisition [Line Items]
Cash paid		$ 0
Assets acquired		4,611,160
Liabilities assumed		3,813,727
Goodwill		446,069
Business Combination, Consideration Transferred		797,433
Loans and leases		$ 1,553,720
Common Stock [Member]
Business Acquisition [Line Items]
Stock Issued During Period, Shares, Acquisitions											9,298,451		18,135,845
Core Deposits [Member] | CU Bancorp [Member]
Business Acquisition [Line Items]
Loans and leases	$ 2,700,000

Goodwill and Other Intangible49

Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Goodwill	$ 2,173,949	$ 2,176,291	$ 1,720,479
Goodwill	2,548,670	2,173,949	2,176,291
CapitalSource Inc. [Member]
Goodwill [Roll Forward]
Goodwill, Subsequent Recognition of Deferred Tax Asset			7,901
Square 1 Financial, Inc. [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period			447,911
Goodwill, Subsequent Recognition of Deferred Tax Asset			$ 1,842
Pacific Western Equipment Finance [Member]
Goodwill [Roll Forward]
Goodwill, Subsequent Recognition of Deferred Tax Asset		$ 500
CU Bancorp [Member] | CU Bancorp [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period	$ 374,721

Goodwill and Other Intangible50

Goodwill and Other Intangible Assets (Details 1) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-lived Intangible Assets [Roll Forward]
Balance, beginning of year				$ 64,187				$ 95,524	$ 64,187	$ 95,524	$ 53,090
Balance, beginning of year				(27,821)				(42,304)	(27,821)	(42,304)	(35,886)
Additions due to acquisitions										0	45,426
Amortization	$ (16,085)	$ (1,450)	$ (1,700)	$ (500)	$ 0	$ 0	$ 0	$ (200)	(14,240)	(16,517)	(9,410)
Fully amortized portion									(2,190)	(29,637)	(2,992)
Write-off due to the asset financing reorganization										(1,363)
Balance, end of year	119,497				64,187				119,497	64,187	95,524
Net CDI and CRI, end of year	(39,871)				(27,821)				(39,871)	(27,821)	(42,304)
Net CDI and CRI, end of year	$ 79,626				$ 36,366				79,626	36,366	53,220
CDI and CRI [Member]
Finite-lived Intangible Assets [Roll Forward]
Fully amortized portion									(2,190)	(29,637)	(2,992)
Write-off due to the asset financing reorganization										$ 1,700
Pacific Western Equipment Finance [Member]
Finite-lived Intangible Assets [Roll Forward]
Indefinite-lived Intangible Assets, Written off Related to Sale of Business Unit									0		0
CDI and CRI [Member] | Pacific Western Equipment Finance [Member]
Finite-lived Intangible Assets [Roll Forward]
Indefinite-lived Intangible Assets, Written off Related to Sale of Business Unit									0		$ 0
CU Bancorp [Member]
Finite-lived Intangible Assets [Roll Forward]
Additions due to acquisitions									$ 57,500

Goodwill and Other Intangible51

Goodwill and Other Intangible Assets (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gain (Loss) on Sale of Capital Leases, Net	$ 0	$ (720)	$ 0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	5 years
Aggregate Amortization Expense 2018	$ 24,400
Aggregate Amortization Expense 2019	19,600
Aggregate Amortization Expense 2020	15,300
Aggregate Amortization Expense 2021	11,700
Aggregate Amortization Expense 2022	$ 7,900
Pacific Western Equipment Finance [Member]
Goodwill, Subsequent Recognition of Deferred Tax Asset		$ (500)

Investment Securities (Details)

Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 3,721,525	$ 3,213,655
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	68,965	32,386
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(16,059)	(22,211)
Securities available-for-sale, at fair value	3,774,431	3,223,830
Government agency and government-sponsored enterprise pass through securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	243,375	499,185
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3,743	6,222
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(844)	(2,964)
Securities available-for-sale, at fair value	246,274	502,443
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	277,638	145,258
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	968	1,528
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(2,897)	(497)
Securities available-for-sale, at fair value	275,709	146,289
Private Label Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	122,816	122,707
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3,813	4,199
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(642)	(1,437)
Securities available-for-sale, at fair value	125,987	125,469
Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,627,707	1,447,064
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	53,700	15,406
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,339)	(6,011)
Securities available-for-sale, at fair value	1,680,068	1,456,459
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,169,969	555,552
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2,758	1,798
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(8,758)	(9,658)
Securities available-for-sale, at fair value	1,163,969	547,692
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	17,000	47,100
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2,295	680
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	(271)
Securities available-for-sale, at fair value	19,295	47,509
Collateralized Loan Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	6,960	155,440
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	55	1,685
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	(238)
Securities available-for-sale, at fair value	7,015	156,887
SBA asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	160,214	179,085
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	695	510
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(575)	(750)
Securities available-for-sale, at fair value	160,334	178,845
Other securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	95,846	62,264
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	938	358
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,004)	(385)
Securities available-for-sale, at fair value	$ 95,780	$ 62,237

Investment Securities (Details

Investment Securities (Details 1) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ (1,026,780)	$ (1,366,218)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(223,832)	(264,479)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(1,250,612)	(1,630,697)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(8,928)	(19,706)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(7,131)	(2,505)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(16,059)	(22,211)
Government agency and government-sponsored enterprise pass through securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(44,795)	(149,281)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(26,010)	(122,902)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(70,805)	(272,183)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(311)	(1,691)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(533)	(1,273)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(844)	(2,964)
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(163,014)	(44,111)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(20,928)	(25,316)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(183,942)	(69,427)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,452)	(416)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(445)	(81)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2,897)	(497)
Private Label Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(50,521)	(49,067)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(5,035)	(30,155)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(55,556)	(79,222)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(500)	(906)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(142)	(531)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(642)	(1,437)
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(67,936)	(644,424)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(32,326)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(100,262)	(644,424)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(365)	(6,011)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(974)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1,339)	(6,011)
Commercial Mortgage Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(579,373)	(349,550)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(129,060)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(708,433)	(349,550)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3,777)	(9,658)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(4,981)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(8,758)	(9,658)
Corporate Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		(29,829)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		(29,829)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(271)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		(271)
Collateralized Loan Obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		(12,450)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		(39,231)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		(51,681)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(37)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		(201)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		(238)
SBA asset-backed securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(74,904)	(69,293)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	(39,024)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(74,904)	(108,317)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(575)	(407)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	(343)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(575)	(750)
Other securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(46,237)	(18,213)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(10,473)	(7,851)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(56,710)	(26,064)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(948)	(309)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(56)	(76)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (1,004)	$ (385)

Investment Securities (Detail54

Investment Securities (Details 2) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investment Securities, Available-for-Sale, Amortized Cost
Due in one year or less	$ 14,398
Due after one year through five years	375,559
Due after five years through ten years	1,128,639
Due after ten years	2,202,929
Total	3,721,525	$ 3,213,655
Investment Securities, Available-for-Sale, Estimated Fair Value
Due in one year or less	15,091
Due after one year through five years	378,522
Due after five years through ten years	1,130,138
Due after ten years	2,250,680
Securities available‑for‑sale	$ 3,774,431	$ 3,223,830

Investment Securities (Detail55

Investment Securities (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Interest Income, Securities, Operating, Taxable	$ 52,981	$ 46,097	$ 35,103
Interest Income, Securities, Operating, Tax Exempt	43,355	41,885	25,219
Investment Income, Dividend	1,866	2,575	4,046
Investment Income, Interest and Dividend	$ 98,202	$ 90,557	$ 64,368

Investment Securities (Detail56

Investment Securities (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 20, 2017	Oct. 06, 2015
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities Pledged As Collateral Amortized Cost	$ 449,200
Proceeds from sales of securities available-for-sale	759,300	$ 393,509	$ 1,035,926
Available-for-sale Securities, Gross Realized Gains	3,300	11,100	4,500
Available-for-sale Securities, Gross Realized Losses	3,800	1,600	700
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Reclassification Adjustments, Net of Tax	24,709	(16,244)	3,621
Federal Home Loan Bank stock, at cost	$ 20,790	$ 21,870
Federal Home Loan Bank Minimum Stock Ownership As Percent Of Outstanding Advances	0.00%	2.70%
Purchases of FHLB Stock	$ 12,800
Redemptions of FHLB stock	(25,800)
Federal Home Loan Bank of San Francisco [Member]
Schedule of Available-for-sale Securities [Line Items]
Increase (Decrease) in Marketable Securities, Restricted	(1,100)
Available-for-sale Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales of securities available-for-sale	355,400	$ 384,000	208,400
CU Bancorp [Member]
Schedule of Available-for-sale Securities [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities				$ 446,980
FHLB stock				$ 11,902
Square 1 Financial, Inc. [Member]
Schedule of Available-for-sale Securities [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities					$ 2,193,538
FHLB stock					$ 2,787
CU Bancorp [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains	0
CU Bancorp [Member] | Available-for-sale Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales of securities available-for-sale	$ 404,500
Square 1 Financial, Inc. [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains			0
Square 1 Financial, Inc. [Member] | Available-for-sale Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales of securities available-for-sale			$ 823,800

Loans and Leases (Details)

Loans and Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 17,032,221	$ 15,520,537
Loans and Leases Receivable, Deferred Income	(59,478)	(64,583)
Loans held for investment, net	16,972,743	15,455,954
Loans and Leases Receivable, Allowance	(139,456)	(157,238)
Loans and leases, net	16,833,287	15,298,716
Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	16,974,171	15,412,092
Loans and Leases Receivable, Deferred Income	(59,464)	(64,562)
Loans held for investment, net	16,914,707	15,347,530
Loans and Leases Receivable, Allowance	(133,012)	(143,755)	$ (105,534)
Loans and leases, net	16,781,695	15,203,775
Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	58,050	108,445
Loans and Leases Receivable, Deferred Income	(14)	(21)
Loans held for investment, net	58,036	108,424
Loans and Leases Receivable, Allowance	(6,444)	(13,483)
Loans and leases, net	51,592	94,941
NonPCI and PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Deferred Income		(59,478)
Loans and leases, net		15,298,716
Mortgages [Member] | Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	7,815,355	5,635,675
Loans held for investment, net	7,798,991	5,617,956
Loans and Leases Receivable, Allowance	(34,981)	(37,765)	(36,654)
Mortgages [Member] | Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	53,658	92,793
Mortgages [Member] | NonPCI and PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	7,869,013	5,728,468
Real Estate Construction [Member] | Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	1,611,287	975,032
Loans held for investment, net	1,591,229	962,839
Loans and Leases Receivable, Allowance	(13,055)	(10,045)	(7,137)
Real Estate Construction [Member] | Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	2,409
Real Estate Construction [Member] | NonPCI and PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	1,611,287	977,441
Commercial Portfolio Segment [Member] | Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	7,137,978	8,426,236
Loans held for investment, net	7,114,920	8,391,560
Loans and Leases Receivable, Allowance	(82,726)	(93,853)	(61,082)
Commercial Portfolio Segment [Member] | Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	4,158	12,994
Commercial Portfolio Segment [Member] | NonPCI and PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	7,142,136	8,439,230
Consumer Portfolio Segment [Member] | Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	409,551	375,149
Loans held for investment, net	409,567	375,175
Loans and Leases Receivable, Allowance	(2,250)	(2,092)	$ (661)
Consumer Portfolio Segment [Member] | Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	234	249
Consumer Portfolio Segment [Member] | NonPCI and PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 409,785	$ 375,398

Loans and Leases (Details 1)

Loans and Leases (Details 1) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Delinquent loans in loan portfolio
30-89 Days Past Due	$ 3,200	$ 3,000
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	14,200	15,900
Loans held for investment, net	16,972,743	15,455,954
Non Purchased Credit Impaired Loans and Leases [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	48,435	31,569
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	14,165	15,945
Financing Receivable, Recorded Investment, Past Due	62,600	47,514
Current	16,852,107	15,300,016
Loans held for investment, net	16,914,707	15,347,530
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	36,069	14,284
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	11,129	5,302
Financing Receivable, Recorded Investment, Past Due	47,198	19,586
Current	7,751,793	5,598,370
Loans held for investment, net	7,798,991	5,617,956
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	29,070	8,590
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	9,107	3,303
Financing Receivable, Recorded Investment, Past Due	38,177	11,893
Current	5,323,310	4,341,740
Loans held for investment, net	5,361,487	4,353,633
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	6,999	5,694
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	2,022	1,999
Financing Receivable, Recorded Investment, Past Due	9,021	7,693
Current	2,428,483	1,256,630
Loans held for investment, net	2,437,504	1,264,323
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	2,081	364
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Financing Receivable, Recorded Investment, Past Due	2,081	364
Current	1,589,148	962,475
Loans held for investment, net	1,591,229	962,839
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	0	0
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Financing Receivable, Recorded Investment, Past Due	0	0
Current	769,075	578,838
Loans held for investment, net	769,075	578,838
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	2,081	364
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Financing Receivable, Recorded Investment, Past Due	2,081	364
Current	820,073	383,637
Loans held for investment, net	822,154	384,001
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	9,723	16,697
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	3,036	10,643
Financing Receivable, Recorded Investment, Past Due	12,759	27,340
Current	7,102,161	8,364,220
Loans held for investment, net	7,114,920	8,391,560
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	562	224
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Financing Receivable, Recorded Investment, Past Due	562	224
Current	409,005	374,951
Loans held for investment, net	409,567	375,175
Non Purchased Credit Impaired Loans and Leases [Member] | Asset Based [Member] | Commercial Portfolio Segment [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	1,512	1,500
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	2
Financing Receivable, Recorded Investment, Past Due	1,512	1,502
Current	3,010,188	2,607,543
Loans held for investment, net	3,011,700	2,609,045
Non Purchased Credit Impaired Loans and Leases [Member] | Venture Capital Loans [Member] | Commercial Portfolio Segment [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	6,533	13,589
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	760	5,769
Financing Receivable, Recorded Investment, Past Due	7,293	19,358
Current	2,115,418	1,963,798
Loans held for investment, net	2,122,711	1,983,156
Non Purchased Credit Impaired Loans and Leases [Member] | Cash Flow [Member] | Commercial Portfolio Segment [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	1,334	191
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	1,586	1,821
Financing Receivable, Recorded Investment, Past Due	2,920	2,012
Current	1,320,594	3,105,380
Loans held for investment, net	1,323,514	3,107,392
Non Purchased Credit Impaired Loans and Leases [Member] | Equipment Finance Commercial Financing Receivable [Member] | Commercial Portfolio Segment [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	344	1,417
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	690	3,051
Financing Receivable, Recorded Investment, Past Due	1,034	4,468
Current	655,961	687,499
Loans held for investment, net	$ 656,995	$ 691,967

Loans and Leases (Details 2)

Loans and Leases (Details 2) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 155,784	$ 170,599
Loans held for investment, net	16,972,743	15,455,954
Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	155,784	170,599
Loans held for investment, net	16,914,707	15,347,530
Non Purchased Credit Impaired Loans and Leases [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	16,758,923	15,176,931
Non Purchased Credit Impaired Loans and Leases [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	278,405	409,645
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	68,913	69,335
Loans held for investment, net	7,798,991	5,617,956
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	7,730,078	5,548,621
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	102,220	117,181
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	65,563	62,454
Loans held for investment, net	5,361,487	4,353,633
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	5,295,924	4,291,179
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	93,795	99,641
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	3,350	6,881
Loans held for investment, net	2,437,504	1,264,323
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	2,434,154	1,257,442
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	8,425	17,540
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	0	364
Loans held for investment, net	1,591,229	962,839
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	1,591,229	962,475
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	0	773
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	0	0
Loans held for investment, net	769,075	578,838
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	769,075	578,838
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	0	409
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	0	364
Loans held for investment, net	822,154	384,001
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	822,154	383,637
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	0	364
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	86,851	100,561
Loans held for investment, net	7,114,920	8,391,560
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	7,028,069	8,290,999
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	175,922	291,267
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Asset Based [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	3,174	2,118
Loans held for investment, net	3,011,700	2,609,045
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Asset Based [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	3,008,526	2,606,927
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Asset Based [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	35,305	28,112
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	30,938	32,848
Loans held for investment, net	656,995	691,967
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	626,057	659,119
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	30,938	32,848
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Venture Capital Loans [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	29,424	11,687
Loans held for investment, net	2,122,711	1,983,156
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Venture Capital Loans [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	2,093,287	1,971,469
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Venture Capital Loans [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	49,671	52,646
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	1,323,514	3,107,392
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	1,300,199	3,053,484
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	23,315	53,908
Loans held for investment, net	60,008	177,661
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	20	339
Loans held for investment, net	409,567	375,175
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	409,547	374,836
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	$ 263	$ 424

Loans and Leases (Details 3)

Loans and Leases (Details 3) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	$ 16,972,743	$ 15,455,954
Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	16,914,707	15,347,530
Non Purchased Credit Impaired Loans and Leases [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	278,405	409,645
Non Purchased Credit Impaired Loans and Leases [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	16,636,302	14,937,885
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	7,798,991	5,617,956
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	102,220	117,181
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	7,696,771	5,500,775
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	5,361,487	4,353,633
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	93,795	99,641
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	5,267,692	4,253,992
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	2,437,504	1,264,323
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	8,425	17,540
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	2,429,079	1,246,783
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	1,591,229	962,839
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	0	773
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	1,591,229	962,066
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	769,075	578,838
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	0	409
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	769,075	578,429
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	822,154	384,001
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	0	364
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	822,154	383,637
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	7,114,920	8,391,560
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	175,922	291,267
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	6,938,998	8,100,293
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Asset Based [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	3,011,700	2,609,045
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Asset Based [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	35,305	28,112
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Asset Based [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	2,976,395	2,580,933
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Venture Capital Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	2,122,711	1,983,156
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Venture Capital Loans [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	49,671	52,646
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Venture Capital Loans [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	2,073,040	1,930,510
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	1,323,514	3,107,392
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	60,008	177,661
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	1,263,506	2,929,731
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	656,995	691,967
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	30,938	32,848
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	626,057	659,119
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	409,567	375,175
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	263	424
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	$ 409,304	$ 374,751

Loans and Leases (Details 4)

Loans and Leases (Details 4) - USD ($) $ in Thousands	Dec. 31, 2017		Dec. 31, 2016
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 155,784		$ 170,599
Impaired Financing Receivable Performing Restructured Loans	56,838		64,952
Impaired Financing Receivable, Recorded Investment	212,622		235,551
Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment, Nonaccrual Status	155,784		170,599
Impaired Financing Receivable, Recorded Investment	212,622	[1]	235,551
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member]
Financing Receivable, Recorded Investment, Nonaccrual Status	68,913		69,335
Impaired Financing Receivable Performing Restructured Loans	47,560		54,750
Impaired Financing Receivable, Recorded Investment	116,473	[1]	124,085
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment, Nonaccrual Status	0		364
Impaired Financing Receivable Performing Restructured Loans	5,690		6,893
Impaired Financing Receivable, Recorded Investment	5,690	[1]	7,257
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Nonaccrual Status	86,851		100,561
Impaired Financing Receivable Performing Restructured Loans	3,488		3,157
Impaired Financing Receivable, Recorded Investment	90,339	[1]	103,718
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Nonaccrual Status	20		339
Impaired Financing Receivable Performing Restructured Loans	100		152
Impaired Financing Receivable, Recorded Investment	$ 120	[1]	$ 491
[1]	Excludes loans held for sale carried at lower of cost or fair value.

Loans and Leases (Details 5)

Loans and Leases (Details 5) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, Recorded Investment		$ 212,622		$ 235,551
Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, Related Allowance		13,621		24,933
Impaired Financing Receivable, Recorded Investment		212,622	[1]	235,551
Impaired Financing Receivable, Unpaid Principal Balance		287,236	[1]	279,952
Impaired Financing Receivable, Average Recorded Investment	[3]	185,740	[2]	154,727		$ 121,757
Impaired Financing Receivable, Interest Income, Accrual Method		4,101		3,216		2,126
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, Related Allowance		970		6,851
Impaired Financing Receivable, Recorded Investment		116,473	[1]	124,085
Impaired Financing Receivable, Unpaid Principal Balance		129,909	[1]	133,985
Impaired Financing Receivable, Average Recorded Investment	[3]	111,721	[2]	82,562		52,985
Impaired Financing Receivable, Interest Income, Accrual Method		3,643		2,803		1,549
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		15,750	[1]	63,325
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		16,548	[1]	65,031
Impaired Financing Receivable, Related Allowance		628		6,266
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		93,827	[1]	44,557
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		105,923	[1]	51,402
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	[3]	15,538	[2]	26,870		17,833
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		881		898		1,130
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	[3]	89,554	[2]	41,917		28,366
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		2,648		1,506		345
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		2,787	[1]	8,424
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		2,957	[1]	8,612
Impaired Financing Receivable, Related Allowance		342		585
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		4,109	[1]	7,779
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		4,481	[1]	8,940
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	[3]	2,787	[2]	6,521		2,143
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		55		255		33
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	[3]	3,842	[2]	7,254		4,643
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		59		144		41
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, Related Allowance		0		0
Impaired Financing Receivable, Recorded Investment		5,690	[1]	7,257
Impaired Financing Receivable, Unpaid Principal Balance		5,689	[1]	7,259
Impaired Financing Receivable, Average Recorded Investment	[3]	5,690	[2]	7,257		7,800
Impaired Financing Receivable, Interest Income, Accrual Method		306		238		255
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		5,690	[1]	6,680
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		5,689	[1]	6,680
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	[3]	5,690	[2]	6,680		7,053
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		306		224		240
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		0	[1]	213
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		0	[1]	213
Impaired Financing Receivable, Related Allowance		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		0	[1]	364
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		0	[1]	366
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	[3]	0	[2]	213		747
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		0		14		15
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	[3]	0	[2]	364		0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		0		0		0
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, Related Allowance		12,635		17,912
Impaired Financing Receivable, Recorded Investment		90,339	[1]	103,718
Impaired Financing Receivable, Unpaid Principal Balance		151,445	[1]	138,136
Impaired Financing Receivable, Average Recorded Investment	[3]	68,209	[2]	64,509		59,254
Impaired Financing Receivable, Interest Income, Accrual Method		144		166		307
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Asset Based [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		1,311	[1]	4,395
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		1,337	[1]	4,861
Impaired Financing Receivable, Related Allowance		51		2,144
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		3,519	[1]	664
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		5,559	[1]	1,652
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	[3]	1,236	[2]	3,842		0
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		53		134		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	[3]	1,640	[2]	528		124
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		49		18		0
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		0	[1]	1,524
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		0	[1]	4,636
Impaired Financing Receivable, Related Allowance		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		30,939	[1]	31,324
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		50,433	[1]	53,319
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	[3]	0	[2]	508		8,475
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	[3]	30,653	[2]	30,767		30,363
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		0		0		0
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Venture Capital Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		16,565	[1]	5,821
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		17,203	[1]	5,880
Impaired Financing Receivable, Related Allowance		4,267		3,294
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		14,534	[1]	5,866
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		40,029	[1]	8,939
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		10,228	[2],[3]	1,227	[3]	12,590
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		0		0		32
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	[3]	2,860	[2]	2,446		2,752
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		0		0		89
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		19,093	[1]	51,272
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		28,614	[1]	52,910
Impaired Financing Receivable, Related Allowance		8,317		12,474
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		4,378	[1]	2,852
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		8,270	[1]	5,939
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	[3]	19,093	[2]	22,736		3,204
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		7		10		56
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	[3]	2,499	[2]	2,455		1,746
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		35		4		130
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		100	[1]	270
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		100	[1]	280
Impaired Financing Receivable, Related Allowance		16		170
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		20	[1]	221
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		93	[1]	292
Impaired Financing Receivable, Recorded Investment		120	[1]	491
Impaired Financing Receivable, Unpaid Principal Balance		193	[1]	572
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	[3]	100	[2]	233		355
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		8		0		15
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	[3]	20	[2]	166		1,363
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		0		9		0
Impaired Financing Receivable, Average Recorded Investment	[3]	120	[2]	399		1,718
Impaired Financing Receivable, Interest Income, Accrual Method		$ 8		$ 9		$ 15
[1]	Excludes loans held for sale carried at lower of cost or fair value.
[2]	Excludes loans held for sale carried at lower of cost or fair value.
[3]	For the loans and leases (excluding PCI loans) reported as impaired at December 31, 2017, 2016 and 2015, amounts were calculated based on the period of time such loans and leases were impaired during the reported period.

Loans and Leases (Details 6)

Loans and Leases (Details 6)		12 Months Ended
		Dec. 31, 2017USD ($)contractContract		Dec. 31, 2016USD ($)contractContract		Dec. 31, 2015USD ($)contractContract
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts		50	[1]	54	[2]	97	[3]
Financing Receivable, Modifications, Pre-Modification Recorded Investment		$ 69,737,000	[1]	$ 100,161,000	[2]	$ 175,728,000	[3]
Financing Receivable, Modifications, Post-Modification Recorded Investment		$ 59,237,000	[1]	$ 89,443,000	[2]	$ 174,858,000	[3]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts		1	[1]	4	[2]	3	[3]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	[4]	$ 1,000	[1]	$ 6,502,000		$ 2,825,000	[3]
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down		$ 68,000		$ 0		$ 96,900
Mortgages [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts		5		12		21
Financing Receivable, Modifications, Pre-Modification Recorded Investment		$ 2,527,000		$ 13,833,000		$ 43,536,000
Financing Receivable, Modifications, Post-Modification Recorded Investment		$ 2,463,000		$ 6,099,000		$ 43,012,000
Financing Receivable, Modifications, Subsequent Default, Number of Contracts		0		0		2
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	[4]	$ 0		$ 0		$ 2,670,000
Mortgages [Member] | Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts		8		10		18
Financing Receivable, Modifications, Pre-Modification Recorded Investment		$ 1,328,000		$ 7,091,000		$ 3,128,000
Financing Receivable, Modifications, Post-Modification Recorded Investment		$ 489,000		$ 6,439,000		$ 2,961,000
Financing Receivable, Modifications, Subsequent Default, Number of Contracts		0		2		1
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	[4]	$ 0		$ 5,000,000		$ 155,000
Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts		1				8
Financing Receivable, Modifications, Pre-Modification Recorded Investment		$ 362,000				$ 23,881,000
Financing Receivable, Modifications, Post-Modification Recorded Investment		$ 0				$ 23,881,000
Financing Receivable, Modifications, Subsequent Default, Number of Contracts		0		0		0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	[4]	$ 0		$ 0		$ 0
Commercial Portfolio Segment [Member] | Cash Flow [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract		14		14		25
Financing Receivable, Modifications, Pre-Modification Recorded Investment		$ 27,703,000		$ 30,788,000		$ 2,718,000
Financing Receivable, Modifications, Post-Modification Recorded Investment		$ 18,468,000		$ 30,788,000		$ 2,539,000
Commercial Portfolio Segment [Member] | Asset Based [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract		10		5		13
Financing Receivable, Modifications, Pre-Modification Recorded Investment		$ 7,987,000		$ 2,158,000		$ 8,400,000
Financing Receivable, Modifications, Post-Modification Recorded Investment		$ 7,987,000		$ 2,158,000		$ 8,400,000
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | Contract		0		2		0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	[4]	$ 0		$ 1,502,000		$ 0
Commercial Portfolio Segment [Member] | Venture Capital Loans [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract		11
Financing Receivable, Modifications, Pre-Modification Recorded Investment		$ 29,733,000
Financing Receivable, Modifications, Post-Modification Recorded Investment		$ 29,733,000
Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts				7		10
Financing Receivable, Modifications, Pre-Modification Recorded Investment				$ 44,196,000		$ 93,868,000
Financing Receivable, Modifications, Post-Modification Recorded Investment				$ 42,572,000		$ 93,868,000
Financing Receivable, Modifications, Subsequent Default, Number of Contracts				0		0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	[4]			$ 0		$ 0
Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts		1		5		2
Financing Receivable, Modifications, Pre-Modification Recorded Investment		$ 97,000		$ 850,000		$ 197,000
Financing Receivable, Modifications, Post-Modification Recorded Investment		$ 97,000		$ 142,000		$ 197,000
Equipment Finance Commercial Financing Receivable [Member] | Cash Flow [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | Contract		1
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	[4]	$ 1,000
Equipment Finance Commercial Financing Receivable [Member] | Venture Capital Loans [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | Contract		0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	[4]	$ 0
Commercial Portfolio Segment [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | Contract				0		0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	[4]			$ 0		$ 0
Commercial Real Estate Construction Loan Receivable [Member] | Real Estate Construction [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts				1
Financing Receivable, Modifications, Pre-Modification Recorded Investment				$ 1,245,000
Financing Receivable, Modifications, Post-Modification Recorded Investment				$ 1,245,000
Consumer Portfolio Segment [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | Contract		0		0		0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	[4]	$ 0		$ 0		$ 0
[1]	Represents the balance at December 31, 2017, and is net of charge-offs of $68,000
[2]	Represents the balance at December 31, 2016, and there were
[3]	Represents the balance at December 31, 2015, and is net of charge-offs of $96,900.
[4]	The population of defaulted restructured loans for the period indicated includes only those loans restructured during the preceding 12-month period. For example, for the year ended December 31, 2017, the population of defaulted restructured loans includes only those loans restructured after December 31, 2016. The table excludes defaulted troubled restructurings in those classes for which the recorded investment was zero at the end of the period.

Loans and Leases (Details 7)

Loans and Leases (Details 7) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	$ 157,238
Loans and Leases Receivable, Allowance, ending balance	139,456	$ 157,238
Loans held for investment, net	16,972,743	15,455,954
Non Purchased Credit Impaired Loans and Leases [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	143,755	105,534
Allowance for Loan and Lease Losses, Write-offs	(74,142)	(35,092)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	11,185	13,102
Provision for Loan and Lease Losses	52,214	60,211
Loans and Leases Receivable, Allowance, ending balance	133,012	143,755
Financing Receivable, Individually Evaluated for Impairment	13,621	24,933
Financing Receivable, Collectively Evaluated for Impairment	119,391	118,822
Financing Receivable, Individually Evaluated for Impairment	210,735	234,430
Financing Receivable, Collectively Evaluated for Impairment	16,703,972	15,113,100
Loans held for investment, net	16,914,707	15,347,530
Purchased Credit Impaired Loans and Leases [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	13,483
Loans and Leases Receivable, Allowance, Covered, beginning balance	13,483	9,577
Allowance for Loan and Lease Losses, Write-offs	(6,154)	(862)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	363	39
Provision for Loan and Lease Losses	(1,248)	4,729
Loans and Leases Receivable, Allowance, ending balance	6,444	13,483
Loans and Leases Receivable, Allowance, Covered, ending balance	6,444	13,483
Receivables Acquired With Deteriorated Credit Quality, Allowance For Credit Losses	6,444	13,483
Receivables Acquired with Deteriorated Credit Quality	58,036	108,424
Loans held for investment, net	58,036	108,424
NonPCI and PCI Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable Allowance Covered And Noncovered, beginning balance	157,238	115,111
Allowance for Loan and Lease Losses, Write-offs	(80,296)	(35,954)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	11,548	13,141
Provision for Loan and Lease Losses	50,966	64,940
Loans and Leases Receivable Allowance Covered And Noncovered, ending balance	139,456	157,238
Loans and Leases Receivable Net Of Deferred Income Covered And Noncovered	16,972,743	15,455,954
Mortgages [Member] | Non Purchased Credit Impaired Loans and Leases [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	37,765	36,654
Allowance for Loan and Lease Losses, Write-offs	(2,410)	(2,059)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	1,209	4,519
Provision for Loan and Lease Losses	(1,583)	(1,349)
Loans and Leases Receivable, Allowance, ending balance	34,981	37,765
Financing Receivable, Individually Evaluated for Impairment	970	6,851
Financing Receivable, Collectively Evaluated for Impairment	34,011	30,914
Financing Receivable, Individually Evaluated for Impairment	115,319	123,348
Financing Receivable, Collectively Evaluated for Impairment	7,683,672	5,494,608
Loans held for investment, net	7,798,991	5,617,956
Real Estate Construction [Member] | Non Purchased Credit Impaired Loans and Leases [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	10,045	7,137
Allowance for Loan and Lease Losses, Write-offs	0	0
Allowance for Loan and Lease Loss, Recovery of Bad Debts	429	673
Provision for Loan and Lease Losses	2,581	2,235
Loans and Leases Receivable, Allowance, ending balance	13,055	10,045
Financing Receivable, Individually Evaluated for Impairment	0	0
Financing Receivable, Collectively Evaluated for Impairment	13,055	10,045
Financing Receivable, Individually Evaluated for Impairment	5,690	7,257
Financing Receivable, Collectively Evaluated for Impairment	1,585,539	955,582
Loans held for investment, net	1,591,229	962,839
Commercial Portfolio Segment [Member] | Non Purchased Credit Impaired Loans and Leases [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	93,853	61,082
Allowance for Loan and Lease Losses, Write-offs	(70,709)	(32,210)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	9,415	7,794
Provision for Loan and Lease Losses	50,167	57,187
Loans and Leases Receivable, Allowance, ending balance	82,726	93,853
Financing Receivable, Individually Evaluated for Impairment	12,635	17,912
Financing Receivable, Collectively Evaluated for Impairment	70,091	75,941
Financing Receivable, Individually Evaluated for Impairment	89,626	103,431
Financing Receivable, Collectively Evaluated for Impairment	7,025,294	8,288,129
Loans held for investment, net	7,114,920	8,391,560
Consumer Portfolio Segment [Member] | Non Purchased Credit Impaired Loans and Leases [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	2,092	661
Allowance for Loan and Lease Losses, Write-offs	(1,023)	(823)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	132	116
Provision for Loan and Lease Losses	1,049	2,138
Loans and Leases Receivable, Allowance, ending balance	2,250	2,092
Financing Receivable, Individually Evaluated for Impairment	16	170
Financing Receivable, Collectively Evaluated for Impairment	2,234	1,922
Financing Receivable, Individually Evaluated for Impairment	100	394
Financing Receivable, Collectively Evaluated for Impairment	409,467	374,781
Loans held for investment, net	$ 409,567	$ 375,175

Loans and Leases Loans and Leas

Loans and Leases Loans and Leases (Details 8) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	$ 139,456				$ 157,238				$ 139,456	$ 157,238
Reserve for Unfunded Loan Commitments	28,635				17,523				28,635	17,523	$ 16,734
Financing Receivable, Allowance for Credit Losses	168,091				174,761				168,091	174,761	131,845
Reserve for Unfunded Loan Commitments, Charge-offs									0	0
Financing Receivable, Allowance for Credit Losses, Write-downs									80,296	35,954
Financing Receivable, Allowance for Credit Losses, Recovery									11,548	13,141
Reserve for Unfunded Loan Commitments, Recoveries									0	0
Reserve for Unfunded Loan Commitments, Net Charge-offs									0	0
Financing Receivable, Allowance For Credit Losses, Net Charge-offs									(68,748)	(22,813)
Provision for credit losses	6,406	$ 15,119	$ 11,499	$ 24,728	23,215	$ 8,471	$ 13,903	$ (20,140)	57,752	65,729	45,481
Reserve for Unfunded Loan Commitments, Fair Value									4,326
Reserve for Unfunded Commitments, Provision									6,786	789
Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	6,444				13,483				6,444	13,483
Allowance for Loan and Lease Losses, Write-offs									6,154	862
Allowance for Loan and Lease Losses Write-offs, Net									(5,791)	(823)
Allowance for Loan and Lease Loss, Recovery of Bad Debts									363	39
Provision for Loan and Lease Losses									(1,248)	4,729
Loans and Leases Receivable, Allowance, Covered	6,444				13,483				6,444	13,483	9,577
Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	133,012				143,755				133,012	143,755	105,534
Financing Receivable, Allowance for Credit Losses	$ 161,647				$ 161,278				161,647	161,278	$ 122,268
Allowance for Loan and Lease Losses, Write-offs									74,142	35,092
Financing Receivable, Allowance for Credit Losses, Write-downs									74,142	35,092
Financing Receivable, Allowance for Credit Losses, Recovery									11,185	13,102
Allowance for Loan and Lease Losses Write-offs, Net									(62,957)	(21,990)
Allowance for Loan and Lease Loss, Recovery of Bad Debts									11,185	13,102
Financing Receivable, Allowance For Credit Losses, Net Charge-offs									(62,957)	(21,990)
Provision for Loan and Lease Losses									52,214	60,211
Provision for credit losses									$ 59,000	61,000
Reserve for Unfunded Commitments, Provision										$ 4,326

Loans and Leases (Details 9)

Loans and Leases (Details 9) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Purchased Credit Impaired Loans Composition [Line Items]
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down	$ 68,000	$ 0	$ 96,900
Loans held for investment, net	16,972,743,000	15,455,954,000
Loans and Leases Receivable, Allowance	(139,456,000)	(157,238,000)
Purchased Credit Impaired Loans and Leases [Member]
Purchased Credit Impaired Loans Composition [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount, Covered	80,229,000	134,273,000
Loan Discounts	(22,193,000)	(25,849,000)
Loans held for investment, net	58,036,000	108,424,000
Loans and Leases Receivable, Allowance	(6,444,000)	(13,483,000)
Loans and Leases Receivable, Net Reported Amount, Covered	51,592,000	94,941,000
Mortgages [Member] | Purchased Credit Impaired Loans and Leases [Member]
Purchased Credit Impaired Loans Composition [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount, Covered	72,399,000	112,982,000
Real Estate Construction [Member] | Purchased Credit Impaired Loans and Leases [Member]
Purchased Credit Impaired Loans Composition [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount, Covered	0	1,901,000
Commercial Portfolio Segment [Member] | Purchased Credit Impaired Loans and Leases [Member]
Purchased Credit Impaired Loans Composition [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount, Covered	7,568,000	19,109,000
Consumer Portfolio Segment [Member] | Purchased Credit Impaired Loans and Leases [Member]
Purchased Credit Impaired Loans Composition [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount, Covered	$ 262,000	$ 281,000

Loans and Leases (Details 10)

Loans and Leases (Details 10) - Purchased Credit Impaired Loans and Leases [Member] - Covered [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net, beginning balance	$ 94,941	$ 179,468	$ 276,792
Accretable yield, beginning balance	(55,944)	(85,636)	(106,856)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net, ending balance	51,592	94,941	179,468
Accretable yield, ending balance	(45,580)	(55,944)	(85,636)
Carrying Amount [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Additions			16,455
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Accretion	14,739	51,907	31,857
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Disposals of Loans	(59,336)	(131,705)	(148,436)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Period Increase (Decrease)	0	0	0
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Provision for Loan Losses	1,248	(4,729)	2,800
Accretable Yield [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Additions			(2,852)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Accretion	14,739	51,907	31,857
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Disposals of Loans	0	0	0
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Period Increase (Decrease)	(4,375)	(22,215)	(7,785)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Provision for Loan Losses	$ 0	$ 0	$ 0

Loans and Leases (Details 11)

Loans and Leases (Details 11) - Purchased Credit Impaired Loans and Leases [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	$ 58,036	$ 108,424
Classified [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	15,455	31,660
Nonclassified [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	42,581	76,764
Mortgages [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	53,644	92,775
Mortgages [Member] | Classified [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	11,063	19,445
Mortgages [Member] | Nonclassified [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	42,581	73,330
Real Estate Construction [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	0	2,408
Real Estate Construction [Member] | Classified [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	0	1,023
Real Estate Construction [Member] | Nonclassified [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	0	1,385
Commercial Portfolio Segment [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	4,158	12,992
Commercial Portfolio Segment [Member] | Classified [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	4,158	10,943
Commercial Portfolio Segment [Member] | Nonclassified [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	0	2,049
Consumer Portfolio Segment [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	234	249
Consumer Portfolio Segment [Member] | Classified [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	234	249
Consumer Portfolio Segment [Member] | Nonclassified [Member]
Financing Receivable Recorded Investment By Credit Risk [Line Items]
Loans And Leases Net Of Discounts Covered	$ 0	$ 0

Loans and Leases (Details Textu

Loans and Leases (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Loans Receivable Held-for-sale, Amount	$ 1,500,000
Loans held for sale, at lower of cost or fair value	481,100	$ 0
Loan Receivable Held-For-Sale, Charge-offs	957	0	$ 0
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	10,800	8,000
Financing Receivable, Recorded Investment, Nonaccrual Status	155,784	170,599
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	14,200	15,900
Financing Receivable Recorded Investment Thirty to Eighty Nine Days Past Due	3,200	3,000
Financing Receivable Recorded Investment Nonaccrual Status Current	138,400	151,700
Unfunded Commitments For Troubled Debt Restructurings	4,500	4,600
Cash Flow [Member]
Business Acquisition [Line Items]
Proceeds from Sale of Loans Held-for-sale	1,000,000
Cash Flow [Member]
Business Acquisition [Line Items]
Loan Receivable Held-For-Sale, Charge-offs	0
Non Purchased Credit Impaired Loans and Leases [Member]
Business Acquisition [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	155,784	170,599
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	14,165	15,945
Financing Receivable Recorded Investment Thirty to Eighty Nine Days Past Due	$ 48,435	$ 31,569
Non Purchased Credit Impaired Loans and Leases [Member] | Credit Concentration Risk [Member]
Business Acquisition [Line Items]
Concentration Risk, Percentage	77.00%
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 120,000

Foreclosed Assets Foreclosed 70

Foreclosed Assets Foreclosed Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Real Estate Owned Net	$ 1,302	$ 11,876
Other Real Estate Owned Net including Foreclosed Assets	1,329	12,976	$ 22,120	$ 43,721
Other Repossessed Assets	27	1,100
Foreclosed assets, net	1,329	12,976
Construction and Land Development [Member]
Other Real Estate Owned Net	219	11,224
Multi Family [Member]
Other Real Estate Owned Net	0	652
Residential Mortgage [Member]
Other Real Estate Owned Net	1,019	0
Commercial Real Estate [Member]
Other Real Estate Owned Net	$ 64	$ 0

Foreclosed Assets Foreclosed 71

Foreclosed Assets Foreclosed Assets (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Foreclosed assets, net	$ 1,329	$ 12,976	$ 22,120	$ 43,721
Loans transferred to foreclosed assets		781	13,472
Other Real Estate and Foreclosed Assets, Other Additions	1,385	0	0
Provision for Other Real Estate Owned and Foreclosed Assets	(2,138)	(2,576)	(5,228)
Sales of Other Real Estate Owned Foreclosed Assets CORES	$ (11,474)	$ (7,349)	$ (29,845)

Foreclosed Assets Foreclosed 72

Foreclosed Assets Foreclosed Assets (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Foreclosed Assets Valuation Allowance	$ 14	$ 12,696	$ 10,246	$ 12,123
Provision for losses on foreclosed assets	2,138	2,576	5,228
Foreclosed Assets, Valuation Allowance, Reductions Related to Sales	$ (14,820)	$ (126)	$ (7,105)

Premises and Equipment, Net (De

Premises and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Premises and Equipment, Net [Abstract]
Land	$ 1,243	$ 5,505
Buildings and Improvements	8,154	14,929
Furniture and Fixtures	43,250	38,806
Leasehold Improvements	42,521	38,967
Property, Plant and Equipment, Gross	95,168	98,207
Accumulated Depreciation and Amortization	(63,316)	(59,613)
Property, Plant and Equipment, Net	$ 31,852	$ 38,594

Premises and Equipment, Net (74

Premises and Equipment, Net (Details 1) $ in Thousands	Dec. 31, 2017USD ($)
Premises and Equipment, Net [Abstract]
2,018	$ 30,574
2,019	28,098
2,020	25,544
2,021	21,346
2,022	15,494
Thereafter	34,107
Total	$ 155,163

Premises and Equipment, Net (75

Premises and Equipment, Net (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Premises and Equipment, Net [Abstract]
Depreciation and Amortization	$ 7,600,000	$ 8,200,000	$ 8,100,000
Operating Leases, Rent Expense, Gross	31,700,000	30,000,000	26,200,000
Operating Leases, Income Statement, Lease Revenue	481,000	$ 500,000	$ 487,000
Future Minimum Sublease Rental Income	$ 21,100,000

Deposits Deposits (Details)

Deposits Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deposits [Abstract]
Interest checking deposits	$ 2,711,250	$ 1,462,305
Money market deposits	4,890,567	4,865,961
Savings deposits	690,353	711,039
Time deposits $250,000 and under	1,709,980	1,758,434
Time deposits over $250,000	355,342	413,856
Total interest-bearing deposits	$ 10,357,492	$ 9,211,595

Deposits Deposits (Details 1)

Deposits Deposits (Details 1) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Time Deposits Balance [Line Items]
Time Deposit Maturities, Next Twelve Months	$ 1,931,134
Time Deposit Maturities, Year Two	87,275
Time Deposit Maturities, Year Three	20,264
Time Deposit Maturities, Year Four	17,296
Time Deposit Maturities, Year Five	9,220
Time Deposit Maturities, after Year Five	133
Time Deposits	2,065,322	$ 2,172,290
Deposits Exceeding FDIC Insurance Limit of $250,000 [Member]
Time Deposits Balance [Line Items]
Time Deposit Maturities, Next Twelve Months	337,257
Time Deposit Maturities, Year Two	9,870
Time Deposit Maturities, Year Three	3,713
Time Deposit Maturities, Year Four	1,607
Time Deposit Maturities, Year Five	2,895
Time Deposit Maturities, after Year Five	0
Time Deposits	355,342
Deposits FDC Insured $250,000 and Under [Member]
Time Deposits Balance [Line Items]
Time Deposit Maturities, Next Twelve Months	1,593,877
Time Deposit Maturities, Year Two	77,405
Time Deposit Maturities, Year Three	16,551
Time Deposit Maturities, Year Four	15,689
Time Deposit Maturities, Year Five	6,325
Time Deposit Maturities, after Year Five	133
Time Deposits	$ 1,709,980

Deposits (Details Textual)

Deposits (Details Textual) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Domestic Deposits, Brokered [Line Items]
Interest-bearing Domestic Deposit, Brokered	$ 863,202	$ 1,174,487
Time deposits over $250,000	355,342	413,856
Time deposits $250,000 and under	1,709,980	1,758,434
Time Deposits Balance [Domain]
Domestic Deposits, Brokered [Line Items]
Interest-bearing Domestic Deposit, Brokered	732,200	405,500
Non-maturity Deposits [Member]
Domestic Deposits, Brokered [Line Items]
Interest-bearing Domestic Deposit, Brokered	$ 800,000	$ 1,200,000

Borrowings and Subordinated D79

Borrowings and Subordinated Debentures (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Borrowings	$ 467,342,000	$ 905,812,000
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Non-Recourse Debt	$ 342,000	$ 812,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	6.87%	6.41%
Unused lines of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 0
American Financial Exchange [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 0	$ 40,000,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	0.00%	0.81%
Federal Home Loan Bank of San Francisco [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	1.41%	0.59%
Line of Credit, Current	$ 332,000,000	$ 735,000,000
Federal Home Loan Bank of San Francisco [Member] | Unused lines of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding		$ 130,000,000
Federal Home Loan Bank of San Francisco [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	1.34%	0.55%
Line of Credit, Current	$ 135,000,000	$ 130,000,000

Borrowings and Subordinated D80

Borrowings and Subordinated Debentures Borrowings and Subordinated Debentures (Details 1) $ in Thousands, € in Millions	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2017EUR (€)	Dec. 31, 2016USD ($)
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 555,146		$ 538,973
Debt Instrument, Unamortized Discount	(92,709)		(98,229)
Subordinated debentures	$ 462,437		440,744
Debt Instrument Date Issued	Jun. 30, 2006
Debt Instrument, Maturity Date	Sep. 18, 2036
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.85
Subordinated Debt Trust V Due September 2033 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 10,310		$ 10,310
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	4.70%	4.70%	4.09%
Debt Instrument Date Issued	Aug. 15, 2003
Debt Instrument, Maturity Date	Sep. 17, 2033
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 3.10
Subordinated Debt Trust VI Due September 2033 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 10,310		$ 10,310
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	4.64%	4.64%	4.01%
Debt Instrument Date Issued	Sep. 3, 2003
Debt Instrument, Maturity Date	Sep. 15, 2033
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 3.05
Subordinated Debt Trust CII Due September 2033 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 5,155		$ 5,155
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	4.55%	4.55%	3.95%
Debt Instrument Date Issued	Sep. 17, 2003
Debt Instrument, Maturity Date	Sep. 17, 2033
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 2.95
Subordinated Debt Trust VII Due April 2034 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 61,856		$ 61,856
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	4.13%	4.13%	3.64%
Debt Instrument Date Issued	Feb. 5, 2004
Debt Instrument, Maturity Date	Apr. 23, 2034
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 2.75
Subordinated Debt Trust CIII Due September 2035 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 20,619		$ 20,619
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.28%	3.28%	2.65%
Debt Instrument Date Issued	Aug. 15, 2005
Debt Instrument, Maturity Date	Sep. 15, 2035
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.69
Subordinated Debt Trust FCCI Due March 2037 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 16,495		$ 16,495
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.19%	3.19%	2.56%
Debt Instrument Date Issued	Jan. 25, 2007
Debt Instrument, Maturity Date	Mar. 15, 2037
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.60
Subordinated Debt Trust FCBI Due December 2035 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 10,310		$ 10,310
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.14%	3.14%	2.51%
Debt Instrument Date Issued	Sep. 30, 2005
Debt Instrument, Maturity Date	Dec. 15, 2035
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.55
Trust Preferred Securities Two Thousand Five Series One [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 82,475		$ 82,475
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.54%	3.54%	2.91%
Debt Instrument Date Issued	Nov. 21, 2005
Debt Instrument, Maturity Date	Dec. 15, 2035
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Trust Preferred Securities Two Thousand Five Series Two [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 128,866		$ 128,866
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.33%	3.33%	2.84%
Debt Instrument Date Issued	Dec. 14, 2005
Debt Instrument, Maturity Date	Jan. 30, 2036
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Two Thousand Six One Term Debt Securitization [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 51,545		$ 51,545
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.33%	3.33%	2.84%
Debt Instrument Date Issued	Feb. 22, 2006
Debt Instrument, Maturity Date	Apr. 30, 2036
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Two Thousand Six Two Term Debt Securitization [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 51,550		$ 51,550
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.33%	3.33%	2.84%
Debt Instrument Date Issued	Sep. 27, 2006
Debt Instrument, Maturity Date	Oct. 30, 2036
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Trust Preferred Securities Two Thousand Six Series Three [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 30,986		$ 27,185
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	1.72%	1.72%	1.74%
Debt Instrument Date Issued	Sep. 29, 2006
Debt Instrument, Maturity Date	Oct. 30, 2036
Debt Instrument, Basis Spread on Variable Rate	3 month EURIBOR + 2.05
Liability, Reporting Currency Denominated, Value | €		€ 25.8
Trust Preferred Securities Two Thousand Six Series Four [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 16,470		$ 16,470
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.33%	3.33%	2.84%
Debt Instrument Date Issued	Dec. 5, 2006
Debt Instrument, Maturity Date	Jan. 30, 2037
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Trust Preferred Securities Two Thousand Six Series Five [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 6,650		$ 6,650
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.33%	3.33%	2.84%
Debt Instrument Date Issued	Dec. 19, 2006
Debt Instrument, Maturity Date	Jan. 30, 2037
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Two Thousand Seven One Term Debt Securitization [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 39,177		$ 39,177
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.33%	3.33%	2.84%
Debt Instrument Date Issued	Jun. 13, 2007
Debt Instrument, Maturity Date	Jul. 30, 2037
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Subordinated Debentures Trust I Due March 2035 [Domain]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 6,186		$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate			0.00%
Debt Instrument Date Issued	Dec. 10, 2004
Debt Instrument, Maturity Date	Mar. 15, 2035
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 2.05
Subordinated Debentures Trust II Due March 2036 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 3,093		$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate			0.00%
Debt Instrument Date Issued	Dec. 23, 2005
Debt Instrument, Maturity Date	Mar. 15, 2036
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.75
Subordinated Debentures Trust III Due September 2036 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 3,093		$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate			0.00%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust V Due September 2033 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	3.10%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust VI Due September 2033 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	3.05%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust CII Due September 2033 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.95%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust VII Due April 2034 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.75%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust CIII Due September 2035 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.69%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust FCCI Due March 2037 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.60%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust FCBI Due December 2035 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.55%
London Interbank Offered Rate (LIBOR) [Member] | Trust Preferred Securities Two Thousand Five Series One [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Trust Preferred Securities Two Thousand Five Series Two [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Two Thousand Six One Term Debt Securitization [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Two Thousand Six Two Term Debt Securitization [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Trust Preferred Securities Two Thousand Six Series Four [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Trust Preferred Securities Two Thousand Six Series Five [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Two Thousand Seven One Term Debt Securitization [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debentures Trust I Due March 2035 [Domain]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.05%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.64%	3.64%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debentures Trust II Due March 2036 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.75%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.34%	3.34%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debentures Trust III Due September 2036 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.85%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.44%	3.44%
Euribor Rate [Member] | Trust Preferred Securities Two Thousand Six Series Three [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.05%

Borrowings and Subordinated D81

Borrowings and Subordinated Debentures (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Debt Instruments Weighted Average Remaining Maturity Period	1 year 6 months 20 days
Unused lines of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 0
Line of Credit Facility, Current Borrowing Capacity	75,000,000
Debt Instrument, Unused Borrowing Capacity, Fee	0
American Financial Exchange [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	0	$ 40,000,000
Federal Home Loan Bank of San Francisco [Member]
Debt Instrument [Line Items]
Loans Pledged as Collateral	5,500,000,000
Federal Home Loan Bank of San Francisco [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	3,789,949,000
Line of Credit, Current	332,000,000	735,000,000
Federal Home Loan Bank of San Francisco [Member] | Unused lines of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	135,000,000
Line of Credit Facility, Amount Outstanding		130,000,000
Federal Reserve Bank Advances [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	0	0
Loans Pledged as Collateral	2,300,000,000
Federal Reserve Bank Advances [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	1,766,188,000
Maturity Overnight [Member] | American Financial Exchange [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding		26,000,000
Maturity Overnight [Member] | Federal Home Loan Bank of San Francisco [Member]
Debt Instrument [Line Items]
Line of Credit, Current	$ 332,000,000	435,000,000
Maturity Less than 30 Days [Member] | American Financial Exchange [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding		14,000,000
Maturity Less than 30 Days [Member] | Federal Home Loan Bank of San Francisco [Member]
Debt Instrument [Line Items]
Line of Credit, Current		$ 300,000,000

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Loan commitments to extend credit	$ 6,234,061	$ 4,166,703
Standby letters of credit	320,063	211,398
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability	$ 6,554,124	$ 4,378,101

Commitments and Contingencies83

Commitments and Contingencies (Details Textual) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Long-term Purchase Commitment [Line Items]
Commitment To Contribute Capital	$ 62.6	$ 26.6
Private Equity Funds [Member]
Long-term Purchase Commitment [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	$ 2.5	$ 2.8

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Securities available‑for‑sale	$ 3,774,431	$ 3,223,830
Warrants Not Settleable in Cash, Fair Value Disclosure		5,497
Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	3,774,431	3,223,830
Derivative Asset, Fair Value of Collateral	1,873	694
Warrants Not Settleable in Cash, Fair Value Disclosure	5,161	5,497
Assets, Fair Value Disclosure, Recurring	3,779,592	3,230,021
Derivative Liability, Fair Value of Collateral	1,379	3,285
Level 1
Securities available‑for‑sale		2,080
Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	5,922	2,080
Derivative Asset, Fair Value of Collateral	0	0
Warrants Not Settleable in Cash, Fair Value Disclosure	0	0
Assets, Fair Value Disclosure, Recurring	5,922	2,080
Derivative Liability, Fair Value of Collateral	0	0
Level 2
Securities available‑for‑sale		3,156,475
Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	3,703,526	3,156,475
Derivative Asset, Fair Value of Collateral	1,873	694
Warrants Not Settleable in Cash, Fair Value Disclosure	0	0
Assets, Fair Value Disclosure, Recurring	3,703,526	3,157,169
Derivative Liability, Fair Value of Collateral	1,379	3,285
Level 3
Securities available‑for‑sale		65,275
Warrants Not Settleable in Cash, Fair Value Disclosure		5,497	$ 4,914
Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	64,983	65,275
Derivative Asset, Fair Value of Collateral	0	0
Warrants Not Settleable in Cash, Fair Value Disclosure	5,161	5,497
Assets, Fair Value Disclosure, Recurring	70,144	70,772
Derivative Liability, Fair Value of Collateral	0	0
Government agency and government-sponsored enterprise pass through securities [Member]
Securities available‑for‑sale	246,274	502,443
Government agency and government-sponsored enterprise pass through securities [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Government agency and government-sponsored enterprise pass through securities [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	246,274	502,443
Government agency and government-sponsored enterprise pass through securities [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Securities available‑for‑sale	275,709	146,289
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	275,709	146,289
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Private Label Collateralized Mortgage Obligations [Member]
Securities available‑for‑sale	125,987	125,469
Collateralized Mortgage Obligations [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Collateralized Mortgage Obligations [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	103,113	68,567
Collateralized Mortgage Obligations [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	22,874	56,902
Municipal Securities [Member]
Securities available‑for‑sale	1,680,068	1,456,459
Municipal Securities [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Municipal Securities [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	1,680,068	1,456,459
Municipal Securities [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Commercial Mortgage Backed Securities [Member]
Securities available‑for‑sale	1,163,969	547,692
Commercial Mortgage Backed Securities [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Commercial Mortgage Backed Securities [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	1,163,969	547,692
Commercial Mortgage Backed Securities [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Corporate Debt Securities [Member]
Securities available‑for‑sale	19,295	47,509
Corporate Debt Securities [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Corporate Debt Securities [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	19,295	47,509
Corporate Debt Securities [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Collateralized Loan Obligations [Member]
Securities available‑for‑sale	7,015	156,887
Collateralized Loan Obligations [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Collateralized Loan Obligations [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	7,015	156,887
Collateralized Loan Obligations [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
SBA asset-backed securities [Member]
Securities available‑for‑sale	160,334	178,845
SBA asset-backed securities [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
SBA asset-backed securities [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	160,334	178,845
SBA asset-backed securities [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Other securities [Member]
Securities available‑for‑sale	95,780	62,237
Other securities [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	5,922	2,080
Other securities [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	47,749	51,784
Other securities [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	$ 42,109
Other securities [Member] | Level 3 | Fair Value, Measurements, Recurring [Member] | Square 1 Financial, Inc. [Member]
Securities available‑for‑sale		$ 8,373

Fair Value Measurements (Deta85

Fair Value Measurements (Details 1) - Level 3 - Fair Value, Measurements, Recurring [Member]	12 Months Ended
	Dec. 31, 2017
Minimum [Member] | Private Label CMOs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Inputs, Prepayment Rate	3.60%
Fair Value Inputs, Probability of Default	0.10%
Fair Value Inputs, Loss Severity	4.00%
Fair Value Inputs, Discount Rate	1.80%
Minimum [Member] | Asset-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Inputs, Prepayment Rate	5.00%
Fair Value Inputs, Probability of Default	1.00%
Fair Value Inputs, Loss Severity	10.00%
Fair Value Inputs, Discount Rate	3.20%
Maximum [Member] | Private Label CMOs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Inputs, Prepayment Rate	43.60%
Fair Value Inputs, Probability of Default	15.30%
Fair Value Inputs, Loss Severity	102.00%
Fair Value Inputs, Discount Rate	10.30%
Maximum [Member] | Asset-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Inputs, Prepayment Rate	15.00%
Fair Value Inputs, Probability of Default	2.00%
Fair Value Inputs, Loss Severity	60.00%
Fair Value Inputs, Discount Rate	4.30%
Weighted Average [Member] | Private Label CMOs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Inputs, Prepayment Rate	8.60%
Fair Value Inputs, Probability of Default	2.50%
Fair Value Inputs, Loss Severity	55.80%
Fair Value Inputs, Discount Rate	5.30%
Weighted Average [Member] | Asset-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Inputs, Prepayment Rate	13.80%
Fair Value Inputs, Probability of Default	1.90%
Fair Value Inputs, Loss Severity	53.90%
Fair Value Inputs, Discount Rate	3.60%
Weighted Average [Member] | Warrant [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Volatility	16.70%
Risk-free interest rate	2.10%
Remaining life assumption (in years)	3 years 8 months

Fair Value Measurements (Deta86

Fair Value Measurements (Details 2) - Fair Value, Measurements, Recurring [Member] - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Covered Private Label Collateralized Mortgage Obligations Member [Domain]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, beginning balance	$ 56,902	$ 81,241	$ 33,947
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings	2,256	1,636	1,104
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(742)	(1,648)	(1,388)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(4,732)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	574	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	(21,165)	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(10,219)	(24,327)	(3,881)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	51,459
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, ending balance	22,874	56,902	81,241
Other securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, beginning balance	8,373	18,200	0
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings	367	96	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(937)	94	0
Stock and Warrants Purchases During Period	42,910	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(8,604)	(10,017)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	18,200
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, ending balance	$ 42,109	$ 8,373	$ 18,200

Fair Value Measurements (Deta87

Fair Value Measurements (Details 3) - USD ($) $ in Thousands	Oct. 06, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Warrants Not Settleable in Cash, Fair Value Disclosure			$ 5,497
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Warrants, Acquired From Acquisition	$ 5,552		4,914
Gain on Sale of Investments		$ 2,532	1,402	$ 530
Proceeds from Issuance of Warrants		(3,093)	(1,894)	(1,529)
Stock and Warrants Issued During Period, Value, Preferred Stock and Warrants		$ 1,407	1,911	363
Equity Warrants Transfers to Available For Sale Securities			(836)	2
Warrants Not Settleable in Cash, Fair Value Disclosure			$ 5,497	$ 4,914

Fair Value Measurements (Deta88

Fair Value Measurements (Details 4) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Held-for-sale, Fair Value Disclosure	$ 483,563
Loans Receivable, Fair Value Disclosure	17,023,098
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	17,017,955
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	544,658	$ 161,215
Fair Value, Measurements, Nonrecurring [Member] | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	488,706	12,885
Fair Value, Measurements, Nonrecurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	55,952	148,330
Non Purchased Credit Impaired Loans and Leases [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	61,095	149,749
Non Purchased Credit Impaired Loans and Leases [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	0	0
Loans Held-for-sale, Fair Value Disclosure	0
Non Purchased Credit Impaired Loans and Leases [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	5,143	1,661
Loans Held-for-sale, Fair Value Disclosure	483,563
Non Purchased Credit Impaired Loans and Leases [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	55,952	148,088
Loans Held-for-sale, Fair Value Disclosure	$ 0
Other real estate and foreclosed assets [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		11,224
Other real estate and foreclosed assets [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		0
Other real estate and foreclosed assets [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		11,224
Cost-method Investments [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		242
Cost-method Investments [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		0
Cost-method Investments [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		0
Cost-method Investments [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		242
Third party appraisals [Domain] | Other real estate and foreclosed assets [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		$ 0

Fair Value Measurements (Deta89

Fair Value Measurements (Details 5) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loan Receivable Held-For-Sale, Charge-offs	$ 957	$ 0	$ 0
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	544,658	161,215
Total Net Gain (Loss) from Nonrecurring Assets	21,393	45,826	20,840
Other real estate and foreclosed assets [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		11,224
Total Net Gain (Loss) from Nonrecurring Assets	14	2,576	4,726
Non Purchased Credit Impaired Loans and Leases [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	61,095	149,749
Total Net Gain (Loss) from Nonrecurring Assets	20,422	43,240	16,097
Cost-method Investments [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		242
Total Net Gain (Loss) from Nonrecurring Assets	0	10	$ 17
Level 1 | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	0	0
Level 1 | Other real estate and foreclosed assets [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		0
Level 1 | Non Purchased Credit Impaired Loans and Leases [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	0	0
Level 1 | Cost-method Investments [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		0
Level 2 | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	488,706	12,885
Level 2 | Other real estate and foreclosed assets [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		11,224
Level 2 | Non Purchased Credit Impaired Loans and Leases [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	5,143	1,661
Level 2 | Cost-method Investments [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		0
Level 3 | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	55,952	148,330
Level 3 | Non Purchased Credit Impaired Loans and Leases [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	$ 55,952	148,088
Level 3 | Cost-method Investments [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		242
Third party appraisals [Domain] | Level 3 | Other real estate and foreclosed assets [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		$ 0

Fair Value Measurements (Deta90

Fair Value Measurements (Details 6) - Fair Value, Measurements, Nonrecurring [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	$ 544,658	$ 161,215
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	55,952	148,330
Non Purchased Credit Impaired Loans and Leases [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	61,095	149,749
Non Purchased Credit Impaired Loans and Leases [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	55,952	148,088
Cost-method Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		242
Cost-method Investments [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		$ 242
Discount Rates [Member] | Discounted Cash Flow [Member] | Non Purchased Credit Impaired Loans and Leases [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	$ 41,984
Discount Rates [Member] | Minimum [Member] | Discounted Cash Flow [Member] | Non Purchased Credit Impaired Loans and Leases [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	2.00%
Discount Rates [Member] | Maximum [Member] | Discounted Cash Flow [Member] | Non Purchased Credit Impaired Loans and Leases [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	10.20%
Discount Rates [Member] | Weighted Average [Member] | Discounted Cash Flow [Member] | Non Purchased Credit Impaired Loans and Leases [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	7.43%
No Discounts [Member] | Third party appraisals [Domain] | Non Purchased Credit Impaired Loans and Leases [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	$ 13,968

Fair Value Measurements (Deta91

Fair Value Measurements (Details 7) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 233,215	$ 337,965
Interest-earning deposits in financial institutions	165,222	81,705
Securities available-for-sale, at fair value		3,223,830
Securities available-for-sale, at fair value	3,774,431	3,223,830
Federal Home Loan Bank stock, at cost	20,790	21,870
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	20,790	21,870
Cost Method Investments	977	1,416
Cost Method Investments, Fair Value Disclosure	9,573	3,843
Loans and leases, net	16,833,287	15,298,716
Loans Receivable, Fair Value Disclosure	17,023,098
Warrants and Rights Outstanding		5,497
Derivative Asset	1,873	694
Warrants Not Settleable in Cash, Fair Value Disclosure		5,497
Deposits, Savings Deposits	15,937,012	12,523,834
Interest-bearing Domestic Deposit, Brokered	863,202	1,174,487
Time Deposits	2,065,322	2,172,290
Deposits, Fair Value Disclosure	2,055,104	2,166,187
Borrowings	467,342	905,812
Long-term Debt, Fair Value	467,343	905,838
Subordinated debentures	462,437	440,744
Subordinated Debt Obligations, Fair Value Disclosure	444,383	424,507
Derivative Liability		3,285
Loans held for sale, at lower of cost or fair value	481,100	0
Loans Held-for-sale, Fair Value Disclosure	483,563
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	233,215	337,965
Interest-earning deposits in financial institutions	165,222	81,705
Securities available-for-sale, at fair value		2,080
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	0	0
Cost Method Investments, Fair Value Disclosure	0	0
Deposits, Savings Deposits	0	0
Interest-bearing Domestic Deposit, Brokered	0	0
Deposits, Fair Value Disclosure	0	0
Long-term Debt, Fair Value	467,000	591,000
Subordinated Debt Obligations, Fair Value Disclosure	0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	0	0
Interest-earning deposits in financial institutions	0	0
Securities available-for-sale, at fair value		3,156,475
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	20,790	21,870
Cost Method Investments, Fair Value Disclosure	0	0
Deposits, Savings Deposits	15,937,012	12,523,834
Interest-bearing Domestic Deposit, Brokered	863,202	1,174,487
Deposits, Fair Value Disclosure	2,055,104	2,166,187
Long-term Debt, Fair Value	343	314,838
Subordinated Debt Obligations, Fair Value Disclosure	444,383	424,507
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	0	0
Interest-earning deposits in financial institutions	0	0
Securities available-for-sale, at fair value		65,275
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	0	0
Cost Method Investments, Fair Value Disclosure	9,573	3,843
Loans Receivable, Fair Value Disclosure	17,017,955
Warrants Not Settleable in Cash, Fair Value Disclosure		5,497	$ 4,914
Deposits, Savings Deposits	0	0
Interest-bearing Domestic Deposit, Brokered	0	0
Deposits, Fair Value Disclosure	0	0
Long-term Debt, Fair Value	0	0
Subordinated Debt Obligations, Fair Value Disclosure	0	0
NonPCI and PCI Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases, net		15,298,716
Loans Receivable, Fair Value Disclosure		15,494,808
NonPCI and PCI Loans [Member] | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable, Fair Value Disclosure		0
NonPCI and PCI Loans [Member] | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable, Fair Value Disclosure		1,661
NonPCI and PCI Loans [Member] | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable, Fair Value Disclosure		15,493,147
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	3,774,431	3,223,830
Derivative Asset, Fair Value of Collateral	1,873	694
Warrants Not Settleable in Cash, Fair Value Disclosure	5,161	5,497
Derivative Liability, Fair Value of Collateral	1,379	3,285
Fair Value, Measurements, Recurring [Member] | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	5,922	2,080
Derivative Asset, Fair Value of Collateral	0	0
Warrants Not Settleable in Cash, Fair Value Disclosure	0	0
Derivative Liability, Fair Value of Collateral	0	0
Fair Value, Measurements, Recurring [Member] | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	3,703,526	3,156,475
Derivative Asset, Fair Value of Collateral	1,873	694
Warrants Not Settleable in Cash, Fair Value Disclosure	0	0
Derivative Liability, Fair Value of Collateral	1,379	3,285
Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	64,983	65,275
Derivative Asset, Fair Value of Collateral	0	0
Warrants Not Settleable in Cash, Fair Value Disclosure	5,161	5,497
Derivative Liability, Fair Value of Collateral	0	$ 0
Non Purchased Credit Impaired Loans and Leases [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Held-for-sale, Fair Value Disclosure	0
Non Purchased Credit Impaired Loans and Leases [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Held-for-sale, Fair Value Disclosure	483,563
Non Purchased Credit Impaired Loans and Leases [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Held-for-sale, Fair Value Disclosure	$ 0

Fair Value Measurements (Deta92

Fair Value Measurements (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale, at fair value	$ 3,774,431,000	$ 3,223,830,000
Warrants Not Settleable in Cash, Fair Value Disclosure		5,497,000
Threshold for loans that are considered individually significant for allowance analysis purposes		250,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale, at fair value		65,275,000
Warrants Not Settleable in Cash, Fair Value Disclosure		5,497,000	$ 4,914,000
Equity Warrants Transfers to Available For Sale Securities		836,000	(2,000)
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale, at fair value	3,774,431,000	3,223,830,000
Warrants Not Settleable in Cash, Fair Value Disclosure	5,161,000	5,497,000
Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale, at fair value	64,983,000	65,275,000
Warrants Not Settleable in Cash, Fair Value Disclosure	5,161,000	5,497,000
Covered Private Label Collateralized Mortgage Obligations Member [Domain] | Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	574,000	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	21,165,000	0	$ 0
Private Label Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale, at fair value	125,987,000	125,469,000
Other securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale, at fair value	95,780,000	62,237,000
Other securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale, at fair value	42,109,000
Warrant [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	$ (1,182,000)
Square 1 Financial, Inc. [Member] | Other securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale, at fair value		$ 8,373,000

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal	$ 74,769	$ 101,530	$ 11,950
Current State and Local Tax Expense	38,933	52,551	28,167
Current Income Tax Expense	113,702	154,081	40,117
Deferred Federal Income Tax Expense	63,463	55,857	128,436
Deferred State and Local Income Tax Expense	19,748	(4,168)	11,964
Deferred Income Tax Expense (Benefit)	83,211	51,689	140,400
Income Tax Expense (Benefit), Continuing Operations, Discontinued Operations	$ 196,913	$ 205,770	$ 180,517

Income Taxes (Details 1)

Income Taxes (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	$ 194,156	$ 195,278	$ 168,047
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	33,729	32,896	29,009
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount	(15,510)	(13,992)	(8,274)
Income Tax Reconciliation Change In Cash Surrender Value Of Life Insurance	(1,853)	(1,544)	(884)
Income Tax Credits and Adjustments	(2,054)	(1,439)	(2,441)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Amount	1,781	1,257	1,005
Nondeductible acquisition-related expense	1,608	0	876
Deferred Tax Assets, Tax Deferred Expense	1,157	(2,268)	(5,529)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	(13,071)	8,689	2,917
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	(1,156)	0	0
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount	(1,874)	4,271	1,625
Income Tax Expense (Benefit), Continuing Operations, Discontinued Operations	$ 196,913	$ 205,770	$ 180,517

Income Taxes (Details 2)

Income Taxes (Details 2) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Provision for Loan Losses	$ 60,349	$ 81,380
Interest on nonaccrual loans	8,519	7,485
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation	6,174	3,148
Deferred Tax Assets, Property, Plant and Equipment	3,789	7,395
Deferred tax assets, unrealized losses on other real estate owned	248	5,546
Deferred Tax Assets, State Taxes	3,781	7,187
Deferred Tax Assets, Operating Loss Carryforwards	70,269	57,416
Deferred Tax Assets, Capital Loss Carryforwards	14,264	17,740
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities	25,986	43,366
Deferred Tax Assets, Other	4,654	7,207
Deferred Tax Assets, Equity Method Investments	7,549	15,195
Deferred Tax Assets, Goodwill and Intangible Assets	15,641	29,996
Tax Credit Carryforward, Deferred Tax Asset	5,651	16,493
Deferred Tax Assets, Gross	236,081	311,347
Deferred Tax Assets, Valuation Allowance	(94,120)	(100,920)
Deferred Tax Assets, Net of Valuation Allowance	141,961	210,427
Deferred Tax Liabilities, Goodwill and Intangible Assets	21,529	12,792
Deferred Tax Liabilities, Tax Deferred Income	9,735	13,389
Deferred Tax Liabilities, Other Comprehensive Income	15,107	4,118
Deferred Tax Liabilities, Regulatory Assets	744	1,098
Deferred Tax Liabilities, Subordinated Debt	24,518	37,499
Deferred Tax Liabilities, Leasing Arrangements	65,286	41,785
Deferred Tax Assets, Investments	9,207	11,793
Deferred Tax Liabilities, Other	7,303	5,634
Deferred Tax Liabilities, Gross	144,222	116,315
Deferred Tax Liabilities, Net	(2,261)
Deferred Tax Assets, Net	$ 0	$ 94,112

Income Taxes (Details 3)

Income Taxes (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Balance, beginning of year	$ 9,985	$ 15,155
Increase based on tax positions related to prior years	5,725	17,099
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions	(767)	(1,901)
Reductions related to settlements	(3,795)	(19,833)
Reductions for tax positions as a result of a lapse of the applicable statute of limitations	(939)	$ (535)
Balance, end of year	$ 10,209

Income Taxes (Details Textual)

Income Taxes (Details Textual) - USD ($) $ in Thousands, shares in Millions	Oct. 06, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statutory Federal Income Tax Rate		35.00%
Income Taxes Receivable		$ 98,800
Taxes Payable, Current			$ 7,400
Deferred Tax Assets, Valuation Allowance		94,120	100,920
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense		6,300
Unused Federal operating loss carryforwards		0
Unused State operating loss carryforwards		1,100,000
Unused Federal capital loss carryforwards		33,500
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		5,700
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit			1,500
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense		200	(600)	$ (2,400)
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued		500	300
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount		13,071	(8,689)	$ (2,917)
Valuation Allowances and Reserves, Period Increase (Decrease)		$ (6,800)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent		21.00%
Minimum [Member]
State operating loss carryforwards expiration date		Dec. 31, 2018
Open Tax Year		2,009
Maximum [Member]
State operating loss carryforwards expiration date		Dec. 31, 2037
Federal capital loss carryforward expiration date		12/31/2021
Foreign tax credit carryforward expiration date		Dec. 31, 2021
Open Tax Year		2,016
State and Local Jurisdiction [Member] | Minimum [Member]
Income Tax Examination, Year under Examination		2,009
State and Local Jurisdiction [Member] | Maximum [Member]
Income Tax Examination, Year under Examination		2,015
Internal Revenue Service (IRS) [Member] | Minimum [Member]
Income Tax Examination, Year under Examination		2,011
Internal Revenue Service (IRS) [Member] | Maximum [Member]
Income Tax Examination, Year under Examination		2,012
Shares Of Common Stock [Member] | Square 1 Financial, Inc. [Member]
Stock Issued During Period, Shares, New Issues	18.1
Unrecognized Tax Rate Benefit (Negative Benefit) [Member]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		$ 2,200	$ 1,100
Expires 2018 [Member]
Unused Federal capital loss carryforwards		30,500
Valuation Allowance, Tax Credit Carryforward [Member]
Valuation Allowances and Reserves, Period Increase (Decrease)		$ (11,600)

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net earnings		$ 84,037	$ 101,466	$ 93,647	$ 78,668					$ 357,818	$ 352,166	$ 299,619
Participating Securities, Distributed and Undistributed Earnings (Loss), Basic	[1]									4,184
Net earnings from continuing operations						$ 85,647	$ 93,895	$ 82,168	$ 90,456
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic	[1]										(3,988)	(2,892)
Net earnings allocated to common shares										$ 353,634	$ 348,178	$ 296,727
Weighted-average basic shares and unvested restricted stock outstanding										123,060	121,670	107,401
Less: weighted-average unvested restricted stock outstanding										(1,447)	(1,431)	(1,074)
Weighted-average basic shares outstanding										121,613	120,239	106,327
Earnings Per Share, Basic (usd per share)										$ 2.91	$ 2.90	$ 2.79
Diluted income per share (usd per share)										$ 2.91	$ 2.90	$ 2.79
[1]	Represents cash dividends paid to holders of unvested restricted stock, net of forfeitures, plus undistributed earnings amounts available to holders of unvested restricted stock, if any.

Stock Based Compensation Plan99

Stock Based Compensation Plan Stock-based Compensation Plan (Details)	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Shares
Beginning balance | shares	1,476,132
Granted | shares	557,955
Shares vesting | shares	(498,186)
Forfeited | shares	(99,781)
Ending balance | shares	1,436,120
(Per Share)
Beginning balance | $ / shares	$ 39.83
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value | $ / shares	50.08
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Grant Date Fair Value | $ / shares	40.20
Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price | $ / shares	42.87
Ending balance | $ / shares	$ 43.47
Performance Shares [Member]
Shares
Beginning balance | shares	153,715
Granted | shares	85,310
Shares vesting | shares	0
Forfeited | shares	0
Ending balance | shares	239,025
(Per Share)
Beginning balance | $ / shares	$ 27.32
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value | $ / shares	57.80
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Grant Date Fair Value | $ / shares	0
Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price | $ / shares	0
Ending balance | $ / shares	$ 38.20

Stock Based Compensation Pla100

Stock Based Compensation Plan Stock-based Compensation Plan (Details Textual) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		$ 8.9	$ 8.4	$ 5.6
Equity Instruments Other than Options, Nonvested, Number		1,436,120	1,476,132
Vesting period of time-based restricted stock, lower limit	3 years
Vesting period of time-based restricted stock, higher limit	4 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 50.08
Granted			$ 36.05	$ 46.18
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value		$ 24.9	$ 14.4	$ 14.7
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Intrinsic Value, Amount Per Share		$ 27.32
Restricted Stock [Member] | Vesting Based On Service [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		$ 24.9	$ 22.7	$ 15
Restricted Stock Awards And Performance Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized		$ 49
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity Instruments Other than Options, Nonvested, Number		239,025	153,715
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 57.80
PacWest 2003 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized		4,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		3,638,497
PacWest 2003 Stock Incentive Plan [Member] | Time-Based Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity Instruments Other than Options, Nonvested, Number		1,436,120
Outstanding at Year-End [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Terms		1 year 5 months 20 days

Benefit Plans Benefit Plans (De

Benefit Plans Benefit Plans (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)yr	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Benefit Plans [Abstract]
Minimum Hours Of Work Required By Participants	1,000
Minimum Age Of Work Required By Participants | yr	18
Maximum Annual Contributions Per Employee, Percent	60.00%
Cost Recognized | $	$ 4	$ 3.7	$ 2.8

Stockholders' Equity (Details T

Stockholders' Equity (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 14, 2018	Nov. 15, 2017	Oct. 17, 2016
Treasury Stock, Shares, Acquired	188,870	141,358	180,822
Treasury Stock Acquired, Average Cost Per Share	$ 50.17	$ 37.59	$ 46.4645243389
Stock Repurchase Program, Authorized Amount					$ 150,000,000	$ 400,000,000
Stock Repurchased and Retired During Period, Shares	2,081,227	652,835
Stock Repurchased and Retired During Period, Value	$ 99,700,000	$ 27,900,000
Stock Repurchase and Retired During Period, Weighted Average Price	$ 47.89	$ 42.78
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 112,500,000
Subsequent Event [Member]
Stock Repurchase Program, Authorized Amount				$ 350,000,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount				$ 350,000,000

Dividend Availability and Re103

Dividend Availability and Regulatory Matters Dividend Availability and Regulatory Matters (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	6.00%
Tier One Leverage Capital	$ 2,361,800	$ 2,286,203
Tier One Leverage Capital to Average Assets	11.75%	11.40%
Tier One Leverage Capital Required to be Well Capitalized	$ 1,107,900	$ 959,477
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
Excess Tier One Leverage Capital	$ 1,253,900	$ 1,326,726
Tier One Risk Based Common Equity	$ 2,361,800	$ 2,286,203
Tier One Risk Based Common Equity to Risk Weighted Assets	11.91%	11.78%
Tier One Risk Based Common Equity Required to be Well Capitalized	$ 1,407,743	$ 1,206,960
Tier One Risk Based Common Equity Required to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Excess Common Equity Tier One Capital	$ 954,057	$ 1,079,243
Tier One Risk Based Capital	$ 2,361,800	$ 2,286,203
Tier One Risk Based Capital to Risk Weighted Assets	11.91%	11.78%
Tier One Risk Based Capital Required to be Well Capitalized	$ 1,732,607	$ 1,485,490
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Excess Tier One Risk Based Capital	$ 629,193	$ 800,713
Capital	$ 2,978,643	$ 2,889,163
Capital to Risk Weighted Assets	12.69%	12.72%
Capital Required to be Well Capitalized	$ 2,165,759	$ 1,856,862
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Excess Capital	$ 812,884	$ 1,032,301
Pacific Western Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier One Leverage Capital	$ 2,574,561	$ 2,184,097
Tier One Leverage Capital to Average Assets	10.66%	11.91%
Tier One Leverage Capital Required to be Well Capitalized	$ 1,095,656	$ 957,630
Excess Tier One Leverage Capital	1,478,905	1,226,467
Tier One Risk Based Common Equity	$ 2,574,561	$ 2,184,097
Tier One Risk Based Common Equity to Risk Weighted Assets	10.91%	12.31%
Tier One Risk Based Common Equity Required to be Well Capitalized	$ 1,405,299	$ 1,205,541
Excess Common Equity Tier One Capital	1,169,262	978,556
Tier One Risk Based Capital	$ 2,574,561	$ 2,184,097
Tier One Risk Based Capital to Risk Weighted Assets	10.91%	12.31%
Tier One Risk Based Capital Required to be Well Capitalized	$ 1,729,599	$ 1,483,742
Excess Tier One Risk Based Capital	844,962	700,355
Capital	$ 2,742,624	$ 2,358,829
Capital to Risk Weighted Assets	13.75%	15.56%
Capital Required to be Well Capitalized	$ 2,161,999	$ 1,854,678
Excess Capital	$ 580,625	$ 504,151

Dividend Availability and Re104

Dividend Availability and Regulatory Matters Dividend Availability and Regulatory Matters (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Compliance with Regulatory Capital Requirements for Mortgage Companies [Line Items]
Proceeds from Dividends Received	$ 265,000,000
Retained earnings	$ 723,471,000	$ 366,073,000
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	6.00%
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Tier One Risk Based Capital Required to be Well Capitalized	6.50%	6.50%
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
Deferred Tax Assets, Regulatory Assets and Liabilities	$ 200,000
Common Equity Tier One Capital Ratio	4.50%
Supplementary Leverage Ratio	4.00%
Subordinated debentures	$ 462,437,000	$ 440,744,000
Tier One Capital, Trust Preferred Securities Capital Portion	0
Tier Two Capital, Trust Preferred Securities Capital Portion	448,800,000
Pacific Western Bank [Member]
Compliance with Regulatory Capital Requirements for Mortgage Companies [Line Items]
Retained earnings	434,800,000
Deferred Tax Assets, Regulatory Assets and Liabilities	$ 56,000

Condensed Financial Informat105

Condensed Financial Information Of Parent Company Parent Company Information (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Cash	$ 398,437	$ 419,670
Other assets	540,723	319,779
Total assets	24,994,876	21,869,767
Subordinated debentures	462,437	440,744
Total liabilities	20,017,278	17,390,712
Stockholders' Equity Attributable to Parent Only	4,977,598	4,479,055	$ 4,397,691	$ 3,506,230
Total liabilities and stockholders' equity	24,994,876	21,869,767
Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Cash	185,511	494,765
Investments In Consolidated Banking Subsidiaries	4,869,391	4,053,711
Other assets	76,458	67,074
Total assets	5,131,360	4,615,550
Subordinated debentures	147,233	134,360
Other Liabilities	6,529	2,135
Total liabilities	153,762	136,495
Stockholders' Equity Attributable to Parent Only	4,977,598	4,479,055
Total liabilities and stockholders' equity	$ 5,131,360	$ 4,615,550

Condensed Financial Informat106

Condensed Financial Information Of Parent Company Parent Company Information (Details 1) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Investment Income, Dividend									$ 1,866	$ 2,575	$ 4,046
Interest Expense	$ 21,641	$ 19,276	$ 17,071	$ 14,957	$ 13,468	$ 13,220	$ 13,297	$ 14,636	72,945	54,621	60,592
Income Tax Expense (Benefit)	(56,440)	(37,945)	54,902	47,626	$ (49,716)	$ (48,479)	$ (49,726)	$ (57,849)	(196,913)	(205,770)	(180,517)
Net earnings	$ 84,037	$ 101,466	$ 93,647	$ 78,668					357,818	352,166	299,619
Parent Only
Condensed Financial Statements, Captions [Line Items]
Other Income									3,393	2,146	1,458
Investment Income, Dividend									265,000	259,000	214,000
Total Income									268,393	261,146	215,458
Interest Expense									5,519	4,816	4,279
Operating Expenses									8,273	7,732	6,983
Total Expenses									13,792	12,548	11,262
Net earnings from continuing operations									254,601	248,598	204,196
Income Tax Expense (Benefit)									19,957	2,612	4,225
Income Loss From Continuing Operations Before Income Loss From Equity Method Investments									274,558	251,210	208,421
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions									83,260	100,956	91,198
Net earnings									$ 357,818	$ 352,166	$ 299,619

Condensed Financial Informat107

Condensed Financial Information Of Parent Company Parent Company Information (Details 2) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net earnings	$ 84,037	$ 101,466	$ 93,647	$ 78,668	$ 357,818	$ 352,166	$ 299,619
Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract]
(Increase) decrease in other assets					(118,477)	6,441	48,172
Loss (gain) on sale of securities, net					541	(9,485)	(3,744)
Tax effect included in stockholders' equity of restricted stock vesting					0	(4,406)	(841)
Earned stock compensation					25,568	23,319	15,630
Net cash provided by operating activities					483,968	581,107	593,878
Net Cash Provided by (Used in) Investing Activities [Abstract]
Cash acquired in acquisitions, net of cash consideration paid					160,318	0	260,936
Payments to Acquire Available-for-sale Securities					(1,298,105)	(375,261)	(992,680)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Tax effect of restricted stock vesting included in stockholders' equity					0	4,406	841
Restricted stock surrendered					9,476	5,313	8,400
Cash dividends paid, net					(247,403)	(243,437)	(215,110)
Net cash (used in) provided by financing activities					(537,942)	400,629	131,879
Cash and Cash Equivalents, at Carrying Value	398,437				398,437	419,670	396,486	$ 313,226
Supplemental Cash Flow Information [Abstract]
shares of unvested restricted stock, respectively)	1,305				1,305	1,228
Parent Only
Condensed Financial Statements, Captions [Line Items]
Net earnings					357,818	352,166	299,619
Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract]
(Increase) decrease in other assets					(34,274)	96,668	145,709
Increase (Decrease) in Operating Liabilities					4,857	(17,311)	9,115
Loss (gain) on sale of securities, net					(15)	(405)	0
Tax effect included in stockholders' equity of restricted stock vesting					0	4,406	841
Earned stock compensation					25,568	23,319	14,994
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions					(83,260)	(100,956)	(91,198)
Net cash provided by operating activities					270,694	357,887	379,080
Net Cash Provided by (Used in) Investing Activities [Abstract]
Cash acquired in acquisitions, net of cash consideration paid					(223,818)	0	3,021
Payments to Acquire Available-for-sale Securities					426	995	0
Net Cash Provided by (Used in) Investing Activities, Continuing Operations					(223,392)	995	3,021
Net Cash Provided by (Used in) Financing Activities [Abstract]
Tax effect of restricted stock vesting included in stockholders' equity					0	(4,406)	(841)
Restricted stock surrendered					(109,153)	(33,244)	(8,400)
Increase (Decrease) in Notes Receivables					0	0	(50,000)
Cash dividends paid, net					(247,403)	(243,437)	(215,110)
Net cash (used in) provided by financing activities					(356,556)	(281,087)	(274,351)
Net Cash Provided by (Used in) Continuing Operations					(309,254)	77,795	107,750
Cash and Cash Equivalents, at Carrying Value	185,511				185,511	494,765	416,970	$ 309,220
Supplemental Cash Flow Information [Abstract]
shares of unvested restricted stock, respectively)	$ 446,233				$ 446,233	$ 0	$ 797,433

Selected Quarterly Financial108

Selected Quarterly Financial Data Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest Income (Expense), Net [Abstract]
Interest Income	$ 284,597	$ 260,966	$ 259,544	$ 247,409	$ 261,773	$ 247,855	$ 247,054	$ 259,230	$ 1,052,516	$ 1,015,912	$ 883,938
Interest expense	(21,641)	(19,276)	(17,071)	(14,957)	(13,468)	(13,220)	(13,297)	(14,636)	(72,945)	(54,621)	(60,592)
Net interest income	262,956	241,690	242,473	232,452	248,305	234,635	233,757	244,594	979,571	961,291	823,346
Provision for credit losses	6,406	15,119	11,499	24,728	23,215	8,471	13,903	(20,140)	57,752	65,729	45,481
FDIC loss sharing expense, net					0	0	(6,502)	(2,415)	0	(8,917)	(18,246)
Noninterest Income [Abstract]
(Loss) gain on sale of securities	(3,329)	1,236	1,651	(99)	515	382	478	8,110	(541)	9,485	3,744
Noninterest Income, Other	30,124	30,146	33,631	35,213	28,380	26,538	28,145	28,844
Total noninterest income	26,795	31,382	35,282	35,114	28,895	26,920	22,121	34,539	128,573	112,475	84,310
Foreclosed Assets (Income) Expense, Net	475	(2,191)	157	(143)	(2,693)	248	3	561
Noninterest Expense [Abstract]
Amortization	(16,085)	(1,450)	(1,700)	(500)	0	0	0	(200)	(14,240)	(16,517)	(9,410)
Acquisition, integration and reorganization costs	(127,258)	(114,901)	(116,164)	(115,901)	(115,929)	(110,958)	(110,084)	(111,049)	(19,735)	(200)	(21,247)
Total noninterest expense	(142,868)	(118,542)	(117,707)	(116,544)	(118,622)	(110,710)	(110,081)	(110,688)	(495,661)	(450,101)	(382,039)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent [Abstract]
Earnings from continuing operations before taxes	140,477	139,411	148,549	126,294	135,363	142,374	131,894	148,305	554,731	557,936	480,136
Income Tax Expense (Benefit)	(56,440)	(37,945)	54,902	47,626	(49,716)	(48,479)	(49,726)	(57,849)	(196,913)	(205,770)	(180,517)
Net earnings	$ 84,037	$ 101,466	$ 93,647	$ 78,668					$ 357,818	$ 352,166	$ 299,619
Net earnings from continuing operations					$ 85,647	$ 93,895	$ 82,168	$ 90,456
Earnings Per Share, Basic [Abstract]
Basic and diluted earnings per share (usd per share)	$ 0.66	$ 0.84	$ 0.77	$ 0.65	$ 0.71	$ 0.77	$ 0.68	$ 0.74

Subsequent Events Subsequent Ev

Subsequent Events Subsequent Events (Details Textual) - USD ($)	Feb. 28, 2018	Feb. 20, 2018	Feb. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 14, 2018	Nov. 15, 2017	Oct. 17, 2016
Subsequent Event [Line Items]
Stock Repurchase Program, Authorized Amount								$ 150,000,000	$ 400,000,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount				$ 112,500,000
Dividends declared per share (usd per share)				$ 2	$ 2	$ 2
Subsequent Event [Member]
Subsequent Event [Line Items]
Stock Repurchase Program, Authorized Amount							$ 350,000,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount							$ 350,000,000
Dividends Payable, Date to be Paid	Feb. 28, 2018
Dividends Payable, Date of Record		Feb. 20, 2018
Dividend Declared [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends declared per share (usd per share)			$ 0.50