Western Alliance Bancorporation (WAL) 10-Q27 Apr 182018 Q1 Quarterly reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2018	Apr. 23, 2018
Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Trading Symbol	WAL
Entity Registrant Name	WESTERN ALLIANCE BANCORPORATION
Entity Central Index Key	1,212,545
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		105,860,364

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets:
Cash and due from banks	$ 149,737	$ 181,191
Interest-bearing deposits in other financial institutions	289,634	235,577
Cash, cash equivalents, and restricted cash	439,371	416,768
Money Market Funds, at Carrying Value	5	0
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	3,405,462	3,499,519
Held-to-maturity Securities	262,304	255,050
Investments in restricted stock, at cost	66,519	65,785
Loans:
Loans, net of deferred loan fees and costs	15,560,453	15,093,935
Less: Allowance for credit losses	(144,659)	(140,050)
Net loans held for investment	15,415,794	14,953,885
Premises and equipment, net	116,702	118,719
Other assets acquired through foreclosure, net	30,194	28,540
Bank owned life insurance	168,619	167,764
Goodwill	289,895	289,895
Other intangible assets, net	10,455	10,853
Deferred tax assets, net	27,374	5,780
Investments in LIHTC	288,911	267,023
Other assets	239,126	249,504
Total assets	20,760,731	20,329,085
Deposits:
Non-interest-bearing demand	7,502,036	7,433,962
Interest-bearing	9,852,502	9,538,570
Total deposits	17,354,538	16,972,532
Customer repurchase agreements	21,676	26,017
Other borrowings	300,000	390,000
Qualifying debt	363,935	376,905
Other liabilities	426,819	333,933
Total liabilities	18,466,968	18,099,387
Commitments and Contingencies
Stockholders’ equity:
Common stock - par value $0.0001; 200,000,000 authorized; 107,611,765 shares issued at March 31, 2018 and 107,057,520 at December 31, 2017	10	10
Treasury stock, at cost (1,751,022 shares at March 31, 2018 and 1,570,155 shares at December 31, 2017)	(46,469)	(40,173)
Additional paid in capital	1,431,460	1,424,540
Accumulated other comprehensive (loss)	(41,662)	(3,145)
Retained earnings	950,424	848,466
Total stockholders’ equity	2,293,763	2,229,698
Total liabilities and stockholders’ equity	$ 20,760,731	$ 20,329,085

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Amortized cost of investment securities available for sale	$ 3,474,049	$ 3,515,401
Held-to-maturity Securities, Fair Value	$ 255,418	$ 256,314
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	107,611,765	107,057,520
Common stock, shares outstanding	105,860,743	105,487,365

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Interest income:
Loans, including fees	$ 205,959	$ 172,553
Investment securities	25,772	16,571
Dividends	1,478	2,229
Other	1,488	912
Total interest income	234,697	192,265
Interest expense:
Deposits	14,173	8,412
Other borrowings	1,326	190
Qualifying debt	4,969	4,338
Other	9	16
Total interest expense	20,477	12,956
Net interest income	214,220	179,309
Provision for credit losses	6,000	4,250
Net interest income after provision for credit losses	208,220	175,059
Non-interest income:
Service charges and fees	5,745	4,738
Card income	1,972	1,492
Income from equity investments	1,460	692
Foreign currency income	1,202	1,042
Lending related income and gains (losses) on sale of loans, net	978	422
Income from bank owned life insurance	928	948
Gain (loss) on sales of investment securities, net	0	635
Unrealized (losses) gains on assets measured at fair value, net	(1,074)	(1)
Other income	432	631
Total non-interest income	11,643	10,599
Non-interest expense:
Salaries and employee benefits	62,133	51,620
Occupancy	6,864	6,894
Legal, professional, and directors' fees	6,003	8,803
Data processing	5,207	5,264
Insurance	3,869	3,228
Deposit costs	2,926	1,741
Business development	1,728	2,063
Card expense	942	731
Marketing	596	721
Loan and repossessed asset expenses	583	1,278
Intangible amortization	398	689
Net (gain) loss on sales / valuations of repossessed and other assets	(1,228)	(543)
Other expense	8,128	5,338
Total non-interest expense	98,149	87,827
Income before provision for income taxes	121,714	97,831
Income tax expense	20,814	24,489
Net income	$ 100,900	$ 73,342
Earnings per share available to common stockholders:
Basic	$ 0.97	$ 0.71
Diluted	$ 0.96	$ 0.70
Weighted average number of common shares outstanding:
Basic	104,530	103,987
Diluted	105,324	104,836

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 100,900	$ 73,342
Other comprehensive (loss) income, net:
Unrealized (loss) gain on AFS securities, net of tax effect of $12,714 and $(5,670), respectively	(38,914)	9,169
Unrealized (loss) gain on SERP, net of tax effect of $2 and $1, respectively	(11)	(1)
Unrealized gain (loss) on junior subordinated debt, net of tax effect of $(478) and $757, respectively	1,466	(1,229)
Realized (gain) loss on sale of AFS securities included in income, net of tax effect of $0 and $242, respectively	0	(393)
Net other comprehensive (loss) income	(37,459)	7,546
Comprehensive income	$ 63,441	$ 80,888

CONSOLIDATED STATEMENTS OF COM6

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Unrealized gain on securities available-for-sale securities, tax	$ (12,714)	$ 5,670
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	2	1
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Debt Carried at Fair Value, Tax	(478)	757
Realized gain on sale of securities, tax	$ 0	$ 242

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated (Deficit) [Member]	Treasury Stock [Member]
Beginning balance at Dec. 31, 2016	$ 1,891,529	$ 10	$ 1,400,140	$ (4,695)	$ 522,436	$ (26,362)
Beginning balance, shares at Dec. 31, 2016		105,071,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	73,342				73,342
Exercise of stock options, shares		9,000
Exercise of stock options	184		184
Restricted stock grants, net, shares		549,000
Restricted stock grants, net	$ 6,619		6,619
Treasury Stock, Shares, Acquired	(201,306)	201,000
Restricted Stock Award, Forfeitures	$ 10,243					10,243
Other comprehensive (loss) income, net	7,546			7,546
Ending balance at Mar. 31, 2017	1,969,515	$ 10	1,406,943	2,851	596,316	(36,605)
Ending balance, shares at Mar. 31, 2017		105,428,000
Retained earnings	848,466
Beginning balance at Dec. 31, 2017	2,229,698	$ 10	1,424,540	(3,145)	848,466	(40,173)
Beginning balance, shares at Dec. 31, 2017		105,487,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	100,900				100,900
Exercise of stock options, shares		9,000
Exercise of stock options	215		215
Restricted stock grants, net, shares		546,000
Restricted stock grants, net	$ 6,705		6,705
Treasury Stock, Shares, Acquired	(180,867)	181,000
Restricted Stock Award, Forfeitures	$ 6,296					(6,296)
Other comprehensive (loss) income, net	(37,459)			(37,459)
Ending balance at Mar. 31, 2018	2,293,763	$ 10	$ 1,431,460	$ (41,662)	$ 950,424	$ (46,469)
Ending balance, shares at Mar. 31, 2018		105,861,000
Retained earnings	$ 950,424

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 100,900	$ 73,342
Adjustments to reconcile net income to cash provided by operating activities:
Provision for credit losses	6,000	4,250
Depreciation and amortization	3,407	3,211
Stock-based compensation	6,705	6,342
Excess tax benefit of stock-based compensation	(3,971)	(4,593)
Deferred income taxes	(9,372)	2,401
Amortization of net premiums for investment securities	3,920	4,007
Amortization of tax credit investments	8,128	5,931
Accretion of fair market value adjustments on loans acquired from business combinations	(5,738)	(6,393)
Accretion and amortization of fair market value adjustments on other assets and liabilities acquired from business combinations	475	767
Income from bank owned life insurance	(928)	(948)
(Gains) / Losses on:
Sales of investment securities	0	(635)
Unrealized (losses) gains on assets measured at fair value, net	(1,074)	(1)
Sale of loans	(678)	52
Other assets acquired through foreclosure, net	(1,242)	106
Valuation adjustments of other repossessed assets, net	47	(380)
Sale of premises, equipment, and other assets, net	(33)	47
Changes in, net of acquisitions:
Other assets	9,744	4,864
Other liabilities	(30,122)	(4,398)
Net cash provided by operating activities	88,316	87,972
Investment securities - measured at fair value
Principal pay downs and maturities	0	33
Investment securities - AFS
Purchases	(67,949)	(185,199)
Principal pay downs and maturities	105,242	90,585
Proceeds from sales	0	15,170
Purchases	7,800	10,533
Principal pay downs and maturities	243	0
Purchase of investment tax credits	(13,376)	(3,516)
Purchase of SBIC investments	263	0
(Purchase) sale of money market investments, net	(5)	(90)
Proceeds from bank owned life insurance	72	0
(Purchase) liquidation of restricted stock	734	154
Loan fundings and principal collections, net	(367,437)	(342,069)
Purchase of premises, equipment, and other assets, net	(576)	(2,575)
Proceeds from sale of other real estate owned and repossessed assets, net	5,285	2,889
Net cash used in investing activities	(347,298)	(435,459)
Cash flows from financing activities:
Net increase (decrease) in deposits	382,006	806,106
Net increase (decrease) in borrowings	(94,340)	(86,017)
Proceeds from exercise of common stock options	215	184
Cash paid for tax withholding on vested restricted stock	(6,296)	(10,243)
Net cash provided by financing activities	281,585	710,030
Net increase (decrease) in cash, cash equivalents, and restricted cash	22,603	362,543
Cash, cash equivalents, and restricted cash at beginning of period	416,768	284,491
Cash, cash equivalents, and restricted cash at end of period	439,371	647,034
Cash paid during the period for:
Interest	25,303	17,851
Income taxes	9,881	(23)
Non-cash investing and financing activity:
Transfers to other assets acquired through foreclosure, net	5,744	0
Unfunded commitments originated	30,000	30,869
Change in unrealized (loss) gain on AFS securities, net of tax	(38,914)	9,169
Change in unrealized gain (loss) on junior subordinated debt, net of tax	1,466	(1,229)
Change in unfunded obligations	$ 120,512	$ 114,727

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
Summary of Significant Accounting Policies	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Nature of operation WAL is a bank holding company headquartered in Phoenix, Arizona, incorporated under the laws of the state of Delaware. WAL provides a full spectrum of deposit, lending, treasury management, international banking, and online banking products and services through its wholly-owned banking subsidiary, WAB. WAB operates the following full-service banking divisions: ABA, BON, FIB, Bridge, and TPB. The Company also serves business customers through a national platform of specialized financial services including AAB, Corporate Finance, Equity Fund Resources, HFF, Life Sciences Group, Mortgage Warehouse Lending, Public and Nonprofit Finance, Renewable Resource Group, Resort Finance, and Technology Finance. In addition, the Company has two non-bank subsidiaries, LVSP, which holds and manages certain non-performing loans and OREO and a captive insurance company formed and licensed under the laws of the State of Arizona, CS Insurance Company. CS Insurance Company was established as part of the Company's overall enterprise risk management strategy. Basis of presentation The accounting and reporting policies of the Company are in accordance with GAAP and conform to practices within the financial services industry. The accounts of the Company and its consolidated subsidiaries are included in the Consolidated Financial Statements. Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management's estimates and judgments are ongoing and are based on experience, current and expected future conditions, third-party evaluations and various other assumptions that management believes are reasonable under the circumstances. The results of these estimates form the basis for making judgments about the carrying values of assets and liabilities, as well as identifying and assessing the accounting treatment with respect to commitments and contingencies. Actual results may differ from those estimates and assumptions used in the Consolidated Financial Statements and related notes. Material estimates that are particularly susceptible to significant changes in the near term relate to the determination of the allowance for credit losses; estimated cash flows related to PCI loans; fair value determinations related to acquisitions and certain assets and liabilities carried at fair value; and accounting for income taxes. Principles of consolidation As of March 31, 2018 , WAL has the following significant wholly-owned subsidiaries: WAB, LVSP, and eight unconsolidated subsidiaries used as business trusts in connection with the issuance of trust-preferred securities. The Bank has the following significant wholly-owned subsidiaries: WABT, which holds certain investment securities, municipal and nonprofit loans, and leases; WA PWI, LLC, which holds certain limited partnerships invested primarily in low income housing tax credits and small business investment corporations; and BW Real Estate, Inc., which operates as a real estate investment trust and holds certain of WAB's real estate loans and related securities. The Company does not have any other significant entities that should be considered for consolidation. All significant intercompany balances and transactions have been eliminated in consolidation. Reclassifications Certain amounts reported in prior periods may have been reclassified in the Consolidated Financial Statements to conform to the current presentation. The reclassifications have no effect on net income or stockholders’ equity as previously reported. Interim financial information The accompanying Unaudited Consolidated Financial Statements as of and for the three months ended March 31, 2018 and 2017 have been prepared in condensed format and, therefore, do not include all of the information and footnotes required by GAAP for complete financial statements. These statements have been prepared on a basis that is substantially consistent with the accounting principles applied to the Company's audited Consolidated Financial Statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 . The information furnished in these interim statements reflects all adjustments which are, in the opinion of management, necessary for a fair statement of the results for each respective period presented. Such adjustments are of a normal, recurring nature. The results of operations in the interim statements are not necessarily indicative of the results that may be expected for any other quarter or for the full year. The interim financial information should be read in conjunction with the Company's audited Consolidated Financial Statements. Investment securities Investment securities may be classified as HTM, AFS, or measured at fair value. The appropriate classification is initially decided at the time of purchase. Securities classified as HTM are those debt securities that the Company has both the intent and ability to hold to maturity regardless of changes in market conditions, liquidity needs, or general economic conditions. These securities are carried at amortized cost. The sale of a security within three months of its maturity date or after the majority of the principal outstanding has been collected is considered a maturity for purposes of classification and disclosure. Securities classified as AFS or trading securities measured at fair value are reported as an asset in the Consolidated Balance Sheet at their estimated fair value. As the fair value of AFS debt securities changes, the changes are reported net of income tax as an element of OCI, except for other-than-temporarily-impaired securities. Upon adoption of ASU 2016-01, the fair value changes in AFS equity securities are recognized as part of non-interest income, see "Recently adopted accounting guidance" below for further discussion. When AFS debt securities are sold, the unrealized gain or loss is reclassified from OCI to non-interest income. The changes in the fair values of trading securities are reported in non-interest income. Securities classified as AFS are both equity and debt securities that the Company intends to hold for an indefinite period of time, but not necessarily to maturity. Any decision to sell a security classified as AFS would be based on various factors, including significant movements in interest rates, changes in the maturity mix of the Company’s assets and liabilities, liquidity needs, decline in credit quality, and regulatory capital considerations. Interest income is recognized based on the coupon rate and increased by accretion of discounts earned or decreased by the amortization of premiums paid over the contractual life of the security, adjusted for prepayment estimates, using the interest method. In estimating whether there are any OTTI losses, management considers the 1) length of time and the extent to which the fair value has been less than amortized cost; 2) financial condition and near term prospects of the issuer; 3) impact of changes in market interest rates; and 4) intent and ability of the Company to retain its investment for a period of time sufficient to allow for any anticipated recovery in fair value and whether it is not more likely than not the Company would be required to sell the security. Declines in the fair value of individual AFS debt securities that are deemed to be other-than-temporary are reflected in earnings when identified. The fair value of the debt security then becomes the new cost basis. For individual debt securities where the Company does not intend to sell the security and it is not more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis, the other-than-temporary decline in fair value of the debt security related to 1) credit loss is recognized in earnings; and 2) interest rate, market, or other factors is recognized in other comprehensive income or loss. For individual debt securities where the Company either intends to sell the security or more likely than not will not recover all of its amortized cost, the OTTI is recognized in earnings equal to the entire difference between the security's cost basis and its fair value at the balance sheet date. For individual debt securities for which a credit loss has been recognized in earnings, interest accruals and amortization and accretion of premiums and discounts are suspended when the credit loss is recognized. Interest received after accruals have been suspended is recognized on a cash basis. Restricted stock WAB is a member of the Federal Reserve System and, as part of its membership, is required to maintain stock in the FRB in a specified ratio to its capital. In addition, WAB is a member of the FHLB system and, accordingly, maintains an investment in capital stock of the FHLB based on the borrowing capacity used. The Bank also maintains an investment in its primary correspondent bank. All of these investments are considered equity securities with no actively traded market. Therefore, the shares are considered restricted investment securities. These investments are carried at cost, which is equal to the value at which they may be redeemed. The dividend income received from the stock is reported in interest income. The Company conducts a periodic review and evaluation of its restricted stock to determine if any impairment exists. No impairment has been recorded to date. Loans, held for sale Loans, held for sale consist of SBA loans that the Company originates (or acquires) and intends to sell. These loans are carried at the lower of aggregate cost or fair value. Fair value is determined based on available market data for similar assets, expected cash flows, and appraisals of underlying collateral or the credit quality of the borrower. Gains and losses on the sale of loans are recognized pursuant to ASC 860, Transfers and Servicing . Interest income of these loans is accrued daily and loan origination fees and costs are deferred and included in the cost basis of the loan. The Company issues various representations and warranties associated with these loan sales. The Company has not experienced any losses as a result of these representations and warranties. Loans, held for investment The Company generally holds loans for investment and has the intent and ability to hold loans until their maturity. Therefore, they are reported at book value. Net loans are stated at the amount of unpaid principal, adjusted for net deferred fees and costs, purchase accounting fair value adjustments, and an allowance for credit losses. In addition, the book value of loans that are subject to a fair value hedge is adjusted for changes in value attributable to the effective portion of the hedged benchmark interest rate risk. The Company may also acquire loans through a business combination. These acquired loans are recorded at estimated fair value on the date of purchase, which is comprised of unpaid principal adjusted for estimated credit losses and interest rate fair value adjustments. Loans are evaluated individually at the acquisition date to determine if there has been credit deterioration since origination. Such loans may then be aggregated and accounted for as a pool of loans based on common characteristics. When the Company acquires such loans, the yield that may be accreted (accretable yield) is limited to the excess of the Company’s estimate of undiscounted cash flows expected to be collected over the Company’s initial investment in the loan. The excess of contractual cash flows over the cash flows expected to be collected may not be recognized as an adjustment to yield, loss, or a valuation allowance. Subsequent increases in cash flows expected to be collected generally are recognized prospectively through adjustment of the loan’s yield over the remaining life. Subsequent decreases to cash flows expected to be collected are recognized as impairment. The Company may not carry over or create a valuation allowance in the initial accounting for loans acquired under these circumstances. For purchased loans that are not deemed impaired at the acquisition date, fair value adjustments attributable to both credit and interest rates are accreted (or amortized) over the contractual life of the individual loan. For additional information, see " Note 3. Loans, Leases and Allowance for Credit Losses " of these Notes to Unaudited Consolidated Financial Statements. Loan fees collected for the origination of loans less direct loan origination costs (net deferred loan fees) are amortized over the contractual life of the loan through interest income. If the loan has scheduled payments, the amortization of the net deferred loan fee is calculated using the interest method over the contractual life of the loan. If the loan does not have scheduled payments, such as a line of credit, the net deferred loan fee is recognized as interest income on a straight-line basis over the contractual life of the loan commitment. Commitment fees based on a percentage of a customer’s unused line of credit and fees related to standby letters of credit are recognized over the commitment period. When loans are repaid, any remaining unamortized balances of premiums, discounts, or net deferred fees are recognized as interest income. Non-accrual loans: When a borrower discontinues making payments as contractually required by the note, the Company must determine whether it is appropriate to continue to accrue interest. The Company ceases accruing interest income when the loan has become delinquent by more than 90 days or when management determines that the full repayment of principal and collection of interest according to contractual terms is no longer likely. The Company may decide to continue to accrue interest on certain loans more than 90 days delinquent if the loans are well secured by collateral and in the process of collection. For all loan types, when a loan is placed on non-accrual status, all interest accrued but uncollected is reversed against interest income in the period in which the status is changed and, the Company makes a loan-level decision to apply either the cash basis or cost recovery method. The Company recognizes income on a cash basis only for those non-accrual loans for which the collection of the remaining principal balance is not in doubt. Under the cost recovery method, subsequent payments received from the customer are applied to principal and generally no further interest income is recognized until the principal has been paid in full or until circumstances have changed such that payments are again consistently received as contractually required. Impaired loans: A loan is identified as impaired when it is no longer probable that interest and principal will be collected according to the contractual terms of the original loan agreement. Generally, impaired loans are classified as non-accrual. However, in certain instances, impaired loans may continue on an accrual basis, if full repayment of all principal and interest is expected and the loan is both well secured and in the process of collection. Impaired loans are measured for reserve requirements in accordance with ASC 310, Receivables, based on the present value of expected future cash flows discounted at the loan's effective interest rate or, as a practical expedient, at the loan's observable market price or the fair value of the collateral less applicable disposition costs if the loan is collateral dependent. The amount of an impairment reserve, if any, and any subsequent changes are recorded as a provision for credit losses. Losses are recorded as a charge-off when losses are confirmed. In addition to management's internal loan review process, regulators may from time to time direct the Company to modify loan grades, loan impairment calculations, or loan impairment methodology. Troubled Debt Restructured Loans : A TDR loan is a loan on which the Company, for reasons related to a borrower’s financial difficulties, grants a concession to the borrower that the Company would not otherwise consider. The loan terms that have been modified or restructured due to a borrower’s financial situation include, but are not limited to, a reduction in the stated interest rate, an extension of the maturity or renewal of the loan at an interest rate below current market, a reduction in the face amount of the debt, a reduction in the accrued interest, or deferral of interest payments. A TDR loan is also considered impaired. A TDR loan may be returned to accrual status when the loan is brought current, has performed in accordance with the contractual restructured terms for a reasonable period of time (generally six months) and the ultimate collectability of the total contractual restructured principal and interest is no longer in doubt. However, such loans continue to be considered impaired. Consistent with regulatory guidance, a TDR loan that is subsequently modified in another restructuring agreement but has shown sustained performance and classification as a TDR, will be removed from TDR status provided that the modified terms were market-based at the time of modification. Allowance for credit losses Credit risk is inherent in the business of extending loans and leases to borrowers, for which the Company must maintain an adequate allowance for credit losses. The allowance for credit losses is established through a provision for credit losses recorded to expense. Loans are charged against the allowance for credit losses when management believes that the contractual principal or interest will not be collected. Subsequent recoveries, if any, are credited to the allowance. The allowance is an amount believed adequate to absorb estimated probable losses on existing loans that may become uncollectable, based on evaluation of the collectability of loans and prior credit loss experience, together with other factors. The Company formally re-evaluates and establishes the appropriate level of the allowance for credit losses on a quarterly basis. The allowance consists of specific and general components. The specific allowance applies to impaired loans. For impaired collateral dependent loans, the reserve is calculated based on the collateral value, net of estimated disposition costs. Generally, the Company obtains independent collateral valuation analysis for each loan every twelve months. Loans not collateral dependent are evaluated based on the expected future cash flows discounted at the original contractual interest rate. The general allowance covers all non-impaired loans and incorporates several quantitative and qualitative factors, which are used for all of the Company's portfolio segments. Quantitative factors include company-specific, ten-year historical net charge-offs stratified by loans with similar characteristics. Qualitative factors include: 1) levels of and trends in delinquencies and impaired loans; 2) levels of and trends in charge-offs and recoveries; 3) trends in volume and terms of loans; 4) changes in underwriting standards or lending policies; 5) experience, ability, depth of lending staff; 6) national and local economic trends and conditions; 7) changes in credit concentrations; 8) out-of-market exposures; 9) changes in quality of loan review system; and 10) changes in the value of underlying collateral. Due to the credit concentration of the Company's loan portfolio in real estate secured loans, the value of collateral is heavily dependent on real estate values in Arizona, Nevada, and California. While management uses the best information available to make its evaluation, future adjustments to the allowance may be necessary if there are significant changes in economic or other conditions. In addition, regulators, as an integral part of their examination processes, periodically review the Bank's allowance for credit losses, and may require the Bank to make additions to the allowance based on their judgment about information available to them at the time of their examination. Management regularly reviews the assumptions and formulae used in determining the allowance and makes adjustments if required to reflect the current risk profile of the portfolio. Goodwill and other intangible assets The Company records as goodwill the excess of the purchase price over the fair value of the identifiable net assets acquired in accordance with applicable guidance. The Company performs its annual goodwill and intangibles impairment tests as of October 1 each year, or more often if events or circumstances indicate that the carrying value may not be recoverable. The Company can first elect to assess, through qualitative factors, whether it is more likely than not that goodwill is impaired. If the qualitative assessment indicates potential impairment, the Company will proceed with a two-step process. The first step tests for impairment, while the second step, if necessary, measures the impairment. The resulting impairment amount, if any, is charged to current period earnings as non-interest expense. The Company’s intangible assets consist primarily of core deposit intangible assets that are amortized over periods ranging from 5 to 10 years. The Company considers the remaining useful lives of its core deposit intangible assets each reporting period, as required by ASC 350, Intangibles—Goodwill and Other, to determine whether events and circumstances warrant a revision to the remaining period of amortization. If the estimate of an intangible asset’s remaining useful life has changed, the remaining carrying amount of the intangible asset is amortized prospectively over the revised remaining useful life. The Company has not revised its estimates of the useful lives of its core deposit intangibles during the three months ended March 31, 2018 and 2017 . Other assets acquired through foreclosure Other assets acquired through foreclosure consist primarily of properties acquired as a result of, or in-lieu-of, foreclosure. Properties or other assets (primarily repossessed assets formerly leased) are classified as OREO and other repossessed property and are initially reported at fair value of the asset less estimated selling costs. Subsequent adjustments are based on the lower of carrying value or fair value less estimated costs to sell the property. Costs related to the development or improvement of the assets are capitalized and costs related to holding the assets are charged to non-interest expense. Property is evaluated regularly to ensure the recorded amount is supported by its current fair value and valuation allowances. Treasury shares The Company separately presents treasury shares, which represent shares surrendered to the Company equal in value to the statutory payroll tax withholding obligations arising from the vesting of employee restricted stock awards. Treasury shares are carried at cost. Derivative financial instruments The Company uses interest-rate swaps to mitigate interest-rate risk associated with changes to 1) the fair value of certain fixed-rate financial instruments (fair value hedges) and 2) certain cash flows related to future interest payments on variable rate financial instruments (cash flow hedges). The Company recognizes derivatives as assets or liabilities in the Consolidated Balance Sheet at their fair value in accordance with ASC 815, Derivatives and Hedging . The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and further, on the type of hedging relationship. On the date the derivative contract is entered into, the Company designates the derivative as a fair value hedge or cash flow hedge. Derivative instruments designated in a hedge relationship to mitigate exposure to changes in the fair value of an asset or liability attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivative instruments designated in a hedge relationship to mitigate exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. Changes in the fair value of a derivative that is designated and qualifies as a fair value hedge, along with changes in the fair value of the hedged asset or liability that are attributable to the hedged risk are recorded in current-period earnings. For a cash flow hedge, the effective portion of the change in the fair value of the derivative is recorded in AOCI and reclassified into earnings in the same period or periods during which the hedged transaction affects earnings. Any ineffective portion of the change in fair value of a cash flow hedge is recognized immediately in non-interest income in the Consolidated Income Statement. Under both the fair value and cash flow hedge scenarios, changes in the fair value of derivatives not considered to be highly effective in hedging the change in fair value or the expected cash flows of the hedged item are recognized in earnings as non-interest income during the period of the change. The Company documents its hedge relationships, including identification of the hedging instruments and the hedged items, as well as its risk management objectives and strategies for undertaking the hedge transaction at the time the derivative contract is executed. Both at inception and at least quarterly thereafter, the Company assesses whether the derivatives used in hedging transactions are highly effective (as defined in the guidance) in offsetting changes in either the fair value or cash flows of the hedged item. Retroactive effectiveness is assessed, as well as the continued expectation that the hedge will remain effective prospectively. The Company discontinues hedge accounting prospectively when it is determined that a hedge is no longer highly effective. When hedge accounting is discontinued on a fair value hedge that no longer qualifies as an effective hedge, the derivative continues to be reported at fair value in the Consolidated Balance Sheet, but the carrying amount of the hedged item is no longer adjusted for future changes in fair value. The adjustment to the carrying amount of the hedged item that existed at the date hedge accounting is discontinued is amortized over the remaining life of the hedged item into earnings. Derivative instruments that are not designated as hedges, so called free-standing derivatives, are reported in the Consolidated Balance Sheet at fair value and the changes in fair value are recognized in earnings as non-interest income during the period of change. The Company may in the normal course of business purchase a financial instrument or originate a loan that contains an embedded derivative instrument. Upon purchasing the instrument or originating the loan, the Company assesses whether the economic characteristics of the embedded derivative are clearly and closely related to the economic characteristics of the remaining component of the financial instrument (i.e., the host contract) and whether a separate instrument with the same terms as the embedded instrument would meet the definition of a derivative instrument. When it is determined that the embedded derivative possesses economic characteristics that are not clearly and closely related to the economic characteristics of the host contract and a separate instrument with the same terms would qualify as a derivative instrument, the embedded derivative is separated from the host contract and carried at fair value. However, in cases where the host contract is measured at fair value, with changes in fair value reported in current earnings, or the Company is unable to reliably identify and measure an embedded derivative for separation from its host contract, the entire contract is carried in the Consolidated Balance Sheet at fair value and is not designated as a hedging instrument. Off-balance sheet instruments In the ordinary course of business, the Company has entered into off-balance sheet financial instrument arrangements consisting of commitments to extend credit and standby letters of credit. Such financial instruments are recorded in the Consolidated Financial Statements when they are funded. They involve, to varying degrees, elements of credit risk in excess of amounts recognized in the Consolidated Balance Sheet. Losses would be experienced when the Company is contractually obligated to make a payment under these instruments and must seek repayment from the borrower, which may not be as financially sound in the current period as they were when the commitment was originally made. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. The Company enters into credit arrangements that generally provide for the termination of advances in the event of a covenant violation or other event of default. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer’s creditworthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the Company upon extension of credit, is based on management’s credit evaluation of the party. The commitments are collateralized by the same types of assets used as loan collateral. As with outstanding loans, the Company applies qualitative factors and utilization rates to its off-balance sheet obligations in determining an estimate of losses inherent in these contractual obligations. The estimate for credit losses on off-balance sheet instruments is included in other liabilities and the charge to income that establishes this liability is included in non-interest expense. The Company also has off-balance sheet arrangements related to its derivative instruments. Derivative instruments are recognized in the Consolidated Financial Statements at fair value and their notional values are carried off-balance sheet. See " Note 9. Derivatives and Hedging Activities " of these Notes to Unaudited Consolidated Financial Statements for further discussion. Business combinations Business combinations are accounted for under the acquisition method of accounting in accordance with ASC 805, Business Combinations. Under the acquisition method, the acquiring entity in a business combination recognizes all of the acquired assets and assumed liabilities at their estimated fair values as of the date of acquisition. Any excess of the purchase price over the fair value of net assets and other identifiable intangible assets acquired is recorded as goodwill. To the extent the fair value of net assets acquired, including identified intangible assets, exceeds the purchase price, a bargain purchase gain is recognized. Changes to estimated fair values from a business combination are recognized as an adjustment to goodwill during the measurement period and are recognized in the proper reporting period in which the adjustment amounts are determined. Results of operations of an acquired business are included in the Consolidated Income Statement from the date of acquisition. Acquisition-related costs, including conversion and restructuring charges, are expensed as incurred. Fair values of financial instruments The Company uses fair value measurements to record fair value adjustments to certain assets and liabilities. ASC 820, Fair Value Measurement , establishes a framework for measuring fair value and a three-level valuation hierarchy for disclosure of fair value measurement, as well as enhances disclosure requirements for fair value measurements. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. The Company uses various valuation approaches, including market, income, and/or cost approaches. ASC 820 establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability developed based on market data obtained from sources independent of the Company.

Investment Securities

Investment Securities	3 Months Ended
Investment Securities	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investment Securities	The carrying amounts and fair values of investment securities at March 31, 2018 and December 31, 2017 are summarized as follows: March 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (in thousands) Held-to-maturity Tax-exempt $ 262,304 $ 795 $ (7,681 ) $ 255,418 Available-for-sale CDO $ 50 $ 19,403 $ — $ 19,453 Commercial MBS issued by GSEs 110,347 60 (5,434 ) 104,973 Corporate debt securities 105,040 140 (3,504 ) 101,676 CRA investments 51,771 — (925 ) 50,846 Preferred stock 92,959 1,191 (832 ) 93,318 Private label residential MBS 839,655 32 (20,691 ) 818,996 Residential MBS issued by GSEs 1,676,686 210 (49,997 ) 1,626,899 Tax-exempt 499,045 6,083 (7,207 ) 497,921 Trust preferred securities 32,000 — (3,383 ) 28,617 U.S. government sponsored agency securities 64,000 — (3,710 ) 60,290 U.S. treasury securities 2,496 — (23 ) 2,473 Total AFS securities $ 3,474,049 $ 27,119 $ (95,706 ) $ 3,405,462 December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (in thousands) Held-to-maturity Tax-exempt $ 255,050 $ 4,514 $ (3,250 ) $ 256,314 Available-for-sale CDO $ 50 $ 21,807 $ — $ 21,857 Commercial MBS issued by GSEs 113,069 46 (4,038 ) 109,077 Corporate debt securities 105,044 261 (1,822 ) 103,483 CRA investments 51,133 — (517 ) 50,616 Preferred stock 52,172 1,160 (136 ) 53,196 Private label residential MBS 874,261 756 (6,493 ) 868,524 Residential MBS issued by GSEs 1,719,188 810 (30,703 ) 1,689,295 Tax-exempt 501,988 10,893 (1,971 ) 510,910 Trust preferred securities 32,000 — (3,383 ) 28,617 U.S. government sponsored agency securities 64,000 — (2,538 ) 61,462 U.S. treasury securities 2,496 — (14 ) 2,482 Total AFS securities $ 3,515,401 $ 35,733 $ (51,615 ) $ 3,499,519 The Company conducts an OTTI analysis on a quarterly basis. The initial indication of OTTI for both debt and equity securities is a decline in the market value below the amount recorded for an investment, and taking into account the severity and duration of the decline. Another potential indication of OTTI is a downgrade below investment grade. In determining whether an impairment is OTTI, the Company considers the length of time and the extent to which the market value has been below cost, recent events specific to the issuer, including investment downgrades by rating agencies and economic conditions of its industry, and the Company’s ability and intent to hold the investment for a period of time sufficient to allow for any anticipated recovery. For marketable equity securities, the Company also considers the issuer’s financial condition, capital strength, and near-term prospects. For debt securities, for the purpose of an OTTI analysis, the Company also considers the cause of the price decline (general level of interest rates, credit spreads, and industry and issuer-specific factors), the issuer’s financial condition, near-term prospects, and current ability to make future payments in a timely manner, as well as the issuer’s ability to service debt, and any change in agencies’ ratings at the evaluation date from the acquisition date and any likely imminent action. The Company has reviewed securities for which there is an unrealized loss in accordance with its accounting policy for OTTI described above and determined that there are no impairment charges for the three months ended March 31, 2018 and 2017 . The Company does not consider any securities to be other-than-temporarily impaired as of March 31, 2018 and December 31, 2017 . No assurance can be made that OTTI will not occur in future periods. Information pertaining to securities with gross unrealized losses at March 31, 2018 and December 31, 2017 , aggregated by investment category and length of time that individual securities have been in a continuous loss position follows: March 31, 2018 Less Than Twelve Months More Than Twelve Months Total Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (in thousands) Held-to-Maturity Tax-exempt $ 7,681 $ 208,272 $ — $ — $ 7,681 $ 208,272 Available-for-sale Commercial MBS issued by GSEs $ 262 $ 11,999 $ 5,172 $ 91,109 $ 5,434 $ 103,108 Corporate debt securities 2,200 57,799 1,304 38,696 3,504 96,495 CRA investments — — 925 50,846 925 50,846 Preferred stock 832 47,808 — — 832 47,808 Private label residential MBS 13,613 625,316 7,078 188,584 20,691 813,900 Residential MBS issued by GSEs 25,817 1,096,496 24,180 512,464 49,997 1,608,960 Tax-exempt 3,278 173,905 3,929 67,415 7,207 241,320 Trust preferred securities — — 3,383 28,617 3,383 28,617 U.S. government sponsored agency securities 94 4,906 3,616 55,384 3,710 60,290 U.S. treasury securities 23 2,473 — — 23 2,473 Total AFS securities $ 46,119 $ 2,020,702 $ 49,587 $ 1,033,115 $ 95,706 $ 3,053,817 December 31, 2017 Less Than Twelve Months More Than Twelve Months Total Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (in thousands) Held-to-maturity Tax-exempt $ 3,250 $ 107,921 $ — $ — $ 3,250 $ 107,921 Available-for-sale Commercial MBS issued by GSEs $ 161 $ 13,565 $ 3,877 $ 93,641 $ 4,038 $ 107,206 Corporate debt securities 1,398 78,602 424 19,576 1,822 98,178 CRA investments — — 517 50,616 517 50,616 Preferred stock 136 7,357 — — 136 7,357 Private label residential MBS 3,115 480,885 3,378 188,710 6,493 669,595 Residential MBS issued by GSEs 13,875 999,478 16,828 523,270 30,703 1,522,748 Tax-exempt 17 6,159 1,954 69,674 1,971 75,833 Trust preferred securities — — 3,383 28,617 3,383 28,617 U.S. government sponsored agency securities 14 4,986 2,524 56,476 2,538 61,462 U.S. treasury securities 14 2,482 — — 14 2,482 Total AFS securities $ 18,730 $ 1,593,514 $ 32,885 $ 1,030,580 $ 51,615 $ 2,624,094 At March 31, 2018 and December 31, 2017 , the Company’s unrealized losses relate primarily to market interest rate increases since the securities' original purchase date. The total number of securities in an unrealized loss position at March 31, 2018 is 401 , compared to 302 at December 31, 2017 . In analyzing an issuer’s financial condition, management considers whether the securities are issued by the federal government or its agencies, whether downgrades by bond rating agencies have occurred, and industry analysis reports. Since material downgrades have not occurred and management does not intend to sell the debt securities in an unrealized loss position in the foreseeable future, none of the securities described in the above table or in this paragraph are deemed to be OTTI. The amortized cost and fair value of securities as of March 31, 2018 , by contractual maturities, are shown below. MBS are shown separately as individual MBS are comprised of pools of loans with varying maturities. Therefore, these securities are listed separately in the maturity summary. March 31, 2018 Amortized Cost Estimated Fair Value (in thousands) Held-to-maturity Due in one year or less $ 1,200 $ 1,208 After one year through five years 10,100 10,206 After five years through ten years 14,847 14,475 After ten years 236,157 229,529 Total HTM securities $ 262,304 $ 255,418 Available-for-sale Due in one year or less $ 55,801 $ 54,879 After one year through five years 15,947 16,242 After five years through ten years 256,070 251,220 After ten years 519,543 532,253 Mortgage-backed securities 2,626,688 2,550,868 Total AFS securities $ 3,474,049 $ 3,405,462 The following tables summarize the carrying amount of the Company’s investment ratings position as of March 31, 2018 and December 31, 2017 : March 31, 2018 AAA Split-rated AAA/AA+ AA+ to AA- A+ to A- BBB+ to BBB- BB+ and below Unrated Totals (in thousands) Held-to-maturity Tax-exempt $ — $ — $ — $ — $ — $ — $ 262,304 $ 262,304 Available-for-sale CDO $ — $ — $ — $ — $ — $ 19,453 $ — $ 19,453 Commercial MBS issued by GSEs — 104,973 — — — — — 104,973 Corporate debt securities — — — 72,747 28,929 — — 101,676 CRA investments — 25,078 — — — — 25,768 50,846 Preferred stock — — — 10,118 64,444 4,031 14,725 93,318 Private label residential MBS 748,064 — 67,405 998 879 1,650 — 818,996 Residential MBS issued by GSEs — 1,626,899 — — — — — 1,626,899 Tax-exempt 62,746 24,635 243,818 163,250 — — 3,472 497,921 Trust preferred securities — — — — 28,617 — — 28,617 U.S. government sponsored agency securities — 60,290 — — — — — 60,290 U.S. treasury securities — 2,473 — — — — — 2,473 Total AFS securities (1) $ 810,810 $ 1,844,348 $ 311,223 $ 247,113 $ 122,869 $ 25,134 $ 43,965 $ 3,405,462 (1) Where ratings differ, the Company uses an average of the available ratings by major credit agencies. December 31, 2017 AAA Split-rated AAA/AA+ AA+ to AA- A+ to A- BBB+ to BBB- BB+ and below Unrated Totals (in thousands) Held-to-maturity Tax-exempt $ — $ — $ — $ — $ — $ — $ 255,050 $ 255,050 Available-for-sale CDO $ — $ — $ — $ — $ — $ 21,857 $ — $ 21,857 Commercial MBS issued by GSEs — 109,077 — — — — — 109,077 Corporate debt securities — — — 74,293 29,190 — — 103,483 CRA investments — 25,349 — — — — 25,267 50,616 Preferred stock — — — 10,388 23,822 4,104 14,882 53,196 Private label residential MBS 809,242 — 55,161 1,350 931 1,840 — 868,524 Residential MBS issued by GSEs — 1,689,295 — — — — — 1,689,295 Tax-exempt 64,893 25,280 249,200 167,994 — — 3,543 510,910 Trust preferred securities — — — — 28,617 — — 28,617 U.S. government sponsored agency securities — 61,462 — — — — — 61,462 U.S. treasury securities — 2,482 — — — — — 2,482 Total AFS securities (1) $ 874,135 $ 1,912,945 $ 304,361 $ 254,025 $ 82,560 $ 27,801 $ 43,692 $ 3,499,519 (1) Where ratings differ, the Company uses an average of the available ratings by major credit agencies. Securities with carrying amounts of approximately $1.01 billion and $913.7 million at March 31, 2018 and December 31, 2017 , respectively, were pledged for various purposes as required or permitted by law. The following table presents gross gains and losses on sales of investment securities: Three Months Ended March 31, 2018 2017 (in thousands) Gross gains $ — $ 636 Gross losses — (1 ) Net gains on sales of investment securities $ — $ 635

Loans, Leases and Allowance for

Loans, Leases and Allowance for Credit Losses	3 Months Ended
Loans, Leases and Allowance for Credit Losses	Mar. 31, 2018
Receivables [Abstract]
Loans, Leases and Allowance for Credit Losses	The composition of the Company’s held for investment loan portfolio is as follows: March 31, 2018 December 31, 2017 (in thousands) Commercial and industrial $ 6,944,381 $ 6,841,381 Commercial real estate - non-owner occupied 3,925,301 3,904,011 Commercial real estate - owner occupied 2,264,650 2,241,613 Construction and land development 1,957,489 1,632,204 Residential real estate 418,127 425,940 Consumer 50,505 48,786 Loans, net of deferred loan fees and costs 15,560,453 15,093,935 Allowance for credit losses (144,659 ) (140,050 ) Total loans HFI $ 15,415,794 $ 14,953,885 Net deferred loan fees and costs as of March 31, 2018 and December 31, 2017 total $32.6 million and $25.3 million , respectively, which is a reduction in the carrying value of loans. Net unamortized purchase discounts on secondary market loan purchases total $8.0 million and $8.5 million as of March 31, 2018 and December 31, 2017 , respectively. Total loans held for investment are also net of interest rate and credit marks on acquired loans, which are a net reduction in the carrying value of loans. Interest rate marks were $13.0 million and $14.1 million as of March 31, 2018 and December 31, 2017 , respectively. Credit marks were $23.1 million and $27.0 million as of March 31, 2018 and December 31, 2017 , respectively. The following table presents the contractual aging of the recorded investment in past due loans held for investment by class of loans: March 31, 2018 Current 30-59 Days 60-89 Days Over 90 Days Past Due Total Total (in thousands) Commercial and industrial $ 6,932,086 $ 5,094 $ 4,970 $ 2,231 $ 12,295 $ 6,944,381 Commercial real estate Owner occupied 2,263,102 1,418 — 130 1,548 2,264,650 Non-owner occupied 3,732,372 — — 2,799 2,799 3,735,171 Multi-family 190,130 — — — — 190,130 Construction and land development Construction 1,259,939 — — — — 1,259,939 Land 697,550 — — — — 697,550 Residential real estate 413,726 1,397 — 3,004 4,401 418,127 Consumer 49,907 — 259 339 598 50,505 Total loans $ 15,538,812 $ 7,909 $ 5,229 $ 8,503 $ 21,641 $ 15,560,453 December 31, 2017 Current 30-59 Days 60-89 Days Over 90 days Total Total (in thousands) Commercial and industrial $ 6,835,385 $ 2,245 $ 669 $ 3,082 $ 5,996 $ 6,841,381 Commercial real estate Owner occupied 2,240,457 1,026 — 130 1,156 2,241,613 Non-owner occupied 3,696,729 2,993 — 2,847 5,840 3,702,569 Multi-family 201,442 — — — — 201,442 Construction and land development Construction 1,090,176 — — — — 1,090,176 Land 536,917 — — 5,111 5,111 542,028 Residential real estate 411,857 6,874 1,487 5,722 14,083 425,940 Consumer 48,408 83 213 82 378 48,786 Total loans $ 15,061,371 $ 13,221 $ 2,369 $ 16,974 $ 32,564 $ 15,093,935 The following table presents the recorded investment in non-accrual loans and loans past due ninety days or more and still accruing interest by class of loans: March 31, 2018 December 31, 2017 Non-accrual loans Loans past due 90 days or more and still accruing Non-accrual loans Loans past due 90 days or more and still accruing Current Past Due/ Total Current Past Due/ Total (in thousands) Commercial and industrial $ 16,103 $ 8,081 $ 24,184 $ 37 $ 17,913 $ 4,113 $ 22,026 $ 43 Commercial real estate Owner occupied — 131 131 — 1,089 792 1,881 — Non-owner occupied — 2,799 2,799 — — 5,840 5,840 — Multi-family — — — — — — — — Construction and land development Construction — — — — — — — — Land — — — — 868 5,111 5,979 — Residential real estate 6,127 3,717 9,844 — 2,039 6,078 8,117 — Consumer — 339 339 — — 82 82 — Total $ 22,230 $ 15,067 $ 37,297 $ 37 $ 21,909 $ 22,016 $ 43,925 $ 43 The reduction in interest income associated with loans on non-accrual status was approximately $0.6 million for each of the three months ended March 31, 2018 and 2017 . The Company utilizes an internal asset classification system as a means of reporting problem and potential problem loans. Under the Company’s risk rating system, the Company classifies problem and potential problem loans as Special Mention, Substandard, Doubtful, and Loss. Substandard loans include those characterized by well-defined weaknesses and carry the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. Loans classified as Doubtful, or risk rated nine, have all the weaknesses inherent in those classified as Substandard with the added characteristic that the weaknesses present make collection or liquidation in full, on the basis of currently existing facts, conditions and values, highly questionable and improbable. The final rating of Loss covers loans considered uncollectible and having such little recoverable value that it is not practical to defer writing off the asset. Loans that do not currently expose the Company to sufficient risk to warrant classification in one of the aforementioned categories, but possess weaknesses that warrant management’s close attention, are deemed to be Special Mention. Risk ratings are updated, at a minimum, quarterly. The following tables present gross loans by risk rating: March 31, 2018 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Commercial and industrial $ 6,756,803 $ 100,928 $ 82,499 $ 4,151 $ — $ 6,944,381 Commercial real estate Owner occupied 2,168,305 42,472 53,232 641 — 2,264,650 Non-owner occupied 3,696,971 26,716 11,484 — — 3,735,171 Multi-family 190,130 — — — — 190,130 Construction and land development Construction 1,255,462 4,477 — — — 1,259,939 Land 695,821 905 824 — — 697,550 Residential real estate 398,814 9,146 10,167 — — 418,127 Consumer 49,613 58 834 — — 50,505 Total $ 15,211,919 $ 184,702 $ 159,040 $ 4,792 $ — $ 15,560,453 March 31, 2018 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Current (up to 29 days past due) $ 15,206,755 $ 184,306 $ 143,622 $ 4,129 $ — $ 15,538,812 Past due 30 - 59 days 5,091 374 2,444 — — 7,909 Past due 60 - 89 days 73 22 5,134 — — 5,229 Past due 90 days or more — — 7,840 663 — 8,503 Total $ 15,211,919 $ 184,702 $ 159,040 $ 4,792 $ — $ 15,560,453 December 31, 2017 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Commercial and industrial $ 6,675,574 $ 85,781 $ 76,328 $ 3,698 $ — $ 6,841,381 Commercial real estate Owner occupied 2,149,465 43,122 48,397 629 — 2,241,613 Non-owner occupied 3,676,711 11,166 14,692 — — 3,702,569 Multi-family 201,442 — — — — 201,442 Construction and land development Construction 1,072,342 4,477 13,357 — — 1,090,176 Land 535,412 637 5,979 — — 542,028 Residential real estate 408,527 8,971 8,442 — — 425,940 Consumer 47,824 878 84 — — 48,786 Total $ 14,767,297 $ 155,032 $ 167,279 $ 4,327 $ — $ 15,093,935 December 31, 2017 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Current (up to 29 days past due) $ 14,758,149 $ 154,295 $ 145,934 $ 2,993 $ — $ 15,061,371 Past due 30 - 59 days 7,966 518 4,737 — — 13,221 Past due 60 - 89 days 1,182 219 968 — — 2,369 Past due 90 days or more — — 15,640 1,334 — 16,974 Total $ 14,767,297 $ 155,032 $ 167,279 $ 4,327 $ — $ 15,093,935 The table below reflects the recorded investment in loans classified as impaired: March 31, 2018 December 31, 2017 (in thousands) Impaired loans with a specific valuation allowance under ASC 310 (1) $ 9,598 $ 19,315 Impaired loans without a specific valuation allowance under ASC 310 (2) 87,994 79,239 Total impaired loans $ 97,592 $ 98,554 Valuation allowance related to impaired loans (3) $ (5,562 ) $ (5,606 ) (1) Includes TDR loans of $3.0 million and $3.7 million at March 31, 2018 and December 31, 2017 , respectively. (2) Includes TDR loans of $48.2 million and $48.8 million at March 31, 2018 and December 31, 2017 , respectively. (3) Includes valuation allowance related to TDR loans of $1.0 million and $1.2 million at March 31, 2018 and December 31, 2017 , respectively. The following table presents impaired loans by class: March 31, 2018 December 31, 2017 (in thousands) Commercial and industrial $ 43,459 $ 34,156 Commercial real estate Owner occupied 8,107 10,430 Non-owner occupied 17,654 21,251 Multi-family — — Construction and land development Construction — — Land 9,812 15,426 Residential real estate 18,185 17,170 Consumer 375 121 Total $ 97,592 $ 98,554 A valuation allowance is established for an impaired loan when the fair value of the loan is less than the recorded investment. In certain cases, portions of impaired loans are charged-off to realizable value instead of establishing a valuation allowance and are included, when applicable, in the table above as “Impaired loans without a specific valuation allowance under ASC 310.” However, before concluding that an impaired loan needs no associated valuation allowance, an assessment is made to consider all available and relevant information for the method used to evaluate impairment and the type of loan being assessed. The valuation allowance disclosed above is included in the allowance for credit losses reported in the Consolidated Balance Sheets as of March 31, 2018 and December 31, 2017 . The following table presents the average investment in impaired loans and income recognized on impaired loans: Three Months Ended March 31, 2018 2017 (in thousands) Average balance on impaired loans $ 93,081 $ 103,387 Interest income recognized on impaired loans 873 921 Interest recognized on non-accrual loans, cash basis 438 332 The following table presents the average investment in impaired loans by loan class: Three Months Ended March 31, 2018 2017 (in thousands) Commercial and industrial $ 36,849 $ 26,101 Commercial real estate Owner occupied 9,043 21,128 Non-owner occupied 18,925 24,399 Multi-family — — Construction and land development Construction — — Land 10,281 14,432 Residential real estate 17,799 17,103 Consumer 184 224 Total $ 93,081 $ 103,387 The average investment in TDR loans was $48.3 million and $60.4 million for the three months ended March 31, 2018 and 2017 , respectively. The following table presents interest income on impaired loans by class: Three Months Ended March 31, 2018 2017 (in thousands) Commercial and industrial $ 250 $ 144 Commercial real estate Owner occupied 127 177 Non-owner occupied 262 239 Multi-family — — Construction and land development Construction — — Land 130 221 Residential real estate 104 139 Consumer — 1 Total $ 873 $ 921 The Company is not committed to lend significant additional funds on these impaired loans. The following table summarizes nonperforming assets: March 31, 2018 December 31, 2017 (in thousands) Non-accrual loans (1) $ 37,297 $ 43,925 Loans past due 90 days or more on accrual status (2) 37 43 Accruing troubled debt restructured loans 43,766 42,431 Total nonperforming loans 81,100 86,399 Other assets acquired through foreclosure, net 30,194 28,540 Total nonperforming assets $ 111,294 $ 114,939 (1) Includes non-accrual TDR loans of $7.4 million and $10.1 million at March 31, 2018 and December 31, 2017 , respectively. (2) Includes less than $0.1 million from loans acquired with deteriorated credit quality at each of the periods ended March 31, 2018 and December 31, 2017 . Loans Acquired with Deteriorated Credit Quality Changes in the accretable yield for loans acquired with deteriorated credit quality are as follows: Three Months Ended March 31, 2018 2017 (in thousands) Balance, at beginning of period $ 9,324 $ 15,177 Reclassifications from non-accretable to accretable yield (1) 683 — Accretion to interest income (313 ) (907 ) Reversal of fair value adjustments upon disposition of loans (1,586 ) (458 ) Balance, at end of period $ 8,108 $ 13,812 (1) The primary drivers of reclassification from non-accretable to accretable yield resulted from changes in estimated cash flows. Allowance for Credit Losses The following table summarizes the changes in the allowance for credit losses by portfolio type: Three Months Ended March 31, Construction and Land Development Commercial Real Estate Residential Real Estate Commercial and Industrial Consumer Total (in thousands) 2018 Beginning Balance $ 19,511 $ 31,495 $ 5,478 $ 82,793 $ 773 $ 140,050 Charge-offs — — 107 3,517 — 3,624 Recoveries (1,388 ) (126 ) (250 ) (459 ) (10 ) (2,233 ) Provision 1,695 1,247 (102 ) 3,143 17 6,000 Ending balance $ 22,594 $ 32,868 $ 5,519 $ 82,878 $ 800 $ 144,659 2017 Beginning Balance $ 21,175 $ 25,673 $ 3,851 $ 73,333 $ 672 $ 124,704 Charge-offs — — 115 2,594 34 2,743 Recoveries (277 ) (533 ) (251 ) (328 ) (49 ) (1,438 ) Provision (355 ) 1,798 425 2,362 20 4,250 Ending balance $ 21,097 $ 28,004 $ 4,412 $ 73,429 $ 707 $ 127,649 The following table presents impairment method information related to loans and allowance for credit losses by loan portfolio segment: Commercial Real Estate-Owner Occupied Commercial Real Estate-Non-Owner Occupied Commercial and Industrial Residential Real Estate Construction and Land Development Consumer Total Loans (in thousands) Loans as of March 31, 2018; Recorded Investment Impaired loans with an allowance recorded $ — $ — $ 9,425 $ 173 $ — $ — $ 9,598 Impaired loans with no allowance recorded 8,107 17,654 34,034 18,012 9,812 375 87,994 Total loans individually evaluated for impairment 8,107 17,654 43,459 18,185 9,812 375 97,592 Loans collectively evaluated for impairment 2,248,803 3,805,229 6,900,885 399,346 1,947,677 50,130 15,352,070 Loans acquired with deteriorated credit quality 7,740 102,418 37 596 — — 110,791 Total recorded investment $ 2,264,650 $ 3,925,301 $ 6,944,381 $ 418,127 $ 1,957,489 $ 50,505 $ 15,560,453 Unpaid Principal Balance Impaired loans with an allowance recorded $ — $ — $ 12,250 $ 173 $ — $ — $ 12,423 Impaired loans with no allowance recorded 15,029 24,431 63,541 26,801 26,440 10,950 167,192 Total loans individually evaluated for impairment 15,029 24,431 75,791 26,974 26,440 10,950 179,615 Loans collectively evaluated for impairment 2,248,803 3,805,229 6,900,885 399,346 1,947,677 50,130 15,352,070 Loans acquired with deteriorated credit quality 9,945 124,803 4,412 715 — — 139,875 Total unpaid principal balance $ 2,273,777 $ 3,954,463 $ 6,981,088 $ 427,035 $ 1,974,117 $ 61,080 $ 15,671,560 Related Allowance for Credit Losses Impaired loans with an allowance recorded $ — $ — $ 5,389 $ 173 $ — $ — $ 5,562 Impaired loans with no allowance recorded — — — — — — — Total loans individually evaluated for impairment — — 5,389 173 — — 5,562 Loans collectively evaluated for impairment 14,475 17,566 77,487 5,346 22,594 800 138,268 Loans acquired with deteriorated credit quality — 827 2 — — — 829 Total allowance for credit losses $ 14,475 $ 18,393 $ 82,878 $ 5,519 $ 22,594 $ 800 $ 144,659 Commercial Real Estate-Owner Occupied Commercial Real Estate-Non-Owner Occupied Commercial and Industrial Residential Real Estate Construction and Land Development Consumer Total Loans (in thousands) Loans as of December 31, 2017; Recorded Investment Impaired loans with an allowance recorded $ — $ — $ 19,315 $ — $ — $ — $ 19,315 Impaired loans with no allowance recorded 10,430 21,250 14,842 17,170 15,426 121 79,239 Total loans individually evaluated for impairment 10,430 21,250 34,157 17,170 15,426 121 98,554 Loans collectively evaluated for impairment 2,221,614 3,777,219 6,807,181 408,169 1,616,778 48,665 14,879,626 Loans acquired with deteriorated credit quality 9,569 105,542 43 601 — — 115,755 Total recorded investment $ 2,241,613 $ 3,904,011 $ 6,841,381 $ 425,940 $ 1,632,204 $ 48,786 $ 15,093,935 Unpaid Principal Balance Impaired loans with an allowance recorded $ — $ — $ 20,795 $ — $ — $ — $ 20,795 Impaired loans with no allowance recorded 17,459 28,028 42,261 26,057 32,289 10,695 156,789 Total loans individually evaluated for impairment 17,459 28,028 63,056 26,057 32,289 10,695 177,584 Loans collectively evaluated for impairment 2,221,614 3,777,219 6,807,181 408,169 1,616,778 48,665 14,879,626 Loans acquired with deteriorated credit quality 12,619 128,440 3,146 720 — — 144,925 Total unpaid principal balance $ 2,251,692 $ 3,933,687 $ 6,873,383 $ 434,946 $ 1,649,067 $ 59,360 $ 15,202,135 Related Allowance for Credit Losses Impaired loans with an allowance recorded $ — $ — $ 5,606 $ — $ — $ — $ 5,606 Impaired loans with no allowance recorded — — — — — — — Total loans individually evaluated for impairment — — 5,606 — — — 5,606 Loans collectively evaluated for impairment 13,884 16,135 76,919 5,500 19,599 776 132,813 Loans acquired with deteriorated credit quality — 1,629 2 — — — 1,631 Total allowance for credit losses $ 13,884 $ 17,764 $ 82,527 $ 5,500 $ 19,599 $ 776 $ 140,050 Troubled Debt Restructurings A TDR loan is a loan on which the Company, for reasons related to a borrower’s financial difficulties, grants a concession to the borrower that the Company would not otherwise consider. The loan terms that have been modified or restructured due to a borrower’s financial situation include, but are not limited to, a reduction in the stated interest rate, an extension of the maturity or renewal of the loan at an interest rate below current market, a reduction in the face amount of the debt, a reduction in the accrued interest, or deferral of interest payments. The majority of the Company's modifications are extensions in terms or deferral of payments which result in no lost principal or interest followed by reductions in interest rates or accrued interest. A TDR loan is also considered impaired. Consistent with regulatory guidance, a TDR loan that is subsequently modified in another restructuring agreement but has shown sustained performance and classification as a TDR, will be removed from TDR status provided that the modified terms were market-based at the time of modification. During the three months ended March 31, 2018 , the Company had five new TDR loans with a recorded investment of $15.0 million and one new TDR loan with a recorded investment of $4.9 million during the three months ended March 31, 2017 . No principal amounts were forgiven and there were no waived fees or other expenses resulting from the TDRs during the three months ended March 31, 2018 and 2017 . During the three months ended March 31, 2018 , there were no TDR loans for which there was a payment default. During the three months ended March 31, 2017 , there was one commercial and industrial TDR loan with a recorded investment of $0.1 million for which there was a payment default. A TDR loan is deemed to have a payment default when it becomes past due 90 days, goes on non-accrual, or is restructured again. Payment defaults, along with other qualitative indicators, are considered by management in the determination of the allowance for credit losses. At March 31, 2018 , th ere was one commercial and industrial loan commitment outstanding on TDR loans for less than $0.1 million and at December 31, 2017 there were no loan commitments outstanding on TDR loans. Loan Purchases and Sales For the three months ended March 31, 2018 and 2017 , secondary market loan purchases totaled $141.5 million and $253.3 million , respectively. For 2018 , these purchased loans consisted of $118.3 million of commercial and industrial loans and $23.2 million of residential real estate loans. For 2017 , these purchased loans consisted of $200.3 million of commercial and industrial loans and $53.0 million of residential real estate loans. During the three months ended March 31, 2018 , the Company sold loans which primarily consisted of commercial and industrial loans with a carrying value of $31.0 million and recognized a net gain of $0.7 million . During the three months ended March 31, 2017 , the Company sold CRE loans with a carrying value of $9.2 million and recognized a loss of less than of $0.1 million on the sales.

Other Assets Acquired Through F

Other Assets Acquired Through Foreclosure	3 Months Ended
Other Assets Acquired Through Foreclosure	Mar. 31, 2018
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Other Assets Acquired Through Foreclosure	The following table represents the changes in other assets acquired through foreclosure: Three Months Ended March 31, 2018 Gross Balance Valuation Allowance Net Balance (in thousands) Balance, beginning of period $ 32,552 $ (4,012 ) $ 28,540 Transfers to other assets acquired through foreclosure, net 5,744 — 5,744 Proceeds from sale of other real estate owned and repossessed assets, net (5,294 ) 9 (5,285 ) Valuation adjustments, net — (47 ) (47 ) Gains (losses), net (1) 1,242 1,242 Balance, end of period $ 34,244 $ (4,050 ) $ 30,194 Three Months Ended March 31, 2017 Balance, beginning of period $ 54,138 $ (6,323 ) $ 47,815 Proceeds from sale of other real estate owned and repossessed assets, net (3,113 ) 224 (2,889 ) Valuation adjustments, net — 380 380 Gains (losses), net (1) (106 ) — (106 ) Balance, end of period $ 50,919 $ (5,719 ) $ 45,200 (1) There was $1.0 million in net gains related to initial transfers to other assets during the three months ended March 31, 2018 and compared to zero during the three months ended March 31, 2017 . At March 31, 2018 and 2017 , the majority of the Company’s repossessed assets consisted of properties located in Nevada. The Company held 18 properties at March 31, 2018 , compared to 19 at December 31, 2017 , and 25 at March 31, 2017 .

Other Borrowings

Other Borrowings	3 Months Ended
Other Borrowings	Mar. 31, 2018
Debt Disclosure [Abstract]
Other Borrowings	The following table summarizes the Company’s borrowings as of March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (in thousands) Short-Term: FHLB advances $ 300,000 $ 390,000 Total short-term borrowings $ 300,000 $ 390,000 The Company maintains other lines of credit with correspondent banks totaling $145.0 million . These lines of credit are unsecured, of which $45.0 million has a floating interest rate of one-month LIBOR plus 3.25% and $100.0 million has a rate equivalent to the federal funds effective rate. As of March 31, 2018 and December 31, 2017 , there were no outstanding balances on the Company's lines of credit. The Company maintains lines of credit with the FHLB and the FRB. The Company’s borrowing capacity is determined based on collateral pledged, generally consisting of investment securities and loans, at the time of the borrowing. At March 31, 2018 , the Company had $300.0 million in short-term FHLB overnight advances with an interest rate of 1.87% . At December 31, 2017 , short-term FHLB advances of $390.0 million had an interest rate of 1.41% . As of March 31, 2018 and December 31, 2017 , the Company had additional available credit with the FHLB of approximately $2.20 billion and $1.91 billion , respectively, and with the FRB of approximately $1.22 billion and $1.11 billion , respectively.

Qualifying Debt

Qualifying Debt	3 Months Ended
Qualifying Debt	Mar. 31, 2018
Qualifying Debt Disclosure [Abstract]
Qualifying Debt	Subordinated Debt The Parent has $175.0 million of subordinated debentures, which was recorded net of issuance costs of $5.5 million , and matures July 1, 2056. Beginning on or after July 1, 2021, the Company may redeem the debentures, in whole or in part, at their principal amount plus any accrued and unpaid interest. The debentures have a fixed interest rate of 6.25% per annum. WAB has $150.0 million of subordinated debt, which was recorded net of debt issuance costs of $1.8 million , and matures July 15, 2025. The subordinated debt has a fixed interest rate of 5.00% through June 30, 2020 and then converts to a variable rate of 3.20% plus three-month LIBOR through maturity. To hedge the interest rate risk on the Company's subordinated debt issuances, the Company entered into fair value interest rate hedges with receive fixed/pay variable swaps. The carrying value of all subordinated debt issuances, which includes the fair value of the related hedges, totals $297.5 million and $308.6 million at March 31, 2018 and December 31, 2017 , respectively. Junior Subordinated Debt The Company has formed or acquired through acquisition eight statutory business trusts, which exist for the exclusive purpose of issuing Cumulative Trust Preferred Securities. With the exception of debt issued by Bridge Capital Trust I and Bridge Capital Trust II, junior subordinated debt is recorded at fair value at each reporting date due to the FVO election made by the Company under ASC 825. The Company did not make the FVO election for the junior subordinated debt acquired as part of the Bridge acquisition. Accordingly, the carrying value of these trusts does not reflect the current fair value of the debt and includes a fair market value adjustment established at acquisition that is being accreted over the remaining life of the trusts. The carrying value of junior subordinated debt was $66.4 million and $68.3 million at March 31, 2018 and December 31, 2017 , respectively. The weighted average interest rate of all junior subordinated debt as of March 31, 2018 was 4.65% , which is three-month LIBOR plus the contractual spread of 2.34%, compared to a weighted average interest rate of 4.03% at December 31, 2017 .

Stockholders' Equity

Stockholders' Equity	3 Months Ended
Stockholders' Equity	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Stockholder's Equity	Stock-Based Compensation Restricted Stock Awards Restricted stock awards granted to employees generally vest over a three -year period. Stock grants made to non-employee WAL directors in 2018 will be fully vested at June 30, 2018. The Company estimates the compensation expense for stock grants based upon the grant date fair value. Stock compensation expense is recognized on a straight-line basis over the requisite service period for the entire award. The aggregate grant date fair value for the restricted stock awards granted during the three months ended March 31, 2018 was $21.9 million . Stock compensation expense related to restricted stock awards and stock options granted to employees are included in Salaries and employee benefits in the Consolidated Income Statement. For restricted stock awards granted to WAL directors, the related stock compensation expense is included in Legal, professional, and directors' fees. For the three months ended March 31, 2018 , the Company recognized $4.3 million in stock-based compensation expense related to all restricted stock award grants, compared to $4.5 million for the three months ended March 31, 2017 . In addition, the Company previously granted shares of restricted stock to certain members of executive management that had both performance and service conditions that affect vesting. There were no such grants made during the three months ended March 31, 2018 , however expense is still being recognized for the grants made in 2016 and 2017 as they also have a three -year vesting period. For the three months ended March 31, 2018 , the Company recognized $0.6 million in stock-based compensation expense related to these performance-based restricted stock grants, compared to $0.4 million for the three months ended March 31, 2017 . Performance Stock Units The Company grants members of its executive management performance stock units that do not vest unless the Company achieves a specified cumulative EPS target over a three-year performance period. The number of shares issued will vary based on the cumulative EPS target that is achieved. The Company estimates the cost of performance stock units based upon the grant date fair value and expected vesting percentage over the three-year performance period. For the three months ended March 31, 2018 , the Company recognized $1.6 million in stock-based compensation expense related to these performance stock units, compared to $1.3 million for the three months ended March 31, 2017 . The three-year performance period for the 2015 grant ended on December 31, 2017, and the Company's cumulative EPS for the performance period exceeded the level required for a maximum award under the terms of the grant. As a result, executive management members were entitled to the maximum award of 202,074 shares, which was paid out in the first quarter of 2018 . Treasury Shares The Company purchased 180,867 treasury shares at a weighted average price of $59.02 per share and 201,306 at a weighted average price of $50.88 per share during the three months ended March 31, 2018 and 2017 , respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	3 Months Ended
Accumulated Other Comprehensive Income	Mar. 31, 2018
Equity [Abstract]
Accumulated Other Comprehensive Income	The following table summarizes the changes in accumulated other comprehensive income (loss) by component, net of tax, for the periods indicated: Three Months Ended March 31, Unrealized holding (losses) gains on AFS Unrealized holding gains on SERP Unrealized holding gains (losses) on junior subordinated debt Impairment loss on securities Total (in thousands) Balance, December 31, 2017 $ (10,026 ) $ 385 $ 6,352 $ 144 $ (3,145 ) Balance, January 1, 2018 (1) (12,556 ) 469 7,740 144 (4,203 ) Other comprehensive (loss) income before reclassifications (38,914 ) (11 ) 1,466 — (37,459 ) Amounts reclassified from accumulated other comprehensive income — — — — — Net current-period other comprehensive (loss) income (38,914 ) (11 ) 1,466 — (37,459 ) Balance, March 31, 2018 $ (51,470 ) $ 458 $ 9,206 $ 144 $ (41,662 ) Balance, December 31, 2016 $ (14,916 ) $ 121 $ 9,956 $ 144 $ (4,695 ) Other comprehensive income (loss) before reclassifications 9,169 (1 ) (1,229 ) — 7,939 Amounts reclassified from accumulated other comprehensive income (393 ) — — — (393 ) Net current-period other comprehensive income (loss) 8,776 (1 ) (1,229 ) — 7,546 Balance, March 31, 2017 $ (6,140 ) $ 120 $ 8,727 $ 144 $ 2,851 (1) As adjusted for adoption of ASU 2016-01 and ASU 2018-02, see " Note 1. Summary of Significant Accounting Policies " for further discussion. The following table presents reclassifications out of accumulated other comprehensive income (loss): Three Months Ended March 31, Income Statement Classification 2018 2017 (in thousands) Gain on sales of investment securities, net $ — $ 635 Income tax expense — (242 ) Net of tax $ — $ 393

Derivatives and Hedging

Derivatives and Hedging	3 Months Ended
Derivatives and Hedging	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging Activities	The Company is a party to various derivative instruments. Derivative instruments are contracts between two or more parties that have a notional amount and an underlying variable, require a small or no initial investment, and allow for the net settlement of positions. A derivative’s notional amount serves as the basis for the payment provision of the contract and takes the form of units, such as shares or dollars. A derivative’s underlying variable is a specified interest rate, security price, commodity price, foreign exchange rate, index, or other variable. The interaction between the notional amount and the underlying variable determines the number of units to be exchanged between the parties and influences the fair value of the derivative contract. The primary type of derivatives that the Company uses are interest rate swaps. Generally, these instruments are used to help manage the Company's exposure to interest rate risk and meet client financing and hedging needs. Derivatives are recorded at fair value in the Consolidated Balance Sheets, after taking into account the effects of bilateral collateral and master netting agreements. These agreements allow the Company to settle all derivative contracts held with the same counterparty on a net basis, and to offset net derivative positions with related cash collateral, where applicable. As of March 31, 2018 , December 31, 2017 , and March 31, 2017 , the Company does not have any significant outstanding cash flow hedges or free-standing derivatives. Derivatives Designated in Hedge Relationships The Company utilizes derivatives that have been designated as part of a hedge relationship in accordance with the applicable accounting guidance to minimize the exposure to changes in benchmark interest rates and volatility of net interest income and EVE to interest rate fluctuations. The primary derivative instruments used to manage interest rate risk are interest rate swaps, which convert the contractual interest rate index of agreed-upon amounts of assets and liabilities (i.e., notional amounts) to another interest rate index. The Company has entered into pay fixed/receive variable interest rate swaps designated as fair value hedges of certain fixed rate loans. As a result, the Company receives variable-rate interest payments in exchange for making fixed-rate payments over the lives of the contracts without exchanging the notional amounts. The Company has also entered into receive fixed/pay variable interest rate swaps, designated as fair value hedges on its fixed rate subordinated debt offerings. As a result, the Company is paying a floating rate of three-month LIBOR plus 3.16% and is receiving semi-annual fixed payments of 5.00% to match the payments on the $150.0 million subordinated debt. For the fair value hedge on the Parent's $175.0 million subordinated debentures issued on June 16, 2016, the Company is paying a floating rate of three-month LIBOR plus 3.25% and is receiving quarterly fixed payments of 6.25% to match the payments on the debt. Derivatives Not Designated in Hedge Relationships Management also enters into certain foreign exchange derivative contracts which are not designated as accounting hedges. These derivative contracts include spot, forward and forward window contracts. The purpose of these derivative contracts is to mitigate foreign currency risk on transactions entered into, or on behalf of customers. Contracts with customers, along with the related derivative trades the Company places, are both remeasured at fair value, and are referred to as economic hedges since they economically offset the Company's exposure. For the three months ended March 31, 2018 and 2017 , changes in the fair value related to these derivative contracts totaled $0.5 million and $1.0 million , respectively, and are included in Other non-interest income in the Consolidated Income Statements. As of March 31, 2018 and December 31, 2017 , the following amounts are reflected in the Consolidated Balance Sheet related to cumulative basis adjustments for fair value hedges: March 31, 2018 December 31, 2017 Carrying Value of Hedged Assets/(Liabilities) Cumulative Amount of the Fair Value Hedging Adjustment (1) Carrying Value of Hedged Assets/(Liabilities) Cumulative Amount of the Fair Value Hedging Adjustment (1) (in thousands) Loans - HFI, net of deferred loan fees and costs $ 671,363 $ 18,063 $ 699,452 $ 41,919 Qualifying debt (297,506 ) 21,193 (308,608 ) 9,959 (1) Included in the carrying value of the hedged assets/(liabilities). For the Company's derivative instruments that are designated and qualify as a fair value hedge, the gain or loss on the derivative instrument as well as the offsetting loss or gain on the hedged item attributable to the hedged risk are recognized in current earnings in the same line item as the offsetting loss or gain on the related interest rate swaps. For loans, the gain or loss on the hedged item is included in interest income and for subordinated debt, the gain or loss on the hedged item is included in interest expense. Fair Values, Volume of Activity, and Gain/Loss Information Related to Derivative Instruments The following table summarizes the fair values of the Company's derivative instruments on a gross and net basis as of March 31, 2018 , December 31, 2017 , and March 31, 2017 . The change in the notional amounts of these derivatives from March 31, 2017 to March 31, 2018 indicates the volume of the Company's derivative transaction activity during these periods. The derivative asset and liability balances are presented on a gross basis, prior to the application of bilateral collateral and master netting agreements. Total derivative assets and liabilities are adjusted to take into account the impact of legally enforceable master netting agreements that allow the Company to settle all derivative contracts with the same counterparty on a net basis and to offset the net derivative position with the related collateral. Where master netting agreements are not in effect or are not enforceable under bankruptcy laws, the Company does not adjust those derivative amounts with counterparties. The fair value of derivative contracts, after taking into account the effects of master netting agreements, is included in other assets or other liabilities in the Consolidated Balance Sheets, as indicated in the following table: March 31, 2018 December 31, 2017 March 31, 2017 Fair Value Fair Value Fair Value Notional Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities (in thousands) Derivatives designated as hedging instruments: Fair value hedges Interest rate swaps $ 989,379 $ 3,533 $ 42,789 $ 993,432 $ 1,703 $ 53,581 $ 1,035,151 $ 1,985 $ 59,136 Total 989,379 3,533 42,789 993,432 1,703 53,581 1,035,151 1,985 59,136 Netting adjustments (1) — 3,493 3,493 — 896 896 — 1,947 1,947 Net derivatives in the balance sheet $ 989,379 $ 40 $ 39,296 $ 993,432 $ 807 $ 52,685 $ 1,035,151 $ 38 $ 57,189 Derivatives not designated as hedging instruments: Foreign currency contracts (2) $ 90,855 $ 684 $ 394 $ 85,335 $ 1,232 $ 983 $ 68,298 $ 327 $ 111 Interest rate swaps 36,840 1,170 1,170 36,969 776 776 38,192 796 796 Total $ 127,695 $ 1,854 $ 1,564 $ 122,304 $ 2,008 $ 1,759 $ 106,490 $ 1,123 $ 907 (1) Netting adjustments represent the amounts recorded to convert the Company's derivative balances from a gross basis to a net basis in accordance with the applicable accounting guidance. (2) Prior period derivative asset / liability netting adjustments have been made to conform to current presentation. Counterparty Credit Risk Like other financial instruments, derivatives contain an element of credit risk. This risk is measured as the expected positive replacement value of the contracts. Management generally enters into bilateral collateral and master netting agreements that provide for the net settlement of all contracts with the same counterparty. Additionally, management monitors counterparty credit risk exposure on each contract to determine appropriate limits on the Company's total credit exposure across all product types. In general, the Company has a zero credit threshold with regard to derivative exposure with counterparties. Management reviews the Company's collateral positions on a daily basis and exchanges collateral with counterparties in accordance with standard ISDA documentation and other related agreements. The Company generally holds collateral in the form of cash deposits or highly rated securities issued by the U.S. Treasury or government-sponsored enterprises, such as GNMA, FNMA, and FHLMC. The total collateral netted against net derivative liabilities totaled $40.1 million at March 31, 2018 , $53.6 million at December 31, 2017 , and $59.1 million at March 31, 2017 . The following table summarizes the Company's largest exposure to an individual counterparty at the dates indicated: March 31, 2018 December 31, 2017 March 31, 2017 (in thousands) Largest gross exposure (derivative asset) to an individual counterparty $ 2,515 $ 893 $ 3,569 Collateral posted by this counterparty — — 4,680 Derivative liability with this counterparty 20,624 40,340 — Collateral pledged to this counterparty 29,719 60,476 1,340 Net exposure after netting adjustments and collateral $ — $ — $ 229 Credit Risk Contingent Features Management has entered into certain derivative contracts that require the Company to post collateral to the counterparties when these contracts are in a net liability position. Conversely, the counterparties may be required to post collateral when these contracts are in a net asset position. The amount of collateral to be posted is based on the amount of the net liability and exposure thresholds. As of March 31, 2018 , December 31, 2017 , and March 31, 2017 the aggregate fair value of all derivative contracts with credit risk contingent features (i.e., those containing collateral posting provisions) held by the Company that were in a net liability position totaled $39.3 million , $52.7 million , and $57.2 million , respectively. As of March 31, 2018 , the Company was in an over-collateralized net position of $12.1 million after considering $52.2 million of collateral held in the form of cash and securities. As of December 31, 2017 and March 31, 2017 , the Company was in an over-collateralized position of $25.0 million and $11.7 million , respectively.

Earnings per Share

Earnings per Share	3 Months Ended
Earnings per Share	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share	Diluted EPS is based on the weighted average outstanding common shares during each period, including common stock equivalents. Basic EPS is based on the weighted average outstanding common shares during the period. The following table presents the calculation of basic and diluted EPS: Three Months Ended March 31, 2018 2017 (in thousands, except per share amounts) Weighted average shares - basic 104,530 103,987 Dilutive effect of stock awards 794 849 Weighted average shares - diluted 105,324 104,836 Net income available to common stockholders $ 100,900 $ 73,342 Earnings per share - basic 0.97 0.71 Earnings per share - diluted 0.96 0.70 The Company had no anti-dilutive stock options outstanding at each of the periods ended March 31, 2018 and 2017 .

Income Taxes

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	The effective tax rate was 17.10% and 25.03% for the three months ended March 31, 2018 and 2017 , respectively. The decrease in the effective tax rate is due primarily to the decrease in the Federal statutory rate for 2018. As of March 31, 2018 , the net deferred tax asset was $27.4 million , an increase of $21.6 million from December 31, 2017 . This overall increase in the net deferred tax asset was primarily the result of recognizing previously deferred income and decreases in the fair market value of AFS securities. Although realization is not assured, the Company believes that the realization of the recognized deferred tax asset of $27.4 million at March 31, 2018 is more-likely-than-not based on expectations as to future taxable income and based on available tax planning strategies within the meaning of ASC 740, Income Taxes, that could be implemented if necessary to prevent a carryover from expiring. At March 31, 2018 and December 31, 2017 , the Company had no deferred tax valuation allowance. As of March 31, 2018 , the Company’s gross federal NOL carryovers, a portion of which are subject to limitations under Section 382 of the IRC, totaled approximately $135.6 million for which a deferred tax asset of $24.0 million has been recorded reflecting the expected benefit of these federal NOL carryovers. The Company also has varying gross amounts of state NOL carryovers with California and Arizona being the most significant. The ending gross California and Arizona NOL carryovers totaled approximately $19.1 million and $13.3 million , respectively. A deferred tax asset of $2.8 million has been recorded to reflect the expected benefit of all state NOL carryovers. Investments in LIHTC The Company invests in LIHTC funds that are designed to generate a return primarily through the realization of federal tax credits. Investments in LIHTC and unfunded LIHTC obligations are included as part of other assets and other liabilities, respectively, in the Consolidated Balance Sheets and total $288.9 million and $167.9 million , respectively, as of March 31, 2018 , compared to $267.0 million and $151.3 million as of December 31, 2017 . For the three months ended March 31, 2018 and 2017 , $8.1 million and $5.9 million , respectively, of amortization related to LIHTC investments was recognized as a component of income tax expense.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Unfunded Commitments and Letters of Credit The Company is party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit and standby letters of credit. They involve, to varying degrees, elements of credit risk in excess of amounts recognized in the Consolidated Balance Sheets. Lines of credit are obligations to lend money to a borrower. Credit risk arises when the borrower's current financial condition may indicate less ability to pay than when the commitment was originally made. In the case of standby letters of credit, the risk arises from the potential failure of the customer to perform according to the terms of a contract. In such a situation, the third party might draw on the standby letter of credit to pay for completion of the contract and the Company would look to its customer to repay these funds with interest. To minimize the risk, the Company uses the same credit policies in making commitments and conditional obligations as it would for a loan to that customer. Standby letters of credit and financial guarantees are commitments issued by the Company to guarantee the performance of a customer to a third party in borrowing arrangements. The Company generally has recourse to recover from the customer any amounts paid under the guarantees. Typically, letters of credit issued have expiration dates within one year. A summary of the contractual amounts for unfunded commitments and letters of credit are as follows: March 31, 2018 December 31, 2017 (in thousands) Commitments to extend credit, including unsecured loan commitments of $437,437 at March 31, 2018 and $364,638 at December 31, 2017 $ 6,500,031 $ 5,851,158 Credit card commitments and financial guarantees 186,613 153,752 Standby letters of credit, including unsecured letters of credit of $12,148 at March 31, 2018 and $11,664 at December 31, 2017 181,068 161,966 Total $ 6,867,712 $ 6,166,876 Commitments to extend credit are agreements to lend to a customer provided that there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. The Company enters into credit arrangements that generally provide for the termination of advances in the event of a covenant violation or other event of default. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer’s creditworthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the Company upon extension of credit, is based on management’s credit evaluation of the party. The commitments are collateralized by the same types of assets used as loan collateral. The Company has exposure to credit losses from unfunded commitments and letters of credit. As funds have not been disbursed on these commitments, they are not reported as loans outstanding. Credit losses related to these commitments are included in other liabilities as a separate loss contingency and are not included in the allowance for credit losses reported in " Note 3. Loans, Leases and Allowance for Credit Losses " of these Unaudited Consolidated Financial Statements. This loss contingency for unfunded loan commitments and letters of credit was $7.2 million and $6.2 million as of March 31, 2018 and December 31, 2017 , respectively. Changes to this liability are adjusted through other expense in the Consolidated Income Statement. Concentrations of Lending Activities The Company’s lending activities are driven in large part by the customers served in the market areas where the Company has branch offices in the states of Arizona, Nevada, and California. Despite the geographic concentration of lending activities, the Company does not have a single external customer from which it derives 10% or more of its revenues. The Company monitors concentrations within four broad categories: geography, industry, product, and collateral. The Company's loan portfolio includes significant credit exposure to the CRE market. As of March 31, 2018 and December 31, 2017 , CRE related loans accounted for approximately 52% of total loans. Substantially all of these loans are secured by first liens with an initial loan to value ratio of generally not more than 75% . Approximately 37% and 36% of these CRE loans, excluding construction and land loans, were owner-occupied at March 31, 2018 and December 31, 2017 , respectively. Contingencies The Company is involved in various lawsuits of a routine nature that are being handled and defended in the ordinary course of the Company’s business. Expenses are being incurred in connection with these lawsuits, but in the opinion of management, based in part on consultation with outside legal counsel, the resolution of these lawsuits and associated defense costs will not have a material impact on the Company’s financial position, results of operations, or cash flows. Lease Commitments The Company leases the majority of its office locations and many of these leases contain multiple renewal options and provisions for increased rents. Total rent expense of $2.5 million and $2.6 million for the three months ended March 31, 2018 and 2017 , respectively, was included in Occupancy expense in these Unaudited Consolidated Financial Statements.

Fair Value Accounting

Fair Value Accounting	3 Months Ended
Fair Value Accounting	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Accounting	The fair value of an asset or liability is the price that would be received to sell that asset or paid to transfer that liability in an orderly transaction occurring in the principal market (or most advantageous market in the absence of a principal market) for such asset or liability. In estimating fair value, the Company utilizes valuation techniques that are consistent with the market approach, the income approach, and/or the cost approach. Such valuation techniques are consistently applied. Inputs to valuation techniques include the assumptions that market participants would use in pricing an asset or liability. ASC 825 establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy under ASC 825 are described in " Note 1. Summary of Significant Accounting Policies " of these Notes to Unaudited Consolidated Financial Statements. In general, fair value is based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally-developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. These adjustments may include amounts to reflect counterparty credit quality and the Company’s creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. The Company’s valuation methodologies may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. While management believes the Company’s valuation methodologies are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different estimate of fair value at the reporting date. Furthermore, the reported fair value amounts have not been comprehensively revalued since the presentation dates, and therefore, estimates of fair value after the balance sheet date may differ significantly from the amounts presented herein. A more detailed description of the valuation methodologies used for assets and liabilities measured at fair value is set forth below. Transfers between levels in the fair value hierarchy are recognized as of the end of the month following the event or change in circumstances that caused the transfer. Under ASC 825, the Company elected the FVO treatment for junior subordinated debt issued by WAL. This election is irrevocable and results in the recognition of unrealized gains and losses on these items at each reporting date. These unrealized gains and losses are recognized as part of other comprehensive income rather than earnings. The Company did not elect FVO treatment for the junior subordinated debt assumed in the Bridge Capital Holdings acquisition. For the three months ended March 31, 2018 and 2017 , gains and losses from fair value changes on junior subordinated debt were as follows: Changes in Fair Values for Items Measured at Fair Value Unrealized Gain/(Loss) on Assets and Liabilities Measured at Fair Value, Net Interest Income on Securities Interest Expense on Junior Subordinated Debt Total Changes Included in Current-Period Earnings Total Changes Included in OCI (in thousands) Three Months Ended March 31, 2018 Junior subordinated debt $ 1,944 $ — $ 904 $ 904 $ 1,466 Total $ 1,944 $ — $ 904 $ 904 $ 1,466 Three Months Ended March 31, 2017 Securities measured at fair value $ (1 ) $ 7 $ — $ 6 $ — Junior subordinated debt (1,986 ) — (749 ) (749 ) (1,229 ) Total $ (1,987 ) $ 7 $ (749 ) $ (743 ) $ (1,229 ) During the year ended December 31, 2017, the Company sold all of its investment securities measured at fair value. No significant gain or loss was recognized upon sale of these securities. Fair value on a recurring basis Financial assets and financial liabilities measured at fair value on a recurring basis include the following: Securities measured at fair value: All of the Company’s securities measured at fair value, which consist of MBS, are reported at fair value utilizing Level 2 inputs in the same manner as described below for AFS securities. AFS securities: Preferred stock and CRA investments are reported at fair value utilizing Level 1 inputs. Other securities classified as AFS are reported at fair value utilizing Level 2 inputs. For these securities, the Company obtains fair value measurements from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information, and the bond’s terms and conditions, among other things. Independent pricing service: The Company's independent pricing service provides pricing information on the majority of the Company's Level 1 and 2 securities. Management independently evaluates the fair value measurements received from the Company's third party pricing service through multiple review steps. First, management reviews what has transpired in the marketplace with respect to interest rates, credit spreads, volatility, and mortgage rates, among other things, and develops an expectation of changes to the securities' valuations from the previous quarter. Then, management obtains market values from additional sources. The pricing service provides management with observable market data including interest rate curves and mortgage prepayment speed grids, as well as dealer quote sheets, new bond offering sheets, and historical trade documentation. Management reviews the assumptions and decides whether they are reasonable. Management may compare interest rates, credit spreads, and prepayments speeds used as part of the assumptions to those that management believes are reasonable. Management may price securities using the provided assumptions to determine whether they can develop similar prices on like securities. Any discrepancies between management’s review and the prices provided by the vendor are discussed with the vendor and the Company’s other valuation advisors. Lastly, management selects a sample of investment securities and compares the values provided by its primary third party pricing service to the market values obtained from secondary sources and evaluates those with notable variances. Interest rate swaps: Interest rate swaps are reported at fair value utilizing Level 2 inputs. The Company obtains dealer quotations to value its interest rate swaps. Junior subordinated debt: The Company estimates the fair value of its junior subordinated debt using a discounted cash flow model which incorporates the effect of the Company’s own credit risk in the fair value of the liabilities (Level 3). The Company’s cash flow assumptions are based on contractual cash flows as the Company anticipates that it will pay the debt according to its contractual terms. As of March 31, 2018 , the Company estimates the discount rate at 6.65% , which represents an implied credit spread of 4.34% plus three-month LIBOR ( 2.31% ). As of December 31, 2017 , the Company estimated the discount rate at 5.61% , which was a 3.92% credit spread plus three-month LIBOR ( 1.69% ). The fair value of assets and liabilities measured at fair value on a recurring basis was determined using the following inputs as of the periods presented: Fair Value Measurements at the End of the Reporting Period Using: Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Fair Value (in thousands) March 31, 2018 Assets: Available-for-sale CDO $ — $ 19,453 $ — $ 19,453 Commercial MBS issued by GSEs — 104,973 — 104,973 Corporate debt securities — 101,676 — 101,676 CRA investments 50,846 — — 50,846 Preferred stock 93,318 — — 93,318 Private label residential MBS — 818,996 — 818,996 Residential MBS issued by GSEs — 1,626,899 — 1,626,899 Tax-exempt — 497,921 — 497,921 Trust preferred securities — 28,617 — 28,617 U.S. government sponsored agency securities — 60,290 — 60,290 U.S. treasury securities — 2,473 — 2,473 Total AFS securities $ 144,164 $ 3,261,298 $ — $ 3,405,462 Derivative assets (1) $ — $ 5,387 $ — $ 5,387 Liabilities: Junior subordinated debt (2) $ — $ — $ 54,290 $ 54,290 Derivative liabilities (1) — 44,353 — 44,353 (1) Derivative assets and liabilities relate to interest rate swaps, see " Note 9. Derivatives and Hedging Activities ." In addition, the carrying value of loans is increased by $18,063 and the net carrying value of subordinated debt is decreased by $21,193 as of March 31, 2018 , which relates to the fair value of the hedges put in place to mitigate against fluctuations in interest rates. (2) Includes only the portion of junior subordinated debt that is recorded at fair value at each reporting period pursuant to the election of FVO treatment. Fair Value Measurements at the End of the Reporting Period Using: Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Fair Value (in thousands) December 31, 2017 Assets: Available-for-sale CDO $ — $ 21,857 $ — $ 21,857 Commercial MBS issued by GSEs — 109,077 — 109,077 Corporate debt securities — 103,483 — 103,483 CRA investments 50,616 — — 50,616 Preferred stock 53,196 — — 53,196 Private label residential MBS — 868,524 — 868,524 Residential MBS issued by GSEs — 1,689,295 — 1,689,295 Tax-exempt — 510,910 — 510,910 Trust preferred securities — 28,617 — 28,617 U.S. government sponsored agency securities — 61,462 — 61,462 U.S. treasury securities — 2,482 — 2,482 Total AFS securities $ 103,812 $ 3,395,707 $ — $ 3,499,519 Derivative assets (1) $ — $ 3,711 $ — $ 3,711 Liabilities: Junior subordinated debt (2) $ — $ — $ 56,234 $ 56,234 Derivative liabilities (1) — 55,340 — 55,340 (1) Derivative assets and liabilities relate to interest rate swaps, see " Note 9. Derivatives and Hedging Activities ." In addition, the carrying value of loans is increased by $41,919 and the net carrying value of subordinated debt is decreased by $9,959 as of December 31, 2017 , which relates to the fair value of the hedges put in place to mitigate against fluctuations in interest rates. (2) Includes only the portion of junior subordinated debt that is recorded at fair value at each reporting period pursuant to the election of FVO treatment. For the three months ended March 31, 2018 and 2017 , the change in Level 3 liabilities measured at fair value on a recurring basis was as follows: Junior Subordinated Debt Three Months Ended March 31, 2018 2017 (in thousands) Beginning balance $ (56,234 ) $ (50,410 ) Transfers into Level 3 — — Total gains (losses) for the period Included in other comprehensive income 1,944 (1,986 ) Ending balance $ (54,290 ) $ (52,396 ) For Level 3 liabilities measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017 , the significant unobservable inputs used in the fair value measurements were as follows: March 31, 2018 Valuation Technique Significant Unobservable Inputs Input Value (in thousands) Junior subordinated debt $ 54,290 Discounted cash flow Implied credit rating of the Company 6.65 % December 31, 2017 Valuation Technique Significant Unobservable Inputs Input Value (in thousands) Junior subordinated debt $ 56,234 Discounted cash flow Implied credit rating of the Company 5.61 % The significant unobservable inputs used in the fair value measurement of the Company’s junior subordinated debt as of March 31, 2018 and December 31, 2017 was the implied credit risk for the Company, calculated as the difference between the 20-year 'BB' rated financial index over the corresponding swap index. Fair value on a nonrecurring basis Certain assets are measured at fair value on a nonrecurring basis. That is, the assets are not measured at fair value on an ongoing basis, but are subject to fair value adjustments in certain circumstances (for example, when there is evidence of impairment). The following table presents such assets carried on the Balance Sheet by caption and by level within the ASC 825 hierarchy: Fair Value Measurements at the End of the Reporting Period Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Active Markets for Similar Assets (Level 2) Unobservable Inputs (Level 3) (in thousands) As of March 31, 2018; Impaired loans with specific valuation allowance $ 4,036 $ — $ — $ 4,036 Impaired loans without specific valuation allowance (1) 63,639 — — 63,639 Other assets acquired through foreclosure 30,194 — — 30,194 As of December 31, 2017: Impaired loans with specific valuation allowance $ 13,709 $ — $ — $ 13,709 Impaired loans without specific valuation allowance (1) 63,607 — — 63,607 Other assets acquired through foreclosure 28,540 — — 28,540 (1) Net of loan balances with charge-offs of $24.4 million and $15.6 million as of March 31, 2018 and December 31, 2017 , respectively. For Level 3 assets measured at fair value on a nonrecurring basis as of March 31, 2018 and December 31, 2017 , the significant unobservable inputs used in the fair value measurements were as follows: March 31, 2018 Valuation Technique(s) Significant Unobservable Inputs Range (in thousands) Impaired loans $ 67,675 Collateral method Third party appraisal Costs to sell 4.0% to 10.0% Discounted cash flow method Discount rate Contractual loan rate 4.0% to 7.0% Scheduled cash collections Probability of default 0% to 20.0% Proceeds from non-real estate collateral Loss given default 0% to 70.0% Other assets acquired through foreclosure 30,194 Collateral method Third party appraisal Costs to sell 4.0% to 10.0% December 31, 2017 Valuation Technique(s) Significant Unobservable Inputs Range (in thousands) Impaired loans $ 77,316 Collateral method Third party appraisal Costs to sell 4.0% to 10.0% Discounted cash flow method Discount rate Contractual loan rate 4.0% to 7.0% Scheduled cash collections Probability of default 0% to 20.0% Proceeds from non-real estate collateral Loss given default 0% to 70.0% Other assets acquired through foreclosure 28,540 Collateral method Third party appraisal Costs to sell 4.0% to 10.0% Impaired loans: The specific reserves for collateral dependent impaired loans are based on collateral value, net of estimated disposition costs and other identified quantitative inputs. Collateral value is determined based on independent third-party appraisals or internally-developed discounted cash flow analyses. Appraisals may utilize a single valuation approach or a combination of approaches, including comparable sales and the income approach. Fair value is determined, where possible, using market prices derived from an appraisal or evaluation, which are considered to be Level 2. However, certain assumptions and unobservable inputs are often used by the appraiser, therefore qualifying the assets as Level 3 in the fair value hierarchy. In addition, when adjustments are made to an appraised value to reflect various factors such as the age of the appraisal or known changes in the market or the collateral, such valuation inputs are considered unobservable and the fair value measurement is categorized as a Level 3 measurement. Internal discounted cash flow analyses are also utilized to estimate the fair value of impaired loans, which considers internally-developed, unobservable inputs such as discount rates, default rates, and loss severity. Total Level 3 impaired loans had an estimated fair value of $67.7 million and $77.3 million at March 31, 2018 and December 31, 2017 , respectively. Impaired loans with a specific valuation allowance had a gross estimated fair value of $9.6 million and $19.3 million at March 31, 2018 and December 31, 2017 , respectively, which was reduced by a specific valuation allowance of $5.6 million for each period. Other assets acquired through foreclosure: Other assets acquired through foreclosure consist of properties acquired as a result of, or in-lieu-of, foreclosure. These assets are initially reported at the fair value determined by independent appraisals using appraised value less estimated cost to sell. Such properties are generally re-appraised every twelve months. There is risk for subsequent volatility. Costs relating to the development or improvement of the assets are capitalized and costs relating to holding the assets are charged to expense. Fair value is determined, where possible, using market prices derived from an appraisal or evaluation, which are considered to be Level 2. However, certain assumptions and unobservable inputs are often used by the appraiser, therefore qualifying the assets as Level 3 in the fair value hierarchy. When significant adjustments are based on unobservable inputs, such as when a current appraised value is not available or management determines the fair value of the collateral is further impaired below the appraised value and there is no observable market price, the resulting fair value measurement has been categorized as a Level 3 measurement. The Company had $30.2 million and $28.5 million of such assets at March 31, 2018 and December 31, 2017 , respectively. Credit vs. non-credit losse s Under the provisions of ASC 320, Investments-Debt and Equity Securities , OTTI is separated into the amount of total impairment related to the credit loss and the amount of the total impairment related to all other factors. The amount of the total OTTI related to the credit loss is recognized in earnings. The amount of the total impairment related to all other factors is recognized in OCI. For the three months ended March 31, 2018 and 2017 , the Company determined that no securities experienced credit losses. There is no OTTI balance recognized in comprehensive income as of March 31, 2018 and 2017 . Fair Value Of Financial Instruments The estimated fair value of the Company’s financial instruments is as follows: March 31, 2018 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (in thousands) Financial assets: Investment securities: HTM $ 262,304 $ — $ 255,418 $ — $ 255,418 AFS 3,405,462 144,164 3,261,298 — 3,405,462 Derivative assets 5,387 — 5,387 — 5,387 Loans, net 15,415,794 — 15,254,388 67,675 15,322,063 Accrued interest receivable 80,398 — 80,398 — 80,398 Financial liabilities: Deposits $ 17,354,538 $ — $ 17,360,147 $ — $ 17,360,147 Customer repurchase agreements 21,676 — 21,676 — 21,676 FHLB advances 300,000 — 300,000 — 300,000 Qualifying debt 363,935 — 331,190 64,842 396,032 Derivative liabilities 44,353 — 44,353 — 44,353 Accrued interest payable 11,540 — 11,540 — 11,540 December 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (in thousands) Financial assets: Investment securities: HTM $ 255,050 $ — $ 256,314 $ — $ 256,314 AFS 3,499,519 103,812 3,395,707 — 3,499,519 Derivative assets 3,711 — 3,711 — 3,711 Loans, net 14,953,885 — 14,577,010 77,316 14,654,326 Accrued interest receivable 85,517 — 85,517 — 85,517 Financial liabilities: — Deposits $ 16,972,532 $ — $ 16,980,066 $ — $ 16,980,066 Customer repurchase agreements 26,017 — 26,017 — 26,017 FHLB advances 390,000 — 390,000 — 390,000 Qualifying debt 376,905 — 336,803 67,210 404,013 Derivative liabilities 55,340 — 55,340 — 55,340 Accrued interest payable 16,366 — 16,366 — 16,366 Interest rate risk The Company assumes interest rate risk (the risk to the Company’s earnings and capital from changes in interest rate levels) as a result of its normal operations. As a result, the fair values of the Company’s financial instruments, as well as its future net interest income will change when interest rate levels change and that change may be either favorable or unfavorable to the Company. Interest rate risk exposure is measured using interest rate sensitivity analysis to determine the Company's change in EVE and net interest income resulting from hypothetical changes in interest rates. If potential changes to EVE and net interest income resulting from hypothetical interest rate changes are not within the limits established by the BOD, the BOD may direct management to adjust the asset and liability mix to bring interest rate risk within BOD-approved limits. WAB has an ALCO charged with managing interest rate risk within the BOD-approved limits. Limits are structured to prohibit an interest rate risk profile that does not conform to both management and BOD risk tolerances. There is also ALCO reporting at the Parent level for reviewing interest rate risk for the Company, which gets reported to the BOD and its Finance and Investment Committee. Fair value of commitments The estimated fair value of standby letters of credit outstanding at March 31, 2018 and December 31, 2017 is insignificant. Loan commitments on which the committed interest rates are less than the current market rate are also insignificant at March 31, 2018 and December 31, 2017 .

Segments

Segments	3 Months Ended
Segments	Mar. 31, 2018
Segment Reporting [Abstract]
Segments	The Company's reportable segments are aggregated based primarily on geographic location, services offered, and markets served. The Company's regional segments, which include Arizona, Nevada, Southern California, and Northern California, provide full service banking and related services to their respective markets. The operations from the regional segments correspond to the following banking divisions: ABA in Arizona, BON and FIB in Nevada, TPB in Southern California, and Bridge in Northern California. The Company's NBL segments provide specialized banking services to niche markets. The Company's NBL reportable segments include HOA Services, Public & Nonprofit Finance, Technology & Innovation, HFF, and Other NBLs. These NBLs are managed centrally and are broader in geographic scope than the Company's other segments, though still predominately located within the Company's core market areas. The HOA Services NBL corresponds to the AAB division. The operations of Public and Nonprofit Finance are combined into one reportable segment. The Technology & Innovation NBL includes the operations of Equity Fund Resources, Life Sciences Group, Renewable Resource Group, and Technology Finance. The HFF NBL includes the hotel franchise loan portfolio acquired from GE Capital US Holdings, Inc. on April 20, 2016. The Other NBLs segment consists of Corporate Finance, Mortgage Warehouse Lending, and Resort Finance. The Corporate & Other segment consists of corporate-related items, income and expense items not allocated to the Company's other reportable segments, and inter-segment eliminations. The Company's segment reporting process begins with the assignment of all loan and deposit accounts directly to the segments where these products are originated and/or serviced. Equity capital is assigned to each segment based on the risk profile of their assets and liabilities. With the exception of goodwill, which is assigned a 100% weighting, equity capital allocations ranged from 0% to 12% during the year, with a funds credit provided for the use of this equity as a funding source. Any excess or deficient equity not allocated to segments based on risk is assigned to the Corporate & Other segment. Net interest income, provision for credit losses, and non-interest expense amounts are recorded in their respective segment to the extent that the amounts are directly attributable to those segments. Net interest income is recorded in each segment on a TEB with a corresponding increase in income tax expense, which is eliminated in the Corporate & Other segment. Further, net interest income of a reportable segment includes a funds transfer pricing process that matches assets and liabilities with similar interest rate sensitivity and maturity characteristics. Using this funds transfer pricing methodology, liquidity is transferred between users and providers. A net user of funds has lending/investing in excess of deposits/borrowings and a net provider of funds has deposits/borrowings in excess of lending/investing. A segment that is a user of funds is charged for the use of funds, while a provider of funds is credited through funds transfer pricing, which is determined based on the average life of the assets or liabilities in the portfolio. The net income amount for each reportable segment is further derived by the use of expense allocations. Certain expenses not directly attributable to a specific segment are allocated across all segments based on key metrics, such as number of employees, average loan balances, and average deposit balances. These types of expenses include information technology, operations, human resources, finance, risk management, credit administration, legal, and marketing. Income taxes are applied to each segment based on the effective tax rate for the geographic location of the segment. Any difference in the corporate tax rate and the aggregate effective tax rates in the segments are adjusted in the Corporate & Other segment. The following is a summary of operating segment information for the periods indicated: Regional Segments Balance Sheet: Consolidated Company Arizona Nevada Southern California Northern California At March 31, 2018 (in millions) Assets: Cash, cash equivalents, and investment securities $ 4,173.7 $ 2.1 $ 8.5 $ 2.2 $ 2.5 Loans, net of deferred loan fees and costs 15,560.4 3,472.7 1,819.6 2,013.6 1,271.4 Less: allowance for credit losses (144.7 ) (33.9 ) (17.9 ) (20.3 ) (11.2 ) Total loans 15,415.7 3,438.8 1,801.7 1,993.3 1,260.2 Other assets acquired through foreclosure, net 30.2 2.3 15.0 — 0.2 Goodwill and other intangible assets, net 300.4 — 23.2 — 156.3 Other assets 840.7 46.4 58.3 14.8 15.1 Total assets $ 20,760.7 $ 3,489.6 $ 1,906.7 $ 2,010.3 $ 1,434.3 Liabilities: Deposits $ 17,354.5 $ 5,020.6 $ 3,648.1 $ 2,423.8 $ 1,814.4 Borrowings and qualifying debt 663.9 — — — — Other liabilities 448.6 10.9 16.2 1.9 10.5 Total liabilities 18,467.0 5,031.5 3,664.3 2,425.7 1,824.9 Allocated equity: 2,293.7 24.7 21.8 10.3 7.6 Total liabilities and stockholders' equity $ 20,760.7 $ 5,056.2 $ 3,686.1 $ 2,436.0 $ 1,832.5 Excess funds provided (used) — 1,566.6 1,779.4 425.7 398.2 National Business Lines Balance Sheet: HOA Public & Nonprofit Finance Technology & Innovation Hotel Franchise Finance Other NBLs Corporate & Other At March 31, 2018 Assets: (in millions) Cash, cash equivalents, and investment securities $ — $ — $ — $ — $ — $ 4,158.4 Loans, net of deferred loan fees and costs 167.0 1,539.8 1,168.9 1,378.7 2,725.4 3.3 Less: allowance for credit losses (1.7 ) (15.5 ) (10.3 ) (6.3 ) (27.5 ) (0.1 ) Total loans 165.3 1,524.3 1,158.6 1,372.4 2,697.9 3.2 Other assets acquired through foreclosure, net — — — — — 12.7 Goodwill and other intangible assets, net — — 120.8 0.1 — — Other assets 0.8 14.7 6.8 6.4 13.4 664.0 Total assets $ 166.1 $ 1,539.0 $ 1,286.2 $ 1,378.9 $ 2,711.3 $ 4,838.3 Liabilities: Deposits $ 2,475.3 $ — $ 1,733.5 $ — $ — $ 238.8 Borrowings and qualifying debt — — — — — 663.9 Other liabilities 1.6 21.5 1.2 (0.3 ) 124.3 260.8 Total liabilities 2,476.9 21.5 1,734.7 (0.3 ) 124.3 1,163.5 Allocated equity: 5.9 1.3 11.1 8.3 9.3 2,193.4 Total liabilities and stockholders' equity $ 2,482.8 $ 22.8 $ 1,745.8 $ 8.0 $ 133.6 $ 3,356.9 Excess funds provided (used) 2,316.7 (1,516.2 ) 459.6 (1,370.9 ) (2,577.7 ) (1,481.4 ) Regional Segments Consolidated Company Arizona Nevada Southern California Northern California At December 31, 2017 (in millions) Assets: Cash, cash equivalents, and investment securities $ 4,237.1 $ 2.1 $ 8.2 $ 2.1 $ 1.7 Loans, net of deferred loan fees and costs 15,093.9 3,323.7 1,844.8 1,934.7 1,275.5 Less: allowance for credit losses (140.0 ) (31.5 ) (18.1 ) (19.5 ) (13.2 ) Total loans 14,953.9 3,292.2 1,826.7 1,915.2 1,262.3 Other assets acquired through foreclosure, net 28.5 2.3 13.3 — 0.2 Goodwill and other intangible assets, net 300.7 — 23.2 — 156.5 Other assets 808.9 46.3 58.8 14.4 15.1 Total assets $ 20,329.1 $ 3,342.9 $ 1,930.2 $ 1,931.7 $ 1,435.8 Liabilities: Deposits $ 16,972.5 $ 4,841.3 $ 3,951.4 $ 2,461.1 $ 1,681.7 Borrowings and qualifying debt 766.9 — — — — Other liabilities 360.0 11.6 20.9 3.2 11.9 Total liabilities 18,099.4 4,852.9 3,972.3 2,464.3 1,693.6 Allocated equity: 2,229.7 396.5 263.7 221.8 303.1 Total liabilities and stockholders' equity $ 20,329.1 $ 5,249.4 $ 4,236.0 $ 2,686.1 $ 1,996.7 Excess funds provided (used) — 1,906.5 2,305.8 754.4 560.9 National Business Lines HOA Public & Nonprofit Finance Technology & Innovation Hotel Franchise Finance Other NBLs Corporate & Other At December 31, 2017 Assets: (in millions) Cash, cash equivalents, and investment securities $ — $ — $ — $ — $ — $ 4,223.0 Loans, net of deferred loan fees and costs 162.1 1,580.4 1,097.9 1,327.7 2,543.0 4.1 Less: allowance for credit losses (1.6 ) (15.6 ) (11.4 ) (4.0 ) (25.0 ) (0.1 ) Total loans 160.5 1,564.8 1,086.5 1,323.7 2,518.0 4.0 Other assets acquired through foreclosure, net — — — — — 12.7 Goodwill and other intangible assets, net — — 120.9 0.1 — — Other assets 0.9 17.9 6.0 5.9 15.5 628.1 Total assets $ 161.4 $ 1,582.7 $ 1,213.4 $ 1,329.7 $ 2,533.5 $ 4,867.8 Liabilities: Deposits $ 2,230.4 $ — $ 1,737.6 $ — $ — $ 69.0 Borrowings and qualifying debt — — — — — 766.9 Other liabilities 1.2 42.4 0.8 0.4 5.5 262.1 Total liabilities 2,231.6 42.4 1,738.4 0.4 5.5 1,098.0 Allocated equity: 59.4 126.5 244.1 108.3 206.0 300.3 Total liabilities and stockholders' equity $ 2,291.0 $ 168.9 $ 1,982.5 $ 108.7 $ 211.5 $ 1,398.3 Excess funds provided (used) 2,129.6 (1,413.8 ) 769.1 (1,221.0 ) (2,322.0 ) (3,469.5 ) Regional Segments Consolidated Company Arizona Nevada Southern California Northern California Three Months Ended March 31, 2018 (in thousands) Net interest income (expense) $ 214,220 $ 54,555 $ 36,690 $ 27,802 $ 22,255 Provision for (recovery) credit losses 6,000 1,434 (1,723 ) 729 1,548 Net interest income (expense) after provision for credit losses 208,220 53,121 38,413 27,073 20,707 Non-interest income 11,643 1,416 3,333 1,001 2,547 Non-interest expense (98,149 ) (21,504 ) (14,084 ) (13,646 ) (12,503 ) Income (loss) before income taxes 121,714 33,033 27,662 14,428 10,751 Income tax expense (benefit) 20,814 8,321 5,903 4,135 3,098 Net income $ 100,900 $ 24,712 $ 21,759 $ 10,293 $ 7,653 National Business Lines HOA Public & Nonprofit Finance Technology & Innovation Hotel Franchise Finance Other NBLs Corporate & Other Three Months Ended March 31, 2018 (in thousands) Net interest income (expense) $ 15,359 $ 3,746 $ 22,821 $ 14,185 $ 18,811 $ (2,004 ) Provision for (recovery) credit losses 47 (207 ) 1,651 1,236 1,285 — Net interest income (expense) after provision for credit losses 15,312 3,953 21,170 12,949 17,526 (2,004 ) Non-interest income 150 — 3,051 13 224 (92 ) Non-interest expense (7,803 ) (2,174 ) (9,833 ) (2,206 ) (5,662 ) (8,734 ) Income (loss) before income taxes 7,659 1,779 14,388 10,756 12,088 (10,830 ) Income tax expense (benefit) 1,761 409 3,309 2,474 2,780 (11,376 ) Net income $ 5,898 $ 1,370 $ 11,079 $ 8,282 $ 9,308 $ 546 Regional Segments Consolidated Company Arizona Nevada Southern California Northern California Three Months Ended March 31, 2017 (in thousands) Net interest income (expense) $ 179,309 $ 43,907 $ 35,296 $ 25,218 $ 22,035 Provision for (recovery of) credit losses 4,250 14 (211 ) 91 396 Net interest income (expense) after provision for credit losses 175,059 43,893 35,507 25,127 21,639 Non-interest income 10,599 1,113 2,133 743 2,113 Non-interest expense (87,827 ) (18,622 ) (15,870 ) (12,703 ) (12,709 ) Income (loss) before income taxes 97,831 26,384 21,770 13,167 11,043 Income tax expense (benefit) 24,489 10,350 7,620 5,537 4,643 Net income (loss) $ 73,342 $ 16,034 $ 14,150 $ 7,630 $ 6,400 National Business Lines HOA Public & Nonprofit Finance Technology & Innovation Hotel Franchise Finance Other NBLs Corporate & Other Three Months Ended March 31, 2017 (in thousands) Net interest income (expense) $ 12,748 $ 6,485 $ 18,166 $ 13,581 $ 14,143 $ (12,270 ) Provision for (recovery) credit losses 127 509 296 — 3,527 (499 ) Net interest income (expense) after provision for credit losses 12,621 5,976 17,870 13,581 10,616 (11,771 ) Non-interest income 141 70 1,873 — 721 1,692 Non-interest expense (7,147 ) (2,323 ) (8,779 ) (2,988 ) (4,721 ) (1,965 ) Income (loss) before income taxes 5,615 3,723 10,964 10,593 6,616 (12,044 ) Income tax expense (benefit) 2,106 1,402 4,111 3,972 2,481 (17,733 ) Net income $ 3,509 $ 2,321 $ 6,853 $ 6,621 $ 4,135 $ 5,689

Related Party Transactions

Related Party Transactions	3 Months Ended
Related Party Transactions	Mar. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions Disclosure [Text Block]	Principal stockholders, directors, and executive officers of the Company, their immediate family members, and companies they control or own more than a 10% interest in, are considered to be related parties. In the ordinary course of business, the Company engages in various related party transactions, including extending credit and bank service transactions. All related party transactions are subject to review and approval pursuant to the Company's Related Party Transactions policy. On April 1, 2017, the Company hired an executive officer who was previously the Managing Partner of an external consulting firm that the Company actively uses for risk management services. Prior to joining the Company, the executive officer sold his interest in this external consulting firm and was paid with a combination of cash and a $1.0 million note that will be paid in equal installments ending in 2019. Expenses to this external consulting firm as well as sponsorships, donations and other services to related parties totaled less than $0.5 million for the three months ended March 31, 2018 and less than $1.5 million for the three months ended March 31, 2017 .

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2018
Accounting Policies [Abstract]
Nature of Operation	Nature of operation WAL is a bank holding company headquartered in Phoenix, Arizona, incorporated under the laws of the state of Delaware. WAL provides a full spectrum of deposit, lending, treasury management, international banking, and online banking products and services through its wholly-owned banking subsidiary, WAB. WAB operates the following full-service banking divisions: ABA, BON, FIB, Bridge, and TPB. The Company also serves business customers through a national platform of specialized financial services including AAB, Corporate Finance, Equity Fund Resources, HFF, Life Sciences Group, Mortgage Warehouse Lending, Public and Nonprofit Finance, Renewable Resource Group, Resort Finance, and Technology Finance. In addition, the Company has two non-bank subsidiaries, LVSP, which holds and manages certain non-performing loans and OREO
Basis of Presentation	Basis of presentation The accounting and reporting policies of the Company are in accordance with GAAP and conform to practices within the financial services industry. The accounts of the Company and its consolidated subsidiaries are included in the Consolidated Financial Statements.
Use of Estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management's estimates and judgments are ongoing and are based on experience, current and expected future conditions, third-party evaluations and various other assumptions that management believes are reasonable under the circumstances. The results of these estimates form the basis for making judgments about the carrying values of assets and liabilities, as well as identifying and assessing the accounting treatment with respect to commitments and contingencies. Actual results may differ from those estimates and assumptions used in the Consolidated Financial Statements and related notes. Material estimates that are particularly susceptible to significant changes in the near term relate to the determination of the allowance for credit losses; estimated cash flows related to PCI loans; fair value determinations related to acquisitions and certain assets and liabilities carried at fair value; and accounting for income taxes.
Principles of Consolidation	Principles of consolidation As of March 31, 2018 , WAL has the following significant wholly-owned subsidiaries: WAB, LVSP, and eight unconsolidated subsidiaries used as business trusts in connection with the issuance of trust-preferred securities. The Bank has the following significant wholly-owned subsidiaries: WABT, which holds certain investment securities, municipal and nonprofit loans, and leases; WA PWI, LLC, which holds certain limited partnerships invested primarily in low income housing tax credits and small business investment corporations; and BW Real Estate, Inc., which operates as a real estate investment trust and holds certain of WAB's real estate loans and related securities. The Company does not have any other significant entities that should be considered for consolidation. All significant intercompany balances and transactions have been eliminated in consolidation.
Reclassifications	Reclassifications Certain amounts reported in prior periods may have been reclassified in the Consolidated Financial Statements to conform to the current presentation. The reclassifications have no effect on net income or stockholders’ equity as previously reported.
Investment Securities	Investment securities Investment securities may be classified as HTM, AFS, or measured at fair value. The appropriate classification is initially decided at the time of purchase. Securities classified as HTM are those debt securities that the Company has both the intent and ability to hold to maturity regardless of changes in market conditions, liquidity needs, or general economic conditions. These securities are carried at amortized cost. The sale of a security within three months of its maturity date or after the majority of the principal outstanding has been collected is considered a maturity for purposes of classification and disclosure. Securities classified as AFS or trading securities measured at fair value are reported as an asset in the Consolidated Balance Sheet at their estimated fair value. As the fair value of AFS debt securities changes, the changes are reported net of income tax as an element of OCI, except for other-than-temporarily-impaired securities. Upon adoption of ASU 2016-01, the fair value changes in AFS equity securities are recognized as part of non-interest income, see "Recently adopted accounting guidance" below for further discussion. When AFS debt securities are sold, the unrealized gain or loss is reclassified from OCI to non-interest income. The changes in the fair values of trading securities are reported in non-interest income. Securities classified as AFS are both equity and debt securities that the Company intends to hold for an indefinite period of time, but not necessarily to maturity. Any decision to sell a security classified as AFS would be based on various factors, including significant movements in interest rates, changes in the maturity mix of the Company’s assets and liabilities, liquidity needs, decline in credit quality, and regulatory capital considerations. Interest income is recognized based on the coupon rate and increased by accretion of discounts earned or decreased by the amortization of premiums paid over the contractual life of the security, adjusted for prepayment estimates, using the interest method. In estimating whether there are any OTTI losses, management considers the 1) length of time and the extent to which the fair value has been less than amortized cost; 2) financial condition and near term prospects of the issuer; 3) impact of changes in market interest rates; and 4) intent and ability of the Company to retain its investment for a period of time sufficient to allow for any anticipated recovery in fair value and whether it is not more likely than not the Company would be required to sell the security. Declines in the fair value of individual AFS debt securities that are deemed to be other-than-temporary are reflected in earnings when identified. The fair value of the debt security then becomes the new cost basis. For individual debt securities where the Company does not intend to sell the security and it is not more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis, the other-than-temporary decline in fair value of the debt security related to 1) credit loss is recognized in earnings; and 2) interest rate, market, or other factors is recognized in other comprehensive income or loss. For individual debt securities where the Company either intends to sell the security or more likely than not will not recover all of its amortized cost, the OTTI is recognized in earnings equal to the entire difference between the security's cost basis and its fair value at the balance sheet date. For individual debt securities for which a credit loss has been recognized in earnings, interest accruals and amortization and accretion of premiums and discounts are suspended when the credit loss is recognized. Interest received after accruals have been suspended is recognized on a cash basis.
Restricted Stock	Restricted stock WAB is a member of the Federal Reserve System and, as part of its membership, is required to maintain stock in the FRB in a specified ratio to its capital. In addition, WAB is a member of the FHLB system and, accordingly, maintains an investment in capital stock of the FHLB based on the borrowing capacity used. The Bank also maintains an investment in its primary correspondent bank. All of these investments are considered equity securities with no actively traded market. Therefore, the shares are considered restricted investment securities. These investments are carried at cost, which is equal to the value at which they may be redeemed. The dividend income received from the stock is reported in interest income. The Company conducts a periodic review and evaluation of its restricted stock to determine if any impairment exists.
Loans, held for sale	Loans, held for sale Loans, held for sale consist of SBA loans that the Company originates (or acquires) and intends to sell. These loans are carried at the lower of aggregate cost or fair value. Fair value is determined based on available market data for similar assets, expected cash flows, and appraisals of underlying collateral or the credit quality of the borrower. Gains and losses on the sale of loans are recognized pursuant to ASC 860, Transfers and Servicing . Interest income of these loans is accrued daily and loan origination fees and costs are deferred and included in the cost basis of the loan. The Company issues various representations and warranties associated with these loan sales. The Company has not experienced any losses as a result of these representations and warranties.
Loans, Interest and Fees from Loans	Loans, held for investment The Company generally holds loans for investment and has the intent and ability to hold loans until their maturity. Therefore, they are reported at book value. Net loans are stated at the amount of unpaid principal, adjusted for net deferred fees and costs, purchase accounting fair value adjustments, and an allowance for credit losses. In addition, the book value of loans that are subject to a fair value hedge is adjusted for changes in value attributable to the effective portion of the hedged benchmark interest rate risk. The Company may also acquire loans through a business combination. These acquired loans are recorded at estimated fair value on the date of purchase, which is comprised of unpaid principal adjusted for estimated credit losses and interest rate fair value adjustments. Loans are evaluated individually at the acquisition date to determine if there has been credit deterioration since origination. Such loans may then be aggregated and accounted for as a pool of loans based on common characteristics. When the Company acquires such loans, the yield that may be accreted (accretable yield) is limited to the excess of the Company’s estimate of undiscounted cash flows expected to be collected over the Company’s initial investment in the loan. The excess of contractual cash flows over the cash flows expected to be collected may not be recognized as an adjustment to yield, loss, or a valuation allowance. Subsequent increases in cash flows expected to be collected generally are recognized prospectively through adjustment of the loan’s yield over the remaining life. Subsequent decreases to cash flows expected to be collected are recognized as impairment. The Company may not carry over or create a valuation allowance in the initial accounting for loans acquired under these circumstances. For purchased loans that are not deemed impaired at the acquisition date, fair value adjustments attributable to both credit and interest rates are accreted (or amortized) over the contractual life of the individual loan. For additional information, see " Note 3. Loans, Leases and Allowance for Credit Losses " of these Notes to Unaudited Consolidated Financial Statements. Loan fees collected for the origination of loans less direct loan origination costs (net deferred loan fees) are amortized over the contractual life of the loan through interest income. If the loan has scheduled payments, the amortization of the net deferred loan fee is calculated using the interest method over the contractual life of the loan. If the loan does not have scheduled payments, such as a line of credit, the net deferred loan fee is recognized as interest income on a straight-line basis over the contractual life of the loan commitment. Commitment fees based on a percentage of a customer’s unused line of credit and fees related to standby letters of credit are recognized over the commitment period. When loans are repaid, any remaining unamortized balances of premiums, discounts, or net deferred fees are recognized as interest income. Non-accrual loans: When a borrower discontinues making payments as contractually required by the note, the Company must determine whether it is appropriate to continue to accrue interest. The Company ceases accruing interest income when the loan has become delinquent by more than 90 days or when management determines that the full repayment of principal and collection of interest according to contractual terms is no longer likely. The Company may decide to continue to accrue interest on certain loans more than 90 days delinquent if the loans are well secured by collateral and in the process of collection. For all loan types, when a loan is placed on non-accrual status, all interest accrued but uncollected is reversed against interest income in the period in which the status is changed and, the Company makes a loan-level decision to apply either the cash basis or cost recovery method. The Company recognizes income on a cash basis only for those non-accrual loans for which the collection of the remaining principal balance is not in doubt. Under the cost recovery method, subsequent payments received from the customer are applied to principal and generally no further interest income is recognized until the principal has been paid in full or until circumstances have changed such that payments are again consistently received as contractually required. Impaired loans: A loan is identified as impaired when it is no longer probable that interest and principal will be collected according to the contractual terms of the original loan agreement. Generally, impaired loans are classified as non-accrual. However, in certain instances, impaired loans may continue on an accrual basis, if full repayment of all principal and interest is expected and the loan is both well secured and in the process of collection. Impaired loans are measured for reserve requirements in accordance with ASC 310, Receivables, based on the present value of expected future cash flows discounted at the loan's effective interest rate or, as a practical expedient, at the loan's observable market price or the fair value of the collateral less applicable disposition costs if the loan is collateral dependent. The amount of an impairment reserve, if any, and any subsequent changes are recorded as a provision for credit losses. Losses are recorded as a charge-off when losses are confirmed. In addition to management's internal loan review process, regulators may from time to time direct the Company to modify loan grades, loan impairment calculations, or loan impairment methodology. Troubled Debt Restructured Loans : A TDR loan is a loan on which the Company, for reasons related to a borrower’s financial difficulties, grants a concession to the borrower that the Company would not otherwise consider. The loan terms that have been modified or restructured due to a borrower’s financial situation include, but are not limited to, a reduction in the stated interest rate, an extension of the maturity or renewal of the loan at an interest rate below current market, a reduction in the face amount of the debt, a reduction in the accrued interest, or deferral of interest payments. A TDR loan is also considered impaired. A TDR loan may be returned to accrual status when the loan is brought current, has performed in accordance with the contractual restructured terms for a reasonable period of time (generally six months) and the ultimate collectability of the total contractual restructured principal and interest is no longer in doubt. However, such loans continue to be considered impaired. Consistent with regulatory guidance, a TDR loan that is subsequently modified in another restructuring agreement but has shown sustained performance and classification as a TDR, will be removed from TDR status provided that the modified terms were market-based at the time of modification.
Allowance for Credit Losses	Allowance for credit losses Credit risk is inherent in the business of extending loans and leases to borrowers, for which the Company must maintain an adequate allowance for credit losses. The allowance for credit losses is established through a provision for credit losses recorded to expense. Loans are charged against the allowance for credit losses when management believes that the contractual principal or interest will not be collected. Subsequent recoveries, if any, are credited to the allowance. The allowance is an amount believed adequate to absorb estimated probable losses on existing loans that may become uncollectable, based on evaluation of the collectability of loans and prior credit loss experience, together with other factors. The Company formally re-evaluates and establishes the appropriate level of the allowance for credit losses on a quarterly basis. The allowance consists of specific and general components. The specific allowance applies to impaired loans. For impaired collateral dependent loans, the reserve is calculated based on the collateral value, net of estimated disposition costs. Generally, the Company obtains independent collateral valuation analysis for each loan every twelve months. Loans not collateral dependent are evaluated based on the expected future cash flows discounted at the original contractual interest rate. The general allowance covers all non-impaired loans and incorporates several quantitative and qualitative factors, which are used for all of the Company's portfolio segments. Quantitative factors include company-specific, ten-year historical net charge-offs stratified by loans with similar characteristics. Qualitative factors include: 1) levels of and trends in delinquencies and impaired loans; 2) levels of and trends in charge-offs and recoveries; 3) trends in volume and terms of loans; 4) changes in underwriting standards or lending policies; 5) experience, ability, depth of lending staff; 6) national and local economic trends and conditions; 7) changes in credit concentrations; 8) out-of-market exposures; 9) changes in quality of loan review system; and 10) changes in the value of underlying collateral. Due to the credit concentration of the Company's loan portfolio in real estate secured loans, the value of collateral is heavily dependent on real estate values in Arizona, Nevada, and California. While management uses the best information available to make its evaluation, future adjustments to the allowance may be necessary if there are significant changes in economic or other conditions. In addition, regulators, as an integral part of their examination processes, periodically review the Bank's allowance for credit losses, and may require the Bank to make additions to the allowance based on their judgment about information available to them at the time of their examination. Management regularly reviews the assumptions and formulae used in determining the allowance and makes adjustments if required to reflect the current risk profile of the portfolio.
Goodwill and Other Intangible Assets	Goodwill and other intangible assets The Company records as goodwill the excess of the purchase price over the fair value of the identifiable net assets acquired in accordance with applicable guidance. The Company performs its annual goodwill and intangibles impairment tests as of October 1 each year, or more often if events or circumstances indicate that the carrying value may not be recoverable. The Company can first elect to assess, through qualitative factors, whether it is more likely than not that goodwill is impaired. If the qualitative assessment indicates potential impairment, the Company will proceed with a two-step process. The first step tests for impairment, while the second step, if necessary, measures the impairment. The resulting impairment amount, if any, is charged to current period earnings as non-interest expense. The Company’s intangible assets consist primarily of core deposit intangible assets that are amortized over periods ranging from 5 to 10 years. The Company considers the remaining useful lives of its core deposit intangible assets each reporting period, as required by ASC 350, Intangibles—Goodwill and Other, to determine whether events and circumstances warrant a revision to the remaining period of amortization. If the estimate of an intangible asset’s remaining useful life has changed, the remaining carrying amount of the intangible asset is amortized prospectively over the revised remaining useful life.
Other Assets Acquired Through Foreclosure	Other assets acquired through foreclosure Other assets acquired through foreclosure consist primarily of properties acquired as a result of, or in-lieu-of, foreclosure. Properties or other assets (primarily repossessed assets formerly leased) are classified as OREO and other repossessed property and are initially reported at fair value of the asset less estimated selling costs. Subsequent adjustments are based on the lower of carrying value or fair value less estimated costs to sell the property. Costs related to the development or improvement of the assets are capitalized and costs related to holding the assets are charged to non-interest expense. Property is evaluated regularly to ensure the recorded amount is supported by its current fair value and valuation allowances.
Treasury Stock [Text Block]	Treasury shares The Company separately presents treasury shares, which represent shares surrendered to the Company equal in value to the statutory payroll tax withholding obligations arising from the vesting of employee restricted stock awards. Treasury shares are carried at cost.
Derivative Financial Instruments	Derivative financial instruments The Company uses interest-rate swaps to mitigate interest-rate risk associated with changes to 1) the fair value of certain fixed-rate financial instruments (fair value hedges) and 2) certain cash flows related to future interest payments on variable rate financial instruments (cash flow hedges). The Company recognizes derivatives as assets or liabilities in the Consolidated Balance Sheet at their fair value in accordance with ASC 815, Derivatives and Hedging . The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and further, on the type of hedging relationship. On the date the derivative contract is entered into, the Company designates the derivative as a fair value hedge or cash flow hedge. Derivative instruments designated in a hedge relationship to mitigate exposure to changes in the fair value of an asset or liability attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivative instruments designated in a hedge relationship to mitigate exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. Changes in the fair value of a derivative that is designated and qualifies as a fair value hedge, along with changes in the fair value of the hedged asset or liability that are attributable to the hedged risk are recorded in current-period earnings. For a cash flow hedge, the effective portion of the change in the fair value of the derivative is recorded in AOCI and reclassified into earnings in the same period or periods during which the hedged transaction affects earnings. Any ineffective portion of the change in fair value of a cash flow hedge is recognized immediately in non-interest income in the Consolidated Income Statement. Under both the fair value and cash flow hedge scenarios, changes in the fair value of derivatives not considered to be highly effective in hedging the change in fair value or the expected cash flows of the hedged item are recognized in earnings as non-interest income during the period of the change. The Company documents its hedge relationships, including identification of the hedging instruments and the hedged items, as well as its risk management objectives and strategies for undertaking the hedge transaction at the time the derivative contract is executed. Both at inception and at least quarterly thereafter, the Company assesses whether the derivatives used in hedging transactions are highly effective (as defined in the guidance) in offsetting changes in either the fair value or cash flows of the hedged item. Retroactive effectiveness is assessed, as well as the continued expectation that the hedge will remain effective prospectively. The Company discontinues hedge accounting prospectively when it is determined that a hedge is no longer highly effective. When hedge accounting is discontinued on a fair value hedge that no longer qualifies as an effective hedge, the derivative continues to be reported at fair value in the Consolidated Balance Sheet, but the carrying amount of the hedged item is no longer adjusted for future changes in fair value. The adjustment to the carrying amount of the hedged item that existed at the date hedge accounting is discontinued is amortized over the remaining life of the hedged item into earnings. Derivative instruments that are not designated as hedges, so called free-standing derivatives, are reported in the Consolidated Balance Sheet at fair value and the changes in fair value are recognized in earnings as non-interest income during the period of change. The Company may in the normal course of business purchase a financial instrument or originate a loan that contains an embedded derivative instrument. Upon purchasing the instrument or originating the loan, the Company assesses whether the economic characteristics of the embedded derivative are clearly and closely related to the economic characteristics of the remaining component of the financial instrument (i.e., the host contract) and whether a separate instrument with the same terms as the embedded instrument would meet the definition of a derivative instrument. When it is determined that the embedded derivative possesses economic characteristics that are not clearly and closely related to the economic characteristics of the host contract and a separate instrument with the same terms would qualify as a derivative instrument, the embedded derivative is separated from the host contract and carried at fair value. However, in cases where the host contract is measured at fair value, with changes in fair value reported in current earnings, or the Company is unable to reliably identify and measure an embedded derivative for separation from its host contract, the entire contract is carried in the Consolidated Balance Sheet at fair value and is not designated as a hedging instrument.
Off-Balance Sheet Instruments	Off-balance sheet instruments In the ordinary course of business, the Company has entered into off-balance sheet financial instrument arrangements consisting of commitments to extend credit and standby letters of credit. Such financial instruments are recorded in the Consolidated Financial Statements when they are funded. They involve, to varying degrees, elements of credit risk in excess of amounts recognized in the Consolidated Balance Sheet. Losses would be experienced when the Company is contractually obligated to make a payment under these instruments and must seek repayment from the borrower, which may not be as financially sound in the current period as they were when the commitment was originally made. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. The Company enters into credit arrangements that generally provide for the termination of advances in the event of a covenant violation or other event of default. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer’s creditworthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the Company upon extension of credit, is based on management’s credit evaluation of the party. The commitments are collateralized by the same types of assets used as loan collateral. As with outstanding loans, the Company applies qualitative factors and utilization rates to its off-balance sheet obligations in determining an estimate of losses inherent in these contractual obligations. The estimate for credit losses on off-balance sheet instruments is included in other liabilities and the charge to income that establishes this liability is included in non-interest expense. The Company also has off-balance sheet arrangements related to its derivative instruments. Derivative instruments are recognized in the Consolidated Financial Statements at fair value and their notional values are carried off-balance sheet. See " Note 9. Derivatives and Hedging Activities " of these Notes to Unaudited Consolidated Financial Statements for further discussion.
Fair Values of Financial Instruments	Fair values of financial instruments The Company uses fair value measurements to record fair value adjustments to certain assets and liabilities. ASC 820, Fair Value Measurement , establishes a framework for measuring fair value and a three-level valuation hierarchy for disclosure of fair value measurement, as well as enhances disclosure requirements for fair value measurements. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. The Company uses various valuation approaches, including market, income, and/or cost approaches. ASC 820 establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability developed based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the factors market participants would consider in pricing the asset or liability developed based on the best information available in the circumstances. The hierarchy is broken down into three levels based on the reliability of inputs, as follows: • Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. • Level 2 - Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. These might include quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (such as interest rates, prepayment speeds, volatilities, etc.) or model-based valuation techniques where all significant assumptions are observable, either directly or indirectly, in the market. • Level 3 - Valuation is generated from model-based techniques where one or more significant inputs are not observable, either directly or indirectly, in the market. These unobservable assumptions reflect the Company’s own estimates of assumptions that market participants would use in pricing the asset or liability. Valuation techniques may include use of matrix pricing, discounted cash flow models, and similar techniques. The availability of observable inputs varies based on the nature of the specific financial instrument. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, for disclosure purposes, the level in the fair value hierarchy within which the fair value measurement in its entirety falls is determined based on the lowest level input that is significant to the fair value measurement in its entirety. Fair value is a market-based measure considered from the perspective of a market participant who may purchase the asset or assume the liability rather than an entity-specific measure. When market assumptions are available, ASC 820 requires the Company to make assumptions regarding the assumptions that market participants would use to estimate the fair value of the financial instrument at the measurement date. ASC 825, Financial Instruments , requires disclosure of fair value information about financial instruments, whether or not recognized in the balance sheet, for which it is practicable to estimate that value. Management uses its best judgment in estimating the fair value of the Company’s financial instruments; however, there are inherent limitations in any estimation technique. Therefore, for substantially all financial instruments, the fair value estimates presented herein are not necessarily indicative of the amounts the Company could have realized in a sales transaction at March 31, 2018 and 2017 . The estimated fair value amounts for March 31, 2018 and 2017 have been measured as of period-end, and have not been re-evaluated or updated for purposes of these Consolidated Financial Statements subsequent to those dates. As such, the estimated fair values of these financial instruments subsequent to the reporting date may be different than the amounts reported at period-end. The information in " Note 13. Fair Value Accounting " in these Notes to Unaudited Consolidated Financial Statements should not be interpreted as an estimate of the fair value of the entire Company since a fair value calculation is only required for a limited portion of the Company’s assets and liabilities. Due to the wide range of valuation techniques and the degree of subjectivity used in making the estimate, comparisons between the Company’s disclosures and those of other companies or banks may not be meaningful. The following methods and assumptions were used by the Company in estimating the fair value of its financial instruments: Cash and cash equivalents The carrying amounts reported in the Consolidated Balance Sheets for cash and due from banks approximate their fair value. Money market investments The carrying amounts reported in the Consolidated Balance Sheets for money market investments approximate their fair value. Investment securities The fair values of CRA investments, exchange-listed preferred stock, and certain corporate debt securities are based on quoted market prices and are categorized as Level 1 in the fair value hierarchy. The fair values of other investment securities were determined based on matrix pricing. Matrix pricing is a mathematical technique that utilizes observable market inputs including, for example, yield curves, credit ratings, and prepayment speeds. Fair values determined using matrix pricing are generally categorized as Level 2 in the fair value hierarchy. Restricted stock WAB is a member of the Federal Reserve System and the FHLB and, accordingly, maintains investments in the capital stock of the FRB and the FHLB. WAB also maintains an investment in its primary correspondent bank. These investments are carried at cost since no ready market exists for them, and they have no quoted market value. The Company conducts a periodic review and evaluation of its restricted stock to determine if any impairment exists. The fair values of these investments have been categorized as Level 2 in the fair value hierarchy. Loans The fair value of loans is estimated based on discounted cash flows using interest rates currently being offered for loans with similar terms to borrowers with similar credit quality and adjustments that the Company believes a market participant would consider in determining fair value based on a third party independent valuation. As a result, the fair value for loans is categorized as Level 2 in the fair value hierarchy, excluding impaired loans which are categorized as Level 3. Accrued interest receivable and payable The carrying amounts reported in the Consolidated Balance Sheets for accrued interest receivable and payable approximate their fair value. Derivative financial instruments All derivatives are recognized in the Consolidated Balance Sheets at their fair value. The fair value for derivatives is determined based on market prices, broker-dealer quotations on similar products, or other related input parameters. As a result, the fair values have been categorized as Level 2 in the fair value hierarchy. Deposits The fair value disclosed for demand and savings deposits is by definition equal to the amount payable on demand at their reporting date (that is, their carrying amount), which the Company believes a market participant would consider in determining fair value. The carrying amount for variable-rate deposit accounts approximates their fair value. Fair values for fixed-rate certificates of deposit are estimated using a discounted cash flow calculation that applies interest rates currently being offered on certificates to a schedule of aggregated expected monthly maturities on these deposits. The fair value measurement of the deposit liabilities is categorized as Level 2 in the fair value hierarchy. FHLB advances and customer repurchase agreements The fair values of the Company’s borrowings are estimated using discounted cash flow analyses, based on the market rates for similar types of borrowing arrangements. The FHLB advances and customer repurchase agreements have been categorized as Level 2 in the fair value hierarchy due to their short durations. Subordinated debt The fair value of subordinated debt is based on the market rate for the respective subordinated debt security. Subordinated debt has been categorized as Level 3 in the fair value hierarchy. Junior subordinated debt Junior subordinated debt is valued based on a discounted cash flow model which uses as inputs Treasury Bond rates and the 'BB' rated financial index. Junior subordinated debt has been categorized as Level 3 in the fair value hierarchy. Off-balance sheet instruments The fair value of the Company’s off-balance sheet instruments (lending commitments and standby letters of credit) is based on quoted fees currently charged to enter into similar agreements, taking into account the remaining terms of the agreements, and the counterparties’ credit standing.
Recent Accounting Pronouncements	Recent accounting pronouncements In February 2016, the FASB issued guidance within ASU 2016-02, Leases. The amendments in ASU 2016-02 to Topic 842, Leases, require lessees to recognize the lease assets and lease liabilities arising from operating leases in the statement of financial position. The accounting applied by a lessor is largely unchanged from that applied under previous GAAP. The amendments in this ASU are effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. Management is in its implementation assessment stage, which includes identifying the population of the Company's leases that are within the scope of the new guidance, gathering all key lease data, and considering new lease software options that will facilitate application of the new accounting requirements. In June 2016, the FASB issued guidance within ASU 2016-13, Measurement of Credit Losses on Financial Instruments . The amendments in ASU 2016-13 to Topic 326, Financial Instruments - Credit Losses, require that an organization measure all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. The ASU also requires enhanced disclosures, including qualitative and quantitative disclosures that provide additional information about the amounts recorded in the financial statements. Additionally, the ASU amends the accounting for credit losses on AFS debt securities and purchased financial assets with credit deterioration. The amendments in this ASU are effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Management has formed a Steering Committee and established an implementation team made up of subject matter experts across different functions within the Company, including Finance, Risk, Credit, and IT, that will facilitate all phases of planning and implementation of the new guidance. Under the direction of the Company's CECL Steering Committee and in partnership with its Enterprise Project Management Office, the implementation team has completed its gap assessment and are fully engaged with the implementation of its plan. Key initiatives underway include model development, data adequacy and formation, accounting policy drafting and software solution installations. Further, the team is also in the process of evaluating its control framework to identify risks resulting from new processes, judgments, and data. In March 2017, the FASB issued guidance within ASU 2017-08, Premium Amortization on Purchased Callable Debt Securities . The amendments in ASU 2017-08 to Subtopic 310-20, Receivables-Nonrefundable Fees and Other Costs, shorten the amortization period for certain purchased callable debt securities held at a premium to the earliest call date, which more closely align the amortization period of premiums and discounts to expectations incorporated in market pricing on the underlying securities. Under current GAAP, entities generally amortize the premium as an adjustment of yield over the contractual life of the instrument. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. The amendments in this ASU should be applied on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The amendments in this ASU are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted, including adoption in an interim period. The adoption of this guidance is not expected to have a significant impact on the Company's Consolidated Financial Statements. Recently adopted accounting guidance In May 2014, the FASB issued guidance within ASU 2014-09, Revenue from Contracts with Customers . The amendments in ASU 2014-09 to ASC 606, Revenue from Contracts with Customers, creates a common revenue standard and clarifies the principles for recognizing revenue that can be applied consistently across various transactions, industries, and capital markets. The amendments in the ASU clarify that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. As part of that principle, the entity should identify the contract(s) with the customer, identify the performance obligation(s) of the contract, determine the transaction price, allocate that transaction price to the performance obligation(s) of the contract, and then recognize revenue when or as the entity satisfies the performance obligation(s). The Company adopted ASU 2014-09 on January 1, 2018 using the modified retrospective method. Substantially all of the Company's revenue is generated from interest income related to loans and investment securities, which are not within the scope of this guidance. The contracts that are within the scope of this guidance include service charges and fees on deposit accounts, certain types of card income, and success fees earned from equity investments. The Company has completed its review of contracts and other agreements that are within the scope of this guidance and did not identify any material changes to the timing or amount of revenue recognition. The Company’s accounting policies did not change materially since the principles of revenue recognition in the ASU are largely consistent with current practices applied by the Company. The Company has expanded its qualitative disclosures of performance obligations and disaggregation of significant categories of revenue. See " Note 15. Revenue from Contracts with Customers " for further discussion. In January 2016, the FASB issued guidance within ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities . The amendments in ASU 2016-01 to Subtopic 825-10, Financial Instruments, contain the following elements: 1) requires equity investments to be measured at fair value with changes in fair value recognized in net income; 2) simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; 3) eliminates the requirement for public entities to disclose the methods and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; 4) requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; 5) requires an entity to present separately in OCI the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments; 6) requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or accompanying notes to the financial statements; 7) clarifies that the entity should evaluate the need for a valuation allowance on a deferred tax asset related to AFS securities in combination with the entity's other deferred tax assets. Effective on January 1, 2015, the Company adopted the amendment noted in item 5) above as discussed in the Company's Annual Report on Form 10-K for the year ended December 31, 2015. Effective on January 1, 2018, the Company adopted the other amendments in this guidance. The primary impact on the Company's Consolidated Financial Statements results from the amendments discussed in item 1) above as changes in the fair value of the Company's equity investments are now recognized in net income, rather than in AOCI. As of January 1, 2018, the Company recorded a cumulative-effect adjustment of $0.4 million to decrease accumulated other comprehensive income with a corresponding increase to opening retained earnings. During the three months ended March 31, 2018, the Company recognized a loss of $1.1 million related to fair value changes in equity securities, which was recorded in the Consolidated Income Statement. In August 2016, the FASB issued guidance within ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments. The amendments in ASU 2016-15 to Topic 230, Statement of Cash Flows, provide guidance on eight specific cash flow classification issues: 1) debt prepayment or debt extinguishment costs; 2) settlement of zero-coupon debt instruments; 3) contingent consideration payments made after a business combination; 4) proceeds from the settlement of insurance claims; 5) proceeds from the settlement of corporate-owned life insurance policies, including bank-owned life insurance policies; 6) distributions received from equity method investments; 7) beneficial interest in securitization transactions; and 8) separately identifiable cash flows and the application of the predominance principle. The adoption of this guidance did not have a significant impact on the Company's Consolidated Statement of Cash Flows. In January 2017, the FASB issued guidance within ASU 2017-01, Clarifying the Definition of a Business . The amendments in ASU 2017-01 to Topic 805, Business Combinations, clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The adoption of this guidance did not have a significant impact on the Company's Consolidated Financial Statements. In January 2017, the FASB issued guidance within ASU 2017-04, Simplifying the Test for Goodwill Impairment . The amendments in ASU 2017-04 to Topic 350, Intangibles - Goodwill and Other, modify the concept of impairment from the condition that exists when the carrying amount of goodwill exceeds its implied fair value to the condition that exists when the carrying amount of a reporting unit exceeds its fair value. Accordingly, the amendments eliminate Step 2 from the goodwill impairment test because goodwill impairment will no longer be determined by calculating the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities as if that reporting unit had been acquired in a business combination. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. The adoption of this guidance did not have a significant impact on the Company's Consolidated Financial Statements. In February 2017, the FASB issued guidance within ASU 2017-05, Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets . The amendments in ASU 2017-05 to Subtopic 610-20, Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets, clarify the scope of Subtopic 610-20 and add guidance for partial sales of nonfinancial assets, including partial sales of real estate. Under current GAAP, there are several different accounting models to evaluate whether the transfer of certain assets qualify for sale treatment. The new standard reduces the number of potential accounting models that might apply and clarifies which model does apply in various circumstances. The adoption of this guidance did not have a significant impact on the Company's Consolidated Financial Statements. In May 2017, the FASB issued guidance within ASU 2017-09, Scope of Modification Accounting . The amendments in ASU 2017-09 to Topic 718, Compensation - Stock Compensation, provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. An entity should account for the effects of a modification unless all of the following conditions are met: the fair value of the modified award is the same as the fair value of the original award immediately before the original award is modified; the vesting conditions of the modified award are the same as the vesting conditions of the original award immediately before the original award is modified; and the classification of the modified award as an equity instrument or a liability instrument is the same as the classification of the original award immediately before the original award is modified. The adoption of this guidance did not have a significant impact on the Company's Consolidated Financial Statements. In February 2018, the FASB issued guidance within ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . Under current GAAP, the effect of a change in tax laws or rates on deferred tax liabilities and assets are included in income from continuing operations even in situations in which the related income tax effects of items in AOCI were originally recognized in comprehensive income. Accordingly, as the adjustment of deferred taxes due to the reduction of the historical corporate income tax rate to the newly enacted corporate income tax rate is required to be included in income from continuing operations, the tax effects of items within AOCI do not reflect the current tax rate. The amendments in ASU 2018-02 to Topic 220, Income Statement - Reporting Comprehensive Income, allow a reclassification from AOCI to retained earnings from tax effects resulting from the TCJA. The Company elected to adopt this guidance effective January 1, 2018 and recorded a cumulative-effect adjustment of $0.7 million to decrease accumulated other comprehensive income with a corresponding increase to opening retained earnings.

Investment Securities (Tables)

Investment Securities (Tables)	3 Months Ended
Investment Securities (Tables)	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Carrying Amounts and Fair Values of Investment Securities	The carrying amounts and fair values of investment securities at March 31, 2018 and December 31, 2017 are summarized as follows: March 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (in thousands) Held-to-maturity Tax-exempt $ 262,304 $ 795 $ (7,681 ) $ 255,418 Available-for-sale CDO $ 50 $ 19,403 $ — $ 19,453 Commercial MBS issued by GSEs 110,347 60 (5,434 ) 104,973 Corporate debt securities 105,040 140 (3,504 ) 101,676 CRA investments 51,771 — (925 ) 50,846 Preferred stock 92,959 1,191 (832 ) 93,318 Private label residential MBS 839,655 32 (20,691 ) 818,996 Residential MBS issued by GSEs 1,676,686 210 (49,997 ) 1,626,899 Tax-exempt 499,045 6,083 (7,207 ) 497,921 Trust preferred securities 32,000 — (3,383 ) 28,617 U.S. government sponsored agency securities 64,000 — (3,710 ) 60,290 U.S. treasury securities 2,496 — (23 ) 2,473 Total AFS securities $ 3,474,049 $ 27,119 $ (95,706 ) $ 3,405,462 December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (in thousands) Held-to-maturity Tax-exempt $ 255,050 $ 4,514 $ (3,250 ) $ 256,314 Available-for-sale CDO $ 50 $ 21,807 $ — $ 21,857 Commercial MBS issued by GSEs 113,069 46 (4,038 ) 109,077 Corporate debt securities 105,044 261 (1,822 ) 103,483 CRA investments 51,133 — (517 ) 50,616 Preferred stock 52,172 1,160 (136 ) 53,196 Private label residential MBS 874,261 756 (6,493 ) 868,524 Residential MBS issued by GSEs 1,719,188 810 (30,703 ) 1,689,295 Tax-exempt 501,988 10,893 (1,971 ) 510,910 Trust preferred securities 32,000 — (3,383 ) 28,617 U.S. government sponsored agency securities 64,000 — (2,538 ) 61,462 U.S. treasury securities 2,496 — (14 ) 2,482 Total AFS securities $ 3,515,401 $ 35,733 $ (51,615 ) $ 3,499,519
Unrealized Losses and Fair Value of Investment Securities in Continuous Unrealized Loss Position	Information pertaining to securities with gross unrealized losses at March 31, 2018 and December 31, 2017 , aggregated by investment category and length of time that individual securities have been in a continuous loss position follows: March 31, 2018 Less Than Twelve Months More Than Twelve Months Total Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (in thousands) Held-to-Maturity Tax-exempt $ 7,681 $ 208,272 $ — $ — $ 7,681 $ 208,272 Available-for-sale Commercial MBS issued by GSEs $ 262 $ 11,999 $ 5,172 $ 91,109 $ 5,434 $ 103,108 Corporate debt securities 2,200 57,799 1,304 38,696 3,504 96,495 CRA investments — — 925 50,846 925 50,846 Preferred stock 832 47,808 — — 832 47,808 Private label residential MBS 13,613 625,316 7,078 188,584 20,691 813,900 Residential MBS issued by GSEs 25,817 1,096,496 24,180 512,464 49,997 1,608,960 Tax-exempt 3,278 173,905 3,929 67,415 7,207 241,320 Trust preferred securities — — 3,383 28,617 3,383 28,617 U.S. government sponsored agency securities 94 4,906 3,616 55,384 3,710 60,290 U.S. treasury securities 23 2,473 — — 23 2,473 Total AFS securities $ 46,119 $ 2,020,702 $ 49,587 $ 1,033,115 $ 95,706 $ 3,053,817 December 31, 2017 Less Than Twelve Months More Than Twelve Months Total Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (in thousands) Held-to-maturity Tax-exempt $ 3,250 $ 107,921 $ — $ — $ 3,250 $ 107,921 Available-for-sale Commercial MBS issued by GSEs $ 161 $ 13,565 $ 3,877 $ 93,641 $ 4,038 $ 107,206 Corporate debt securities 1,398 78,602 424 19,576 1,822 98,178 CRA investments — — 517 50,616 517 50,616 Preferred stock 136 7,357 — — 136 7,357 Private label residential MBS 3,115 480,885 3,378 188,710 6,493 669,595 Residential MBS issued by GSEs 13,875 999,478 16,828 523,270 30,703 1,522,748 Tax-exempt 17 6,159 1,954 69,674 1,971 75,833 Trust preferred securities — — 3,383 28,617 3,383 28,617 U.S. government sponsored agency securities 14 4,986 2,524 56,476 2,538 61,462 U.S. treasury securities 14 2,482 — — 14 2,482 Total AFS securities $ 18,730 $ 1,593,514 $ 32,885 $ 1,030,580 $ 51,615 $ 2,624,094
Amortized Cost and Fair Value of Investment Securities by Contractual Maturities	The amortized cost and fair value of securities as of March 31, 2018 , by contractual maturities, are shown below. MBS are shown separately as individual MBS are comprised of pools of loans with varying maturities. Therefore, these securities are listed separately in the maturity summary. March 31, 2018 Amortized Cost Estimated Fair Value (in thousands) Held-to-maturity Due in one year or less $ 1,200 $ 1,208 After one year through five years 10,100 10,206 After five years through ten years 14,847 14,475 After ten years 236,157 229,529 Total HTM securities $ 262,304 $ 255,418 Available-for-sale Due in one year or less $ 55,801 $ 54,879 After one year through five years 15,947 16,242 After five years through ten years 256,070 251,220 After ten years 519,543 532,253 Mortgage-backed securities 2,626,688 2,550,868 Total AFS securities $ 3,474,049 $ 3,405,462
Investment Securities by Credit Rating Type	The following tables summarize the carrying amount of the Company’s investment ratings position as of March 31, 2018 and December 31, 2017 : March 31, 2018 AAA Split-rated AAA/AA+ AA+ to AA- A+ to A- BBB+ to BBB- BB+ and below Unrated Totals (in thousands) Held-to-maturity Tax-exempt $ — $ — $ — $ — $ — $ — $ 262,304 $ 262,304 Available-for-sale CDO $ — $ — $ — $ — $ — $ 19,453 $ — $ 19,453 Commercial MBS issued by GSEs — 104,973 — — — — — 104,973 Corporate debt securities — — — 72,747 28,929 — — 101,676 CRA investments — 25,078 — — — — 25,768 50,846 Preferred stock — — — 10,118 64,444 4,031 14,725 93,318 Private label residential MBS 748,064 — 67,405 998 879 1,650 — 818,996 Residential MBS issued by GSEs — 1,626,899 — — — — — 1,626,899 Tax-exempt 62,746 24,635 243,818 163,250 — — 3,472 497,921 Trust preferred securities — — — — 28,617 — — 28,617 U.S. government sponsored agency securities — 60,290 — — — — — 60,290 U.S. treasury securities — 2,473 — — — — — 2,473 Total AFS securities (1) $ 810,810 $ 1,844,348 $ 311,223 $ 247,113 $ 122,869 $ 25,134 $ 43,965 $ 3,405,462 (1) Where ratings differ, the Company uses an average of the available ratings by major credit agencies. December 31, 2017 AAA Split-rated AAA/AA+ AA+ to AA- A+ to A- BBB+ to BBB- BB+ and below Unrated Totals (in thousands) Held-to-maturity Tax-exempt $ — $ — $ — $ — $ — $ — $ 255,050 $ 255,050 Available-for-sale CDO $ — $ — $ — $ — $ — $ 21,857 $ — $ 21,857 Commercial MBS issued by GSEs — 109,077 — — — — — 109,077 Corporate debt securities — — — 74,293 29,190 — — 103,483 CRA investments — 25,349 — — — — 25,267 50,616 Preferred stock — — — 10,388 23,822 4,104 14,882 53,196 Private label residential MBS 809,242 — 55,161 1,350 931 1,840 — 868,524 Residential MBS issued by GSEs — 1,689,295 — — — — — 1,689,295 Tax-exempt 64,893 25,280 249,200 167,994 — — 3,543 510,910 Trust preferred securities — — — — 28,617 — — 28,617 U.S. government sponsored agency securities — 61,462 — — — — — 61,462 U.S. treasury securities — 2,482 — — — — — 2,482 Total AFS securities (1) $ 874,135 $ 1,912,945 $ 304,361 $ 254,025 $ 82,560 $ 27,801 $ 43,692 $ 3,499,519 (1) Where ratings differ, the Company uses an average of the available ratings by major credit agencies.
Gross Gains and (Losses) on Sales of Investment Securities	The following table presents gross gains and losses on sales of investment securities: Three Months Ended March 31, 2018 2017 (in thousands) Gross gains $ — $ 636 Gross losses — (1 ) Net gains on sales of investment securities $ — $ 635

Loans, Leases and Allowance f26

Loans, Leases and Allowance for Credit Losses (Tables)	3 Months Ended
Loans, Leases and Allowance for Credit Losses (Tables)	Mar. 31, 2018
Receivables [Abstract]
Schedule of Held for Investment Loan Portfolio Composition of Loans, Leases and Allowance for Credit Losses	The composition of the Company’s held for investment loan portfolio is as follows: March 31, 2018 December 31, 2017 (in thousands) Commercial and industrial $ 6,944,381 $ 6,841,381 Commercial real estate - non-owner occupied 3,925,301 3,904,011 Commercial real estate - owner occupied 2,264,650 2,241,613 Construction and land development 1,957,489 1,632,204 Residential real estate 418,127 425,940 Consumer 50,505 48,786 Loans, net of deferred loan fees and costs 15,560,453 15,093,935 Allowance for credit losses (144,659 ) (140,050 ) Total loans HFI $ 15,415,794 $ 14,953,885
Contractual Aging of Loan Portfolio by Class of Loans Including Loans Held for Sale and Excluding Deferred Fees/Costs	The following table presents the contractual aging of the recorded investment in past due loans held for investment by class of loans: March 31, 2018 Current 30-59 Days 60-89 Days Over 90 Days Past Due Total Total (in thousands) Commercial and industrial $ 6,932,086 $ 5,094 $ 4,970 $ 2,231 $ 12,295 $ 6,944,381 Commercial real estate Owner occupied 2,263,102 1,418 — 130 1,548 2,264,650 Non-owner occupied 3,732,372 — — 2,799 2,799 3,735,171 Multi-family 190,130 — — — — 190,130 Construction and land development Construction 1,259,939 — — — — 1,259,939 Land 697,550 — — — — 697,550 Residential real estate 413,726 1,397 — 3,004 4,401 418,127 Consumer 49,907 — 259 339 598 50,505 Total loans $ 15,538,812 $ 7,909 $ 5,229 $ 8,503 $ 21,641 $ 15,560,453 December 31, 2017 Current 30-59 Days 60-89 Days Over 90 days Total Total (in thousands) Commercial and industrial $ 6,835,385 $ 2,245 $ 669 $ 3,082 $ 5,996 $ 6,841,381 Commercial real estate Owner occupied 2,240,457 1,026 — 130 1,156 2,241,613 Non-owner occupied 3,696,729 2,993 — 2,847 5,840 3,702,569 Multi-family 201,442 — — — — 201,442 Construction and land development Construction 1,090,176 — — — — 1,090,176 Land 536,917 — — 5,111 5,111 542,028 Residential real estate 411,857 6,874 1,487 5,722 14,083 425,940 Consumer 48,408 83 213 82 378 48,786 Total loans $ 15,061,371 $ 13,221 $ 2,369 $ 16,974 $ 32,564 $ 15,093,935
Summary of Recorded Investment in Nonaccrual Loans and Loans Past Due 90 Days Still Accruing Interest by Loan Class	The following table presents the recorded investment in non-accrual loans and loans past due ninety days or more and still accruing interest by class of loans: March 31, 2018 December 31, 2017 Non-accrual loans Loans past due 90 days or more and still accruing Non-accrual loans Loans past due 90 days or more and still accruing Current Past Due/ Total Current Past Due/ Total (in thousands) Commercial and industrial $ 16,103 $ 8,081 $ 24,184 $ 37 $ 17,913 $ 4,113 $ 22,026 $ 43 Commercial real estate Owner occupied — 131 131 — 1,089 792 1,881 — Non-owner occupied — 2,799 2,799 — — 5,840 5,840 — Multi-family — — — — — — — — Construction and land development Construction — — — — — — — — Land — — — — 868 5,111 5,979 — Residential real estate 6,127 3,717 9,844 — 2,039 6,078 8,117 — Consumer — 339 339 — — 82 82 — Total $ 22,230 $ 15,067 $ 37,297 $ 37 $ 21,909 $ 22,016 $ 43,925 $ 43
Loans by Risk Rating	The following tables present gross loans by risk rating: March 31, 2018 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Commercial and industrial $ 6,756,803 $ 100,928 $ 82,499 $ 4,151 $ — $ 6,944,381 Commercial real estate Owner occupied 2,168,305 42,472 53,232 641 — 2,264,650 Non-owner occupied 3,696,971 26,716 11,484 — — 3,735,171 Multi-family 190,130 — — — — 190,130 Construction and land development Construction 1,255,462 4,477 — — — 1,259,939 Land 695,821 905 824 — — 697,550 Residential real estate 398,814 9,146 10,167 — — 418,127 Consumer 49,613 58 834 — — 50,505 Total $ 15,211,919 $ 184,702 $ 159,040 $ 4,792 $ — $ 15,560,453 March 31, 2018 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Current (up to 29 days past due) $ 15,206,755 $ 184,306 $ 143,622 $ 4,129 $ — $ 15,538,812 Past due 30 - 59 days 5,091 374 2,444 — — 7,909 Past due 60 - 89 days 73 22 5,134 — — 5,229 Past due 90 days or more — — 7,840 663 — 8,503 Total $ 15,211,919 $ 184,702 $ 159,040 $ 4,792 $ — $ 15,560,453 December 31, 2017 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Commercial and industrial $ 6,675,574 $ 85,781 $ 76,328 $ 3,698 $ — $ 6,841,381 Commercial real estate Owner occupied 2,149,465 43,122 48,397 629 — 2,241,613 Non-owner occupied 3,676,711 11,166 14,692 — — 3,702,569 Multi-family 201,442 — — — — 201,442 Construction and land development Construction 1,072,342 4,477 13,357 — — 1,090,176 Land 535,412 637 5,979 — — 542,028 Residential real estate 408,527 8,971 8,442 — — 425,940 Consumer 47,824 878 84 — — 48,786 Total $ 14,767,297 $ 155,032 $ 167,279 $ 4,327 $ — $ 15,093,935 December 31, 2017 Pass Special Mention Substandard Doubtful Loss Total (in thousands) Current (up to 29 days past due) $ 14,758,149 $ 154,295 $ 145,934 $ 2,993 $ — $ 15,061,371 Past due 30 - 59 days 7,966 518 4,737 — — 13,221 Past due 60 - 89 days 1,182 219 968 — — 2,369 Past due 90 days or more — — 15,640 1,334 — 16,974 Total $ 14,767,297 $ 155,032 $ 167,279 $ 4,327 $ — $ 15,093,935
Impaired Loans by Loan Class	The following table presents impaired loans by class: March 31, 2018 December 31, 2017 (in thousands) Commercial and industrial $ 43,459 $ 34,156 Commercial real estate Owner occupied 8,107 10,430 Non-owner occupied 17,654 21,251 Multi-family — — Construction and land development Construction — — Land 9,812 15,426 Residential real estate 18,185 17,170 Consumer 375 121 Total $ 97,592 $ 98,554
Recorded Investment in Loans Classified as Impaired	The table below reflects the recorded investment in loans classified as impaired: March 31, 2018 December 31, 2017 (in thousands) Impaired loans with a specific valuation allowance under ASC 310 (1) $ 9,598 $ 19,315 Impaired loans without a specific valuation allowance under ASC 310 (2) 87,994 79,239 Total impaired loans $ 97,592 $ 98,554 Valuation allowance related to impaired loans (3) $ (5,562 ) $ (5,606 ) (1) Includes TDR loans of $3.0 million and $3.7 million at March 31, 2018 and December 31, 2017 , respectively. (2) Includes TDR loans of $48.2 million and $48.8 million at March 31, 2018 and December 31, 2017 , respectively. (3) Includes valuation allowance related to TDR loans of $1.0 million and $1.2 million at March 31, 2018 and December 31, 2017 , respectively. The following table presents the average investment in impaired loans and income recognized on impaired loans: Three Months Ended March 31, 2018 2017 (in thousands) Average balance on impaired loans $ 93,081 $ 103,387 Interest income recognized on impaired loans 873 921 Interest recognized on non-accrual loans, cash basis 438 332
Average Investment in Impaired Loans by Loan Class	The following table presents the average investment in impaired loans by loan class: Three Months Ended March 31, 2018 2017 (in thousands) Commercial and industrial $ 36,849 $ 26,101 Commercial real estate Owner occupied 9,043 21,128 Non-owner occupied 18,925 24,399 Multi-family — — Construction and land development Construction — — Land 10,281 14,432 Residential real estate 17,799 17,103 Consumer 184 224 Total $ 93,081 $ 103,387
Interest Income on Impaired Loans by Loan Class	The following table presents interest income on impaired loans by class: Three Months Ended March 31, 2018 2017 (in thousands) Commercial and industrial $ 250 $ 144 Commercial real estate Owner occupied 127 177 Non-owner occupied 262 239 Multi-family — — Construction and land development Construction — — Land 130 221 Residential real estate 104 139 Consumer — 1 Total $ 873 $ 921
Tabular Disclosure of Nonperforming Assets	The following table summarizes nonperforming assets: March 31, 2018 December 31, 2017 (in thousands) Non-accrual loans (1) $ 37,297 $ 43,925 Loans past due 90 days or more on accrual status (2) 37 43 Accruing troubled debt restructured loans 43,766 42,431 Total nonperforming loans 81,100 86,399 Other assets acquired through foreclosure, net 30,194 28,540 Total nonperforming assets $ 111,294 $ 114,939 (1) Includes non-accrual TDR loans of $7.4 million and $10.1 million at March 31, 2018 and December 31, 2017 , respectively. (2)
Accretable Yield Table	Changes in the accretable yield for loans acquired with deteriorated credit quality are as follows: Three Months Ended March 31, 2018 2017 (in thousands) Balance, at beginning of period $ 9,324 $ 15,177 Reclassifications from non-accretable to accretable yield (1) 683 — Accretion to interest income (313 ) (907 ) Reversal of fair value adjustments upon disposition of loans (1,586 ) (458 ) Balance, at end of period $ 8,108 $ 13,812 (1) The primary drivers of reclassification from non-accretable to accretable yield resulted from changes in estimated cash flows.
Allowances for Credit Losses	The following table summarizes the changes in the allowance for credit losses by portfolio type: Three Months Ended March 31, Construction and Land Development Commercial Real Estate Residential Real Estate Commercial and Industrial Consumer Total (in thousands) 2018 Beginning Balance $ 19,511 $ 31,495 $ 5,478 $ 82,793 $ 773 $ 140,050 Charge-offs — — 107 3,517 — 3,624 Recoveries (1,388 ) (126 ) (250 ) (459 ) (10 ) (2,233 ) Provision 1,695 1,247 (102 ) 3,143 17 6,000 Ending balance $ 22,594 $ 32,868 $ 5,519 $ 82,878 $ 800 $ 144,659 2017 Beginning Balance $ 21,175 $ 25,673 $ 3,851 $ 73,333 $ 672 $ 124,704 Charge-offs — — 115 2,594 34 2,743 Recoveries (277 ) (533 ) (251 ) (328 ) (49 ) (1,438 ) Provision (355 ) 1,798 425 2,362 20 4,250 Ending balance $ 21,097 $ 28,004 $ 4,412 $ 73,429 $ 707 $ 127,649 The following table presents impairment method information related to loans and allowance for credit losses by loan portfolio segment: Commercial Real Estate-Owner Occupied Commercial Real Estate-Non-Owner Occupied Commercial and Industrial Residential Real Estate Construction and Land Development Consumer Total Loans (in thousands) Loans as of March 31, 2018; Recorded Investment Impaired loans with an allowance recorded $ — $ — $ 9,425 $ 173 $ — $ — $ 9,598 Impaired loans with no allowance recorded 8,107 17,654 34,034 18,012 9,812 375 87,994 Total loans individually evaluated for impairment 8,107 17,654 43,459 18,185 9,812 375 97,592 Loans collectively evaluated for impairment 2,248,803 3,805,229 6,900,885 399,346 1,947,677 50,130 15,352,070 Loans acquired with deteriorated credit quality 7,740 102,418 37 596 — — 110,791 Total recorded investment $ 2,264,650 $ 3,925,301 $ 6,944,381 $ 418,127 $ 1,957,489 $ 50,505 $ 15,560,453 Unpaid Principal Balance Impaired loans with an allowance recorded $ — $ — $ 12,250 $ 173 $ — $ — $ 12,423 Impaired loans with no allowance recorded 15,029 24,431 63,541 26,801 26,440 10,950 167,192 Total loans individually evaluated for impairment 15,029 24,431 75,791 26,974 26,440 10,950 179,615 Loans collectively evaluated for impairment 2,248,803 3,805,229 6,900,885 399,346 1,947,677 50,130 15,352,070 Loans acquired with deteriorated credit quality 9,945 124,803 4,412 715 — — 139,875 Total unpaid principal balance $ 2,273,777 $ 3,954,463 $ 6,981,088 $ 427,035 $ 1,974,117 $ 61,080 $ 15,671,560 Related Allowance for Credit Losses Impaired loans with an allowance recorded $ — $ — $ 5,389 $ 173 $ — $ — $ 5,562 Impaired loans with no allowance recorded — — — — — — — Total loans individually evaluated for impairment — — 5,389 173 — — 5,562 Loans collectively evaluated for impairment 14,475 17,566 77,487 5,346 22,594 800 138,268 Loans acquired with deteriorated credit quality — 827 2 — — — 829 Total allowance for credit losses $ 14,475 $ 18,393 $ 82,878 $ 5,519 $ 22,594 $ 800 $ 144,659 Commercial Real Estate-Owner Occupied Commercial Real Estate-Non-Owner Occupied Commercial and Industrial Residential Real Estate Construction and Land Development Consumer Total Loans (in thousands) Loans as of December 31, 2017; Recorded Investment Impaired loans with an allowance recorded $ — $ — $ 19,315 $ — $ — $ — $ 19,315 Impaired loans with no allowance recorded 10,430 21,250 14,842 17,170 15,426 121 79,239 Total loans individually evaluated for impairment 10,430 21,250 34,157 17,170 15,426 121 98,554 Loans collectively evaluated for impairment 2,221,614 3,777,219 6,807,181 408,169 1,616,778 48,665 14,879,626 Loans acquired with deteriorated credit quality 9,569 105,542 43 601 — — 115,755 Total recorded investment $ 2,241,613 $ 3,904,011 $ 6,841,381 $ 425,940 $ 1,632,204 $ 48,786 $ 15,093,935 Unpaid Principal Balance Impaired loans with an allowance recorded $ — $ — $ 20,795 $ — $ — $ — $ 20,795 Impaired loans with no allowance recorded 17,459 28,028 42,261 26,057 32,289 10,695 156,789 Total loans individually evaluated for impairment 17,459 28,028 63,056 26,057 32,289 10,695 177,584 Loans collectively evaluated for impairment 2,221,614 3,777,219 6,807,181 408,169 1,616,778 48,665 14,879,626 Loans acquired with deteriorated credit quality 12,619 128,440 3,146 720 — — 144,925 Total unpaid principal balance $ 2,251,692 $ 3,933,687 $ 6,873,383 $ 434,946 $ 1,649,067 $ 59,360 $ 15,202,135 Related Allowance for Credit Losses Impaired loans with an allowance recorded $ — $ — $ 5,606 $ — $ — $ — $ 5,606 Impaired loans with no allowance recorded — — — — — — — Total loans individually evaluated for impairment — — 5,606 — — — 5,606 Loans collectively evaluated for impairment 13,884 16,135 76,919 5,500 19,599 776 132,813 Loans acquired with deteriorated credit quality — 1,629 2 — — — 1,631 Total allowance for credit losses $ 13,884 $ 17,764 $ 82,527 $ 5,500 $ 19,599 $ 776 $ 140,050

Other Assets Acquired Through27

Other Assets Acquired Through Foreclosure (Tables)	3 Months Ended
Other Assets Acquired Through Foreclosure (Tables)	Mar. 31, 2018
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Changes in Other Assets Acquired Through Foreclosure	The following table represents the changes in other assets acquired through foreclosure: Three Months Ended March 31, 2018 Gross Balance Valuation Allowance Net Balance (in thousands) Balance, beginning of period $ 32,552 $ (4,012 ) $ 28,540 Transfers to other assets acquired through foreclosure, net 5,744 — 5,744 Proceeds from sale of other real estate owned and repossessed assets, net (5,294 ) 9 (5,285 ) Valuation adjustments, net — (47 ) (47 ) Gains (losses), net (1) 1,242 1,242 Balance, end of period $ 34,244 $ (4,050 ) $ 30,194 Three Months Ended March 31, 2017 Balance, beginning of period $ 54,138 $ (6,323 ) $ 47,815 Proceeds from sale of other real estate owned and repossessed assets, net (3,113 ) 224 (2,889 ) Valuation adjustments, net — 380 380 Gains (losses), net (1) (106 ) — (106 ) Balance, end of period $ 50,919 $ (5,719 ) $ 45,200 (1) There was $1.0 million in net gains related to initial transfers to other assets during the three months ended March 31, 2018 and compared to zero during the three months ended March 31, 2017

Other Borrowings (Tables)

Other Borrowings (Tables)	3 Months Ended
Other Borrowings (Tables)	Mar. 31, 2018
Debt Disclosure [Abstract]
Company's Borrowings	The following table summarizes the Company’s borrowings as of March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (in thousands) Short-Term: FHLB advances $ 300,000 $ 390,000 Total short-term borrowings $ 300,000 $ 390,000

Accumulated Other Comprehensi29

Accumulated Other Comprehensive Income (Tables)	3 Months Ended
Accumulated Other Comprehensive Income (Tables)	Mar. 31, 2018
Equity [Abstract]
Summary of Changes in Accumulated Other Comprehensive Income	The following table summarizes the changes in accumulated other comprehensive income (loss) by component, net of tax, for the periods indicated: Three Months Ended March 31, Unrealized holding (losses) gains on AFS Unrealized holding gains on SERP Unrealized holding gains (losses) on junior subordinated debt Impairment loss on securities Total (in thousands) Balance, December 31, 2017 $ (10,026 ) $ 385 $ 6,352 $ 144 $ (3,145 ) Balance, January 1, 2018 (1) (12,556 ) 469 7,740 144 (4,203 ) Other comprehensive (loss) income before reclassifications (38,914 ) (11 ) 1,466 — (37,459 ) Amounts reclassified from accumulated other comprehensive income — — — — — Net current-period other comprehensive (loss) income (38,914 ) (11 ) 1,466 — (37,459 ) Balance, March 31, 2018 $ (51,470 ) $ 458 $ 9,206 $ 144 $ (41,662 ) Balance, December 31, 2016 $ (14,916 ) $ 121 $ 9,956 $ 144 $ (4,695 ) Other comprehensive income (loss) before reclassifications 9,169 (1 ) (1,229 ) — 7,939 Amounts reclassified from accumulated other comprehensive income (393 ) — — — (393 ) Net current-period other comprehensive income (loss) 8,776 (1 ) (1,229 ) — 7,546 Balance, March 31, 2017 $ (6,140 ) $ 120 $ 8,727 $ 144 $ 2,851 (1) As adjusted for adoption of ASU 2016-01 and ASU 2018-02, see " Note 1. Summary of Significant Accounting Policies " for further discussion.
Schedule of Reclassifications Out of Accumulated Other Comprehensive Income	The following table presents reclassifications out of accumulated other comprehensive income (loss): Three Months Ended March 31, Income Statement Classification 2018 2017 (in thousands) Gain on sales of investment securities, net $ — $ 635 Income tax expense — (242 ) Net of tax $ — $ 393

Derivatives and Hedging (Tables

Derivatives and Hedging (Tables)	3 Months Ended
Derivatives and Hedging (Tables)	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position	The fair value of derivative contracts, after taking into account the effects of master netting agreements, is included in other assets or other liabilities in the Consolidated Balance Sheets, as indicated in the following table: March 31, 2018 December 31, 2017 March 31, 2017 Fair Value Fair Value Fair Value Notional Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities (in thousands) Derivatives designated as hedging instruments: Fair value hedges Interest rate swaps $ 989,379 $ 3,533 $ 42,789 $ 993,432 $ 1,703 $ 53,581 $ 1,035,151 $ 1,985 $ 59,136 Total 989,379 3,533 42,789 993,432 1,703 53,581 1,035,151 1,985 59,136 Netting adjustments (1) — 3,493 3,493 — 896 896 — 1,947 1,947 Net derivatives in the balance sheet $ 989,379 $ 40 $ 39,296 $ 993,432 $ 807 $ 52,685 $ 1,035,151 $ 38 $ 57,189 Derivatives not designated as hedging instruments: Foreign currency contracts (2) $ 90,855 $ 684 $ 394 $ 85,335 $ 1,232 $ 983 $ 68,298 $ 327 $ 111 Interest rate swaps 36,840 1,170 1,170 36,969 776 776 38,192 796 796 Total $ 127,695 $ 1,854 $ 1,564 $ 122,304 $ 2,008 $ 1,759 $ 106,490 $ 1,123 $ 907 (1) Netting adjustments represent the amounts recorded to convert the Company's derivative balances from a gross basis to a net basis in accordance with the applicable accounting guidance.
Largest Exposure To Individual Counterparty	The following table summarizes the Company's largest exposure to an individual counterparty at the dates indicated: March 31, 2018 December 31, 2017 March 31, 2017 (in thousands) Largest gross exposure (derivative asset) to an individual counterparty $ 2,515 $ 893 $ 3,569 Collateral posted by this counterparty — — 4,680 Derivative liability with this counterparty 20,624 40,340 — Collateral pledged to this counterparty 29,719 60,476 1,340 Net exposure after netting adjustments and collateral $ — $ — $ 229

Earnings per Share (Tables)

Earnings per Share (Tables)	3 Months Ended
Earnings per Share (Tables)	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table presents the calculation of basic and diluted EPS: Three Months Ended March 31, 2018 2017 (in thousands, except per share amounts) Weighted average shares - basic 104,530 103,987 Dilutive effect of stock awards 794 849 Weighted average shares - diluted 105,324 104,836 Net income available to common stockholders $ 100,900 $ 73,342 Earnings per share - basic 0.97 0.71 Earnings per share - diluted 0.96 0.70

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
Commitments and Contingencies (Tables)	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Summary of Contractual Amounts for Unfunded Commitments and Letters of Credit	A summary of the contractual amounts for unfunded commitments and letters of credit are as follows: March 31, 2018 December 31, 2017 (in thousands) Commitments to extend credit, including unsecured loan commitments of $437,437 at March 31, 2018 and $364,638 at December 31, 2017 $ 6,500,031 $ 5,851,158 Credit card commitments and financial guarantees 186,613 153,752 Standby letters of credit, including unsecured letters of credit of $12,148 at March 31, 2018 and $11,664 at December 31, 2017 181,068 161,966 Total $ 6,867,712 $ 6,166,876

Fair Value Accounting (Tables)

Fair Value Accounting (Tables)	3 Months Ended
Fair Value Accounting (Tables)	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Gains and Losses from Fair Value Changes Included in Consolidated Statement of Operations	For the three months ended March 31, 2018 and 2017 , gains and losses from fair value changes on junior subordinated debt were as follows: Changes in Fair Values for Items Measured at Fair Value Unrealized Gain/(Loss) on Assets and Liabilities Measured at Fair Value, Net Interest Income on Securities Interest Expense on Junior Subordinated Debt Total Changes Included in Current-Period Earnings Total Changes Included in OCI (in thousands) Three Months Ended March 31, 2018 Junior subordinated debt $ 1,944 $ — $ 904 $ 904 $ 1,466 Total $ 1,944 $ — $ 904 $ 904 $ 1,466 Three Months Ended March 31, 2017 Securities measured at fair value $ (1 ) $ 7 $ — $ 6 $ — Junior subordinated debt (1,986 ) — (749 ) (749 ) (1,229 ) Total $ (1,987 ) $ 7 $ (749 ) $ (743 ) $ (1,229 )
Fair Value of Assets and Liabilities	The fair value of assets and liabilities measured at fair value on a recurring basis was determined using the following inputs as of the periods presented: Fair Value Measurements at the End of the Reporting Period Using: Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Fair Value (in thousands) March 31, 2018 Assets: Available-for-sale CDO $ — $ 19,453 $ — $ 19,453 Commercial MBS issued by GSEs — 104,973 — 104,973 Corporate debt securities — 101,676 — 101,676 CRA investments 50,846 — — 50,846 Preferred stock 93,318 — — 93,318 Private label residential MBS — 818,996 — 818,996 Residential MBS issued by GSEs — 1,626,899 — 1,626,899 Tax-exempt — 497,921 — 497,921 Trust preferred securities — 28,617 — 28,617 U.S. government sponsored agency securities — 60,290 — 60,290 U.S. treasury securities — 2,473 — 2,473 Total AFS securities $ 144,164 $ 3,261,298 $ — $ 3,405,462 Derivative assets (1) $ — $ 5,387 $ — $ 5,387 Liabilities: Junior subordinated debt (2) $ — $ — $ 54,290 $ 54,290 Derivative liabilities (1) — 44,353 — 44,353 (1) Derivative assets and liabilities relate to interest rate swaps, see " Note 9. Derivatives and Hedging Activities ." In addition, the carrying value of loans is increased by $18,063 and the net carrying value of subordinated debt is decreased by $21,193 as of March 31, 2018 , which relates to the fair value of the hedges put in place to mitigate against fluctuations in interest rates. (2) Includes only the portion of junior subordinated debt that is recorded at fair value at each reporting period pursuant to the election of FVO treatment. Fair Value Measurements at the End of the Reporting Period Using: Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Fair Value (in thousands) December 31, 2017 Assets: Available-for-sale CDO $ — $ 21,857 $ — $ 21,857 Commercial MBS issued by GSEs — 109,077 — 109,077 Corporate debt securities — 103,483 — 103,483 CRA investments 50,616 — — 50,616 Preferred stock 53,196 — — 53,196 Private label residential MBS — 868,524 — 868,524 Residential MBS issued by GSEs — 1,689,295 — 1,689,295 Tax-exempt — 510,910 — 510,910 Trust preferred securities — 28,617 — 28,617 U.S. government sponsored agency securities — 61,462 — 61,462 U.S. treasury securities — 2,482 — 2,482 Total AFS securities $ 103,812 $ 3,395,707 $ — $ 3,499,519 Derivative assets (1) $ — $ 3,711 $ — $ 3,711 Liabilities: Junior subordinated debt (2) $ — $ — $ 56,234 $ 56,234 Derivative liabilities (1) — 55,340 — 55,340 (1) Derivative assets and liabilities relate to interest rate swaps, see " Note 9. Derivatives and Hedging Activities ." In addition, the carrying value of loans is increased by $41,919 and the net carrying value of subordinated debt is decreased by $9,959 as of December 31, 2017 , which relates to the fair value of the hedges put in place to mitigate against fluctuations in interest rates. (2) Includes only the portion of junior subordinated debt that is recorded at fair value at each reporting period pursuant to the election of FVO treatment.
Change in Level 3 Liabilities Measured at Fair Value on Recurring Basis	For the three months ended March 31, 2018 and 2017 , the change in Level 3 liabilities measured at fair value on a recurring basis was as follows: Junior Subordinated Debt Three Months Ended March 31, 2018 2017 (in thousands) Beginning balance $ (56,234 ) $ (50,410 ) Transfers into Level 3 — — Total gains (losses) for the period Included in other comprehensive income 1,944 (1,986 ) Ending balance $ (54,290 ) $ (52,396 )
Assets Measured at Fair Value on Nonrecurring Basis	The following table presents such assets carried on the Balance Sheet by caption and by level within the ASC 825 hierarchy: Fair Value Measurements at the End of the Reporting Period Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Active Markets for Similar Assets (Level 2) Unobservable Inputs (Level 3) (in thousands) As of March 31, 2018; Impaired loans with specific valuation allowance $ 4,036 $ — $ — $ 4,036 Impaired loans without specific valuation allowance (1) 63,639 — — 63,639 Other assets acquired through foreclosure 30,194 — — 30,194 As of December 31, 2017: Impaired loans with specific valuation allowance $ 13,709 $ — $ — $ 13,709 Impaired loans without specific valuation allowance (1) 63,607 — — 63,607 Other assets acquired through foreclosure 28,540 — — 28,540 (1) Net of loan balances with charge-offs of $24.4 million and $15.6 million as of March 31, 2018 and December 31, 2017 , respectively.
Estimated Fair Value of Financial Instruments	The estimated fair value of the Company’s financial instruments is as follows: March 31, 2018 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (in thousands) Financial assets: Investment securities: HTM $ 262,304 $ — $ 255,418 $ — $ 255,418 AFS 3,405,462 144,164 3,261,298 — 3,405,462 Derivative assets 5,387 — 5,387 — 5,387 Loans, net 15,415,794 — 15,254,388 67,675 15,322,063 Accrued interest receivable 80,398 — 80,398 — 80,398 Financial liabilities: Deposits $ 17,354,538 $ — $ 17,360,147 $ — $ 17,360,147 Customer repurchase agreements 21,676 — 21,676 — 21,676 FHLB advances 300,000 — 300,000 — 300,000 Qualifying debt 363,935 — 331,190 64,842 396,032 Derivative liabilities 44,353 — 44,353 — 44,353 Accrued interest payable 11,540 — 11,540 — 11,540 December 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (in thousands) Financial assets: Investment securities: HTM $ 255,050 $ — $ 256,314 $ — $ 256,314 AFS 3,499,519 103,812 3,395,707 — 3,499,519 Derivative assets 3,711 — 3,711 — 3,711 Loans, net 14,953,885 — 14,577,010 77,316 14,654,326 Accrued interest receivable 85,517 — 85,517 — 85,517 Financial liabilities: — Deposits $ 16,972,532 $ — $ 16,980,066 $ — $ 16,980,066 Customer repurchase agreements 26,017 — 26,017 — 26,017 FHLB advances 390,000 — 390,000 — 390,000 Qualifying debt 376,905 — 336,803 67,210 404,013 Derivative liabilities 55,340 — 55,340 — 55,340 Accrued interest payable 16,366 — 16,366 — 16,366

Segments (Tables)

Segments (Tables)	3 Months Ended
Segments (Tables)	Mar. 31, 2018
Segment Reporting [Abstract]
Operating Segment Information	The following is a summary of operating segment information for the periods indicated: Regional Segments Balance Sheet: Consolidated Company Arizona Nevada Southern California Northern California At March 31, 2018 (in millions) Assets: Cash, cash equivalents, and investment securities $ 4,173.7 $ 2.1 $ 8.5 $ 2.2 $ 2.5 Loans, net of deferred loan fees and costs 15,560.4 3,472.7 1,819.6 2,013.6 1,271.4 Less: allowance for credit losses (144.7 ) (33.9 ) (17.9 ) (20.3 ) (11.2 ) Total loans 15,415.7 3,438.8 1,801.7 1,993.3 1,260.2 Other assets acquired through foreclosure, net 30.2 2.3 15.0 — 0.2 Goodwill and other intangible assets, net 300.4 — 23.2 — 156.3 Other assets 840.7 46.4 58.3 14.8 15.1 Total assets $ 20,760.7 $ 3,489.6 $ 1,906.7 $ 2,010.3 $ 1,434.3 Liabilities: Deposits $ 17,354.5 $ 5,020.6 $ 3,648.1 $ 2,423.8 $ 1,814.4 Borrowings and qualifying debt 663.9 — — — — Other liabilities 448.6 10.9 16.2 1.9 10.5 Total liabilities 18,467.0 5,031.5 3,664.3 2,425.7 1,824.9 Allocated equity: 2,293.7 24.7 21.8 10.3 7.6 Total liabilities and stockholders' equity $ 20,760.7 $ 5,056.2 $ 3,686.1 $ 2,436.0 $ 1,832.5 Excess funds provided (used) — 1,566.6 1,779.4 425.7 398.2 National Business Lines Balance Sheet: HOA Public & Nonprofit Finance Technology & Innovation Hotel Franchise Finance Other NBLs Corporate & Other At March 31, 2018 Assets: (in millions) Cash, cash equivalents, and investment securities $ — $ — $ — $ — $ — $ 4,158.4 Loans, net of deferred loan fees and costs 167.0 1,539.8 1,168.9 1,378.7 2,725.4 3.3 Less: allowance for credit losses (1.7 ) (15.5 ) (10.3 ) (6.3 ) (27.5 ) (0.1 ) Total loans 165.3 1,524.3 1,158.6 1,372.4 2,697.9 3.2 Other assets acquired through foreclosure, net — — — — — 12.7 Goodwill and other intangible assets, net — — 120.8 0.1 — — Other assets 0.8 14.7 6.8 6.4 13.4 664.0 Total assets $ 166.1 $ 1,539.0 $ 1,286.2 $ 1,378.9 $ 2,711.3 $ 4,838.3 Liabilities: Deposits $ 2,475.3 $ — $ 1,733.5 $ — $ — $ 238.8 Borrowings and qualifying debt — — — — — 663.9 Other liabilities 1.6 21.5 1.2 (0.3 ) 124.3 260.8 Total liabilities 2,476.9 21.5 1,734.7 (0.3 ) 124.3 1,163.5 Allocated equity: 5.9 1.3 11.1 8.3 9.3 2,193.4 Total liabilities and stockholders' equity $ 2,482.8 $ 22.8 $ 1,745.8 $ 8.0 $ 133.6 $ 3,356.9 Excess funds provided (used) 2,316.7 (1,516.2 ) 459.6 (1,370.9 ) (2,577.7 ) (1,481.4 ) Regional Segments Consolidated Company Arizona Nevada Southern California Northern California At December 31, 2017 (in millions) Assets: Cash, cash equivalents, and investment securities $ 4,237.1 $ 2.1 $ 8.2 $ 2.1 $ 1.7 Loans, net of deferred loan fees and costs 15,093.9 3,323.7 1,844.8 1,934.7 1,275.5 Less: allowance for credit losses (140.0 ) (31.5 ) (18.1 ) (19.5 ) (13.2 ) Total loans 14,953.9 3,292.2 1,826.7 1,915.2 1,262.3 Other assets acquired through foreclosure, net 28.5 2.3 13.3 — 0.2 Goodwill and other intangible assets, net 300.7 — 23.2 — 156.5 Other assets 808.9 46.3 58.8 14.4 15.1 Total assets $ 20,329.1 $ 3,342.9 $ 1,930.2 $ 1,931.7 $ 1,435.8 Liabilities: Deposits $ 16,972.5 $ 4,841.3 $ 3,951.4 $ 2,461.1 $ 1,681.7 Borrowings and qualifying debt 766.9 — — — — Other liabilities 360.0 11.6 20.9 3.2 11.9 Total liabilities 18,099.4 4,852.9 3,972.3 2,464.3 1,693.6 Allocated equity: 2,229.7 396.5 263.7 221.8 303.1 Total liabilities and stockholders' equity $ 20,329.1 $ 5,249.4 $ 4,236.0 $ 2,686.1 $ 1,996.7 Excess funds provided (used) — 1,906.5 2,305.8 754.4 560.9 National Business Lines HOA Public & Nonprofit Finance Technology & Innovation Hotel Franchise Finance Other NBLs Corporate & Other At December 31, 2017 Assets: (in millions) Cash, cash equivalents, and investment securities $ — $ — $ — $ — $ — $ 4,223.0 Loans, net of deferred loan fees and costs 162.1 1,580.4 1,097.9 1,327.7 2,543.0 4.1 Less: allowance for credit losses (1.6 ) (15.6 ) (11.4 ) (4.0 ) (25.0 ) (0.1 ) Total loans 160.5 1,564.8 1,086.5 1,323.7 2,518.0 4.0 Other assets acquired through foreclosure, net — — — — — 12.7 Goodwill and other intangible assets, net — — 120.9 0.1 — — Other assets 0.9 17.9 6.0 5.9 15.5 628.1 Total assets $ 161.4 $ 1,582.7 $ 1,213.4 $ 1,329.7 $ 2,533.5 $ 4,867.8 Liabilities: Deposits $ 2,230.4 $ — $ 1,737.6 $ — $ — $ 69.0 Borrowings and qualifying debt — — — — — 766.9 Other liabilities 1.2 42.4 0.8 0.4 5.5 262.1 Total liabilities 2,231.6 42.4 1,738.4 0.4 5.5 1,098.0 Allocated equity: 59.4 126.5 244.1 108.3 206.0 300.3 Total liabilities and stockholders' equity $ 2,291.0 $ 168.9 $ 1,982.5 $ 108.7 $ 211.5 $ 1,398.3 Excess funds provided (used) 2,129.6 (1,413.8 ) 769.1 (1,221.0 ) (2,322.0 ) (3,469.5 ) Regional Segments Consolidated Company Arizona Nevada Southern California Northern California Three Months Ended March 31, 2018 (in thousands) Net interest income (expense) $ 214,220 $ 54,555 $ 36,690 $ 27,802 $ 22,255 Provision for (recovery) credit losses 6,000 1,434 (1,723 ) 729 1,548 Net interest income (expense) after provision for credit losses 208,220 53,121 38,413 27,073 20,707 Non-interest income 11,643 1,416 3,333 1,001 2,547 Non-interest expense (98,149 ) (21,504 ) (14,084 ) (13,646 ) (12,503 ) Income (loss) before income taxes 121,714 33,033 27,662 14,428 10,751 Income tax expense (benefit) 20,814 8,321 5,903 4,135 3,098 Net income $ 100,900 $ 24,712 $ 21,759 $ 10,293 $ 7,653 National Business Lines HOA Public & Nonprofit Finance Technology & Innovation Hotel Franchise Finance Other NBLs Corporate & Other Three Months Ended March 31, 2018 (in thousands) Net interest income (expense) $ 15,359 $ 3,746 $ 22,821 $ 14,185 $ 18,811 $ (2,004 ) Provision for (recovery) credit losses 47 (207 ) 1,651 1,236 1,285 — Net interest income (expense) after provision for credit losses 15,312 3,953 21,170 12,949 17,526 (2,004 ) Non-interest income 150 — 3,051 13 224 (92 ) Non-interest expense (7,803 ) (2,174 ) (9,833 ) (2,206 ) (5,662 ) (8,734 ) Income (loss) before income taxes 7,659 1,779 14,388 10,756 12,088 (10,830 ) Income tax expense (benefit) 1,761 409 3,309 2,474 2,780 (11,376 ) Net income $ 5,898 $ 1,370 $ 11,079 $ 8,282 $ 9,308 $ 546 Regional Segments Consolidated Company Arizona Nevada Southern California Northern California Three Months Ended March 31, 2017 (in thousands) Net interest income (expense) $ 179,309 $ 43,907 $ 35,296 $ 25,218 $ 22,035 Provision for (recovery of) credit losses 4,250 14 (211 ) 91 396 Net interest income (expense) after provision for credit losses 175,059 43,893 35,507 25,127 21,639 Non-interest income 10,599 1,113 2,133 743 2,113 Non-interest expense (87,827 ) (18,622 ) (15,870 ) (12,703 ) (12,709 ) Income (loss) before income taxes 97,831 26,384 21,770 13,167 11,043 Income tax expense (benefit) 24,489 10,350 7,620 5,537 4,643 Net income (loss) $ 73,342 $ 16,034 $ 14,150 $ 7,630 $ 6,400 National Business Lines HOA Public & Nonprofit Finance Technology & Innovation Hotel Franchise Finance Other NBLs Corporate & Other Three Months Ended March 31, 2017 (in thousands) Net interest income (expense) $ 12,748 $ 6,485 $ 18,166 $ 13,581 $ 14,143 $ (12,270 ) Provision for (recovery) credit losses 127 509 296 — 3,527 (499 ) Net interest income (expense) after provision for credit losses 12,621 5,976 17,870 13,581 10,616 (11,771 ) Non-interest income 141 70 1,873 — 721 1,692 Non-interest expense (7,147 ) (2,323 ) (8,779 ) (2,988 ) (4,721 ) (1,965 ) Income (loss) before income taxes 5,615 3,723 10,964 10,593 6,616 (12,044 ) Income tax expense (benefit) 2,106 1,402 4,111 3,972 2,481 (17,733 ) Net income $ 3,509 $ 2,321 $ 6,853 $ 6,621 $ 4,135 $ 5,689

Summary of Significant Accoun35

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)Subsidiary	Dec. 31, 2017USD ($)
Significant Of Accounting Policies [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017 \| $	$ 3,405,462	$ 3,499,519
Number Of Wholly Owned Subsidiaries Non Bank Subsidiaries \| Subsidiary	2
Number Of Unconsolidated Subsidiaries \| Subsidiary	8
Preferred Stock [Member]
Significant Of Accounting Policies [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017 \| $	$ 93,318	$ 53,196

Investment Securities - Carryin

Investment Securities - Carrying Amounts and Fair Values of Investment Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	$ 262,304	$ 255,050
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	795	4,514
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(7,681)	(3,250)
Held-to-maturity Securities, Fair Value	255,418	256,314
Securities available for sale Total, Amortized Cost	3,474,049	3,515,401
Securities available-for-sale, Gross Unrealized Gains	27,119	35,733
Securities available-for-sale, Gross Unrealized (Losses)	(95,706)	(51,615)
Securities available for sale Total, Estimated Fair Value	3,405,462	3,499,519
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost	64,000	64,000
Securities available-for-sale, Gross Unrealized Gains	0	0
Securities available-for-sale, Gross Unrealized (Losses)	(3,710)	(2,538)
Securities available for sale Total, Estimated Fair Value	60,290	61,462
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost	2,496	2,496
Securities available-for-sale, Gross Unrealized Gains	0	0
Securities available-for-sale, Gross Unrealized (Losses)	(23)	(14)
Securities available for sale Total, Estimated Fair Value	2,473	2,482
Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost	499,045	501,988
Securities available-for-sale, Gross Unrealized Gains	6,083	10,893
Securities available-for-sale, Gross Unrealized (Losses)	(7,207)	(1,971)
Securities available for sale Total, Estimated Fair Value	497,921	510,910
Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost	92,959	52,172
Securities available-for-sale, Gross Unrealized Gains	1,191	1,160
Securities available-for-sale, Gross Unrealized (Losses)	(832)	(136)
Securities available for sale Total, Estimated Fair Value	93,318	53,196
Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost	1,676,686	1,719,188
Securities available-for-sale, Gross Unrealized Gains	210	810
Securities available-for-sale, Gross Unrealized (Losses)	(49,997)	(30,703)
Securities available for sale Total, Estimated Fair Value	1,626,899	1,689,295
Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost	839,655	874,261
Securities available-for-sale, Gross Unrealized Gains	32	756
Securities available-for-sale, Gross Unrealized (Losses)	(20,691)	(6,493)
Securities available for sale Total, Estimated Fair Value	818,996	868,524
Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost	32,000	32,000
Securities available-for-sale, Gross Unrealized Gains	0	0
Securities available-for-sale, Gross Unrealized (Losses)	(3,383)	(3,383)
Securities available for sale Total, Estimated Fair Value	28,617	28,617
Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost	50	50
Securities available-for-sale, Gross Unrealized Gains	19,403	21,807
Securities available-for-sale, Gross Unrealized (Losses)	0	0
Securities available for sale Total, Estimated Fair Value	19,453	21,857
Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost	110,347	113,069
Securities available-for-sale, Gross Unrealized Gains	60	46
Securities available-for-sale, Gross Unrealized (Losses)	(5,434)	(4,038)
Securities available for sale Total, Estimated Fair Value	104,973	109,077
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost	105,040	105,044
Securities available-for-sale, Gross Unrealized Gains	140	261
Securities available-for-sale, Gross Unrealized (Losses)	(3,504)	(1,822)
Securities available for sale Total, Estimated Fair Value	101,676	103,483
CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Amortized Cost	51,771	51,133
Securities available-for-sale, Gross Unrealized Gains	0	0
Securities available-for-sale, Gross Unrealized (Losses)	(925)	(517)
Securities available for sale Total, Estimated Fair Value	50,846	50,616
AAA [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	810,810	874,135
AAA [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	0	0
Securities available for sale Total, Estimated Fair Value	62,746	64,893
AAA [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	748,064	809,242
AAA [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AAA [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Split-rated AAA/AA Plus [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	1,844,348	1,912,945
Split-rated AAA/AA Plus [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	60,290	61,462
Split-rated AAA/AA Plus [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	2,473	2,482
Split-rated AAA/AA Plus [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	0	0
Securities available for sale Total, Estimated Fair Value	24,635	25,280
Split-rated AAA/AA Plus [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Split-rated AAA/AA Plus [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	1,626,899	1,689,295
Split-rated AAA/AA Plus [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Split-rated AAA/AA Plus [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Split-rated AAA/AA Plus [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Split-rated AAA/AA Plus [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	104,973	109,077
Split-rated AAA/AA Plus [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Split-rated AAA/AA Plus [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	25,078	25,349
AA Plus to AA- [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	311,223	304,361
AA Plus to AA- [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	0	0
Securities available for sale Total, Estimated Fair Value	243,818	249,200
AA Plus to AA- [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	67,405	55,161
AA Plus to AA- [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
AA Plus to AA- [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	247,113	254,025
A Plus to A- [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	0	0
Securities available for sale Total, Estimated Fair Value	163,250	167,994
A Plus to A- [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	10,118	10,388
A Plus to A- [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	998	1,350
A Plus to A- [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
A Plus to A- [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	72,747	74,293
A Plus to A- [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	122,869	82,560
BBB Plus to BBB- [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	0	0
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	64,444	23,822
BBB Plus to BBB- [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	879	931
BBB Plus to BBB- [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	28,617	28,617
BBB Plus to BBB- [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BBB Plus to BBB- [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	28,929	29,190
BBB Plus to BBB- [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	25,134	27,801
BB Plus and below [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	0	0
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	4,031	4,104
BB Plus and below [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	1,650	1,840
BB Plus and below [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	19,453	21,857
BB Plus and below [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
BB Plus and below [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	43,965	43,692
Corporate Credit Quality Indicator Unrated [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	262,304	255,050
Securities available for sale Total, Estimated Fair Value	3,472	3,543
Corporate Credit Quality Indicator Unrated [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	14,725	14,882
Corporate Credit Quality Indicator Unrated [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	0	0
Corporate Credit Quality Indicator Unrated [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	25,768	25,267
Rated Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	3,405,462	3,499,519
Rated Securities [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	60,290	61,462
Rated Securities [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	2,473	2,482
Rated Securities [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	262,304	255,050
Securities available for sale Total, Estimated Fair Value	497,921	510,910
Rated Securities [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	93,318	53,196
Rated Securities [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	1,626,899	1,689,295
Rated Securities [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	818,996	868,524
Rated Securities [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	28,617	28,617
Rated Securities [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	19,453	21,857
Rated Securities [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	104,973	109,077
Rated Securities [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	101,676	103,483
Rated Securities [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Total, Estimated Fair Value	$ 50,846	$ 50,616

Investment Securities - Additio

Investment Securities - Additional Information (Detail)	3 Months Ended
Investment Securities - Additional Information (Detail)	Mar. 31, 2018USD ($)positions	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)positions
Investment Identifier [Line Items]
Number Of Securities In Unrealized Position \| positions	401		302
Amount of impairment losses reclassified out of accumulated other comprehensive income into earnings	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	95,706,000		$ 51,615,000
Securities with carrying amounts were pledged	$ 1,010,000,000		$ 913,700,000

Investment Securities - Unreali

Investment Securities - Unrealized Losses and Fair Value of Investment Securities in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 7,681	$ 3,250
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	208,272	107,921
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	7,681	3,250
Held-to-maturity Securities, Fair Value	208,272	107,921
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	46,119	18,730
Available-for-sale securities, Less Than Twelve Months, Fair Value	2,020,702	1,593,514
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	49,587	32,885
Available-for-sale securities, Twelve Months or Longer, Fair Value	1,033,115	1,030,580
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	95,706	51,615
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	3,053,817	2,624,094
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	94	14
Available-for-sale securities, Less Than Twelve Months, Fair Value	4,906	4,986
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	3,616	2,524
Available-for-sale securities, Twelve Months or Longer, Fair Value	55,384	56,476
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	3,710	2,538
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	60,290	61,462
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	2,200	1,398
Available-for-sale securities, Less Than Twelve Months, Fair Value	57,799	78,602
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	1,304	424
Available-for-sale securities, Twelve Months or Longer, Fair Value	38,696	19,576
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	3,504	1,822
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	96,495	98,178
Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	832	136
Available-for-sale securities, Less Than Twelve Months, Fair Value	47,808	7,357
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	0	0
Available-for-sale securities, Twelve Months or Longer, Fair Value	0	0
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	832	136
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	47,808	7,357
Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	25,817	13,875
Available-for-sale securities, Less Than Twelve Months, Fair Value	1,096,496	999,478
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	24,180	16,828
Available-for-sale securities, Twelve Months or Longer, Fair Value	512,464	523,270
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	49,997	30,703
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	1,608,960	1,522,748
Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	3,278	17
Available-for-sale securities, Less Than Twelve Months, Fair Value	173,905	6,159
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	3,929	1,954
Available-for-sale securities, Twelve Months or Longer, Fair Value	67,415	69,674
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	7,207	1,971
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	241,320	75,833
Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	13,613	3,115
Available-for-sale securities, Less Than Twelve Months, Fair Value	625,316	480,885
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	7,078	3,378
Available-for-sale securities, Twelve Months or Longer, Fair Value	188,584	188,710
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	20,691	6,493
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	813,900	669,595
Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	0	0
Available-for-sale securities, Less Than Twelve Months, Fair Value	0	0
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	3,383	3,383
Available-for-sale securities, Twelve Months or Longer, Fair Value	28,617	28,617
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	3,383	3,383
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	28,617	28,617
CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	0	0
Available-for-sale securities, Less Than Twelve Months, Fair Value	0	0
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	925	517
Available-for-sale securities, Twelve Months or Longer, Fair Value	50,846	50,616
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	925	517
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	50,846	50,616
Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	262	161
Available-for-sale securities, Less Than Twelve Months, Fair Value	11,999	13,565
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	5,172	3,877
Available-for-sale securities, Twelve Months or Longer, Fair Value	91,109	93,641
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	5,434	4,038
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	103,108	107,206
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less Than Twelve Months, Aggregate Losses	23	14
Available-for-sale securities, Less Than Twelve Months, Fair Value	2,473	2,482
Available-for-sale securities, Twelve Months or Longer, Aggregate Losses	0	0
Available-for-sale securities, Twelve Months or Longer, Fair Value	0	0
Available-for-sale securities, Continuous Unrealized Loss Position, Aggregate Losses, Total	23	14
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 2,473	$ 2,482

Investment Securities - Amortiz

Investment Securities - Amortized Cost and Fair Value of Investment Securities by Contractual Maturities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	$ 1,200
Held-to-maturity Securities, Debt Maturities, Next Twelve Months, Fair Value	1,208
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	10,100
Held-to-maturity Securities, Debt Maturities, Year Two Through Five, Fair Value	10,206
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	14,847
Held-to-maturity Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value	14,475
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	236,157
Held-to-maturity Securities, Debt Maturities, after Ten Years, Fair Value	229,529
Held-to-maturity Securities	262,304	$ 255,050
Held-to-maturity Securities, Fair Value	255,418	256,314
Securities available for sale, Due in one year or less, Amortized Cost	55,801
Securities available for sale, After one year through five years, Amortized Cost	15,947
Securities available for sale, After five years through ten years, Amortized Cost	256,070
Securities available for sale, After ten years, Amortized Cost	519,543
Securities available for sale, Mortgage backed securities, Amortized Cost	2,626,688
Securities available for sale Total, Amortized Cost	3,474,049	3,515,401
Securities available for sale, Due in one year or less, Estimated Fair Value	54,879
Securities available for sale, After one year through five years, Estimated Fair Value	16,242
Securities available for sale, After five years through ten years, Estimated Fair Value	251,220
Securities available for sale, After ten years, Estimated Fair Value	532,253
Securities available for sale, Mortgage backed securities, Estimated Fair Value	2,550,868
Securities available for sale Total, Estimated Fair Value	$ 3,405,462	$ 3,499,519

Investment Securities - Investm

Investment Securities - Investment Securities by Credit Rating Type (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	$ 262,304	$ 255,050
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	3,405,462	3,499,519
Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	497,921	510,910
Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	1,626,899	1,689,295
Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	104,973	109,077
Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	818,996	868,524
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	60,290	61,462
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	2,473	2,482
Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	93,318	53,196
Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	28,617	28,617
Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	19,453	21,857
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	101,676	103,483
CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	50,846	50,616
Rated Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	3,405,462	3,499,519
Rated Securities [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	262,304	255,050
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	497,921	510,910
Rated Securities [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	1,626,899	1,689,295
Rated Securities [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	104,973	109,077
Rated Securities [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	818,996	868,524
Rated Securities [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	60,290	61,462
Rated Securities [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	2,473	2,482
Rated Securities [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	93,318	53,196
Rated Securities [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	28,617	28,617
Rated Securities [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	19,453	21,857
Rated Securities [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	101,676	103,483
Rated Securities [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	50,846	50,616
AAA [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	810,810	874,135
AAA [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	0	0
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	62,746	64,893
AAA [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	748,064	809,242
AAA [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AAA [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Split-rated AAA/AA Plus [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	1,844,348	1,912,945
Split-rated AAA/AA Plus [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	0	0
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	24,635	25,280
Split-rated AAA/AA Plus [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	1,626,899	1,689,295
Split-rated AAA/AA Plus [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	104,973	109,077
Split-rated AAA/AA Plus [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Split-rated AAA/AA Plus [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	60,290	61,462
Split-rated AAA/AA Plus [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	2,473	2,482
Split-rated AAA/AA Plus [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Split-rated AAA/AA Plus [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Split-rated AAA/AA Plus [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Split-rated AAA/AA Plus [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Split-rated AAA/AA Plus [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	25,078	25,349
AA Plus to AA- [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	311,223	304,361
AA Plus to AA- [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	0	0
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	243,818	249,200
AA Plus to AA- [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	67,405	55,161
AA Plus to AA- [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
AA Plus to AA- [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	247,113	254,025
A Plus to A- [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	0	0
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	163,250	167,994
A Plus to A- [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	998	1,350
A Plus to A- [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	10,118	10,388
A Plus to A- [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
A Plus to A- [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	72,747	74,293
A Plus to A- [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	122,869	82,560
BBB Plus to BBB- [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	0	0
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	879	931
BBB Plus to BBB- [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	64,444	23,822
BBB Plus to BBB- [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	28,617	28,617
BBB Plus to BBB- [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BBB Plus to BBB- [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	28,929	29,190
BBB Plus to BBB- [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	25,134	27,801
BB Plus and below [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	0	0
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	1,650	1,840
BB Plus and below [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	4,031	4,104
BB Plus and below [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	19,453	21,857
BB Plus and below [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
BB Plus and below [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	43,965	43,692
Corporate Credit Quality Indicator Unrated [Member] \| Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities	262,304	255,050
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	3,472	3,543
Corporate Credit Quality Indicator Unrated [Member] \| Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] \| Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] \| Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	14,725	14,882
Corporate Credit Quality Indicator Unrated [Member] \| Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] \| Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Corporate Credit Quality Indicator Unrated [Member] \| CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	$ 25,768	$ 25,267

Investment Securities - Gross G

Investment Securities - Gross Gains and (Losses) on Sales of Investments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Gross gains	$ 0	$ 636
Gross (losses)	0	(1)
Net (losses) gains	$ 0	$ 635

Loans, Leases and Allowance f42

Loans, Leases and Allowance for Credit Losses - Schedule of Held for Investment Loan Portfolio Composition of Loans, Leases and Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit Mark on Acquired Loans	$ 23,100	$ 27,000
Net deferred loan fees and costs	(32,600)	(25,300)
Receivable with Imputed Interest, Discount	8,000	8,500
Loans, net of deferred loan fees and costs	15,560,453	15,093,935
Allowance for credit losses	(144,659)	(140,050)
Loans, net	15,415,794	14,953,885
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	6,944,381	6,841,381
Commercial Real Estate Non Owner Occupied Multi Family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	3,925,301	3,904,011
Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	2,264,650	2,241,613
Allowance for credit losses	(14,475)	(13,884)
Construction and land development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	1,957,489	1,632,204
Allowance for credit losses	(22,594)	(19,599)
Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	418,127	425,940
Allowance for credit losses	(5,519)	(5,500)
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, net of deferred loan fees and costs	50,505	48,786
Allowance for credit losses	$ (800)	$ (776)

Loans, Leases and Allowance f43

Loans, Leases and Allowance for Credit Losses - Contractual Aging of Loan Portfolio by Class of Loans Including Loans Held for Sale and Excluding Deferred Fees/Costs (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 15,538,812	$ 15,061,371
Past Due	21,641	32,564
Total	15,560,453	15,093,935
Financing Receivable, Recorded Investment, Nonaccrual Status	37,297	43,925
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	37	43
Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,263,102	2,240,457
Past Due	1,548	1,156
Total	2,264,650	2,241,613
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	3,732,372	3,696,729
Past Due	2,799	5,840
Total	3,735,171	3,702,569
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	190,130	201,442
Past Due	0	0
Total	190,130	201,442
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	6,932,086	6,835,385
Past Due	12,295	5,996
Total	6,944,381	6,841,381
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	37	43
Construction and land development [Member] \| Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,259,939	1,090,176
Past Due	0	0
Total	1,259,939	1,090,176
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Construction and land development [Member] \| Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	697,550	536,917
Past Due	0	5,111
Total	697,550	542,028
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	413,726	411,857
Past Due	4,401	14,083
Total	418,127	425,940
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	49,907	48,408
Past Due	598	378
Total	50,505	48,786
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	22,230	21,909
Past Due	15,067	22,016
Financing Receivable, Recorded Investment, Nonaccrual Status	37,297	43,925
Non-accrual loans [Member] \| Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	1,089
Past Due	131	792
Financing Receivable, Recorded Investment, Nonaccrual Status	131	1,881
Non-accrual loans [Member] \| Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Past Due	2,799	5,840
Financing Receivable, Recorded Investment, Nonaccrual Status	2,799	5,840
Non-accrual loans [Member] \| Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Past Due	0	0
Financing Receivable, Recorded Investment, Nonaccrual Status	0	0
Non-accrual loans [Member] \| Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	16,103	17,913
Past Due	8,081	4,113
Financing Receivable, Recorded Investment, Nonaccrual Status	24,184	22,026
Non-accrual loans [Member] \| Construction and land development [Member] \| Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Past Due	0	0
Financing Receivable, Recorded Investment, Nonaccrual Status	0	0
Non-accrual loans [Member] \| Construction and land development [Member] \| Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	868
Past Due	0	5,111
Financing Receivable, Recorded Investment, Nonaccrual Status	0	5,979
Non-accrual loans [Member] \| Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	6,127	2,039
Past Due	3,717	6,078
Financing Receivable, Recorded Investment, Nonaccrual Status	9,844	8,117
Non-accrual loans [Member] \| Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Past Due	339	82
Financing Receivable, Recorded Investment, Nonaccrual Status	339	82
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	7,909	13,221
Financing Receivables, 30 to 59 Days Past Due [Member] \| Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,418	1,026
Financing Receivables, 30 to 59 Days Past Due [Member] \| Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	2,993
Financing Receivables, 30 to 59 Days Past Due [Member] \| Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] \| Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	5,094	2,245
Financing Receivables, 30 to 59 Days Past Due [Member] \| Construction and land development [Member] \| Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] \| Construction and land development [Member] \| Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] \| Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,397	6,874
Financing Receivables, 30 to 59 Days Past Due [Member] \| Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	83
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	5,229	2,369
Financing Receivables, 60 to 89 Days Past Due [Member] \| Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] \| Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] \| Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] \| Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	4,970	669
Financing Receivables, 60 to 89 Days Past Due [Member] \| Construction and land development [Member] \| Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] \| Construction and land development [Member] \| Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] \| Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	1,487
Financing Receivables, 60 to 89 Days Past Due [Member] \| Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	259	213
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	8,503	16,974
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	130	130
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2,799	2,847
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2,231	3,082
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Construction and land development [Member] \| Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Construction and land development [Member] \| Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	5,111
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	3,004	5,722
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	$ 339	$ 82

Loans, Leases and Allowance f44

Loans, Leases and Allowance for Credit Losses - Summary of Recorded Investment in Nonaccrual Loans and Loans Past Due 90 Days Still Accruing Interest by Loan Class (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 15,538,812	$ 15,061,371
Total Past Due	21,641	32,564
Total Non-accrual	37,297	43,925
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	37	43
Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,263,102	2,240,457
Total Past Due	1,548	1,156
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	3,732,372	3,696,729
Total Past Due	2,799	5,840
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	190,130	201,442
Total Past Due	0	0
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	6,932,086	6,835,385
Total Past Due	12,295	5,996
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	37	43
Construction and land development [Member] \| Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,259,939	1,090,176
Total Past Due	0	0
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Construction and land development [Member] \| Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	697,550	536,917
Total Past Due	0	5,111
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	413,726	411,857
Total Past Due	4,401	14,083
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	49,907	48,408
Total Past Due	598	378
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Non-accrual loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	22,230	21,909
Total Past Due	15,067	22,016
Total Non-accrual	37,297	43,925
Non-accrual loans [Member] \| Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	1,089
Total Past Due	131	792
Total Non-accrual	131	1,881
Non-accrual loans [Member] \| Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Total Past Due	2,799	5,840
Total Non-accrual	2,799	5,840
Non-accrual loans [Member] \| Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Total Past Due	0	0
Total Non-accrual	0	0
Non-accrual loans [Member] \| Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	16,103	17,913
Total Past Due	8,081	4,113
Total Non-accrual	24,184	22,026
Non-accrual loans [Member] \| Construction and land development [Member] \| Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Total Past Due	0	0
Total Non-accrual	0	0
Non-accrual loans [Member] \| Construction and land development [Member] \| Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	868
Total Past Due	0	5,111
Total Non-accrual	0	5,979
Non-accrual loans [Member] \| Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	6,127	2,039
Total Past Due	3,717	6,078
Total Non-accrual	9,844	8,117
Non-accrual loans [Member] \| Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Total Past Due	339	82
Total Non-accrual	$ 339	$ 82

Loans, Leases and Allowance f45

Loans, Leases and Allowance for Credit Losses - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2018USD ($)SecurityLoan	Mar. 31, 2017USD ($)TDRsSecurityLoan	Dec. 31, 2017USD ($)
Leases [Line Items]
Loans and Leases Receivable, Deferred Income	$ 32,600,000		$ 25,300,000
Financing Receivable, Net	$ 15,560,453,000		15,093,935,000
Financing Receivable, Modifications, Number of Contracts \| SecurityLoan	5	1
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 15,000,000	$ 4,900,000
Financing Receivable, Modifications, Subsequent Default, Recorded Investment		$ 100,000
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	1
Receivable with Imputed Interest, Discount	$ (8,000,000)		(8,500,000)
Financing Receivable, Recorded Investment, Nonaccrual Status	37,297,000		43,925,000
Impaired Financing Receivable, Average Recorded Investment	93,081,000	$ 103,387,000
Aggregate carrying amount of impaired loans	9,598,000		19,315,000
Reduction in interest income due to nonaccrual loans	600,000
Loans And Loans Receivable Purchases	141,500,000	253,300,000
Financing Receivable, Significant Sales	31,000,000	9,200,000
Impaired loans with no allowance recorded	87,994,000		79,239,000
Impaired loans with an allowance recorded	5,562,000		5,606,000
Loans and Leases Receivable, Gain (Loss) on Sales, Net	700,000	100,000
Interest Rate and Credit Marks on Acquired Loans	13,000,000		14,100,000
Credit Mark on Acquired Loans	23,100,000		27,000,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	37,000		43,000
Troubled Debt Restructured Loans [Member]
Leases [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	7,400,000		10,100,000
Impaired Financing Receivable, Average Recorded Investment	48,300,000	60,400,000
Aggregate carrying amount of impaired loans	3,000,000		3,700,000
Loan commitments outstanding	100,000		0
Impaired loans with no allowance recorded	48,200,000		48,800,000
Impaired loans with an allowance recorded	1,000,000		1,200,000
Non-owner occupied [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans	0		0
Impaired loans with no allowance recorded	17,654,000		21,250,000
Impaired loans with an allowance recorded	0		0
Construction and land development [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans	0		0
Impaired loans with no allowance recorded	9,812,000		15,426,000
Impaired loans with an allowance recorded	0		0
Residential real estate [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans	173,000		0
Loans And Loans Receivable Purchases	23,200,000	53,000,000
Impaired loans with no allowance recorded	18,012,000		17,170,000
Impaired loans with an allowance recorded	173,000		0
Commercial and industrial [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans	9,425,000		19,315,000
Loans And Loans Receivable Purchases	118,300,000	200,300,000
Impaired loans with no allowance recorded	34,034,000		14,842,000
Impaired loans with an allowance recorded	5,389,000		5,606,000
Consumer [Member]
Leases [Line Items]
Aggregate carrying amount of impaired loans	0		0
Impaired loans with no allowance recorded	375,000		121,000
Impaired loans with an allowance recorded	0		0
Non-owner occupied [Member] \| Commercial real estate [Member]
Leases [Line Items]
Financing Receivable, Net	3,735,171,000		3,702,569,000
Impaired Financing Receivable, Average Recorded Investment	18,925,000	$ 24,399,000
Receivables Acquired with Deteriorated Credit Quality [Member]
Leases [Line Items]
Impaired loans with an allowance recorded	829,000		1,631,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	100,000		43,000
Receivables Acquired with Deteriorated Credit Quality [Member] \| Non-owner occupied [Member]
Leases [Line Items]
Impaired loans with an allowance recorded	827,000		1,629,000
Receivables Acquired with Deteriorated Credit Quality [Member] \| Construction and land development [Member]
Leases [Line Items]
Impaired loans with an allowance recorded	0		0
Receivables Acquired with Deteriorated Credit Quality [Member] \| Residential real estate [Member]
Leases [Line Items]
Impaired loans with an allowance recorded	0		0
Receivables Acquired with Deteriorated Credit Quality [Member] \| Commercial and industrial [Member]
Leases [Line Items]
Impaired loans with an allowance recorded	2,000		2,000
Receivables Acquired with Deteriorated Credit Quality [Member] \| Consumer [Member]
Leases [Line Items]
Impaired loans with an allowance recorded	$ 0		$ 0

Loans, Leases and Allowance f46

Loans, Leases and Allowance for Credit Losses - Loans by Risk Rating (Detail) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	$ 15,560,453,000	$ 15,093,935,000
Current	15,538,812,000	15,061,371,000
Past Due	21,641,000	32,564,000
Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	6,944,381,000	6,841,381,000
Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	418,127,000	425,940,000
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	50,505,000	48,786,000
Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	2,264,650,000	2,241,613,000
Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	3,735,171,000	3,702,569,000
Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	190,130,000	201,442,000
Construction and land development [Member] \| Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	1,259,939,000	1,090,176,000
Construction and land development [Member] \| Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	697,550,000	542,028,000
Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	15,211,919,000	14,767,297,000
Current	15,206,755,000	14,758,149,000
Pass [Member] \| Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	6,756,803,000	6,675,574,000
Pass [Member] \| Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	398,814,000	408,527,000
Pass [Member] \| Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	49,613,000	47,824,000
Pass [Member] \| Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	2,168,305,000	2,149,465,000
Pass [Member] \| Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	3,696,971,000	3,676,711,000
Pass [Member] \| Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	190,130,000	201,442,000
Pass [Member] \| Construction and land development [Member] \| Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	1,255,462,000	1,072,342,000
Pass [Member] \| Construction and land development [Member] \| Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	695,821,000	535,412,000
Watch [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	184,702,000	155,032,000
Current	184,306,000	154,295,000
Watch [Member] \| Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	100,928,000	85,781,000
Watch [Member] \| Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	9,146,000	8,971,000
Watch [Member] \| Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	58,000	878,000
Watch [Member] \| Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	42,472,000	43,122,000
Watch [Member] \| Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	26,716,000	11,166,000
Watch [Member] \| Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Watch [Member] \| Construction and land development [Member] \| Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	4,477,000	4,477,000
Watch [Member] \| Construction and land development [Member] \| Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	905,000	637,000
Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	159,040,000	167,279,000
Current	143,622,000	145,934,000
Substandard [Member] \| Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	82,499,000	76,328,000
Substandard [Member] \| Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	10,167,000	8,442,000
Substandard [Member] \| Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	834,000	84,000
Substandard [Member] \| Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	53,232,000	48,397,000
Substandard [Member] \| Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	11,484,000	14,692,000
Substandard [Member] \| Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Substandard [Member] \| Construction and land development [Member] \| Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	13,357,000
Substandard [Member] \| Construction and land development [Member] \| Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	824,000	5,979,000
Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	4,792,000	4,327,000
Current	4,129,000	2,993,000
Doubtful [Member] \| Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	4,151,000	3,698,000
Doubtful [Member] \| Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Doubtful [Member] \| Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Doubtful [Member] \| Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	641,000	629,000
Doubtful [Member] \| Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Doubtful [Member] \| Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Doubtful [Member] \| Construction and land development [Member] \| Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Doubtful [Member] \| Construction and land development [Member] \| Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Current	0	0
Loss [Member] \| Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] \| Residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] \| Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] \| Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] \| Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] \| Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] \| Construction and land development [Member] \| Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Loss [Member] \| Construction and land development [Member] \| Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Net	0	0
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	7,909,000	13,221,000
Financing Receivables, 30 to 59 Days Past Due [Member] \| Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	5,091,000	7,966,000
Financing Receivables, 30 to 59 Days Past Due [Member] \| Watch [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	374,000	518,000
Financing Receivables, 30 to 59 Days Past Due [Member] \| Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	2,444,000	4,737,000
Financing Receivables, 30 to 59 Days Past Due [Member] \| Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] \| Loss [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	5,229,000	2,369,000
Financing Receivables, 60 to 89 Days Past Due [Member] \| Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	73,000	1,182,000
Financing Receivables, 60 to 89 Days Past Due [Member] \| Watch [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	22,000	219,000
Financing Receivables, 60 to 89 Days Past Due [Member] \| Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	5,134,000	968,000
Financing Receivables, 60 to 89 Days Past Due [Member] \| Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] \| Loss [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	8,503,000	16,974,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Watch [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	7,840,000	15,640,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	663,000	1,334,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Loss [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	$ 0	$ 0

Loans, Leases and Allowance f47

Loans, Leases and Allowance for Credit Losses - Impaired Loans by Loan Class (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	$ 97,592	$ 98,554
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	43,459	34,156
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	18,185	17,170
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	375	121
Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	8,107	10,430
Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	17,654	21,251
Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	0	0
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	43,459	34,157
Construction and land development [Member] \| Construction [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	0	0
Construction and land development [Member] \| Land [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	$ 9,812	$ 15,426

Loans, Leases and Allowance f48

Loans, Leases and Allowance for Credit Losses - Recorded Investment in Loans Classified as Impaired (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Impaired loans with an allowance recorded	$ 9,598	$ 19,315
Impaired loans with no allowance recorded	87,994	79,239
Total impaired loans	97,592	98,554
Valuation allowance related to impaired loans	$ (5,562)	$ (5,606)

Loans, Leases and Allowance f49

Loans, Leases and Allowance for Credit Losses - Schedule of Average Investment in Impaired Loans and Income Recognized on Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Receivables [Abstract]
Impaired Financing Receivable, Average Recorded Investment	$ 93,081	$ 103,387
Interest income recognized on impaired loans	873	921
Interest recognized on nonaccrual loans, cash basis	$ 438	$ 332

Loans, Leases and Allowance f50

Loans, Leases and Allowance for Credit Losses - Average Investment in Impaired Loans by Loan Class (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	$ 93,081	$ 103,387
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	36,849	26,101
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	17,799	17,103
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	184	224
Troubled Debt Restructured Loans [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	48,300	60,400
Commercial real estate [Member] \| Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	9,043	21,128
Commercial real estate [Member] \| Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	18,925	24,399
Commercial real estate [Member] \| Multi-family [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	0	0
Construction and land development [Member] \| Construction [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	0	0
Construction and land development [Member] \| Land [Member]
Financing Receivable, Impaired [Line Items]
Total average investment in impaired loans by loan class	$ 10,281	$ 14,432

Loans, Leases and Allowance f51

Loans, Leases and Allowance for Credit Losses - Interest Income on Impaired Loans by Loan Class (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	$ 873	$ 921
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	250	144
Owner occupied [Member] \| Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	127	177
Non-owner occupied [Member] \| Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	262	239
Multi-family [Member] \| Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	0	0
Construction [Member] \| Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	0	0
Land [Member] \| Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	130	221
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	104	139
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	$ 0	$ 1

Loans, Leases and Allowance f52

Loans, Leases and Allowance for Credit Losses - Tabular Disclosure of Nonperforming Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 37,297	$ 43,925
Loans past due 90 days or more on accrual status	37	43
Troubled debt restructured loans	43,766	42,431
Total nonperforming loans	81,100	86,399
Other assets acquired through foreclosure, net	30,194	28,540	$ 45,200	$ 47,815
Total nonperforming assets	111,294	114,939
Troubled Debt Restructured Loans [Member]
Financing Receivable, Recorded Investment, Nonaccrual Status	7,400	10,100
Receivables Acquired with Deteriorated Credit Quality [Member]
Loans past due 90 days or more on accrual status	$ 100	$ 43

Loans, Leases and Allowance f53

Loans, Leases and Allowance for Credit Losses - Changes in Accretable Discount for Loans Purchased with Credit Quality Deterioration (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Reclassifications from non-accretable to accretable yield (1)	$ 683
Accretion to interest income	(313)	$ (907)
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	9,324	15,177
Reclassifications from non-accretable to accretable yield (1)		0
Reversal of fair value adjustments upon disposition of loans	(1,586)	(458)
Balance at end of period	$ 8,108	$ 13,812

Loans, Leases and Allowance f54

Loans, Leases and Allowance for Credit Losses - Allowances for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Valuation Allowance [Line Items]
Beginning Balance	$ 140,050	$ 124,704
Charge-offs	3,624	2,743
Recoveries	(2,233)	(1,438)
Provision for credit losses	6,000	4,250
Ending balance	144,659	127,649
Construction and land development [Member]
Valuation Allowance [Line Items]
Beginning Balance	19,511	21,175
Charge-offs	0	0
Recoveries	(1,388)	(277)
Provision for credit losses	1,695	(355)
Ending balance	22,594	21,097
Commercial real estate [Member]
Valuation Allowance [Line Items]
Beginning Balance	31,495	25,673
Charge-offs	0	0
Recoveries	(126)	(533)
Provision for credit losses	1,247	1,798
Ending balance	32,868	28,004
Residential real estate [Member]
Valuation Allowance [Line Items]
Beginning Balance	5,478	3,851
Charge-offs	107	115
Recoveries	(250)	(251)
Provision for credit losses	(102)	425
Ending balance	5,519	4,412
Commercial and industrial [Member]
Valuation Allowance [Line Items]
Beginning Balance	82,793	73,333
Charge-offs	3,517	2,594
Recoveries	(459)	(328)
Provision for credit losses	3,143	2,362
Ending balance	82,878	73,429
Consumer [Member]
Valuation Allowance [Line Items]
Beginning Balance	773	672
Charge-offs	0	34
Recoveries	(10)	(49)
Provision for credit losses	17	20
Ending balance	$ 800	$ 707

Loans, Leases and Allowance f55

Loans, Leases and Allowance for Credit Losses - Summary of Impairment Method Information Related to Loans and Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	$ 9,598	$ 19,315
Impaired loans with no allowance recorded	87,994	79,239
Total loans individually evaluated for impairment	97,592	98,554
Loans collectively evaluated for impairment	15,352,070	14,879,626
Impaired Financing Receivable, Recorded Investment	97,592	98,554
Total recorded investment	15,560,453	15,093,935
Impaired loans with an allowance recorded	12,423	20,795
Impaired loans with no allowance recorded	167,192	156,789
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	179,615	177,584
Loans collectively evaluated for impairment	15,352,070	14,879,626
Financing Receivable Unpaid Principal Balance	15,671,560	15,202,135
Impaired loans with an allowance recorded	5,562	5,606
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	5,562	5,606
Loans collectively evaluated for impairment	138,268	132,813
Total loans held for investment	144,659	140,050
Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	8,107	10,430
Total loans individually evaluated for impairment	8,107	10,430
Loans collectively evaluated for impairment	2,248,803	2,221,614
Total recorded investment	2,264,650	2,241,613
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	15,029	17,459
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	15,029	17,459
Loans collectively evaluated for impairment	2,248,803	2,221,614
Financing Receivable Unpaid Principal Balance	2,273,777	2,251,692
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	14,475	13,884
Total loans held for investment	14,475	13,884
Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	17,654	21,250
Total loans individually evaluated for impairment	17,654	21,250
Loans collectively evaluated for impairment	3,805,229	3,777,219
Total recorded investment	3,925,301	3,904,011
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	24,431	28,028
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	24,431	28,028
Loans collectively evaluated for impairment	3,805,229	3,777,219
Financing Receivable Unpaid Principal Balance	3,954,463	3,933,687
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	17,566	16,135
Total loans held for investment	18,393	17,764
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	9,425	19,315
Impaired loans with no allowance recorded	34,034	14,842
Total loans individually evaluated for impairment	43,459	34,157
Loans collectively evaluated for impairment	6,900,885	6,807,181
Total recorded investment	6,944,381	6,841,381
Impaired loans with an allowance recorded	12,250	20,795
Impaired loans with no allowance recorded	63,541	42,261
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	75,791	63,056
Loans collectively evaluated for impairment	6,900,885	6,807,181
Financing Receivable Unpaid Principal Balance	6,981,088	6,873,383
Impaired loans with an allowance recorded	5,389	5,606
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	5,389	5,606
Loans collectively evaluated for impairment	77,487	76,919
Total loans held for investment	82,878	82,527
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	173	0
Impaired loans with no allowance recorded	18,012	17,170
Total loans individually evaluated for impairment	18,185	17,170
Loans collectively evaluated for impairment	399,346	408,169
Total recorded investment	418,127	425,940
Impaired loans with an allowance recorded	173	0
Impaired loans with no allowance recorded	26,801	26,057
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	26,974	26,057
Loans collectively evaluated for impairment	399,346	408,169
Financing Receivable Unpaid Principal Balance	427,035	434,946
Impaired loans with an allowance recorded	173	0
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	173	0
Loans collectively evaluated for impairment	5,346	5,500
Total loans held for investment	5,519	5,500
Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	9,812	15,426
Total loans individually evaluated for impairment	9,812	15,426
Loans collectively evaluated for impairment	1,947,677	1,616,778
Total recorded investment	1,957,489	1,632,204
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	26,440	32,289
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	26,440	32,289
Loans collectively evaluated for impairment	1,947,677	1,616,778
Financing Receivable Unpaid Principal Balance	1,974,117	1,649,067
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	22,594	19,599
Total loans held for investment	22,594	19,599
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	375	121
Total loans individually evaluated for impairment	375	121
Loans collectively evaluated for impairment	50,130	48,665
Total recorded investment	50,505	48,786
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	10,950	10,695
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment	10,950	10,695
Loans collectively evaluated for impairment	50,130	48,665
Financing Receivable Unpaid Principal Balance	61,080	59,360
Impaired loans with an allowance recorded	0	0
Impaired loans with no allowance recorded	0	0
Total loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	800	776
Total loans held for investment	800	776
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	110,791	115,755
Loans acquired with deteriorated credit quality	139,875	144,925
Impaired loans with an allowance recorded	829	1,631
Receivables Acquired with Deteriorated Credit Quality [Member] \| Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	7,740	9,569
Loans acquired with deteriorated credit quality	9,945	12,619
Impaired loans with an allowance recorded	0	0
Receivables Acquired with Deteriorated Credit Quality [Member] \| Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	102,418	105,542
Loans acquired with deteriorated credit quality	124,803	128,440
Impaired loans with an allowance recorded	827	1,629
Receivables Acquired with Deteriorated Credit Quality [Member] \| Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	37	43
Loans acquired with deteriorated credit quality	4,412	3,146
Impaired loans with an allowance recorded	2	2
Receivables Acquired with Deteriorated Credit Quality [Member] \| Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	596	601
Loans acquired with deteriorated credit quality	715	720
Impaired loans with an allowance recorded	0	0
Receivables Acquired with Deteriorated Credit Quality [Member] \| Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
Loans acquired with deteriorated credit quality	0	0
Impaired loans with an allowance recorded	0	0
Receivables Acquired with Deteriorated Credit Quality [Member] \| Consumer [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
Loans acquired with deteriorated credit quality	0	0
Impaired loans with an allowance recorded	$ 0	$ 0

Other Assets Acquired through56

Other Assets Acquired through Foreclosure - Changes in Other Assets Acquired through Foreclosure (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)Property	Mar. 31, 2017USD ($)Property	Dec. 31, 2017Property
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Balance, beginning of the period, Gross Balance	$ 32,552	$ 54,138
Transfers to other assets acquired through foreclosure, net, Gross Balance	5,744	0
Proceeds from sale of other real estate owned and repossessed assets, net, Gross Balance	(5,294)	(3,113)
Gains (losses), net, Gross Balance	1,242	(106)
Balance, end of period, Gross Balance	34,244	50,919
Balance, beginning of the period, Valuation Allowance	(4,012)	(6,323)
Proceeds from sale of other real estate owned and repossessed assets, net, Valuation Allowance	9	224
Valuation adjustments, net, Valuation Allowance	(47)	380
Balance, end of period, Valuation Allowance	(4,050)	(5,719)
Balance, beginning of the period, Net Balance	28,540	47,815
Transfers to other assets acquired through foreclosure, net, Net Balance	5,744	0
Proceeds from sale of other real estate owned and repossessed assets, net, Net Balance	(5,285)	(2,889)
Valuation adjustments of other repossessed assets, net	(47)	380
Gains (losses), net, Net Balance	1,242	(106)
Balance, end of period, Net Balance	30,194	45,200
Gains Losses On Transfers To Other Real Estate And Foreclosed Assets	$ 1,000	$ 0
Number of Real Estate Properties \| Property	18	25	19

Other Borrowings - Additional I

Other Borrowings - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Debt [Line Items]
FHLB advances	$ 300,000,000		$ 390,000,000
Short-term Debt	300,000,000		390,000,000
Revolving line of credit	$ 0		0
Weighted average interest rate of FHLB and FRB Short-term advances	1.87%	1.41%
FRB [Member]
Debt [Line Items]
Additional available credit with the entity	$ 1,220,000,000		1,110,000,000
Unsecured Credit Facility [Member]
Debt [Line Items]
Secured borrowing credit line	145,000,000
FHLB [Member]
Debt [Line Items]
Additional available credit with the entity	$ 2,200,000,000		$ 1,910,000,000

Qualifying Debt (Details)

Qualifying Debt (Details)	3 Months Ended
Qualifying Debt (Details)	Mar. 31, 2018USD ($)Trust	Dec. 31, 2017USD ($)	Jun. 16, 2016USD ($)	Jun. 29, 2015USD ($)
Debt Instrument [Line Items]
Subordinated Debt	$ 297,500,000	$ 308,600,000
Number of Statutory Business Trusts Formed or Acquired \| Trust	8
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	$ 66,400,000	$ 68,300,000
Subordinated Debt [Member] \| Subordinated Debentures Maturing July 2056 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 175,000,000
Debt Issuance Cost			$ 5,500,000
Debt Instrument, Interest Rate, Stated Percentage			6.25%
Subordinated Debt [Member] \| Subordinated Debentures Maturing July 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 150,000,000
Debt Issuance Cost				$ (1,800,000)
Debt Instrument, Interest Rate, Stated Percentage				0.00%
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate, at Point in Time	4.65%	4.03%

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury Stock, Shares, Acquired	180,867	201,306
Treasury Stock Acquired, Average Cost Per Share	$ 59.02	$ 50.88
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 1.6	$ 1.3
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Granted, Value, Share-based Compensation, Gross	21.9
Allocated Share-based Compensation Expense	4.3	4.5
Executive Officer [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 0.6	$ 0.4

Accumulated Other Comprehensi60

Accumulated Other Comprehensive Income - Summary of Changes in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (3,145)	$ (4,695)
Other comprehensive income before reclassifications	(37,459)	7,939
Amounts reclassified from accumulated other comprehensive income	0	(393)
Net other comprehensive (loss) income	(37,459)	7,546
Ending balance	(41,662)	2,851
Unrealized holding gains (losses) on AFS
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(10,026)	(14,916)
Other comprehensive income before reclassifications	(38,914)	9,169
Amounts reclassified from accumulated other comprehensive income	0	(393)
Net other comprehensive (loss) income	(38,914)	8,776
Ending balance	(51,470)	(6,140)
Financial Liability Instruments, Fair Value Option [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	6,352	9,956
Other comprehensive income before reclassifications	1,466	(1,229)
Amounts reclassified from accumulated other comprehensive income	0	0
Net other comprehensive (loss) income	1,466	(1,229)
Ending balance	9,206	8,727
Impairment loss on securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	144	144
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income	0	0
Net other comprehensive (loss) income	0	0
Ending balance	144	144
Supplemental Employee Retirement Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	385	121
Other comprehensive income before reclassifications	(11)	(1)
Amounts reclassified from accumulated other comprehensive income	0	0
Net other comprehensive (loss) income	(11)	(1)
Ending balance	$ 458	$ 120

Accumulated Other Comprehensi61

Accumulated Other Comprehensive Income - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income	$ 0	$ (242)
Amount reclassified from accumulated other comprehensive income	0	393
Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income	0	393
Realized Gain Loss On Sale Of Investment [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized gains on sales of investment securities	0	635
Income Tax Expense [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income	$ 0	$ 242

Derivatives and Hedging Fair Va

Derivatives and Hedging Fair Value of Derivative Contracts (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Derivatives, Fair Value [Line Items]
Notional Amount		$ 993,432	$ 1,035,151
Derivative Asset, Fair Value		1,703	1,985
Derivative Liability, Fair Value		53,581	59,136
Notional Amount, Netting Adjustments		0	0
Derivative Netting Adjustments		896	1,947
Positive NPVs		807	38
Negative NPVs	$ 39,300	52,685	57,189
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Amount		993,432	1,035,151
Derivative Asset, Fair Value		1,703	1,985
Derivative Liability, Fair Value		53,581	59,136
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	127,695	122,304	106,490
Derivative Liability, Fair Value	1,564	1,759	907
Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	1,854	2,008	1,123
Not Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	36,840	36,969	38,192
Derivative Liability, Fair Value	1,170	776	796
Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	1,170	776	796
Not Designated as Hedging Instrument [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	90,855	85,335	68,298
Derivative Liability, Fair Value	394	983	111
Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	684	$ 1,232	$ 327
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	989,379
Derivative Asset, Fair Value	3,533
Derivative Liability, Fair Value	42,789
Notional Amount, Netting Adjustments	0
Derivative Netting Adjustments	3,493
Positive NPVs	40
Negative NPVs	39,296
Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	989,379
Derivative Asset, Fair Value	3,533
Derivative Liability, Fair Value	$ 42,789

Derivatives and Hedging Largest

Derivatives and Hedging Largest Exposure to Individual Counterparty (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Largest gross exposure (positive derivative NPV) to an individual counterparty		$ 807	$ 38
Largest individual counterparty [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Largest gross exposure (positive derivative NPV) to an individual counterparty	$ 2,515	893	3,569
Collateral posted by this counterparty	0	0	4,680
Negative derivative NPV with this counterparty	20,624	40,340	0
Collateral pledged to this counterparty	29,719	60,476	1,340
Net exposure after netting adjustments and collateral	$ 0	$ 0	$ 229

Derivatives and Hedging Additio

Derivatives and Hedging Additional Information (Detail) - USD ($)	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Jun. 16, 2016	Jun. 29, 2015
Derivative [Line Items]
Derivative, Amount of Hedged Item, Loans	$ 671,363,000	$ 699,452,000
Collateral netted against derivative liabilities	40,100,000	53,600,000	$ 59,100,000
Negative NPVs	39,300,000	52,685,000	57,189,000
Over collateralization net position	12,100,000	25,000,000	$ 11,700,000
Additional collateral held in securities	52,200,000
Fair Value Hedge Assets, Loans	18,063,000	41,919,000
Derivative, Amount of Hedged Item	(297,506,000)	(308,608,000)
Fair Value Hedge Assets	$ 21,193,000	$ 9,959,000
Subordinated Debentures Maturing July 2025 [Member] \| Subordinated Debt [Member]
Derivative [Line Items]
Debt Instrument, Face Amount					$ 150,000,000
Subordinated Debentures Maturing July 2056 [Member] \| Subordinated Debt [Member]
Derivative [Line Items]
Debt Instrument, Face Amount				$ 175,000,000

Earnings per Share (Details)

Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Basic	104,530	103,987
Dilutive Effect Of Stock Options Restricted Stock And Equity Settled Awards	794	849
Diluted	105,324	104,836
Net income available to common shareholders	$ 100,900	$ 73,342
Earnings (loss) per share - basic	$ 0.97	$ 0.71
Earnings (loss) per share - diluted	$ 0.96	$ 0.70
Anti-dilutive stock options outstanding that were not included in computation of diluted earnings per common share	0

Income Taxes Additional Informa

Income Taxes Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation, Percent	17.10%	25.03%
Deferred tax assets, net	$ 27,374	$ 27,400	$ 5,780
Operating Loss Carryforwards, Valuation Allowance	0		0
Increase (Decrease) in Deferred Income Taxes	21,600
Investments in LIHTC	288,911		267,023
Unfunded Low Income Housing Tax Credit Obligations	167,900		$ 151,300
Amortization of tax credit investments	8,128	$ 5,931
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	135,600
Deferred Tax Assets, Operating Loss Carryforwards	24,000
CALIFORNIA
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	19,100
ARIZONA
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	13,300
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward, Amount	$ 2,800

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Loss Contingencies [Line Items]
Letters of credit expiration period	1 year
Percentage of first liens initial loan to value ratio	75.00%
Percentage Of Commercial Real Estate Loans Occupied By Owners	37.00%		36.00%
Operating Leases, Rent Expense, Net	$ 2.5	$ 2.6
Commercial Real Estate Portfolio Segment [Member] \| Loans Receivable [Member] \| Credit Concentration Risk [Member]
Loss Contingencies [Line Items]
Percent of commercial real estate related loans	52.00%	52.00%
Unfunded Loan Commitment [Member]
Loss Contingencies [Line Items]
Loss Contingency Accrual	$ 7.2		$ 6.2

Commitments and Contingencies68

Commitments and Contingencies - Summary of Contractual Amounts for Unfunded Commitments and Letters of Credit (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Other Commitments [Line Items]
Total amount	$ 6,867,712		$ 6,166,876
Percentage Of Commercial Real Estate Loans Occupied By Owners	37.00%		36.00%
Operating Leases, Rent Expense, Net	$ 2,500	$ 2,600
Commitments to extend credit [Member]
Other Commitments [Line Items]
Unsecured Loan Commitments	437,437		$ 364,638
Total amount	6,500,031		5,851,158
Credit card guarantees [Member]
Other Commitments [Line Items]
Total amount	186,613		153,752
Standby letters of credit [Member]
Other Commitments [Line Items]
Total amount	181,068		161,966
Unsecured Letters Of Credit	$ 12,148		$ 11,664
Commercial Real Estate Portfolio Segment [Member] \| Credit Concentration Risk [Member] \| Loans Receivable [Member]
Other Commitments [Line Items]
Concentration Risk, Percentage	52.00%	52.00%

Fair Value Accounting - Gains a

Fair Value Accounting - Gains and Losses from Fair Value Changes Included in Consolidated Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Subordinated Debt Obligations, Fair Value Disclosure	$ 54,290		$ 56,234
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	1,944	$ (1,987)
Interest Income on Securities	0	7
Interest Expense on Junior Subordinated Debt	904	749
Total Changes Included in Current-Period Earnings	904	(743)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	1,466	(1,229)
Trading Securities [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(1)
Interest Income on Securities		7
Interest Expense on Junior Subordinated Debt		0
Total Changes Included in Current-Period Earnings		6
Junior Subordinated Debt [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	1,944	(1,986)
Interest Income on Securities	0	0
Interest Expense on Junior Subordinated Debt	904	(749)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	$ 1,466	$ (1,229)
Junior subordinated debt, Input Value	6.649%		5.608%
Period of basis point spread	4.34%		3.92%
Percentage of LIBOR	2.31%	1.69%
Level 3 [Member] \| Junior Subordinated Debt [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Subordinated Debt Obligations, Fair Value Disclosure	$ 54,290		$ 56,234

Fair Value Accounting - Fair Va

Fair Value Accounting - Fair Value of Assets and Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Hedge Assets, Loans	$ 18,063	$ 41,919
Fair Value Hedge Assets	21,193	9,959
Securities available for sale	3,405,462	3,499,519
Derivative Liability	39,300	52,685	$ 57,189
Subordinated Debt Obligations, Fair Value Disclosure	54,290	56,234
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	3,405,462	3,499,519
Derivative Liability	44,353	55,340
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	144,164	103,812
Derivative Liability	0	0
Subordinated Debt Obligations, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	3,261,298	3,395,707
Derivative Liability	44,353	55,340
Subordinated Debt Obligations, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Derivative Liability	0	0
Subordinated Debt Obligations, Fair Value Disclosure	54,290	56,234
Fair Value, Measurements, Recurring [Member] \| Residential mortgage-backed securities issued by GSEs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,626,899	1,689,295
Fair Value, Measurements, Recurring [Member] \| Residential mortgage-backed securities issued by GSEs \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Residential mortgage-backed securities issued by GSEs \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,626,899	1,689,295
Fair Value, Measurements, Recurring [Member] \| Residential mortgage-backed securities issued by GSEs \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Private label residential mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	818,996	868,524
Fair Value, Measurements, Recurring [Member] \| Private label residential mortgage-backed securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Private label residential mortgage-backed securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	818,996	868,524
Fair Value, Measurements, Recurring [Member] \| Private label residential mortgage-backed securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	104,973	109,077
Fair Value, Measurements, Recurring [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	104,973	109,077
Fair Value, Measurements, Recurring [Member] \| Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	101,676	103,483
Fair Value, Measurements, Recurring [Member] \| Corporate debt securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Corporate debt securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	101,676	103,483
Fair Value, Measurements, Recurring [Member] \| Corporate debt securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Municipal obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	497,921	510,910
Fair Value, Measurements, Recurring [Member] \| Municipal obligations [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Municipal obligations [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	497,921	510,910
Fair Value, Measurements, Recurring [Member] \| Municipal obligations [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	93,318	53,196
Fair Value, Measurements, Recurring [Member] \| Preferred Stock [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	93,318	53,196
Fair Value, Measurements, Recurring [Member] \| Preferred Stock [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Preferred Stock [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| CRA investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	50,846	50,616
Fair Value, Measurements, Recurring [Member] \| CRA investments [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	50,846	50,616
Fair Value, Measurements, Recurring [Member] \| CRA investments [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| CRA investments [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Collateralized debt obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	19,453	21,857
Fair Value, Measurements, Recurring [Member] \| Collateralized debt obligations [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Collateralized debt obligations [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	19,453	21,857
Fair Value, Measurements, Recurring [Member] \| Collateralized debt obligations [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Trust preferred securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	28,617	28,617
Fair Value, Measurements, Recurring [Member] \| Trust preferred securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Trust preferred securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	28,617	28,617
Fair Value, Measurements, Recurring [Member] \| Trust preferred securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	60,290	61,462
Fair Value, Measurements, Recurring [Member] \| US Government-sponsored Enterprises Debt Securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| US Government-sponsored Enterprises Debt Securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	60,290	61,462
Fair Value, Measurements, Recurring [Member] \| US Government-sponsored Enterprises Debt Securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,473	2,482
Fair Value, Measurements, Recurring [Member] \| US Treasury Securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| US Treasury Securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,473	2,482
Fair Value, Measurements, Recurring [Member] \| US Treasury Securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Reported Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	3,405,462	3,499,519
Derivative Liability	$ 44,353	$ 55,340

Fair Value Accounting - Change

Fair Value Accounting - Change in Level 3 Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt	$ 54,290		$ 56,234
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt	$ 54,290		$ 56,234
Loans and Finance Receivables [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Discounted cash flow method		Discounted cash flow method
Other Assets [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Collateral method		Collateral method
Junior Subordinated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	$ 1,944	$ (1,986)
Junior subordinated debt, Input Value	6.649%		5.608%
Junior Subordinated Debt [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt	$ 54,290		$ 56,234
Junior subordinated debt, Valuation Technique	Discounted cash flow		Discounted cash flow
Junior subordinated debt, Significant Unobservable Inputs	Implied credit rating of the Company		Implied credit rating of the Company
Junior Subordinated Debt [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance	$ 56,234	(50,410)	$ (50,410)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3	0	0
Closing balance	$ 54,290	$ (52,396)	$ 56,234
Collateral Method [Member] \| Loans and Finance Receivables [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Collateral method		Collateral method
Third Party Appraisal [Member] \| Loans and Finance Receivables [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Third party appraisal		Third party appraisal
Third Party Appraisal [Member] \| Other Assets [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Third party appraisal		Third party appraisal
Discount Rate [Member] \| Loans and Finance Receivables [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Discount rate		Discount rate
Scheduled Cash Collections [Member] \| Loans and Finance Receivables [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Scheduled cash collections		Scheduled cash collections
Proceeds from Non-Real Estate Collateral [Member] \| Loans and Finance Receivables [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Proceeds from non-real estate collateral		Proceeds from non-real estate collateral

Fair Value Accounting - Assets

Fair Value Accounting - Assets Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded	$ 9,598	$ 19,315
Impaired loans with an allowance recorded	5,562	5,606
Impaired loans without specific valuation allowance	87,994	79,239
Other assets acquired through foreclosure	30,194	28,540	$ 45,200	$ 47,815
Impaired Financing Receivable, Recorded Investment	97,592	98,554
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded	5,600
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded	4,036	13,709
Impaired loans without specific valuation allowance	63,639	63,607
Other assets acquired through foreclosure	30,194	28,540
Fair Value, Measurements, Nonrecurring [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded	0	0
Impaired loans without specific valuation allowance	0	0
Other assets acquired through foreclosure	0	0
Fair Value, Measurements, Nonrecurring [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded	0	0
Impaired loans without specific valuation allowance	0	0
Other assets acquired through foreclosure	0	0
Fair Value, Measurements, Nonrecurring [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded	4,036	13,709
Impaired loans without specific valuation allowance	63,639	63,607
Other assets acquired through foreclosure	30,194	28,540
Impaired Financing Receivable, Recorded Investment	$ 67,675	$ 77,316

Fair Value Accounting - Estimat

Fair Value Accounting - Estimated Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Financing Receivable, Recorded Investment	$ 97,592	$ 98,554
Other Repossessed Assets	30,200	28,500
Financial assets
Held-to-maturity Securities	262,304	255,050
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	3,405,462	3,499,519
Derivative Asset		807	$ 38
Loans, net	15,415,794	14,953,885
Financial liabilities
Deposits	17,354,538	16,972,532
Customer repurchase agreements	21,676	26,017
Junior subordinated debt	54,290	56,234
Derivative Liability	39,300	52,685	$ 57,189
Fair Value, Measurements, Nonrecurring [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Financing Receivable, Recorded Investment	67,675	77,316
Fair Value, Measurements, Nonrecurring [Member] \| Reported Value Measurement [Member]
Financial assets
Held-to-maturity Securities	262,304	255,050
Loans, net	15,415,794	14,953,885
Financial liabilities
Deposits	17,354,538	16,972,532
Junior subordinated debt	363,935	376,905
Fair Value, Measurements, Nonrecurring [Member] \| Fair Value [Member]
Financial assets
Held-to-maturity Securities	255,418	256,314
Loans, net	15,322,063	14,654,326
Financial liabilities
Deposits	17,360,147	16,980,066
Junior subordinated debt	396,032	404,013
Fair Value, Measurements, Nonrecurring [Member] \| Fair Value [Member] \| Level 1 [Member]
Financial assets
Held-to-maturity Securities	0	0
Loans, net	0	0
Financial liabilities
Deposits	0	0
Junior subordinated debt	0	0
Fair Value, Measurements, Nonrecurring [Member] \| Fair Value [Member] \| Level 2 [Member]
Financial assets
Held-to-maturity Securities	255,418	256,314
Loans, net	15,254,388	14,577,010
Financial liabilities
Deposits	17,360,147	16,980,066
Junior subordinated debt	331,190	336,803
Fair Value, Measurements, Nonrecurring [Member] \| Fair Value [Member] \| Level 3 [Member]
Financial assets
Held-to-maturity Securities	0	0
Loans, net	67,675	77,316
Financial liabilities
Deposits	0	0
Junior subordinated debt	64,842	67,210
Fair Value, Measurements, Recurring [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	3,405,462	3,499,519
Derivative Asset	5,387	3,711
Financial liabilities
Derivative Liability	44,353	55,340
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	144,164	103,812
Derivative Asset	0	0
Financial liabilities
Junior subordinated debt	0	0
Derivative Liability	0	0
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	3,261,298	3,395,707
Derivative Asset	5,387	3,711
Financial liabilities
Junior subordinated debt	0	0
Derivative Liability	44,353	55,340
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Derivative Asset	0	0
Financial liabilities
Junior subordinated debt	54,290	56,234
Derivative Liability	0	0
Fair Value, Measurements, Recurring [Member] \| Reported Value Measurement [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	3,405,462	3,499,519
Derivative Asset	5,387	3,711
Accrued Investment Income Receivable	80,398	85,517
Financial liabilities
Customer repurchase agreements	21,676	26,017
Federal Home Loan Bank Borrowings, Fair Value Disclosure	300,000	390,000
Derivative Liability	44,353	55,340
Interest Payable, Current	11,540	16,366
Fair Value, Measurements, Recurring [Member] \| Fair Value [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	3,405,462	3,499,519
Derivative Asset	5,387	3,711
Accrued Investment Income Receivable	80,398	85,517
Financial liabilities
Customer repurchase agreements	21,676	26,017
Federal Home Loan Bank Borrowings, Fair Value Disclosure	300,000	390,000
Derivative Liability	44,353	55,340
Interest Payable, Current	11,540	16,366
Fair Value, Measurements, Recurring [Member] \| Fair Value [Member] \| Level 1 [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	144,164	103,812
Derivative Asset	0	0
Accrued Investment Income Receivable	0	0
Financial liabilities
Customer repurchase agreements	0	0
Federal Home Loan Bank Borrowings, Fair Value Disclosure	0	0
Derivative Liability	0	0
Interest Payable, Current	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value [Member] \| Level 2 [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	3,261,298	3,395,707
Derivative Asset	5,387	3,711
Accrued Investment Income Receivable	80,398	85,517
Financial liabilities
Customer repurchase agreements	21,676	26,017
Federal Home Loan Bank Borrowings, Fair Value Disclosure	300,000	390,000
Derivative Liability	44,353	55,340
Interest Payable, Current	11,540	16,366
Fair Value, Measurements, Recurring [Member] \| Fair Value [Member] \| Level 3 [Member]
Financial assets
Investment securities - AFS, at fair value; amortized cost of $3,474,049 at March 31, 2018 and $3,515,401 at December 31, 2017	0	0
Derivative Asset	0	0
Accrued Investment Income Receivable	0	0
Financial liabilities
Customer repurchase agreements	0	0
Federal Home Loan Bank Borrowings, Fair Value Disclosure	0	0
Derivative Liability	0	0
Interest Payable, Current	$ 0	$ 0
Loans and Finance Receivables [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Discounted cash flow method	Discounted cash flow method
Other Assets [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Collateral method	Collateral method
Collateral Method [Member] \| Loans and Finance Receivables [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Collateral method	Collateral method
Third Party Appraisal [Member] \| Loans and Finance Receivables [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Third party appraisal	Third party appraisal
Fair Value Measurements, Significant Assumptions	Costs to sell	Costs to sell
Third Party Appraisal [Member] \| Other Assets [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Third party appraisal	Third party appraisal
Fair Value Measurements, Significant Assumptions	Costs to sell	Costs to sell
Discount Rate [Member] \| Loans and Finance Receivables [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Discount rate	Discount rate
Fair Value Measurements, Significant Assumptions	Contractual loan rate	Contractual loan rate
Scheduled Cash Collections [Member] \| Loans and Finance Receivables [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Scheduled cash collections	Scheduled cash collections
Fair Value Measurements, Significant Assumptions	Probability of default	Probability of default
Proceeds from Non-Real Estate Collateral [Member] \| Loans and Finance Receivables [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Valuation Technique	Proceeds from non-real estate collateral	Proceeds from non-real estate collateral
Fair Value Measurements, Significant Assumptions	Loss given default	Loss given default

Fair Value Accounting - Additio

Fair Value Accounting - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Financing Receivable, Recorded Investment	$ 97,592		$ 98,554
Aggregate carrying amount of impaired loans	9,598		19,315
Impaired loans with an allowance recorded	(5,562)		(5,606)
Other assets acquired through foreclosure	30,200		28,500
Goodwill	$ 289,895		$ 289,895
Common Stock, Shares, Issued	107,611,765		107,057,520
Collateralized debt obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities contained credit losses	0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded	$ (5,600)
Junior Subordinated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Junior subordinated debt, Input Value	6.649%		5.608%
Period of basis point spread	4.34%		3.92%
Percentage of LIBOR	2.31%	1.69%
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate carrying amount of impaired loans	$ 4,036		$ 13,709
Fair Value, Measurements, Nonrecurring [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Financing Receivable, Recorded Investment	67,675		77,316
Aggregate carrying amount of impaired loans	$ 4,036		$ 13,709

Segments - Operating Segment In

Segments - Operating Segment Information (Detail) - USD ($)	3 Months Ended
Segments - Operating Segment Information (Detail) - USD ($)	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017	Jan. 01, 2017	Dec. 31, 2016
Operating Statistics [Line Items]
Cash, Cash Equivalents and Investment Securities	$ 4,173,700,000			$ 4,237,100,000
Loans, net of deferred loan fees and costs	15,560,400,000			15,093,900,000
Less: Allowance for credit losses	(144,659,000)			(140,050,000)
Total loans held for investment	15,415,700,000			14,953,900,000
Other Repossessed Assets	30,200,000			28,500,000
Intangible Assets, Net (Including Goodwill)	300,400,000			300,700,000
Other Assets Segment	840,700,000			808,900,000
Assets	20,760,731,000			20,329,085,000
Deposits	17,354,538,000			16,972,532,000
Other borrowings	663,900,000			766,900,000
Other Liabilities Segment	448,600,000			360,000,000
Liabilities	18,466,968,000			18,099,387,000
Stockholders' equity	2,293,763,000	$ 1,969,515,000	$ 2,229,698,000	2,229,698,000	$ 1,892,067,000	$ 1,891,529,000
Liabilities and Equity	20,760,731,000			20,329,085,000
Excess Funds Provided by (Used in) Segment Basis	0			0
Net interest income	214,220,000	179,309,000
Provision for Loan, Lease, and Other Losses	6,000,000	4,250,000
Net interest income (loss) after provision for credit losses	208,220,000	175,059,000
Total non-interest income	11,643,000	10,599,000
Non-interest expense	(98,149,000)	(87,827,000)
Income from continuing operations before income taxes	121,714,000	97,831,000
Income tax expense (benefit)	20,814,000	24,489,000
Net income	100,900,000	73,342,000
Northern California [Member]
Operating Statistics [Line Items]
Net interest income		179,309,000
Income from continuing operations before income taxes		97,831,000
Income tax expense (benefit)		24,489,000
Operating Segments [Member] \| HOA Services [Member]
Operating Statistics [Line Items]
Cash, Cash Equivalents and Investment Securities	0			0
Loans, net of deferred loan fees and costs	167,000,000			162,100,000
Less: Allowance for credit losses	(1,700,000)			(1,600,000)
Total loans held for investment	165,300,000			160,500,000
Other Repossessed Assets	0			0
Intangible Assets, Net (Including Goodwill)	0			0
Other Assets Segment	800,000			900,000
Assets	166,100,000			161,400,000
Deposits	2,475,300,000			2,230,400,000
Other borrowings	0			0
Other Liabilities Segment	1,600,000			1,200,000
Liabilities	2,476,900,000			2,231,600,000
Stockholders' equity	5,900,000			59,400,000
Liabilities and Equity	2,482,800,000			2,291,000,000
Excess Funds Provided by (Used in) Segment Basis	2,316,700,000			2,129,600,000
Net interest income	15,359,000	12,748,000
Provision for Loan, Lease, and Other Losses	47,000	127,000
Net interest income (loss) after provision for credit losses	15,312,000	12,621,000
Total non-interest income	150,000	141,000
Non-interest expense	(7,803,000)	(7,147,000)
Income from continuing operations before income taxes	7,659,000	5,615,000
Income tax expense (benefit)	1,761,000	2,106,000
Net income	5,898,000	3,509,000
Operating Segments [Member] \| Public and Non-Profit Finance [Member]
Operating Statistics [Line Items]
Cash, Cash Equivalents and Investment Securities	0			0
Loans, net of deferred loan fees and costs	1,539,800,000			1,580,400,000
Less: Allowance for credit losses	(15,500,000)			(15,600,000)
Total loans held for investment	1,524,300,000			1,564,800,000
Other Repossessed Assets	0			0
Intangible Assets, Net (Including Goodwill)	0			0
Other Assets Segment	14,700,000			17,900,000
Assets	1,539,000,000			1,582,700,000
Deposits	0			0
Other borrowings	0			0
Other Liabilities Segment	21,500,000			42,400,000
Liabilities	21,500,000			42,400,000
Stockholders' equity	1,300,000			126,500,000
Liabilities and Equity	22,800,000			168,900,000
Excess Funds Provided by (Used in) Segment Basis	(1,516,200,000)			(1,413,800,000)
Net interest income	3,746,000	6,485,000
Provision for Loan, Lease, and Other Losses	(207,000)	509,000
Net interest income (loss) after provision for credit losses	3,953,000	5,976,000
Total non-interest income	0	70,000
Non-interest expense	(2,174,000)	(2,323,000)
Income from continuing operations before income taxes	1,779,000	3,723,000
Income tax expense (benefit)	409,000	1,402,000
Net income	1,370,000	2,321,000
Operating Segments [Member] \| Technology and Innovation [Member]
Operating Statistics [Line Items]
Cash, Cash Equivalents and Investment Securities	0			0
Loans, net of deferred loan fees and costs	1,168,900,000			1,097,900,000
Less: Allowance for credit losses	(10,300,000)			(11,400,000)
Total loans held for investment	1,158,600,000			1,086,500,000
Other Repossessed Assets	0			0
Intangible Assets, Net (Including Goodwill)	120,800,000			120,900,000
Other Assets Segment	6,800,000			6,000,000
Assets	1,286,200,000			1,213,400,000
Deposits	1,733,500,000			1,737,600,000
Other borrowings	0			0
Other Liabilities Segment	1,200,000			800,000
Liabilities	1,734,700,000			1,738,400,000
Stockholders' equity	11,100,000			244,100,000
Liabilities and Equity	1,745,800,000			1,982,500,000
Excess Funds Provided by (Used in) Segment Basis	459,600,000			769,100,000
Net interest income	22,821,000	18,166,000
Provision for Loan, Lease, and Other Losses	1,651,000	296,000
Net interest income (loss) after provision for credit losses	21,170,000	17,870,000
Total non-interest income	3,051,000	1,873,000
Non-interest expense	(9,833,000)	(8,779,000)
Income from continuing operations before income taxes	14,388,000	10,964,000
Income tax expense (benefit)	3,309,000	4,111,000
Net income	11,079,000	6,853,000
Operating Segments [Member] \| HFF Loan Portfolio [Member]
Operating Statistics [Line Items]
Cash, Cash Equivalents and Investment Securities	0			0
Loans, net of deferred loan fees and costs	1,378,700,000			1,327,700,000
Less: Allowance for credit losses	(6,300,000)			(4,000,000)
Total loans held for investment	1,372,400,000			1,323,700,000
Other Repossessed Assets	0			0
Intangible Assets, Net (Including Goodwill)	100,000			100,000
Other Assets Segment	6,400,000			5,900,000
Assets	1,378,900,000			1,329,700,000
Deposits	0			0
Other borrowings	0			0
Other Liabilities Segment	(300,000)			400,000
Liabilities	(300,000)			400,000
Stockholders' equity	8,300,000			108,300,000
Liabilities and Equity	8,000,000			108,700,000
Excess Funds Provided by (Used in) Segment Basis	(1,370,900,000)			(1,221,000,000)
Net interest income	14,185,000	13,581,000
Provision for Loan, Lease, and Other Losses	1,236,000	0
Net interest income (loss) after provision for credit losses	12,949,000	13,581,000
Total non-interest income	13,000	0
Non-interest expense	(2,206,000)	(2,988,000)
Income from continuing operations before income taxes	10,756,000	10,593,000
Income tax expense (benefit)	2,474,000	3,972,000
Net income	8,282,000	6,621,000
Operating Segments [Member] \| Other National Business Lines [Member]
Operating Statistics [Line Items]
Cash, Cash Equivalents and Investment Securities	0			0
Loans, net of deferred loan fees and costs	2,725,400,000			2,543,000,000
Less: Allowance for credit losses	(27,500,000)			(25,000,000)
Total loans held for investment	2,697,900,000			2,518,000,000
Other Repossessed Assets	0			0
Intangible Assets, Net (Including Goodwill)	0			0
Other Assets Segment	13,400,000			15,500,000
Assets	2,711,300,000			2,533,500,000
Deposits	0			0
Other borrowings	0			0
Other Liabilities Segment	124,300,000			5,500,000
Liabilities	124,300,000			5,500,000
Stockholders' equity	9,300,000			206,000,000
Liabilities and Equity	133,600,000			211,500,000
Excess Funds Provided by (Used in) Segment Basis	(2,577,700,000)			(2,322,000,000)
Net interest income	18,811,000	14,143,000
Provision for Loan, Lease, and Other Losses	1,285,000	3,527,000
Net interest income (loss) after provision for credit losses	17,526,000	10,616,000
Total non-interest income	224,000	721,000
Non-interest expense	(5,662,000)	(4,721,000)
Income from continuing operations before income taxes	12,088,000	6,616,000
Income tax expense (benefit)	2,780,000	2,481,000
Net income	9,308,000	4,135,000
Corporate & Other
Operating Statistics [Line Items]
Cash, Cash Equivalents and Investment Securities	4,158,400,000			4,223,000,000
Loans, net of deferred loan fees and costs	3,300,000			4,100,000
Less: Allowance for credit losses	(100,000)			(100,000)
Total loans held for investment	3,200,000			4,000,000
Other Repossessed Assets	12,700,000			12,700,000
Intangible Assets, Net (Including Goodwill)	0			0
Other Assets Segment	664,000,000			628,100,000
Assets	4,838,300,000			4,867,800,000
Deposits	238,800,000			69,000,000
Other borrowings	663,900,000			766,900,000
Other Liabilities Segment	260,800,000			262,100,000
Liabilities	1,163,500,000			1,098,000,000
Stockholders' equity	2,193,400,000			300,300,000
Liabilities and Equity	3,356,900,000			1,398,300,000
Excess Funds Provided by (Used in) Segment Basis	(1,481,400,000)			(3,469,500,000)
Net interest income	(2,004,000)	(12,270,000)
Provision for Loan, Lease, and Other Losses	0	(499,000)
Net interest income (loss) after provision for credit losses	(2,004,000)	(11,771,000)
Total non-interest income	(92,000)	1,692,000
Non-interest expense	(8,734,000)	(1,965,000)
Income from continuing operations before income taxes	(10,830,000)	(12,044,000)
Income tax expense (benefit)	(11,376,000)	(17,733,000)
Net income	546,000	5,689,000
Reportable Geographical Components [Member] \| ARIZONA
Operating Statistics [Line Items]
Cash, Cash Equivalents and Investment Securities	2,100,000			2,100,000
Loans, net of deferred loan fees and costs	3,472,700,000			3,323,700,000
Less: Allowance for credit losses	(33,900,000)			(31,500,000)
Total loans held for investment	3,438,800,000			3,292,200,000
Other Repossessed Assets	2,300,000			2,300,000
Intangible Assets, Net (Including Goodwill)	0			0
Other Assets Segment	46,400,000			46,300,000
Assets	3,489,600,000			3,342,900,000
Deposits	5,020,600,000			4,841,300,000
Other borrowings	0			0
Other Liabilities Segment	10,900,000			11,600,000
Liabilities	5,031,500,000			4,852,900,000
Stockholders' equity	24,700,000			396,500,000
Liabilities and Equity	5,056,200,000			5,249,400,000
Excess Funds Provided by (Used in) Segment Basis	1,566,600,000			1,906,500,000
Net interest income	54,555,000	43,907,000
Provision for Loan, Lease, and Other Losses	1,434,000	14,000
Net interest income (loss) after provision for credit losses	53,121,000	43,893,000
Total non-interest income	1,416,000	1,113,000
Non-interest expense	(21,504,000)	(18,622,000)
Income from continuing operations before income taxes	33,033,000	26,384,000
Income tax expense (benefit)	8,321,000	10,350,000
Net income	24,712,000	16,034,000
Reportable Geographical Components [Member] \| NEVADA
Operating Statistics [Line Items]
Cash, Cash Equivalents and Investment Securities	8,500,000			8,200,000
Loans, net of deferred loan fees and costs	1,819,600,000			1,844,800,000
Less: Allowance for credit losses	(17,900,000)			(18,100,000)
Total loans held for investment	1,801,700,000			1,826,700,000
Other Repossessed Assets	15,000,000			13,300,000
Intangible Assets, Net (Including Goodwill)	23,200,000			23,200,000
Other Assets Segment	58,300,000			58,800,000
Assets	1,906,700,000			1,930,200,000
Deposits	3,648,100,000			3,951,400,000
Other borrowings	0			0
Other Liabilities Segment	16,200,000			20,900,000
Liabilities	3,664,300,000			3,972,300,000
Stockholders' equity	21,800,000			263,700,000
Liabilities and Equity	3,686,100,000			4,236,000,000
Excess Funds Provided by (Used in) Segment Basis	1,779,400,000			2,305,800,000
Net interest income	36,690,000	35,296,000
Provision for Loan, Lease, and Other Losses	(1,723,000)	(211,000)
Net interest income (loss) after provision for credit losses	38,413,000	35,507,000
Total non-interest income	3,333,000	2,133,000
Non-interest expense	(14,084,000)	(15,870,000)
Income from continuing operations before income taxes	27,662,000	21,770,000
Income tax expense (benefit)	5,903,000	7,620,000
Net income	21,759,000	14,150,000
Reportable Geographical Components [Member] \| Southern California [Member]
Operating Statistics [Line Items]
Cash, Cash Equivalents and Investment Securities	2,200,000			2,100,000
Loans, net of deferred loan fees and costs	2,013,600,000			1,934,700,000
Less: Allowance for credit losses	(20,300,000)			(19,500,000)
Total loans held for investment	1,993,300,000			1,915,200,000
Other Repossessed Assets	0			0
Intangible Assets, Net (Including Goodwill)	0			0
Other Assets Segment	14,800,000			14,400,000
Assets	2,010,300,000			1,931,700,000
Deposits	2,423,800,000			2,461,100,000
Other borrowings	0			0
Other Liabilities Segment	1,900,000			3,200,000
Liabilities	2,425,700,000			2,464,300,000
Stockholders' equity	10,300,000			221,800,000
Liabilities and Equity	2,436,000,000			2,686,100,000
Excess Funds Provided by (Used in) Segment Basis	425,700,000			754,400,000
Net interest income	27,802,000	25,218,000
Provision for Loan, Lease, and Other Losses	729,000	91,000
Net interest income (loss) after provision for credit losses	27,073,000	25,127,000
Total non-interest income	1,001,000	743,000
Non-interest expense	(13,646,000)	(12,703,000)
Income from continuing operations before income taxes	14,428,000	13,167,000
Income tax expense (benefit)	4,135,000	5,537,000
Net income	10,293,000	7,630,000
Reportable Geographical Components [Member] \| Northern California [Member]
Operating Statistics [Line Items]
Cash, Cash Equivalents and Investment Securities	2,500,000			1,700,000
Loans, net of deferred loan fees and costs	1,271,400,000			1,275,500,000
Less: Allowance for credit losses	(11,200,000)			(13,200,000)
Total loans held for investment	1,260,200,000			1,262,300,000
Other Repossessed Assets	200,000			200,000
Intangible Assets, Net (Including Goodwill)	156,300,000			156,500,000
Other Assets Segment	15,100,000			15,100,000
Assets	1,434,300,000			1,435,800,000
Deposits	1,814,400,000			1,681,700,000
Other borrowings	0			0
Other Liabilities Segment	10,500,000			11,900,000
Liabilities	1,824,900,000			1,693,600,000
Stockholders' equity	7,600,000			303,100,000
Liabilities and Equity	1,832,500,000			1,996,700,000
Excess Funds Provided by (Used in) Segment Basis	398,200,000			$ 560,900,000
Net interest income	22,255,000	22,035,000
Provision for Loan, Lease, and Other Losses	1,548,000	396,000
Net interest income (loss) after provision for credit losses	20,707,000	21,639,000
Total non-interest income	2,547,000	2,113,000
Non-interest expense	(12,503,000)	(12,709,000)
Income from continuing operations before income taxes	10,751,000	11,043,000
Income tax expense (benefit)	3,098,000	4,643,000
Net income	$ 7,653,000	$ 6,400,000

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	$ 0.5	$ 1.5

Revenue from Contracts with Cus

Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Service charges and fees	$ 5,745	$ 4,738
Debit and credit card interchange fees	1,508	1,215
Success fees (2)	781	325
Other income	235	119
Total revenue from contracts with customers	8,269	6,397
Revenues outside the scope of ASC 606 (3)	3,374	4,202
Total non-interest income	11,643	10,599
Operating Segments [Member] \| HOA Services [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	146	141
Debit and credit card interchange fees	3	0
Success fees (2)	0	0
Other income	0	0
Total revenue from contracts with customers	149	141
Revenues outside the scope of ASC 606 (3)	1	0
Total non-interest income	150	141
Operating Segments [Member] \| Public and Non-Profit Finance [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	0	0
Debit and credit card interchange fees	0	0
Success fees (2)	0	0
Other income	0	0
Total revenue from contracts with customers	0	0
Revenues outside the scope of ASC 606 (3)	0	70
Total non-interest income	0	70
Operating Segments [Member] \| Technology and Innovation [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	815	795
Debit and credit card interchange fees	0	0
Success fees (2)	779	180
Other income	0	0
Total revenue from contracts with customers	1,594	975
Revenues outside the scope of ASC 606 (3)	1,457	898
Total non-interest income	3,051	1,873
Operating Segments [Member] \| HFF Loan Portfolio [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	0	0
Debit and credit card interchange fees	0	0
Success fees (2)	0	0
Other income	0	0
Total revenue from contracts with customers	0	0
Revenues outside the scope of ASC 606 (3)	13	0
Total non-interest income	13	0
Operating Segments [Member] \| Other National Business Lines [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	0	0
Debit and credit card interchange fees	0	0
Success fees (2)	0	0
Other income	0	85
Total revenue from contracts with customers	0	85
Revenues outside the scope of ASC 606 (3)	224	636
Total non-interest income	224	721
Reportable Geographical Components [Member] \| ARIZONA
Disaggregation of Revenue [Line Items]
Service charges and fees	917	619
Debit and credit card interchange fees	257	214
Success fees (2)	0	0
Other income	61	11
Total revenue from contracts with customers	1,235	844
Revenues outside the scope of ASC 606 (3)	181	269
Total non-interest income	1,416	1,113
Reportable Geographical Components [Member] \| NEVADA
Disaggregation of Revenue [Line Items]
Service charges and fees	2,069	1,662
Debit and credit card interchange fees	272	234
Success fees (2)	0	0
Other income	69	3
Total revenue from contracts with customers	2,410	1,899
Revenues outside the scope of ASC 606 (3)	923	234
Total non-interest income	3,333	2,133
Reportable Geographical Components [Member] \| Southern California [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	738	496
Debit and credit card interchange fees	139	129
Success fees (2)	0	0
Other income	27	(27)
Total revenue from contracts with customers	904	598
Revenues outside the scope of ASC 606 (3)	97	145
Total non-interest income	1,001	743
Reportable Geographical Components [Member] \| Northern California [Member]
Disaggregation of Revenue [Line Items]
Service charges and fees	1,059	1,028
Debit and credit card interchange fees	837	638
Success fees (2)	2	145
Other income	73	42
Total revenue from contracts with customers	1,971	1,853
Revenues outside the scope of ASC 606 (3)	576	260
Total non-interest income	2,547	2,113
Corporate & Other
Disaggregation of Revenue [Line Items]
Service charges and fees	1	(3)
Debit and credit card interchange fees	0	0
Success fees (2)	0	0
Other income	5	5
Total revenue from contracts with customers	6	2
Revenues outside the scope of ASC 606 (3)	(98)	1,690
Total non-interest income	$ (92)	$ 1,692

Uncategorized Items - wal-20180

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