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