Carrying Amount and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Carrying Amount
Financial assets
Cash and cash equivalents	$ 251,413	$ 193,253
Investment securities, available-for-sale	2,292,079	2,610,760
Investment securities, held-to-maturity	679,707	702,072
Loans held for sale	71,069	56,514
Loans receivable, net of ALLL	5,463,428	4,948,984
Accrued interest receivable	50,138	44,524
Non-marketable equity securities	20,103	27,495
Total financial assets	8,827,937	8,583,602
Financial liabilities
Deposits	7,309,319	6,945,008
FHLB advances	211,833	394,131
Repurchase agreements and other borrowed funds	407,199	430,016
Subordinated debentures	125,956	125,848
Accrued interest payable	3,439	3,517
Interest rate swaps	26,526	19,499
Total financial liabilities	8,084,272	7,918,019
Estimated Fair Value | Level 1
Financial assets
Cash and cash equivalents	251,413	193,253
Investment securities, available-for-sale	0	0
Investment securities, held-to-maturity	0	0
Loans held for sale	71,069	56,514
Loans receivable, net of ALLL	0	0
Accrued interest receivable	50,138	44,524
Non-marketable equity securities	0	0
Total financial assets	372,620	294,291
Financial liabilities
Deposits	5,994,226	5,654,638
FHLB advances	0	0
Repurchase agreements and other borrowed funds	0	0
Subordinated debentures	0	0
Accrued interest payable	3,439	3,517
Interest rate swaps	0	0
Total financial liabilities	5,997,665	5,658,155
Estimated Fair Value | Level 2
Financial assets
Cash and cash equivalents	0	0
Investment securities, available-for-sale	2,292,079	2,610,760
Investment securities, held-to-maturity	714,895	729,513
Loans held for sale	0	0
Loans receivable, net of ALLL	5,354,017	4,851,934
Accrued interest receivable	0	0
Non-marketable equity securities	20,103	27,495
Total financial assets	8,381,094	8,219,702
Financial liabilities
Deposits	1,317,757	1,293,506
FHLB advances	224,335	401,530
Repurchase agreements and other borrowed funds	407,199	430,016
Subordinated debentures	84,084	81,840
Accrued interest payable	0	0
Interest rate swaps	26,526	19,499
Total financial liabilities	2,059,901	2,226,391
Estimated Fair Value | Level 3
Financial assets
Cash and cash equivalents	0	0
Investment securities, available-for-sale	0	0
Investment securities, held-to-maturity	0	0
Loans held for sale	0	0
Loans receivable, net of ALLL	129,187	132,649
Accrued interest receivable	0	0
Non-marketable equity securities	0	0
Total financial assets	129,187	132,649
Financial liabilities
Deposits	0	0
FHLB advances	0	0
Repurchase agreements and other borrowed funds	0	0
Subordinated debentures	0	0
Accrued interest payable	0	0
Interest rate swaps	0	0
Total financial liabilities	$ 0	$ 0