Carrying Amount and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Carrying Amount
Financial Assets
Cash and cash equivalents	$ 193,253	$ 442,409
Investment securities, available-for-sale	2,610,760	2,387,428
Investment securities, held-to-maturity	702,072	520,997
Loans held-for-sale	56,514	46,726
Loans receivable, net of ALLL	4,948,984	4,358,342
Accrued interest receivable	44,524	40,587
Non-marketable equity securities	27,495	52,868
Total financial assets	8,583,602	7,849,357
Financial Liabilities
Deposits	6,945,008	6,345,212
FHLB advances	394,131	296,944
Repurchase agreements and other borrowed funds	430,016	404,418
Subordinated debentures	125,848	125,705
Accrued interest payable	3,517	4,155
Interest rate swaps	19,499	16,668
Total financial liabilities	7,918,019	7,193,102
Estimated Fair Value | Level 1
Financial Assets
Cash and cash equivalents	193,253	442,409
Investment securities, available-for-sale	0	0
Investment securities, held-to-maturity	0	0
Loans held-for-sale	56,514	46,726
Loans receivable, net of ALLL	0	0
Accrued interest receivable	44,524	40,587
Non-marketable equity securities	0	0
Total financial assets	294,291	529,722
Financial Liabilities
Deposits	5,654,638	4,928,771
FHLB advances	0	0
Repurchase agreements and other borrowed funds	0	0
Subordinated debentures	0	0
Accrued interest payable	3,517	4,155
Interest rate swaps	0	0
Total financial liabilities	5,658,155	4,932,926
Estimated Fair Value | Level 2
Financial Assets
Cash and cash equivalents	0	0
Investment securities, available-for-sale	2,610,760	2,387,428
Investment securities, held-to-maturity	729,513	550,946
Loans held-for-sale	0	0
Loans receivable, net of ALLL	4,851,934	4,288,417
Accrued interest receivable	0	0
Non-marketable equity securities	27,495	52,868
Total financial assets	8,219,702	7,279,659
Financial Liabilities
Deposits	1,293,506	1,421,234
FHLB advances	401,530	312,363
Repurchase agreements and other borrowed funds	430,016	404,418
Subordinated debentures	81,840	76,711
Accrued interest payable	0	0
Interest rate swaps	19,499	16,668
Total financial liabilities	2,226,391	2,231,394
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	132,649	149,769
Accrued interest receivable	0	0
Non-marketable equity securities	0	0
Total financial assets	132,649	149,769
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