Carrying Amount and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Carrying Amount
Financial assets
Cash and cash equivalents	$ 237,590	$ 152,541
Investment securities, available-for-sale	2,142,472	2,425,477
Investment securities, held-to-maturity	659,347	675,674
Loans held for sale	37,726	72,927
Loans receivable, net of ALLL	6,215,885	5,554,891
Accrued interest receivable	46,921	45,832
Non-marketable equity securities	23,995	25,550
Total financial assets	9,363,936	8,952,892
Financial liabilities
Deposits	7,797,963	7,372,279
FHLB advances	211,505	251,749
Repurchase agreements and other borrowed funds	456,867	478,090
Subordinated debentures	126,063	125,991
Accrued interest payable	3,535	3,584
Interest rate swaps	13,975	14,725
Total financial liabilities	8,609,908	8,246,418
Estimated Fair Value | Level 1
Financial assets
Cash and cash equivalents	237,590	152,541
Investment securities, available-for-sale	0	0
Investment securities, held-to-maturity	0	0
Loans held for sale	37,726	72,927
Loans receivable, net of ALLL	0	0
Accrued interest receivable	46,921	45,832
Non-marketable equity securities	0	0
Total financial assets	322,237	271,300
Financial liabilities
Deposits	6,620,121	6,090,879
FHLB advances	0	0
Repurchase agreements and other borrowed funds	0	0
Subordinated debentures	0	0
Accrued interest payable	3,535	3,584
Interest rate swaps	0	0
Total financial liabilities	6,623,656	6,094,463
Estimated Fair Value | Level 2
Financial assets
Cash and cash equivalents	0	0
Investment securities, available-for-sale	2,142,472	2,425,477
Investment securities, held-to-maturity	678,495	689,089
Loans held for sale	0	0
Loans receivable, net of ALLL	6,001,018	5,380,286
Accrued interest receivable	0	0
Non-marketable equity securities	23,995	25,550
Total financial assets	8,845,980	8,520,402
Financial liabilities
Deposits	1,179,662	1,283,532
FHLB advances	217,225	257,643
Repurchase agreements and other borrowed funds	456,867	478,090
Subordinated debentures	90,807	85,557
Accrued interest payable	0	0
Interest rate swaps	13,975	14,725
Total financial liabilities	1,958,536	2,119,547
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	123,335	123,382
Accrued interest receivable	0	0
Non-marketable equity securities	0	0
Total financial assets	123,335	123,382
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