Carrying Amount and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Carrying Amount
Financial assets
Cash and cash equivalents	$ 220,210	$ 152,541
Investment securities, available-for-sale	1,886,517	2,425,477
Investment securities, held-to-maturity	655,128	675,674
Loans held for sale	48,709	72,927
Loans receivable, net of ALLL	6,379,857	5,554,891
Accrued interest receivable	50,492	45,832
Non-marketable equity securities	21,890	25,550
Total financial assets	9,262,803	8,952,892
Financial liabilities
Deposits	7,767,154	7,372,279
FHLB advances	153,685	251,749
Repurchase agreements and other borrowed funds	461,839	478,090
Subordinated debentures	126,099	125,991
Accrued interest payable	3,154	3,584
Interest rate swaps	12,748	14,725
Total financial liabilities	8,524,679	8,246,418
Estimated Fair Value | Level 1
Financial assets
Cash and cash equivalents	220,210	152,541
Investment securities, available-for-sale	0	0
Investment securities, held-to-maturity	0	0
Loans held for sale	48,709	72,927
Loans receivable, net of ALLL	0	0
Accrued interest receivable	50,492	45,832
Non-marketable equity securities	0	0
Total financial assets	319,411	271,300
Financial liabilities
Deposits	6,735,130	6,090,879
FHLB advances	0	0
Repurchase agreements and other borrowed funds	0	0
Subordinated debentures	0	0
Accrued interest payable	3,154	3,584
Interest rate swaps	0	0
Total financial liabilities	6,738,284	6,094,463
Estimated Fair Value | Level 2
Financial assets
Cash and cash equivalents	0	0
Investment securities, available-for-sale	1,886,517	2,425,477
Investment securities, held-to-maturity	671,198	689,089
Loans held for sale	0	0
Loans receivable, net of ALLL	6,172,843	5,380,286
Accrued interest receivable	0	0
Non-marketable equity securities	21,890	25,550
Total financial assets	8,752,448	8,520,402
Financial liabilities
Deposits	1,035,141	1,283,532
FHLB advances	153,814	257,643
Repurchase agreements and other borrowed funds	461,839	478,090
Subordinated debentures	90,845	85,557
Accrued interest payable	0	0
Interest rate swaps	12,748	14,725
Total financial liabilities	1,754,387	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	118,816	123,382
Accrued interest receivable	0	0
Non-marketable equity securities	0	0
Total financial assets	118,816	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