Carrying Amount and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Carrying Amount
Financial assets
Cash and cash equivalents	$ 160,333	$ 193,253
Investment securities, available-for-sale	2,487,955	2,610,760
Investment securities, held-to-maturity	680,574	702,072
Loans held for sale	74,140	56,514
Loans receivable, net of ALLL	5,246,231	4,948,984
Accrued interest receivable	47,554	44,524
Non-marketable equity securities	24,791	27,495
Total financial assets	8,721,578	8,583,602
Financial liabilities
Deposits	7,088,816	6,945,008
FHLB advances	328,832	394,131
Repurchase agreements and other borrowed funds	419,253	430,016
Subordinated debentures	125,920	125,848
Accrued interest payable	3,486	3,517
Interest rate swaps	30,040	19,499
Total financial liabilities	7,996,347	7,918,019
Estimated Fair Value | Level 1
Financial assets
Cash and cash equivalents	160,333	193,253
Investment securities, available-for-sale	0	0
Investment securities, held-to-maturity	0	0
Loans held for sale	74,140	56,514
Loans receivable, net of ALLL	0	0
Accrued interest receivable	47,554	44,524
Non-marketable equity securities	0	0
Total financial assets	282,027	294,291
Financial liabilities
Deposits	5,732,871	5,654,638
FHLB advances	0	0
Repurchase agreements and other borrowed funds	0	0
Subordinated debentures	0	0
Accrued interest payable	3,486	3,517
Interest rate swaps	0	0
Total financial liabilities	5,736,357	5,658,155
Estimated Fair Value | Level 2
Financial assets
Cash and cash equivalents	0	0
Investment securities, available-for-sale	2,487,955	2,610,760
Investment securities, held-to-maturity	726,365	729,513
Loans held for sale	0	0
Loans receivable, net of ALLL	5,083,867	4,851,934
Accrued interest receivable	0	0
Non-marketable equity securities	24,791	27,495
Total financial assets	8,322,978	8,219,702
Financial liabilities
Deposits	1,358,788	1,293,506
FHLB advances	340,623	401,530
Repurchase agreements and other borrowed funds	419,253	430,016
Subordinated debentures	80,573	81,840
Accrued interest payable	0	0
Interest rate swaps	30,040	19,499
Total financial liabilities	2,229,277	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	126,438	132,649
Accrued interest receivable	0	0
Non-marketable equity securities	0	0
Total financial assets	126,438	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