Carrying Amount and Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Carrying Amount
Financial assets
Cash and cash equivalents	$ 254,684	$ 187,040
Investment securities, available-for-sale	3,318,953	3,683,005
Loans held for sale	61,505	145,501
Loans receivable, net of ALLL	3,870,334	3,266,571
Accrued interest receivable	44,261	37,770
Non-marketable equity securities	52,192	48,812
Total financial assets	7,601,929	7,368,699
Financial liabilities
Deposits	5,612,880	5,364,461
FHLB advances	967,382	997,013
Repurchase agreements and other borrowed funds	322,779	299,540
Subordinated debentures	125,526	125,418
Accrued interest payable	3,568	4,675
Interest rate swaps	2,004	16,832
Total financial liabilities	7,034,139	6,807,939
Estimated Fair Value | Level 1
Financial assets
Cash and cash equivalents	254,684	187,040
Investment securities, available-for-sale	0	0
Loans held for sale	61,505	145,501
Loans receivable, net of ALLL	0	0
Accrued interest receivable	44,261	37,770
Non-marketable equity securities	0	0
Total financial assets	360,450	370,311
Financial liabilities
Deposits	4,153,782	3,585,126
FHLB advances	0	0
Repurchase agreements and other borrowed funds	0	0
Subordinated debentures	0	0
Accrued interest payable	3,568	4,675
Interest rate swaps	0	0
Total financial liabilities	4,157,350	3,589,801
Estimated Fair Value | Level 2
Financial assets
Cash and cash equivalents	0	0
Investment securities, available-for-sale	3,318,953	3,683,005
Loans held for sale	0	0
Loans receivable, net of ALLL	3,758,724	3,184,987
Accrued interest receivable	0	0
Non-marketable equity securities	52,192	48,812
Total financial assets	7,129,869	6,916,804
Financial liabilities
Deposits	1,486,996	1,789,134
FHLB advances	986,292	1,027,101
Repurchase agreements and other borrowed funds	322,779	299,540
Subordinated debentures	72,554	70,895
Accrued interest payable	0	0
Interest rate swaps	2,004	16,832
Total financial liabilities	2,870,625	3,203,502
Estimated Fair Value | Level 3
Financial assets
Cash and cash equivalents	0	0
Investment securities, available-for-sale	0	0
Loans held for sale	0	0
Loans receivable, net of ALLL	194,190	186,201
Accrued interest receivable	0	0
Non-marketable equity securities	0	0
Total financial assets	194,190	186,201
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