Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Assets
Interest-earning deposits with banks	$ 54,470	$ 389,353
Securities available for sale	1,569,651	1,001,665
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Assets
Cash and due from banks	200,282	124,573
Interest-earning deposits with banks	54,470	389,353
Securities available for sale	1,569,651	1,001,665
FHLB stock	32,833	21,819
Loans held for sale	840	2,563
Loans	4,440,048	2,864,803
FDIC loss-sharing asset	53,559	96,354
Interest rate contracts	10,187	14,921
Liabilities
Deposits	5,948,967	4,042,085
FHLB Advances	34,632	6,644
Repurchase agreements	25,000	25,000
Interest rate contracts	10,187	14,921
Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	200,282	124,573
Interest-earning deposits with banks	54,470	389,353
Securities available for sale	1,569,651	1,001,665
FHLB stock	32,833	21,819
Loans held for sale	840	2,563
Loans	4,397,456	2,944,317
FDIC loss-sharing asset	17,353	26,543
Interest rate contracts	10,187	14,921
Liabilities
Deposits	5,948,473	4,043,221
FHLB Advances	33,301	5,894
Repurchase agreements	26,207	26,464
Interest rate contracts	10,187	14,921
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	200,282	124,573
Interest-earning deposits with banks	54,470	389,353
Securities available for sale	20,417	19,828
FHLB stock	0	0
Loans held for sale	0	0
Loans	0	0
FDIC loss-sharing asset	0	0
Interest rate contracts	0	0
Liabilities
Deposits	5,413,557	3,549,821
FHLB Advances	0	0
Repurchase agreements	0	0
Interest rate contracts	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Securities available for sale	1,549,234	981,837
FHLB stock	32,833	21,819
Loans held for sale	840	2,563
Loans	0	0
FDIC loss-sharing asset	0	0
Interest rate contracts	10,187	14,921
Liabilities
Deposits	534,916	493,400
FHLB Advances	33,301	5,894
Repurchase agreements	26,207	26,464
Interest rate contracts	10,187	14,921
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Securities available for sale	0	0
FHLB stock	0	0
Loans held for sale	0	0
Loans	4,397,456	2,944,317
FDIC loss-sharing asset	17,353	26,543
Interest rate contracts	0	0
Liabilities
Deposits	0	0
FHLB Advances	0	0
Repurchase agreements	0	0
Interest rate contracts	$ 0	$ 0