Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Assets
Interest-earning deposits with banks	$ 45,083	$ 14,531
Securities available for sale	1,639,370	1,664,111
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Assets
Cash and due from banks	191,706	165,030
Interest-earning deposits with banks	45,083	14,531
Securities available for sale	1,639,370	1,664,111
FHLB stock	32,224	32,529
Loans held for sale		735
Loans	4,506,792	4,444,842
FDIC loss-sharing asset	36,837	39,846
Interest rate contracts	9,418	9,044
Liabilities
Deposits	6,044,416	5,959,475
FHLB Advances	6,597	36,606
Repurchase agreements	25,000	25,000
Interest rate contracts	9,418	9,044
Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	191,706	165,030
Interest-earning deposits with banks	45,083	14,531
Securities available for sale	1,639,370	1,664,111
FHLB stock	32,224	32,529
Loans held for sale		735
Loans	4,654,744	4,605,038
FDIC loss-sharing asset	13,512	11,248
Interest rate contracts	9,418	9,044
Liabilities
Deposits	6,043,226	5,958,747
FHLB Advances	5,452	35,080
Repurchase agreements	26,303	26,361
Interest rate contracts	9,418	9,044
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	191,706	165,030
Interest-earning deposits with banks	45,083	14,531
Securities available for sale	20,303	20,114
FHLB stock	0	0
Loans held for sale		0
Loans	0	0
FDIC loss-sharing asset	0	0
Interest rate contracts	0	0
Liabilities
Deposits	5,554,663	5,449,546
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	1,619,067	1,643,997
FHLB stock	32,224	32,529
Loans held for sale		735
Loans	0	0
FDIC loss-sharing asset	0	0
Interest rate contracts	9,418	9,044
Liabilities
Deposits	488,563	509,201
FHLB Advances	5,452	35,080
Repurchase agreements	26,303	26,361
Interest rate contracts	9,418	9,044
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
Loans	4,654,744	4,605,038
FDIC loss-sharing asset	13,512	11,248
Interest rate contracts	0	0
Liabilities
Deposits	0	0
FHLB Advances	0	0
Repurchase agreements	0	0
Interest rate contracts	$ 0	$ 0