Fair Value Measurements (Details 7) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair values of defined benefit pension plan assets by category of the firm
Securities held to maturity	$ 482,410	$ 412,075
Securities available for sale	564,278	501,254
Mortgage loans held for sale	28,433	33,440
Loans covered under loss-share agreements	173,545	181,674
FDIC loss-share indemnification asset	24,963	26,273
Mortgage servicing rights	9,514	8,994
Carrying Value
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	301,615	246,648
Securities held to maturity	482,410	412,075
Securities available for sale	564,278	501,254
Mortgage loans held for sale	28,433	33,440
Loans covered under loss-share agreements	173,545	181,674
Loans not covered under loss-share agreements, net	3,645,835	3,651,679
FDIC loss-share indemnification asset	24,963	26,273
Mortgage servicing rights	9,514	8,994
Derivative instruments	2,343	2,818
Financial liabilities
Deposits	5,004,784	4,841,912
Short-term borrowings		2,283
Federal Home Loan Bank advances	74,416	75,405
Junior subordinated debentures	94,284	94,187
Derivative instruments	3,348	3,096
Level 1
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	301,615	246,648
Securities held to maturity	0	0
Securities available for sale	0	0
Mortgage loans held for sale	0	0
Loans covered under loss-share agreements	0	0
Loans not covered under loss-share agreements, net	0	0
FDIC loss-share indemnification asset	0	0
Mortgage servicing rights	0	0
Derivative instruments	0	0
Financial liabilities
Deposits	3,539,545	3,327,688
Short-term borrowings		2,283
Federal Home Loan Bank advances	0	0
Junior subordinated debentures	0	0
Derivative instruments	0	0
Level 2
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	0	0
Securities held to maturity	484,780	408,567
Securities available for sale	544,900	483,583
Mortgage loans held for sale	28,433	33,440
Loans covered under loss-share agreements	0	0
Loans not covered under loss-share agreements, net	0	0
FDIC loss-share indemnification asset	0	0
Mortgage servicing rights	0	0
Derivative instruments	2,343	2,818
Financial liabilities
Deposits	1,470,862	1,520,667
Short-term borrowings		0
Federal Home Loan Bank advances	79,994	80,989
Junior subordinated debentures	78,855	78,301
Derivative instruments	3,348	3,096
Level 3
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	0	0
Securities held to maturity	0	0
Securities available for sale	19,378	17,671
Mortgage loans held for sale	0	0
Loans covered under loss-share agreements	174,167	182,244
Loans not covered under loss-share agreements, net	3,597,806	3,590,446
FDIC loss-share indemnification asset	24,963	26,273
Mortgage servicing rights	10,485	9,840
Derivative instruments	0	0
Financial liabilities
Deposits	0	0
Short-term borrowings		0
Federal Home Loan Bank advances	0	0
Junior subordinated debentures	0	0
Derivative instruments	0	0
Total
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	301,615	246,648
Securities held to maturity	484,780	408,567
Securities available for sale	564,278	501,254
Mortgage loans held for sale	28,433	33,440
Loans covered under loss-share agreements	174,167	182,244
Loans not covered under loss-share agreements, net	3,597,806	3,590,446
FDIC loss-share indemnification asset	24,963	26,273
Mortgage servicing rights	10,485	9,840
Derivative instruments	2,343	2,818
Financial liabilities
Deposits	5,010,407	4,848,355
Short-term borrowings		2,283
Federal Home Loan Bank advances	79,994	80,989
Junior subordinated debentures	78,855	78,301
Derivative instruments	$ 3,348	$ 3,096