Fair Value Measurements (Details 7) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair values of defined benefit pension plan assets by category of the firm
Securities held to maturity	$ 430,163	$ 412,075
Securities available for sale, at fair value	553,584	501,254
Mortgage loans held for sale	25,628	33,440
Loans covered under loss-share agreements	143,041	181,674
Loans not covered under loss-share agreements, net	3,267,486	2,885,801
FDIC loss-share indemnification asset	12,516	26,273	44,153
Quoted Prices In Active Markets for Identical Assets (Level 1)
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	161,583	246,648
Securities held to maturity	0	0
Securities available for sale, at fair value	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
Derivative instruments	0	0
Financial liabilities
Deposits	3,532,266	3,327,688
Short-term borrowings	32,403	2,283
Other long-term borrowings	237
Federal Home Loan Bank advances	0	0
Junior subordinated debentures	0	0
Derivative instruments	0	0
Significant Other Observable Inputs (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	442,488	408,567
Securities available for sale, at fair value	533,828	483,583
Mortgage loans held for sale	25,628	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
Derivative instruments	3,731	2,819
Financial liabilities
Deposits	1,309,421	1,520,667
Short-term borrowings	0	0
Other long-term borrowings	0
Federal Home Loan Bank advances	92,532	80,989
Junior subordinated debentures	80,971	78,301
Derivative instruments	6,293	3,316
Significant Unobservable Inputs (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, at fair value	19,756	17,671
Mortgage loans held for sale	0	0
Loans covered under loss-share agreements	143,487	182,244
Loans not covered under loss-share agreements, net	3,751,727	3,590,446
FDIC loss-share indemnification asset	12,516	26,273
Mortgage servicing rights	12,378	9,840
Derivative instruments	0	0
Financial liabilities
Deposits	0	0
Short-term borrowings	0	0
Other long-term borrowings	0
Federal Home Loan Bank advances	0	0
Junior subordinated debentures	0	0
Derivative instruments	0	0
Carrying Value
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	161,583	246,648
Securities held to maturity	430,163	412,075
Securities available for sale, at fair value	553,584	501,254
Mortgage loans held for sale	25,628	33,440
Loans covered under loss-share agreements	143,041	181,674
Loans not covered under loss-share agreements, net	3,844,833	3,651,679
FDIC loss-share indemnification asset	12,516	26,273
Mortgage servicing rights	11,662	8,994
Derivative instruments	3,731	2,819
Financial liabilities
Deposits	4,838,418	4,841,912
Short-term borrowings	32,403	2,283
Other long-term borrowings	237
Federal Home Loan Bank advances	61,611	75,405
Junior subordinated debentures	94,574	94,187
Derivative instruments	6,293	3,316
Fair Value
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	161,583	246,648
Securities held to maturity	442,488	408,567
Securities available for sale, at fair value	553,584	501,254
Mortgage loans held for sale	25,628	33,440
Loans covered under loss-share agreements	143,487	182,244
Loans not covered under loss-share agreements, net	3,751,727	3,590,446
FDIC loss-share indemnification asset	12,516	26,273
Mortgage servicing rights	12,378	9,840
Derivative instruments	3,731	2,819
Financial liabilities
Deposits	4,841,687	4,848,355
Short-term borrowings	32,403	2,283
Other long-term borrowings	237
Federal Home Loan Bank advances	92,532	80,989
Junior subordinated debentures	80,971	78,301
Derivative instruments	$ 6,293	$ 3,316