Fair Value Measurements (Details 7) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair values of defined benefit pension plan assets by category of the firm
Securities held to maturity	$ 440,055	$ 317,766
Securities available for sale	464,733	356,311
Mortgage loans held for sale	28,466	34,845
Loans covered under loss-share agreements	195,997	237,088
FDIC loss-share indemnification asset	27,825	44,153
Mortgage servicing rights	8,336	4,233
Carrying Value [Member]
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	233,149	132,420
Securities held to maturity	440,055	317,766
Securities available for sale	464,733	356,311
Mortgage loans held for sale	28,466	34,845
Loans covered under loss-share agreements	195,997	237,088
Loans not covered under loss-share agreements, net	3,685,535	2,528,818
FDIC loss-share indemnification asset	27,825	44,153
Mortgage servicing rights	8,336	4,233
Derivative instruments	3,869	4,654
Financial liabilities
Deposits	4,834,756	3,461,221
Short-term borrowings	6,649	5,254
Federal Home Loan Bank advances	76,429	83,843
Junior subordinated debentures	94,089	75,609
Derivative instruments	4,899	5,514
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	233,149	132,420
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	3,284,858	2,268,568
Short-term borrowings	6,649	5,254
Federal Home Loan Bank advances	0	0
Junior subordinated debentures	0	0
Derivative instruments	0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	0	0
Securities held to maturity	438,014	334,475
Securities available for sale	447,980	341,243
Mortgage loans held for sale	28,466	34,845
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	3,869	4,654
Financial liabilities
Deposits	1,558,356	1,200,785
Short-term borrowings	0	0
Federal Home Loan Bank advances	82,356	99,870
Junior subordinated debentures	71,723	27,985
Derivative instruments	4,899	5,514
Significant Unobservable Inputs (Level 3) [Member]
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	16,753	15,068
Mortgage loans held for sale	0	0
Loans covered under loss-share agreements	195,458	235,890
Loans not covered under loss-share agreements, net	3,644,023	2,452,937
FDIC loss-share indemnification asset	27,825	44,153
Mortgage servicing rights	8,974	4,259
Derivative instruments	0	0
Financial liabilities
Deposits	0	0
Short-term borrowings	0	0
Federal Home Loan Bank advances	0	0
Junior subordinated debentures	0	0
Derivative instruments	0	0
Fair Value [Member]
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	233,149	132,420
Securities held to maturity	438,014	334,475
Securities available for sale	464,733	356,311
Mortgage loans held for sale	28,466	34,845
Loans covered under loss-share agreements	195,458	235,890
Loans not covered under loss-share agreements, net	3,644,023	2,452,937
FDIC loss-share indemnification asset	27,825	44,153
Mortgage servicing rights	8,974	4,259
Derivative instruments	3,869	4,654
Financial liabilities
Deposits	4,843,214	3,469,353
Short-term borrowings	6,649	5,254
Federal Home Loan Bank advances	82,356	99,870
Junior subordinated debentures	71,723	27,985
Derivative instruments	$ 4,899	$ 5,514