Fair Value Measurements (Details 7) - USD ($)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair values of defined benefit pension plan assets by category of the firm
Securities held to maturity	$ 356,282,000	$ 458,400,000
Securities available for sale, at fair value	674,248,000	646,805,000
Mortgage loans held for sale	177,866,000	225,254,000
FDIC loss-share indemnification asset	0	7,149,000	$ 12,516,000
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	306,224,000	211,571,000
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
Loans, net	0	0
FDIC loss-share indemnification asset		0
Mortgage servicing rights	0	0
Derivative instruments	0	0
Financial liabilities
Deposits	5,438,384,000	4,723,312,000
Short-term borrowings	109,676,000	422,279,000
Other long-term borrowings	147,000	192,000
Federal Home Loan Bank advances	0	0
Junior subordinated debentures	0
Subordinated notes	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	362,893,000	473,753,000
Securities available for sale, at fair value	655,859,000	627,336,000
Mortgage loans held for sale	177,866,000	225,254,000
Loans covered under loss-share agreements		0
Loans, net	0	0
FDIC loss-share indemnification asset		0
Mortgage servicing rights	0	0
Derivative instruments	9,108,000	7,498,000
Financial liabilities
Deposits	1,631,027,000	1,502,202,000
Short-term borrowings	0	0
Other long-term borrowings	0	0
Federal Home Loan Bank advances	8,777,000	56,101,000
Junior subordinated debentures	73,301,000
Subordinated notes	101,000,000	78,095,000
Derivative instruments	5,910,000	7,319,000
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	18,389,000	19,469,000
Mortgage loans held for sale	0	0
Loans covered under loss-share agreements		92,528,000
Loans, net	5,989,790,000	5,208,630,000
FDIC loss-share indemnification asset		7,149,000
Mortgage servicing rights	32,064,000	33,283,000
Derivative instruments	0	0
Financial liabilities
Deposits	0	0
Short-term borrowings	0	0
Other long-term borrowings	0	0
Federal Home Loan Bank advances	0	0
Junior subordinated debentures	0
Subordinated notes	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	306,224,000	211,571,000
Securities held to maturity	356,282,000	458,400,000
Securities available for sale, at fair value	674,248,000	646,805,000
Mortgage loans held for sale	177,866,000	225,254,000
Loans covered under loss-share agreements		93,142,000
Loans, net	6,159,972,000	5,277,883,000
FDIC loss-share indemnification asset		7,149,000
Mortgage servicing rights	26,302,000	29,642,000
Derivative instruments	9,108,000	7,498,000
Financial liabilities
Deposits	7,059,137,000	6,218,602,000
Short-term borrowings	109,676,000	422,279,000
Other long-term borrowings	147,000	192,000
Federal Home Loan Bank advances	8,542,000	52,930,000
Junior subordinated debentures	95,643,000
Subordinated notes	98,127,000	95,095,000
Derivative instruments	5,910,000	7,319,000
Fair Value
Fair values of defined benefit pension plan assets by category of the firm
Cash and cash equivalents	306,224,000	211,571,000
Securities held to maturity	362,893,000	473,753,000
Securities available for sale, at fair value	674,248,000	646,805,000
Mortgage loans held for sale	177,866,000	225,254,000
Loans covered under loss-share agreements		92,528,000
Loans, net	5,989,790,000	5,208,630,000
FDIC loss-share indemnification asset		7,149,000
Mortgage servicing rights	32,064,000	33,283,000
Derivative instruments	9,108,000	7,498,000
Financial liabilities
Deposits	7,069,411,000	6,225,514,000
Short-term borrowings	109,676,000	422,279,000
Other long-term borrowings	147,000	192,000
Federal Home Loan Bank advances	8,777,000	56,101,000
Junior subordinated debentures	73,301,000
Subordinated notes	101,000,000	78,095,000
Derivative instruments	$ 5,910,000	$ 7,319,000