Investment Securities - Unrealized Losses and Fair Value of Held to Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value
Less than Twelve Months	$ 8,413	$ 101,621
More than Twelve Months, Fair Value	765,518	1,086,150
Total	773,931	1,187,771
Unrealized Losses
Less than Twelve Months	(34)	(1,207)
More than Twelve Months	(16,721)	(46,532)
Total	(16,755)	(47,739)
U.S. government agency securities
Fair Value
Less than Twelve Months	0	0
More than Twelve Months, Fair Value	5,675	6,074
Total	5,675	6,074
Unrealized Losses
Less than Twelve Months	0	0
More than Twelve Months	(26)	(135)
Total	(26)	(135)
Obligations of states and state agencies
Fair Value
Less than Twelve Months	0	16,098
More than Twelve Months, Fair Value	45,843	138,437
Total	45,843	154,535
Unrealized Losses
Less than Twelve Months	0	(266)
More than Twelve Months	(992)	(5,469)
Total	(992)	(5,735)
Municipal bonds
Fair Value
Less than Twelve Months	4,968	3,335
More than Twelve Months, Fair Value	4,331	60,078
Total	9,299	63,413
Unrealized Losses
Less than Twelve Months	(27)	(37)
More than Twelve Months	(29)	(1,324)
Total	(56)	(1,361)
Obligations of states and political subdivisions
Fair Value
Less than Twelve Months	4,968	19,433
More than Twelve Months, Fair Value	50,174	198,515
Total	55,142	217,948
Unrealized Losses
Less than Twelve Months	(27)	(303)
More than Twelve Months	(1,021)	(6,793)
Total	(1,048)	(7,096)
Residential mortgage-backed securities
Fair Value
Less than Twelve Months	3,445	72,240
More than Twelve Months, Fair Value	674,804	846,671
Total	678,249	918,911
Unrealized Losses
Less than Twelve Months	(7)	(852)
More than Twelve Months	(9,578)	(33,516)
Total	(9,585)	(34,368)
Trust preferred securities
Fair Value
Less than Twelve Months	0	0
More than Twelve Months, Fair Value	29,957	30,055
Total	29,957	30,055
Unrealized Losses
Less than Twelve Months	0	0
More than Twelve Months	(6,004)	(5,923)
Total	(6,004)	(5,923)
Corporate and other debt securities
Fair Value
Less than Twelve Months	0	9,948
More than Twelve Months, Fair Value	4,908	4,835
Total	4,908	14,783
Unrealized Losses
Less than Twelve Months	0	(52)
More than Twelve Months	(92)	(165)
Total	$ (92)	$ (217)

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for 12 months or longer.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position.

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for less than 12 months.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity), in continuous unrealized loss position for less than 12 months.

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