Securities - Amortized Cost and Fair Value of Securities Available for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Amortized cost and fair value of securities available for sale
Amortized Cost	$ 1,253,939	$ 1,264,529
Gross Unrealized Gains	10,357	4,517
Gross Unrealized Losses	(8,943)	(18,269)
Fair Value	1,255,353	1,250,777
Obligations of other U.S. Government agencies and corporations
Amortized cost and fair value of securities available for sale
Amortized Cost	2,532	2,536
Gross Unrealized Gains	16	13
Gross Unrealized Losses	(23)	(38)
Fair Value	2,525	2,511
Obligations of states and political subdivisions
Amortized cost and fair value of securities available for sale
Amortized Cost	179,758	200,798
Gross Unrealized Gains	4,064	3,038
Gross Unrealized Losses	(60)	(567)
Fair Value	183,762	203,269
Trust preferred securities
Amortized cost and fair value of securities available for sale
Amortized Cost	12,259	12,359
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2,013)	(1,726)
Fair Value	10,246	10,633
Other debt securities
Amortized cost and fair value of securities available for sale
Amortized Cost	48,335	44,046
Gross Unrealized Gains	766	192
Gross Unrealized Losses	(122)	(311)
Fair Value	48,979	43,927
Government agency mortgage backed securities \| Residential mortgage backed securities:
Amortized cost and fair value of securities available for sale
Amortized Cost	622,056	621,690
Gross Unrealized Gains	3,783	719
Gross Unrealized Losses	(3,773)	(9,126)
Fair Value	622,066	613,283
Government agency mortgage backed securities \| Commercial mortgage backed securities:
Amortized cost and fair value of securities available for sale
Amortized Cost	21,816	21,957
Gross Unrealized Gains	362	257
Gross Unrealized Losses	(180)	(384)
Fair Value	21,998	21,830
Government agency collateralized mortgage obligations \| Residential mortgage backed securities:
Amortized cost and fair value of securities available for sale
Amortized Cost	321,088	332,697
Gross Unrealized Gains	1,093	274
Gross Unrealized Losses	(2,734)	(5,982)
Fair Value	319,447	326,989
Government agency collateralized mortgage obligations \| Commercial mortgage backed securities:
Amortized cost and fair value of securities available for sale
Amortized Cost	46,095	28,446
Gross Unrealized Gains	273	24
Gross Unrealized Losses	(38)	(135)
Fair Value	$ 46,330	$ 28,335

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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