Securities - Amortized Cost and Fair Value of Securities Available for Sale (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Amortized cost and fair value of securities available for sale
Amortized Cost	$ 1,201,389	$ 674,104
Gross Unrealized Gains	3,200	7,872
Gross Unrealized Losses	(26,983)	(10,488)
Fair Value	1,177,606	671,488
Obligations of other U.S. Government agencies and corporations
Amortized cost and fair value of securities available for sale
Amortized Cost	3,541	3,554
Gross Unrealized Gains	13	40
Gross Unrealized Losses	(48)	(30)
Fair Value	3,506	3,564
Obligations of states and political subdivisions
Amortized cost and fair value of securities available for sale
Amortized Cost	208,885	228,589
Gross Unrealized Gains	2,627	6,161
Gross Unrealized Losses	(1,193)	(269)
Fair Value	210,319	234,481
Trust preferred securities
Amortized cost and fair value of securities available for sale
Amortized Cost	12,351	12,442
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2,047)	(3,054)
Fair Value	10,304	9,388
Other debt securities
Amortized cost and fair value of securities available for sale
Amortized Cost	35,308	17,106
Gross Unrealized Gains	104	260
Gross Unrealized Losses	(447)	(76)
Fair Value	34,965	17,290
Government agency mortgage backed securities \| Residential mortgage backed securities:
Amortized cost and fair value of securities available for sale
Amortized Cost	573,236	196,121
Gross Unrealized Gains	240	888
Gross Unrealized Losses	(12,889)	(3,059)
Fair Value	560,587	193,950
Government agency mortgage backed securities \| Commercial mortgage backed securities:
Amortized cost and fair value of securities available for sale
Amortized Cost	22,094	31,015
Gross Unrealized Gains	203	389
Gross Unrealized Losses	(562)	(234)
Fair Value	21,735	31,170
Government agency collateralized mortgage obligations \| Residential mortgage backed securities:
Amortized cost and fair value of securities available for sale
Amortized Cost	316,642	180,258
Gross Unrealized Gains	13	133
Gross Unrealized Losses	(9,427)	(3,752)
Fair Value	307,228	176,639
Government agency collateralized mortgage obligations \| Commercial mortgage backed securities:
Amortized cost and fair value of securities available for sale
Amortized Cost	29,332	5,019
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(370)	(14)
Fair Value	$ 28,962	$ 5,006

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
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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).

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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).

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