Securities - Amortized Cost and Fair Value, Available for Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Line Items]
Amortized Cost	$ 1,264,529	$ 674,104
Gross Unrealized Gains	4,517	7,872
Gross Unrealized Losses	(18,269)	(10,488)
Fair Value	1,250,777	671,488
Trust preferred securities
Cash and Cash Equivalents [Line Items]
Amortized Cost	12,359	12,442
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,726)	(3,054)
Fair Value	10,633	9,388
Other debt securities
Cash and Cash Equivalents [Line Items]
Amortized Cost	44,046	17,106
Gross Unrealized Gains	192	260
Gross Unrealized Losses	(311)	(76)
Fair Value	43,927	17,290
Obligations of other U.S. Government agencies and corporations
Cash and Cash Equivalents [Line Items]
Amortized Cost	2,536	3,554
Gross Unrealized Gains	13	40
Gross Unrealized Losses	(38)	(30)
Fair Value	2,511	3,564
Obligations of states and political subdivisions
Cash and Cash Equivalents [Line Items]
Amortized Cost	200,798	228,589
Gross Unrealized Gains	3,038	6,161
Gross Unrealized Losses	(567)	(269)
Fair Value	203,269	234,481
Government agency mortgage backed securities \| Residential mortgage backed securities
Cash and Cash Equivalents [Line Items]
Amortized Cost	621,690	196,121
Gross Unrealized Gains	719	888
Gross Unrealized Losses	(9,126)	(3,059)
Fair Value	613,283	193,950
Government agency mortgage backed securities \| Commercial mortgage backed securities
Cash and Cash Equivalents [Line Items]
Amortized Cost	21,957	31,015
Gross Unrealized Gains	257	389
Gross Unrealized Losses	(384)	(234)
Fair Value	21,830	31,170
Government agency collateralized mortgage obligations \| Residential mortgage backed securities
Cash and Cash Equivalents [Line Items]
Amortized Cost	332,697	180,258
Gross Unrealized Gains	274	133
Gross Unrealized Losses	(5,982)	(3,752)
Fair Value	326,989	176,639
Government agency collateralized mortgage obligations \| Commercial mortgage backed securities
Cash and Cash Equivalents [Line Items]
Amortized Cost	28,446	5,019
Gross Unrealized Gains	24	1
Gross Unrealized Losses	(135)	(14)
Fair Value	$ 28,335	$ 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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-Section 50
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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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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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