Summary of Significant Accounting Policies - Schedule of Accumulated Other Comprehensive Income, Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Jan. 01, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 763,298	$ 752,557	$ 745,266	$ 708,146	$ 752,557	$ 708,146
Cumulative effect from change in hedge accounting								$ 27
Adjusted Beginning Balance									$ 708,644
Other comprehensive (loss)/income before reclassifications	(29,223)		3,987		(30,001)	27,227
Amounts reclassified from AOCI	(4,874)		(2,688)		(7,798)	(4,929)
Other comprehensive (loss)/income net of tax	(34,097)	(3,702)	1,299	20,999	(37,799)	22,298
Ending balance	773,742	763,298	766,212	745,266	773,742	766,212
Total [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	21,254	24,956	72,111	51,085	24,956	51,085
Adjusted Beginning Balance							$ 24,956	51,112	$ 51,112
Other comprehensive (loss)/income net of tax	(34,097)	(3,702)	1,299	20,999
Ending balance	(12,843)	21,254	73,410	72,111	(12,843)	73,410
Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member] | Available-for-sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(22,800)	(25,360)	15,094	(1,676)	(25,360)	(1,676)
Adjusted Beginning Balance							(25,360)	(1,676)
Other comprehensive (loss)/income before reclassifications	(21,711)		2,209		(18,393)	20,396
Amounts reclassified from AOCI	(873)		(1,421)		(1,631)	(2,838)
Other comprehensive (loss)/income net of tax	(22,584)		788		(20,024)	17,558
Ending balance	(45,384)	(22,800)	15,882	15,094	(45,384)	15,882
Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member] | Held-to-maturity Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	41,656	43,443	47,201	48,236	43,443	48,236
Adjusted Beginning Balance							43,443	48,236
Other comprehensive (loss)/income before reclassifications	0		0		0	0
Amounts reclassified from AOCI	(3,635)		(1,222)		(5,422)	(2,257)
Other comprehensive (loss)/income net of tax	(3,635)		(1,222)		(5,422)	(2,257)
Ending balance	38,021	41,656	45,979	47,201	38,021	45,979
Cash Flow Hedge [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	2,398	6,873	9,816	4,525	6,873	4,525
Cumulative effect from change in hedge accounting								27
Adjusted Beginning Balance							$ 6,873	$ 4,552
Other comprehensive (loss)/income before reclassifications	(7,512)		1,778		(11,608)	6,831
Amounts reclassified from AOCI	(366)		(45)		(745)	166
Other comprehensive (loss)/income net of tax	(7,878)		1,733		(12,353)	6,997
Ending balance	$ (5,480)	$ 2,398	$ 11,549	$ 9,816	$ (5,480)	$ 11,549