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, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 693,617	$ 799,276	$ 763,298	$ 752,557	$ 799,276	$ 752,557
Other comprehensive income/(loss) before reclassifications	31,454		(29,223)		(68,898)	(30,001)
Amounts reclassified from AOCI	(1,514)		(4,874)		(6,438)	(7,798)
Other comprehensive gain/(loss) net of tax	29,940	(105,276)	(34,097)	(3,702)	(75,336)	(37,799)
Ending balance	824,116	693,617	773,742	763,298	824,116	773,742
Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest | Available-for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(121,858)	(43,397)	(22,800)	(25,360)	(43,397)	(25,360)
Other comprehensive income/(loss) before reclassifications	34,374		(21,711)		(43,310)	(18,393)
Amounts reclassified from AOCI	(777)		(873)		(1,554)	(1,631)
Other comprehensive gain/(loss) net of tax	33,597		(22,584)		(44,864)	(20,024)
Ending balance	(88,261)	(121,858)	(45,384)	(22,800)	(88,261)	(45,384)
Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest | Held-to-Maturity Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	28,351	32,845	41,656	43,443	32,845	43,443
Other comprehensive income/(loss) before reclassifications	0		0		0	0
Amounts reclassified from AOCI	(1,972)		(3,635)		(6,466)	(5,422)
Other comprehensive gain/(loss) net of tax	(1,972)		(3,635)		(6,466)	(5,422)
Ending balance	26,379	28,351	38,021	41,656	26,379	38,021
Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(27,930)	(5,609)	2,398	6,873	(5,609)	6,873
Other comprehensive income/(loss) before reclassifications	(2,920)		(7,512)		(25,588)	(11,608)
Amounts reclassified from AOCI	1,235		(366)		1,582	(745)
Other comprehensive gain/(loss) net of tax	(1,685)		(7,878)		(24,006)	(12,353)
Ending balance	(29,615)	(27,930)	(5,480)	2,398	(29,615)	(5,480)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(121,437)	(16,161)	21,254	24,956	(16,161)	24,956
Other comprehensive gain/(loss) net of tax	29,940	(105,276)	(34,097)	(3,702)
Ending balance	$ (91,497)	$ (121,437)	$ (12,843)	$ 21,254	$ (91,497)	$ (12,843)