Summary of Significant Accounting Policies - Schedule of Reclassification out of Accumulated Other Comprehensive Income (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
Before Tax
Unrealized holding (losses)/gains on available-for-sale-securities, before tax	$ 43,512		$ (27,482)		$ (54,822)	$ (23,282)
Other comprehensive gain/(loss) before tax	37,899		(43,161)		(95,361)	(47,847)
Provision (Benefit)
Unrealized holding (losses)/gains on available-for-sale securities, provision (benefit)	9,138		(5,771)		(11,512)	(4,889)
Other comprehensive (loss)/income provision (benefit)	7,959		(9,064)		(20,025)	(10,048)
After Tax
Unrealized holding (losses)/gains on available-for-sale securities, after tax	34,374		(21,711)		(43,310)	(18,393)
Reclassification adjustments, after tax	(1,514)		(4,874)		(6,438)	(7,798)
Other comprehensive income before reclassifications	31,454		(29,223)		(68,898)	(30,001)
Other comprehensive gain/(loss) net of tax	29,940	$ (105,276)	(34,097)	$ (3,702)	(75,336)	(37,799)
Cash Flow Hedges
Before Tax
Unrealized (losses)/gains on cash flow hedges, before tax	(3,695)		(9,510)		(32,390)	(14,695)
Other comprehensive gain/(loss) before tax	(2,132)		(9,972)		(30,388)	(15,637)
Provision (Benefit)
Unrealized (losses)/gains on cash flow hedges, provision (benefit)	(775)		(1,998)		(6,802)	(3,087)
Other comprehensive (loss)/income provision (benefit)	(447)		(2,094)		(6,382)	(3,284)
After Tax
Reclassification adjustments, after tax	1,235		(366)		1,582	(745)
Other comprehensive income before reclassifications	(2,920)		(7,512)		(25,588)	(11,608)
Other comprehensive gain/(loss) net of tax	(1,685)		(7,878)		(24,006)	(12,353)
Available-for-Sale Securities | Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest
Before Tax
Other comprehensive gain/(loss) before tax	42,527		(28,588)		(56,789)	(25,347)
Provision (Benefit)
Other comprehensive (loss)/income provision (benefit)	8,930		(6,004)		(11,925)	(5,323)
After Tax
Reclassification adjustments, after tax	(777)		(873)		(1,554)	(1,631)
Other comprehensive income before reclassifications	34,374		(21,711)		(43,310)	(18,393)
Other comprehensive gain/(loss) net of tax	33,597		(22,584)		(44,864)	(20,024)
Held-to-Maturity Securities | Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest
Before Tax
Other comprehensive gain/(loss) before tax	(2,496)		(4,601)		(8,184)	(6,863)
Provision (Benefit)
Other comprehensive (loss)/income provision (benefit)	(524)		(966)		(1,718)	(1,441)
After Tax
Reclassification adjustments, after tax	(1,972)		(3,635)		(6,466)	(5,422)
Other comprehensive income before reclassifications	0		0		0	0
Other comprehensive gain/(loss) net of tax	(1,972)		(3,635)		(6,466)	(5,422)
Net Interest Income | Available-for-Sale Securities | Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest | Reclassification out of Accumulated Other Comprehensive Income
Before Tax
Reclassification adjustments, before tax	(971)		(956)		(1,940)	(1,909)
Provision (Benefit)
Reclassification adjustments, provision (benefit)	(204)		(201)		(407)	(401)
After Tax
Reclassification adjustments, after tax	(767)		(755)		(1,533)	(1,508)
Net Interest Income | Held-to-Maturity Securities | Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest | Reclassification out of Accumulated Other Comprehensive Income
Before Tax
Reclassification adjustments, before tax	(2,496)		(4,601)		(8,184)	(6,863)
Provision (Benefit)
Reclassification adjustments, provision (benefit)	(524)		(966)		(1,718)	(1,441)
After Tax
Reclassification adjustments, after tax	(1,972)		(3,635)		(6,466)	(5,422)
Other Income | Available-for-Sale Securities | Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest | Reclassification out of Accumulated Other Comprehensive Income
Before Tax
Reclassification adjustments, before tax	(14)		(150)		(27)	(156)
Provision (Benefit)
Reclassification adjustments, provision (benefit)	(4)		(32)		(6)	(33)
After Tax
Reclassification adjustments, after tax	(10)		(118)		(21)	(123)
Interest Expense | Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income
Before Tax
Reclassification adjustments, before tax	1,563		(462)		2,002	(942)
Provision (Benefit)
Reclassification adjustments, provision (benefit)	328		(96)		420	(197)
After Tax
Reclassification adjustments, after tax	$ 1,235		$ (366)		$ 1,582	$ (745)