Derivatives - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Feb. 28, 2019	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Obligation to return cash collateral provided by counter-party		$ 178,700
Derivative, notional amount		6,710,773	$ 2,696,100
Deferred net gains (loss) on derivatives		$ (800)
Cash Flow Hedges
Derivative [Line Items]
Derivative, notional amount	$ 4,000,000
Derrivative contract term	5 years
Derivative, purchased option price	$ 127,800
Maximum period for hedging transactions		6 years 10 months 24 days
Cash Flow Hedges | Purchased | Interest Rate Collars
Derivative [Line Items]
Derrivative cap interest rate	4.70%
Derrivative floor interest rate	3.00%
Cash Flow Hedges | Sold | Interest Rate Collars
Derivative [Line Items]
Derrivative cap interest rate	3.50%
Derrivative floor interest rate	0.00%
Interest-bearing Deposits in Banks
Derivative [Line Items]
Cash or securities pledged as collateral		$ 19,500	$ 25,300