Derivative Financial Instruments - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Notional amount	$ 9,206,372		$ 13,589,356
Accumulated other comprehensive income (loss)	725,202	$ 1,549,927	1,827,231	$ 1,348,794
Net Unrealized Losses on Interest Rate Agreements Accounted for as Cash Flow Hedges
Derivative [Line Items]
Accumulated other comprehensive income (loss)	(83,666)	(39,883)	(50,939)	$ (34,045)
Derivative Liabilities
Derivative [Line Items]
Notional amount	4,716,372		6,929,494
Mortgage Banking Activities, Net
Derivative [Line Items]
Market valuations gains (losses), net	(37,003)	11,690
Loan purchase commitments and forward sales commitments | Mortgage Banking Activities, Net
Derivative [Line Items]
Market valuations gains (losses), net	18,000	11,000
Interest rate contract
Derivative [Line Items]
Notional amount			4,780,000
TBAs
Derivative [Line Items]
Notional amount	8,980,000		6,610,000
TBAs | Derivative Liabilities
Derivative [Line Items]
Notional amount	4,490,000		4,160,000
Interest rate futures
Derivative [Line Items]
Notional amount			226,000
Interest rate futures | Derivative Liabilities
Derivative [Line Items]
Notional amount	0		12,300
Unsecuritized Residential and Commercial Loans
Derivative [Line Items]
Derivative gain (loss)	(98,000)	(45,000)
Interest rate swaps | Cash Flow Hedging
Derivative [Line Items]
Derivative gain (loss)	(33,000)	$ (6,000)
Derivative, cost of hedge	84,000
Interest rate swaps | Derivative Liabilities
Derivative [Line Items]
Notional amount	0		2,314,300
Interest rate swaps | Derivative Liabilities | Cash Flow Hedging
Derivative [Line Items]
Notional amount	$ 0		$ 139,500