Derivative Financial Instruments - Additional Information (Details) - USD ($)	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Notional amount	$ 224,803,000			$ 224,803,000		$ 13,589,356,000
Accumulated other comprehensive income (loss)	936,576,000	$ 725,202,000	$ 1,564,032,000	936,576,000	$ 1,564,032,000	1,827,231,000	$ 1,549,927,000	$ 1,348,794,000
Net Unrealized Losses on Interest Rate Agreements Accounted for as Cash Flow Hedges
Derivative [Line Items]
Accumulated other comprehensive income (loss)	(82,637,000)	(83,666,000)	(49,384,000)	(82,637,000)	(49,384,000)	(50,939,000)	$ (39,883,000)	$ (34,045,000)
Derivative Liabilities
Derivative [Line Items]
Notional amount	199,932,000			199,932,000		6,929,494,000
Interest Expense
Derivative [Line Items]
Cash flow hedge gain (loss) to be reclassified over the next 12 months				(4,000,000)
Mortgage Banking Activities, Net
Derivative [Line Items]
Market valuations gains (losses), net	(1,443,000)		15,730,000	(38,446,000)	27,420,000
Loan purchase commitments and forward sales commitments | Mortgage Banking Activities, Net
Derivative [Line Items]
Market valuations gains (losses), net	3,000,000		17,000,000	21,000,000	29,000,000
Interest rate contract
Derivative [Line Items]
Notional amount						4,780,000,000
TBAs
Derivative [Line Items]
Notional amount	0			0		6,610,000,000
TBAs | Derivative Liabilities
Derivative [Line Items]
Notional amount	0			0		4,160,000,000
Interest rate futures
Derivative [Line Items]
Notional amount						226,000,000
Interest rate futures | Derivative Liabilities
Derivative [Line Items]
Notional amount	0			0		12,300,000
Unsecuritized Residential and Commercial Loans
Derivative [Line Items]
Derivative gain (loss)	0		(66,000,000)	(98,000,000)	(111,000,000)
Interest rate swaps | Cash Flow Hedging
Derivative [Line Items]
Derivative gain (loss)	0		$ (10,000,000)	(33,000,000)	$ (15,000,000)
Derivative, cost of hedge		$ 84,000,000
Interest rate swaps | Derivative Liabilities
Derivative [Line Items]
Notional amount	0			0		2,314,300,000
Interest rate swaps | Derivative Liabilities | Cash Flow Hedging
Derivative [Line Items]
Notional amount	$ 0			$ 0		$ 139,500,000