Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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Derivative Financial Instruments - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) counterparty	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Derivative [Line Items]
Notional amount	$ 7,052,359		$ 5,911,385
Accumulated other comprehensive income (loss)	$ 1,549,927	$ 1,219,983	1,348,794	$ 1,212,287
Number of counterparties \| counterparty	2
Net Unrealized Losses on Interest Rate Agreements Accounted for as Cash Flow Hedges
Derivative [Line Items]
Accumulated other comprehensive income (loss)	$ (40,000)	(34,522)	(34,000)	$ (42,953)
Derivative Liabilities
Derivative [Line Items]
Notional amount	3,881,623		2,953,724
Mortgage Banking Activities, Net
Derivative [Line Items]
Market valuations gains (losses), net	11,690	26,238
Residential loan purchase and forward sale commitments \| Mortgage Banking Activities, Net
Derivative [Line Items]
Market valuations gains (losses), net	11,311	(6,968)
Interest rate contract
Derivative [Line Items]
Notional amount	3,970,000		3,850,000
TBAs
Derivative [Line Items]
Notional amount	2,180,000		1,460,000
TBAs \| Derivative Liabilities
Derivative [Line Items]
Notional amount	1,265,000		935,000
Unsecuritized Residential and Commercial Loans
Derivative [Line Items]
Derivative gain (loss)	(45,000)	67,000
Interest rate swaps \| Cash Flow Hedging
Derivative [Line Items]
Derivative gain (loss)	(6,000)	$ 8,000
Interest rate swaps \| Derivative Liabilities
Derivative [Line Items]
Notional amount	2,296,000		1,742,000
Interest rate swaps \| Derivative Liabilities \| Cash Flow Hedging
Derivative [Line Items]
Notional amount	$ 139,500		$ 139,500