Derivatives and Hedging - Credit and Market Risks (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Derivatives [Line Items]
Derivative assets		$ 46,217,000		$ 46,217,000		$ 41,390,000
Derivative, collateral, right to reclaim cash	[1]	174,188,000		174,188,000		94,979,000
Derivative, collateral, obligation to return	[1]	3,502,000		3,502,000		5,860,000
Other assets
Derivatives [Line Items]
Derivative, collateral, right to reclaim cash		221,000,000		221,000,000		150,000,000
Deposits
Derivatives [Line Items]
Derivative, collateral, obligation to return		12,000,000		12,000,000		12,000,000
Free-standing derivatives not designated as hedging instrument
Derivatives [Line Items]
Derivative assets	[2]	769,712,000		769,712,000		344,247,000
Free-standing derivatives not designated as hedging instrument | Interest rate swap
Derivatives [Line Items]
Derivative assets		749,000,000		749,000,000
Gain (loss) on derivative instruments held for trading purposes, net		0	$ 0	0	$ 0
Gain (loss) on derivative instruments held for non-trading purposes, net		0	$ 0	0	$ 0
Derivatives designated as hedging instrument
Derivatives [Line Items]
Derivative assets	[2]	12,408,000		12,408,000		$ 10,735,000
Derivatives designated as hedging instrument | Interest rate swap | Over the counter
Derivatives [Line Items]
Credit risk derivatives, at fair value, net		$ 12,000,000		$ 12,000,000

[1] The actual amount of collateral received/pledged is limited to the asset/liability balance and does not include excess collateral received/pledged. When excess collateral exists, the collateral shown in the table above has been allocated based on the percentage of the actual amount of collateral posted.

[2] Derivative assets, except for trading account assets that are recorded as a component of trading account assets on the Company's Unaudited Condensed Consolidated Balance Sheets, are recorded in other assets on the Company’s Unaudited Condensed Consolidated Balance Sheets.