Derivative Instruments - Derivatives - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	$ 11,729,000,000		$ 12,129,000,000
Cash	176,000,000		151,000,000
Pledged collateral, securities	61,000,000		90,000,000
Cash collateral held	22,000,000		24,000,000
Securities Received as Collateral		$ 1,000,000	1,000,000
Collateral Securities Repledged, Delivered, or Used	0		0
Fair Value of Securities Received as Collateral that Have Been Resold or Repledged	0		0
Asset Pledged as Collateral [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash	0		0
Over the Counter [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Pledged collateral, securities	60,000,000		83,000,000
Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Loss on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring	0	$ 0
AOCI Attributable to Parent [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	35,000,000
Not Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	9,092,000,000		9,503,000,000
Not Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	$ 7,600,000,000		$ 7,600,000,000