Derivative Instruments - Derivatives - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	$ 12,063,000,000		$ 12,063,000,000		$ 13,706,000,000
Loss on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring		$ 0	0	$ 0
Collateral receivable					1,000,000
Pledged collateral, securities	86,000,000		86,000,000		78,000,000
Cash collateral held	25,000,000		25,000,000		16,000,000
Securities Received as Collateral					1,000,000
Collateral Securities Repledged, Delivered, or Used	0		0		0
Fair Value of Securities Received as Collateral that Have Been Resold or Repledged	0		0		0
Over the Counter [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Pledged collateral, securities	98,000,000		98,000,000		88,000,000
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
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	$ 9,436,000,000		$ 9,436,000,000		$ 11,396,000,000