Derivative Instruments (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Credit Derivatives [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	$ 51,000,000
Cash flow hedge, reclassified to earnings, net	0	$ 0
Non-performance Risk Adjustment	0
Credit Default Swaps [Member]
Credit Derivatives [Line Items]
Collateral Requirement If Netting Agreements Not In Place	$ 2,000,000