Fair Value of Assets and Liabilities (Fair Value Assets Measured on Non-Recurring Basis) (Details) - Partnership Interest [Member] $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)	[1]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets Carrying Value Prior To Impairment	$ 20
Fair Value Assets Gains Losses	$ (17)

[1] Impairments on these investments were recognized at estimated fair value determined using the net asset values of the Company’s ownership interest as provided in the financial statements of the investees. The market for these investments has limited activity and price transparency