Debt (Schedule of Balances Available for Borrowing) (Details) - USD ($) $ in Millions					12 Months Ended
		Dec. 31, 2020		May 08, 2019	Dec. 31, 2020		Dec. 31, 2019
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowings outstanding	[2]	$ 0	[1]		$ 0	[1]	$ 272
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Repayments of Lines of Credit				$ 156
Revolving Credit Facility [Member] | Senior Unsecured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Proceeds from Lines of Credit					685
Repayments of Lines of Credit					963
Line of Credit Facility, Remaining Borrowing Capacity	[3]	$ 1,250			$ 1,250
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member] | Senior Unsecured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.50%

[1] The Company borrowed $685 million and repaid $963 million under its senior unsecured revolving credit facility during the year ended December 31, 2020.

[2] The weighted average interest rate was 0.0% and 1.6% as of December 31, 2020 and 2019, respectively.

[3] The margin for borrowings under the senior unsecured revolving credit facility was 1.5% above LIBOR or EURIBOR at current Company credit ratings.