Revenue - Other Contract Assets and Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Contract Liabilities
Balance at beginning of period	$ 405	$ 294
Unearned revenue from cash received during the period	615	505
Revenue recognized related to contract liability balance	(500)	(394)
Balance at end of period	$ 520	$ 405