Leases - Additional Information Related to Leases (Details) - USD ($) $ in Millions			12 Months Ended
		Jan. 01, 2019	Dec. 31, 2020		Dec. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash outflows from operating leases			$ 26		$ 26
Operating cash outflows from finance lease			4		4
Financing cash outflows from finance lease			6		5
Right-of-use assets obtained in exchange for lease liabilities:
Operating leases		$ 88	$ 4	[1]	106	[1]
Finance lease	[2]				$ 88
Weighted-average remaining lease term:
Weighted-average remaining lease term, Operating leases			3 years 8 months 12 days		4 years 4 months 24 days
Weighted-average remaining lease term, Finance lease			10 years		11 years
Weighted-average discount rate:
Weighted-average discount rate, Operating leases			3.99%		4.11%
Weighted-average discount rate, Finance lease			4.49%		4.49%

[1] Amount related to 2019 includes operating leases, recognized upon adoption of ASC 842 on January 1, 2019 of $88 million, and those that commenced during the year ended December 31, 2019 of $18 million.

[2] Amount related to 2019 represents the finance lease obligation arising from obtaining the ROU asset related to our Headquarters Lease, which was recognized upon the adoption of ASC 842 on January 1, 2019.