Significant Accounting Policies - Additional Information Related to Leases (Parenthetical) (Details) - USD ($) $ in Millions		6 Months Ended
	Jan. 01, 2019	Jun. 30, 2019
Lessee Disclosure [Abstract]
Operating leases	$ 88	$ 97	[1]
Operating leases commenced amount		$ 9

[1] Amount includes operating leases existing on January 1, 2019 of $88 million and those that commenced during the six months ended June 30, 2019 of $9 million.