Employee Benefit Plans - Defined Benefit Pension Plans (Details) - USD ($) $ in Millions	3 Months Ended															12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020	[1]	Jun. 30, 2020	[1]	Mar. 31, 2020	[1]	Dec. 31, 2019	Sep. 30, 2019	[2]	Jun. 30, 2019	[2]	Mar. 31, 2019	[2]	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
(Loss)/gain on disposal of discontinued business, net of income taxes	$ (2)	[1]	$ 0		$ 0		$ 0		$ 12	$ 0		$ 6		$ (1)		$ (2)	$ 18	$ 456
Unrecognized gains																36	0	(33)
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Net pension liability	$ 5								$ 4							5	4
Pension expense																0	0	0
Defined Benefit Pension Plans | Reclassification out of Accumulated Other Comprehensive Income
Defined Benefit Plan Disclosure [Line Items]
(Loss)/gain on disposal of discontinued business, net of income taxes																		(4)
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest
Defined Benefit Plan Disclosure [Line Items]
Unrecognized gains																		$ 5
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Unrecognized gains																$ 1	$ 1

[1] The results of operations for 2020 include impacts related to COVID-19. See Note 26—COVID-19 Related Items for additional details.

[2] The Company sold its North American vacation rentals business on October 22, 2019. This business did not meet the criteria to be classified as a discontinued operation; therefore, its results of operations are reflected within continuing operations through the date of sale.