Stock-Based Compensation - Narrative (Details) - USD ($)			12 Months Ended
	Dec. 20, 2017	Feb. 09, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 20, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ESPP, minimum holding period	3 months
ESPP, number of shares authorized for issuance (in shares)	2,000,000
Stock-based compensation expense			$ 49,000,000	$ 79,000,000	$ 55,000,000
Number of shares available to be granted under ESPP			2,000,000
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum employee contribution percentage into ESPP	10.00%
ESPP discount percentage from market price on last trading day at end of purchase period	5.00%
ESPP offering period	6 months
Stock-based compensation expense			$ 0
Restricted Stock Units and Performance-based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, period for recognition			3 years 3 months 22 days
Unrecognized compensation cost			$ 69,000,000
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 0	$ 1,000,000	$ 1,000,000
Options, granted (in shares)			0	0
Weighted average grant date fair value, options granted in period (USD per share)					$ 11.37
Options, outstanding, intrinsic value			$ 31,000,000
Unrecognized compensation cost, period for recognition			1 year
Options, exercised, intrinsic value			$ 11,000,000	$ 9,000,000	$ 12,000,000
Proceeds from stock options exercised			$ 1,000,000	1,000,000	13,000,000
Stock options | Employee and Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term of options			10 years
Stock options | Employee and Officer | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, award vesting period			3 years
Stock options | Employee and Officer | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, award vesting period			5 years
Stock options | Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, award vesting period			1 year
Contractual term of options			10 years
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 21,000,000	12,000,000	13,000,000
Restricted stock units, vested, fair value			$ 30,000,000	$ 23,000,000	27,000,000
Outstanding (in shares)			1,085,628	1,041,554
Performance-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 9,000,000	$ 10,000,000	13,000,000
Restricted stock units, vested, fair value			$ 96,000,000	$ 8,000,000	7,000,000
Outstanding (in shares)			1,036,925	1,838,227
Performance-based Restricted Stock Units Subject To Service, Market and Performance Based Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding (in shares)			444,959
Performance-based Restricted Stock Units Subject To Service Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding (in shares)			591,966
Cash-settled performance-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 19,000,000	$ 55,000,000	$ 27,000,000
Options, award vesting period		4 years
Unrecognized compensation cost, period for recognition			1 year
Outstanding (in shares)			753,276	1,693,394
Unrecognized compensation cost			$ 24,000,000
Annual vesting percentage		25.00%
Liability for settlement			$ 18,000,000	$ 52,000,000
Weighted average fair value (in usd per share)			$ 57.04	$ 91.59
2016 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized (in shares)						3,400,000.0
Shares available for issuance (in shares)			1,700,000