Stock Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Status of nonvested restricted stock
Net impact due to stock awards modification	$ 2	$ 0
Restricted Stock [Member]
Restricted stock compensation expense
Restricted stock compensation expense	7	7
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 57
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	2 years 3 months 18 days
Status of nonvested restricted stock
Nonvested shares subject to restriction, Beginning Balance	1,516,000
Nonvested shares subject to restriction, weighted average exercise price	$ 42.97
Restricted shares granted to employees	930,338
Granted shares subject to restriction, weighted average exercise price	$ 41.92
Shares subject to restriction, Vested	(665,000)
Vested shares subject to restriction, weighted average exercise price	$ 35.94
Shares subject to restriction, Forfeited	(6,000)
Forfeited shares subject to restriction, weighted average exercise price	$ 45.41
Nonvested shares subject to restriction, Ending Balance	1,775,000
Nonvested shares subject to restriction, weighted average exercise price	$ 44.77
Performance Shares [Member]
Status of nonvested restricted stock
Nonvested shares subject to restriction, Beginning Balance	297,000
Nonvested shares subject to restriction, weighted average exercise price	$ 60.35
Restricted shares granted to employees	190,000
Granted shares subject to restriction, weighted average exercise price	$ 51.52
Shares subject to restriction, Forfeited	(9,000)
Forfeited shares subject to restriction, weighted average exercise price	$ 55.30
Nonvested shares subject to restriction, Ending Balance	478,000
Nonvested shares subject to restriction, weighted average exercise price	$ 56.93
Performance share compensation expense	$ 3	2
Relative Revenue Growth Performance Share Plans [Member]
Status of nonvested restricted stock
Nonvested shares subject to restriction, Beginning Balance	297,000
Nonvested shares subject to restriction, weighted average exercise price	$ 47.03
Restricted shares granted to employees	190,000
Granted shares subject to restriction, weighted average exercise price	$ 41.90
Shares subject to restriction, Forfeited	(9,000)
Forfeited shares subject to restriction, weighted average exercise price	$ 44.12
Nonvested shares subject to restriction, Ending Balance	478,000
Nonvested shares subject to restriction, weighted average exercise price	$ 45.04
Performance share compensation expense	$ (1)	$ 7
2018 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized	7,000,000
Number of shares available for grant	6,000,000
First Half Vested | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of awards vested	50.00%
Vesting period	2 years
Second Half Vested | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years