Stock-Based Compensation - Performance Share Plans (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Plan Modification, Incremental Compensation Cost	$ 2	$ 8	$ 0
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum	200.00%
Performance share plan expense	$ 5	$ 9	$ 10
Performance share plan, shares issued in period	0	0	0
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Nonvested shares, number, beginning balance	297,000	355,000	410,000
Nonvested shares, weighted average price, beginning balance	$ 60.35	$ 32.35	$ 43.99
Nonvested shares, granted	196,000	287,000	201,000
Nonvested shares, weighted average price, granted	$ 51.52	$ 68.38	$ 45.57
Nonvested shares, vested	(160,000)
Nonvested shares, weighted average price, vested	$ 45.78
Nonvested shares, forfeited	(93,000)	(345,000)	(256,000)
Nonvested shares, weighted average price, forfeited	$ 55.82	$ 38.26	$ 61.40
Nonvested shares, number, ending balance	240,000	297,000	355,000
Nonvested shares, weighted average price, ending balance	$ 64.61	$ 60.35	$ 32.35
Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 7
Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 8 months 12 days
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Nonvested shares, number, beginning balance	1,516,000	1,593,000	1,429,000
Nonvested shares, weighted average price, beginning balance	$ 42.97	$ 38.86	$ 44.12
Nonvested shares, granted	1,082,000	737,000	804,000
Nonvested shares, weighted average price, granted	$ 41.66	$ 51.70	$ 40.10
Nonvested shares, vested	(724,000)	(556,000)	(521,000)
Nonvested shares, weighted average price, vested	$ 36.81	$ 42.25	$ 56.53
Nonvested shares, forfeited	(210,000)	(258,000)	(119,000)
Nonvested shares, weighted average price, forfeited	$ 44.82	$ 44.51	$ 38.97
Nonvested shares, number, ending balance	1,664,000	1,516,000	1,593,000
Nonvested shares, weighted average price, ending balance	$ 44.26	$ 42.97	$ 38.86
Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 37
Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 9 months 18 days
Relative Revenue Growth Performance Share Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum	200.00%
Performance share plan expense	$ 7	$ 18	$ 16
Performance share plan, shares issued in period	315,000	249,000	126,000
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Nonvested shares, number, beginning balance	297,000	355,000	320,000
Nonvested shares, weighted average price, beginning balance	$ 47.03	$ 39.42	$ 38.62
Nonvested shares, granted	196,000	287,000	198,000
Nonvested shares, weighted average price, granted	$ 41.90	$ 50.82	$ 40.08
Nonvested shares, vested	(160,000)	(166,000)	(156,000)
Nonvested shares, weighted average price, vested	$ 40.10	$ 38.62	$ 38.62
Nonvested shares, forfeited	(93,000)	(179,000)	(7,000)
Nonvested shares, weighted average price, forfeited	$ 44.30	$ 45.82	$ 39.20
Nonvested shares, number, ending balance	240,000	297,000	355,000
Nonvested shares, weighted average price, ending balance	$ 48.52	$ 47.03	$ 39.42
Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 8
Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 8 months 12 days