Incentive Based Compensation Plans - Stock Option Award Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Beginning of year, stock option awards (in shares)	6,180,007
Granted, stock option awards (in shares)	648,526
Exercised, stock option awards (in shares)	(84,804)
Canceled, stock option awards (in shares)	(1,083,998)
End of year, stock option awards (in shares)	5,659,731	6,180,007
Exercisable at end of year, stock option awards (in shares)	4,323,312
Expected to vest, stock option awards (in shares)	1,319,850
Weighted Average Exercise Price
Beginning of year, weighted average exercise price (in dollars per share)	$ 24.39
Granted, weighted average exercise price (in dollars per share)	16.79	$ 14.52	$ 15.80
Exercises, weighted average exercise price (in dollars per share)	8.17
Canceled, weighted average exercise price (in dollars per share)	25.45
End of year, weighted average exercise price (in dollars per share)	23.55	$ 24.39
Exercisable at end of year, weighted average exercise price (in dollars per share)	25.96
Expected to vest, weighted average exercise price (in dollars per share)	$ 15.76
Share-based Payment Arrangement [Abstract]
Outstanding at end of year, Weighted Average Remaining Contractual Term	5 years
Exercisable at end of year, Weighted Average Remaining Contractual Term	4 years
Expected to vest, Weighted Average Remaining Contractual Term	8 years
Outstanding at end of year, Average Intrinsic Value	$ 3
Exercisable at end of year, Average Intrinsic Value	3
Expected to vest, Average Intrinsic Value	0
Stock option awards, intrinsic value		$ 13
Unrecognized compensation costs	$ 5
Unrecognized compensation costs, period for recognition	1 year