Stockholders' Equity - Common Stock Repurchased (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Jan. 23, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Common stock repurchased (in shares)	17,000,000	16,962,199	0	0
Average purchase price per share (in dollars per share)		$ 9.86	$ 0	$ 0
Shares repurchased related to employee stock-based compensation plans (in shares)		1,369,630	3,087,396	3,358,417
Average purchase price per share (in dollars per share)		$ 10.85	$ 11.32	$ 11.96
Common shares issued (in shares)		3,743,705	6,392,634	6,831,108
Repurchase amount	$ 167	$ 33