Stockholders' Equity - Common Stock Repurchased (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Shares repurchased related to employee stock-based compensation plans (in shares)	3,354,730	3,008,913	1,365,277
Average purchase price per share (in dollars per share)	$ 7.83	$ 9.65	$ 8.93
Common shares issued (in shares)	5,955,045	5,873,309	2,013,805