Stockholders' Equity - Common Stock Repurchased (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Shares repurchased related to employee stock-based compensation plans (in shares)	3,008,913	1,365,277	6,365,002
Average purchase price per share (in dollars per share)	$ 9.65	$ 8.93	$ 21.76
Common shares issued (in shares)	5,873,309	2,013,805	9,702,976