Stockholders' Equity - Common stock repurchased (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Equity [Abstract]
Shares repurchased related to employee stock-based compensation plans (in shares)	1,389,096	[1]	2,115,470	[1]
Average purchase price per share (in dollars per share)	$ 9.46		$ 23.56
Common shares issued (in shares)	3,130,839	[2]	4,238,182	[2]

[1] Comprises shares withheld from stock option exercises and vesting of restricted stock for employees’ tax withholding obligations and shares tendered by employees to satisfy option exercise costs.

[2] Common shares issued under our various compensation and benefit plans.