Stockholders' Equity (Details 3) (Stock options, USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock options
Number of shares
Outstanding at the beginning of the period (in shares)	10,823
Granted (in shares)	1,911
Exercised (in shares)	(5,216)
Cancelled/forfeited/expired (in shares)	(239)
Outstanding at the end of the period (in shares)	7,279	10,823
Exercisable at the end of the period (in shares)	3,948
Weighted Average Exercise Price Per Share
Outstanding at the beginning of the period (in dollars per share)	$ 11.30
Granted (in dollars per share)	$ 15.88
Exercised (in dollars per share)	$ 11.89
Cancelled/forfeited/expired (in dollars per share)	$ 11.19
Outstanding at the end of the period (in dollars per share)	$ 12.08	$ 11.30
Exercisable at the end of the period (in dollars per share)	$ 11.52
Average Remaining Contractual Term
Outstanding at the end of the period	4 years 3 months 11 days
Exercisable at the end of the period	3 years 1 month 17 days
Aggregate Intrinsic Value
Outstanding at the end of the period	$ 202,078,000
Exercisable at the end of the period	111,685,000
Weighted average fair value of options granted (in dollars per share)	$ 7.10	$ 3.55	$ 4.85
Intrinsic value of options exercised	69,600,000	7,600,000	686,000
Cash received from exercise of stock options	62,000,000	8,700,000	2,800,000
Weighted-average fair value of options exercised (in dollars per share)	$ 25.24
Unrecognized estimated non-cash stock-based compensation expense	$ 9,600,000
Weighted average period for recognition	1 year 1 month 6 days