Stockholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended	22 Months Ended		1 Months Ended	3 Months Ended
	Jun. 30, 2012	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014 2006 Equity Incentive Plan (2006 Plan)	May 12, 2014 2006 Equity Incentive Plan (2006 Plan) Nonvested stock units issued (NSUs) Subsequent Event	Mar. 31, 2014 2006 Equity Incentive Plan (2006 Plan) Nonvested stock units issued (NSUs) Award granted in 2012	Mar. 31, 2014 2006 Equity Incentive Plan (2006 Plan) Nonvested stock units issued (NSUs) Award granted in 2013
Stockholders' equity
NSUs granted that will vest at the end of each of the three years after the performance goals are achieved (as a percent)						33.30%	33.30%
Common stock reserved for issuance (in shares)				6,000,000
Maximum number of shares that may be issued through the exercise of incentive stock options				4,500,000
Award vesting period of the grants					3 years	3 years
Maximum stock repurchase amount approved by Board of Directors	$ 200,000
Remaining stock repurchase amount approved by Board of Directors			79,300
Number of shares repurchased		0	2,765,000
Repurchase of common stock, payments			120,700
Average stock price of shares repurchased (in dollars per share)			$ 43.66
Number of shares granted					19,000
Weighted average grant date fair value					$ 78.78
Compensation cost not yet recognized					$ 1,500