Stockholders' Equity (Details) (USD $)	1 Months Ended	3 Months Ended	6 Months Ended	1 Months Ended			3 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	1 Months Ended
	Jun. 30, 2012	Sep. 30, 2014	Sep. 30, 2014	Oct. 24, 2014 Subsequent Event	Sep. 30, 2014 Minimum	Sep. 30, 2014 Maximum	Sep. 30, 2014 Maximum	Sep. 30, 2014 2006 Equity Incentive Plan (2006 Plan)	Sep. 30, 2014 2006 Equity Incentive Plan (2006 Plan) Nonvested stock units issued (NSUs)	Sep. 30, 2014 2006 Equity Incentive Plan (2006 Plan) Nonvested stock units issued (NSUs)	Sep. 30, 2014 2006 Equity Incentive Plan (2006 Plan) Time-based equity award	Sep. 30, 2014 2006 Equity Incentive Plan (2006 Plan) Time-based equity award	Oct. 30, 2014 2006 Equity Incentive Plan (2006 Plan) Time-based equity award Subsequent Event
Stockholders' equity
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
Number of shares granted							160,000		108,000	143,000	4,000	22,000	7,500
Weighted average grant date fair value		$ 98.29							$ 83.34	$ 83.99	$ 82.85	$ 79.47	$ 87.89
NSUs granted that will vest at the end of each of the three years after the performance goals are achieved (as a percent)										33.33%
Award vesting period of the grants										3 years
Compensation cost not yet recognized		$ 12,400,000	$ 12,400,000										$ 650,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options Revenue Targets Range					2,155,000,000	2,447,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Earnings before Interest, Taxes, Depreciation, and Amortization, Target Range					336,000,000	394,000,000
Maximum stock repurchase amount approved by Board of Directors	200,000,000
Number of shares repurchased		0	2,765,000	157,000
Repurchase of common stock, payments			120,700,000	13,300,000
Average stock price of shares repurchased (in dollars per share)			$ 43.66	$ 84.69
Remaining stock repurchase amount approved by Board of Directors			$ 79,300,000	$ 66,000,000