Stockholders' Equity - Narrative (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 employee_group	Jun. 30, 2013
Components of Stockholders' Equity [Line Items]
Total intrinsic value of options exercised	$ 46,200,000	$ 68,300,000	$ 147,700,000	$ 118,300,000
Proceeds from issuance of common stock	14,469,000	28,846,000	46,917,000	67,992,000
Number of employee groups			2
Weighted-average fair value of employee stock options granted per share	$ 196.93	$ 110.67	$ 207.85	$ 87.87
Stock-based compensation expense	29,300,000	18,000,000	55,100,000	35,700,000
Income tax benefit	$ 11,200,000	$ 6,900,000	$ 21,100,000	$ 13,700,000
2011 Stock Plan [Member]
Components of Stockholders' Equity [Line Items]
Shares reserved for future issuance	3.1		3.1