Stockholders' Equity (Narrative) (Details) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended				0 Months Ended	30 Months Ended
	Apr. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 employee_group	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 2011 Stock Plan [Member]	Jun. 30, 2004 Granted before June 30, 2004 [Member]	Jan. 01, 2007 Granted after June 30, 2004 and bfore January 1, 2007 [Member]	Dec. 31, 2012 Series A Preferred Stock [Member]
Components of Stockholders' Equity [Line Items]
Common stock, shares issued	2,300,000
Preferred Stock, Shares Authorized						9,000,000				1,000,000
Preferred Stock, Par or Stated Value Per Share						$ 0.001				$ 0.001
Shares reserved for future issuance							3,500,000
Total intrinsic value of options exercised		$ 64,500,000	$ 400,000	$ 182,800,000	$ 13,200,000
Proceeds from issuance of common stock		25,561,000	318,000	93,553,000	2,066,000
Exercise period after employment termination								3 months	1 year
Full exercise period				10 years
Number of employee groups				2
Weighted-average fair value of employee stock options granted per share		$ 136.78	$ 32.57	$ 100.08	$ 42.58
Stock-based compensation expense		18,500,000	18,500,000	54,200,000	56,300,000
Income tax benefit			$ 7,100,000	$ 20,800,000	$ 21,700,000