Stockholders' Equity (Narrative) (Details) (USD $)	0 Months Ended	3 Months Ended		6 Months Ended				0 Months Ended	30 Months Ended
	Apr. 26, 2013	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 employee_group	Jun. 30, 2012	Dec. 31, 2012	Jun. 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							3,600,000
Total intrinsic value of options exercised		$ 68,300,000	$ 1,000,000	$ 118,300,000	$ 12,800,000
Proceeds from issuance of common stock		28,846,000	524,000	67,992,000	1,748,000
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		$ 110.67	$ 45.38	$ 87.87	$ 50.11
Stock-based compensation expense		18,000,000	18,500,000	35,700,000	37,800,000
Income tax benefit		$ 6,900,000	$ 7,100,000	$ 13,700,000	$ 14,600,000