Stockholders' Equity (Narrative) (Details) (USD $)	0 Months Ended	1 Months Ended	12 Months Ended			30 Months Ended	72 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended
	Jun. 30, 2004	Nov. 28, 2011	Dec. 31, 2012 employee_groups	Dec. 31, 2011	Dec. 31, 2010	Jan. 01, 2007	Dec. 31, 2012	Dec. 31, 2010 Employee Stock [Member]	Jun. 11, 2010 Stock Repurchase Program [Member]	Dec. 31, 2012 Stock Repurchase Program [Member]	Dec. 31, 2012 Stock Option Plans [Member]	Dec. 31, 2011 Stock Option Plans [Member]	Dec. 31, 2010 Stock Option Plans [Member]	Dec. 31, 2012 Employee Stock [Member]	Dec. 31, 2012 Stock-Based Compensation [Member]	Dec. 31, 2011 Stock-Based Compensation [Member]	Dec. 31, 2010 Stock-Based Compensation [Member]	Dec. 31, 2012 2002 Employee Stock Purchase Plan [Member]	Dec. 31, 2012 2011 Stock Plan [Member]	Mar. 31, 2012 2002 Stock Plan [Member]	Dec. 31, 2012 Series A [Member]	Dec. 31, 2012 Undesignated Stock [Member]
Components of Stockholders' Equity [Line Items]
Common stock, par value			$ 0.001	$ 0.001			$ 0.001
Preferred stock, par value			$ 0.001	$ 0.001			$ 0.001														$ 0.001	$ 0.001
Right to purchase preferred stock, conversion ratio			0.001				0.001
Right to purchase preferred stock, exercise price			$ 350,000				$ 350,000
Percent ownership threshold of common stock to become exercisable			10.00%
Percent ownership threshold of common stock to become exercisable for certain institutional investors			20.00%
Common stock, shares issued		2,900,000	55,398,615	55,398,615			55,398,615
Proceeds from public offering of common stock, net of issuance costs		$ 200,000,000	$ (464,000)	$ 199,947,000	$ 0
Issuance costs				500,000
Preferred stock, shares authorized			10,000,000	10,000,000			10,000,000														1,000,000	9,000,000
Preferred stock, shares issued			0	0			0
Preferred stock, shares outstanding			0	0			0
Number of voting rights per share			1
Common stockholders, voting rights			one vote
Shares available for future issuance																		2,785,721	4,000,000	1,200,000
Total intrinsic value of options exercised											14,700,000	128,100,000	176,000,000
Cash received from option exercised								2,700,000			4,100,000	19,600,000	47,100,000
Purchase price of common stock acquired by employees on closing price																		85.00%
Common stock purchase period																		6 months
Common stock look-back period																		6 months
Employees can invest maximum their gross compensation through payroll deductions for share purchase																		15.00%
Maximum number of shares employee can purchase																		8,334
Shares purchased during period								46,112
Shares purchased average price								$ 58.41
Exercise period after employment termination	3 months					1 year
Full exercise period							10 years
Number of employee groups			2
Dividend yield			0.00%	0.00%	0.00%									0.00%
Expected volatility														45.00%
Risk-free interest rate														0.24%
Expected life (in years)														6 months
Weighted-average fair value of employee stock options granted per share															$ 41.00	$ 84.94	$ 49.31
Weighted-average fair value of shares granted under ESPP per share								$ 21.27
Stock based compensation expense			73,900,000	61,600,000	28,000,000
Income tax benefit			28,500,000	22,800,000	11,200,000
Stock repurchase plan, authorized amount									300,000,000
Stock repurchase program, amount repurchased										259,000,000
Stock repurchase program, remaining authorized repurchase amount										$ 41,000,000