Stockholders' Equity (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Shareholders Equity [Line Items]
Stock-based compensation expense	$ 15,300,000	$ 14,500,000
Unrecognized compensation cost	93,500,000
Total intrinsic value of options exercised	12,800,000	9,500,000
Target revenue period, in years	3 years
Repurchase of common stock, shares		900,000
Repurchase of common stock, value	0	33,000,000
Non-qualified stock options granted to executive officer	583,045
Common shares outstanding	8,437,535		8,824,705
Shares issued pursuant to the ESPP	69,846	47,581
Proceeds from issuance of treasury stock	1,557,000	1,412,000
Employee stock purchase plan [Member]
Shareholders Equity [Line Items]
Stock-based compensation expense	600,000	400,000
Performance Stock Units [Member]
Shareholders Equity [Line Items]
Unrecognized compensation cost	12,400,000
Restricted stock units and performance shares granted to employees	336,330	193,000
Weighted-average period over which unrecognized compensation costs will be recognized, years	3 years
Restricted stock [Member]
Shareholders Equity [Line Items]
Weighted-average grant date fair value of restricted stock units (usd per share)	$ 31.35		31.45
Restricted stock units and performance shares granted to employees	0
Restricted Stock Units (RSUs) [Member]
Shareholders Equity [Line Items]
Restricted stock units and performance shares granted to employees	1,306,003
Non vested stock options [Member]
Shareholders Equity [Line Items]
Unrecognized compensation cost	28,500,000
Weighted-average grant date fair value of stock options (usd per share)	$ 9.33	$ 10.57
Weighted average remaining requisite service period of non-vested stock awards, years	2 years 6 months
Non vested restricted stock units [Member]
Shareholders Equity [Line Items]
Unrecognized compensation cost	$ 52,600,000
Weighted average remaining requisite service period of non-vested restricted stock units, years	2 years 8 months 12 days
Weighted-average grant date fair value of restricted stock units (usd per share)	$ 29.53		34.93
Non vested restricted stock [Member]
Shareholders Equity [Line Items]
Weighted average remaining requisite service period of non-vested stock awards, years	1 year 4 months 24 days