Stock Option Plans - Options Outstanding and Exercisable (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number of Options	7,127
Options Outstanding, Weighted Average Remaining Contractual Life	8 years 0 months 26 days
Options Exercisable, Number of Options	2,890
Options Exercisable, Weighted Average Remaining Contractual Life	7 years 0 months 12 days
$0.34 to $1.65
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower (in usd per share)	$ 0.34
Range of Exercise Prices, Upper (in usd per share)	$ 1.65
Options Outstanding, Number of Options	841
Options Outstanding, Weighted Average Remaining Contractual Life	5 years 6 months 23 days
Options Exercisable, Number of Options	800
Options Exercisable, Weighted Average Remaining Contractual Life	5 years 6 months 9 days
$5.93 to $8.88
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower (in usd per share)	$ 5.93
Range of Exercise Prices, Upper (in usd per share)	$ 8.88
Options Outstanding, Number of Options	1,219
Options Outstanding, Weighted Average Remaining Contractual Life	6 years 10 months 15 days
Options Exercisable, Number of Options	866
Options Exercisable, Weighted Average Remaining Contractual Life	6 years 10 months 16 days
$12.54 to $15.41
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower (in usd per share)	$ 12.54
Range of Exercise Prices, Upper (in usd per share)	$ 15.41
Options Outstanding, Number of Options	596
Options Outstanding, Weighted Average Remaining Contractual Life	7 years 8 months 17 days
Options Exercisable, Number of Options	289
Options Exercisable, Weighted Average Remaining Contractual Life	7 years 8 months 13 days
$16.24 to $18.82
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower (in usd per share)	$ 16.24
Range of Exercise Prices, Upper (in usd per share)	$ 18.82
Options Outstanding, Number of Options	732
Options Outstanding, Weighted Average Remaining Contractual Life	7 years 11 months 28 days
Options Exercisable, Number of Options	458
Options Exercisable, Weighted Average Remaining Contractual Life	8 years 0 months 11 days
$20.85 to $23.94
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower (in usd per share)	$ 20.85
Range of Exercise Prices, Upper (in usd per share)	$ 23.94
Options Outstanding, Number of Options	1,095
Options Outstanding, Weighted Average Remaining Contractual Life	8 years 4 months 16 days
Options Exercisable, Number of Options	366
Options Exercisable, Weighted Average Remaining Contractual Life	8 years 4 months 8 days
$27.75 to $31.44
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower (in usd per share)	$ 27.75
Range of Exercise Prices, Upper (in usd per share)	$ 31.44
Options Outstanding, Number of Options	394
Options Outstanding, Weighted Average Remaining Contractual Life	8 years 10 months 8 days
Options Exercisable, Number of Options	104
Options Exercisable, Weighted Average Remaining Contractual Life	8 years 10 months 5 days
$33.34 to $36.15
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower (in usd per share)	$ 33,340
Range of Exercise Prices, Upper (in usd per share)	$ 36,150
Options Outstanding, Number of Options	609
Options Outstanding, Weighted Average Remaining Contractual Life	9 years 2 months 3 days
Options Exercisable, Number of Options	4
Options Exercisable, Weighted Average Remaining Contractual Life	9 years 1 month 27 days
$40.03 to $45.76
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower (in usd per share)	$ 40,030
Range of Exercise Prices, Upper (in usd per share)	$ 45,760
Options Outstanding, Number of Options	895
Options Outstanding, Weighted Average Remaining Contractual Life	9 years 6 months 8 days
Options Exercisable, Number of Options	2
Options Exercisable, Weighted Average Remaining Contractual Life	9 years 10 months 2 days
$50.42 to $52.72
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower (in usd per share)	$ 50,420
Range of Exercise Prices, Upper (in usd per share)	$ 52,720
Options Outstanding, Number of Options	746
Options Outstanding, Weighted Average Remaining Contractual Life	9 years 8 months 21 days
Options Exercisable, Number of Options	1
Options Exercisable, Weighted Average Remaining Contractual Life	9 years 10 months 30 days