Stock Plans (Details 3) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Options Outstanding
Shares	2,391
Aggregate Intrinsic Value	$ 12,395
Weighted-Average Remaining Contractual Life	6 years 2 months 12 days
Weighted-Average Exercise Price (in dollars per share)	$ 31.65
Options Exercisable
Shares	1,409
Aggregate Intrinsic Value	10,127
Weighted Average Remaining Contractual life	5 years 2 months 12 days
Weighted-Average Exercise Price (in dollars per share)	$ 30.76
Assumptions based on which fair value of each option granted was estimated using the Black-Scholes option-pricing model
Cash received from options exercised	12,056	2,199	5,409
Intrinsic value of options exercised	8,390	2,509	6,800
$8.82 - $17.48
Information about stock options outstanding
Exercise price, low end of range (in dollars per share)	$ 8.82
Exercise price, high end of range (in dollars per share)	$ 17.48
Options Outstanding
Shares	386
Aggregate Intrinsic Value	8,769
Weighted-Average Remaining Contractual Life	1 year 3 months 18 days
Weighted-Average Exercise Price (in dollars per share)	$ 12.15
Options Exercisable
Shares	386
Aggregate Intrinsic Value	8,769
Weighted Average Remaining Contractual life	1 year 3 months 18 days
Weighted-Average Exercise Price (in dollars per share)	$ 12.15
$20.80 - $31.45
Information about stock options outstanding
Exercise price, low end of range (in dollars per share)	$ 20.80
Exercise price, high end of range (in dollars per share)	$ 31.45
Options Outstanding
Shares	347
Aggregate Intrinsic Value	1,626
Weighted-Average Remaining Contractual Life	8 years 9 months 18 days
Weighted-Average Exercise Price (in dollars per share)	$ 30.20
Options Exercisable
Shares	125
Aggregate Intrinsic Value	616
Weighted Average Remaining Contractual life	8 years 8 months 12 days
Weighted-Average Exercise Price (in dollars per share)	$ 29.94
$31.91 - $48.04
Information about stock options outstanding
Exercise price, low end of range (in dollars per share)	$ 31.91
Exercise price, high end of range (in dollars per share)	$ 48.04
Options Outstanding
Shares	1,429
Aggregate Intrinsic Value	2,000
Weighted-Average Remaining Contractual Life	6 years 10 months 24 days
Weighted-Average Exercise Price (in dollars per share)	$ 34.14
Options Exercisable
Shares	669
Aggregate Intrinsic Value	$ 742
Weighted Average Remaining Contractual life	6 years 4 months 24 days
Weighted-Average Exercise Price (in dollars per share)	$ 34.63
$48.90 - $51.70
Information about stock options outstanding
Exercise price, low end of range (in dollars per share)	$ 48.90
Exercise price, high end of range (in dollars per share)	$ 51.70
Options Outstanding
Shares	229
Weighted-Average Remaining Contractual Life	6 years 4 months 24 days
Weighted-Average Exercise Price (in dollars per share)	$ 51.21
Options Exercisable
Shares	229
Weighted Average Remaining Contractual life	6 years 4 months 24 days
Weighted-Average Exercise Price (in dollars per share)	$ 51.21
Stock Options
Assumptions based on which fair value of each option granted was estimated using the Black-Scholes option-pricing model
Weighted average fair value	$ 11.58	$ 13.47	$ 15.56
Dividend yield	0.00%	0.00%	0.00%
Expected volatility factor	44.00%	49.00%	59.00%
Risk-free interest rate	1.19%	1.27%	0.70%
Expected life (in years)	3 years 10 months 24 days	4 years 6 months	4 years 6 months