Stock Plans (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012
Options Outstanding
Number Outstanding (in shares)	2,180,236
Weighted Average Remaining Contractual Life	6 years 1 month 20 days
Weighted Average Exercise Price (in dollars per share)	$ 17.13
Options Exercisable
Number Exercisable (in shares)	1,482,505
Weighted Average Exercise Price (in dollars per share)	$ 16.92
Range of exercise prices from $5.00 to $12.49
Stock options by exercise price range
Exercise prices, low end of range (in dollars per share)	$ 5.00
Exercise prices, high end of range (in dollars per share)	$ 12.49
Options Outstanding
Number Outstanding (in shares)	575,697
Weighted Average Remaining Contractual Life	5 years 8 months 16 days
Weighted Average Exercise Price (in dollars per share)	$ 8.41
Options Exercisable
Number Exercisable (in shares)	338,478
Weighted Average Exercise Price (in dollars per share)	$ 7.65
Range of exercise prices from $12.50 to $14.99
Stock options by exercise price range
Exercise prices, low end of range (in dollars per share)	$ 12.50
Exercise prices, high end of range (in dollars per share)	$ 14.99
Options Outstanding
Number Outstanding (in shares)	522,206
Weighted Average Remaining Contractual Life	3 years 11 months 12 days
Weighted Average Exercise Price (in dollars per share)	$ 14.15
Options Exercisable
Number Exercisable (in shares)	497,206
Weighted Average Exercise Price (in dollars per share)	$ 14.14
Range of exercise prices from $15.00 to $24.99
Stock options by exercise price range
Exercise prices, low end of range (in dollars per share)	$ 15.00
Exercise prices, high end of range (in dollars per share)	$ 24.99
Options Outstanding
Number Outstanding (in shares)	827,111
Weighted Average Remaining Contractual Life	7 years 7 months 10 days
Weighted Average Exercise Price (in dollars per share)	$ 20.41
Options Exercisable
Number Exercisable (in shares)	466,465
Weighted Average Exercise Price (in dollars per share)	$ 20.57
Range of exercise prices from $25.00 to $34.99
Stock options by exercise price range
Exercise prices, low end of range (in dollars per share)	$ 25.00
Exercise prices, high end of range (in dollars per share)	$ 34.99
Options Outstanding
Number Outstanding (in shares)	153,105
Weighted Average Remaining Contractual Life	6 years 11 months 16 days
Weighted Average Exercise Price (in dollars per share)	$ 28.37
Options Exercisable
Number Exercisable (in shares)	108,248
Weighted Average Exercise Price (in dollars per share)	$ 28.20
Range of exercise prices from $35.00 to $100.00
Stock options by exercise price range
Exercise prices, low end of range (in dollars per share)	$ 35.00
Exercise prices, high end of range (in dollars per share)	$ 100.00
Options Outstanding
Number Outstanding (in shares)	102,117
Weighted Average Remaining Contractual Life	6 years 6 months 25 days
Weighted Average Exercise Price (in dollars per share)	$ 38.05
Options Exercisable
Number Exercisable (in shares)	72,108
Weighted Average Exercise Price (in dollars per share)	$ 39.11