Stock Option and Compensation Plans - Options Outstanding and Exercisable by Exercise Price and Options Exercised (Details) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares shares
Options Outstanding
Total Options Outstanding (in shares) | shares	3,805
Weighted Average Remaining Life (Years)	7 years 9 months 7 days
Weighted Average Exercise Price (in dollars per share)	$ 28.18
Aggregate Intrinsic Value of Options Outstanding | $	$ 83
Options Exercisable
Number Exercisable (in shares) | shares	1,831
Weighted Average Exercise Price (in dollars per share)	$ 34.12
Aggregate Intrinsic Value of Options Exercisable | $	$ 78
$0.12-$10.03
Options Outstanding
Total Options Outstanding (in shares) | shares	1,346
Weighted Average Remaining Life (Years)	9 years 1 day
Weighted Average Exercise Price (in dollars per share)	$ 4.72
Options Exercisable
Number Exercisable (in shares) | shares	181
Weighted Average Exercise Price (in dollars per share)	$ 7.25
Exercise prices, low end of range (in dollars per share)	0.12
Exercise prices, high end of range (in dollars per share)	$ 10.03
$10.04-$20.00
Options Outstanding
Total Options Outstanding (in shares) | shares	255
Weighted Average Remaining Life (Years)	5 years 11 months 26 days
Weighted Average Exercise Price (in dollars per share)	$ 13.46
Options Exercisable
Number Exercisable (in shares) | shares	196
Weighted Average Exercise Price (in dollars per share)	$ 13.51
Exercise prices, low end of range (in dollars per share)	10.04
Exercise prices, high end of range (in dollars per share)	$ 20.00
$20.01-$30.00
Options Outstanding
Total Options Outstanding (in shares) | shares	127
Weighted Average Remaining Life (Years)	6 years 4 months 13 days
Weighted Average Exercise Price (in dollars per share)	$ 25.13
Options Exercisable
Number Exercisable (in shares) | shares	112
Weighted Average Exercise Price (in dollars per share)	$ 25.12
Exercise prices, low end of range (in dollars per share)	20.01
Exercise prices, high end of range (in dollars per share)	$ 30.00
$30.01-$40.00
Options Outstanding
Total Options Outstanding (in shares) | shares	910
Weighted Average Remaining Life (Years)	6 years 26 days
Weighted Average Exercise Price (in dollars per share)	$ 32.70
Options Exercisable
Number Exercisable (in shares) | shares	779
Weighted Average Exercise Price (in dollars per share)	$ 32.84
Exercise prices, low end of range (in dollars per share)	30.01
Exercise prices, high end of range (in dollars per share)	$ 40.00
$40.01-$55.00
Options Outstanding
Total Options Outstanding (in shares) | shares	754
Weighted Average Remaining Life (Years)	8 years 11 days
Weighted Average Exercise Price (in dollars per share)	$ 46.43
Options Exercisable
Number Exercisable (in shares) | shares	390
Weighted Average Exercise Price (in dollars per share)	$ 45.83
Exercise prices, low end of range (in dollars per share)	40.01
Exercise prices, high end of range (in dollars per share)	$ 55.00
$55.01-$73.22
Options Outstanding
Total Options Outstanding (in shares) | shares	413
Weighted Average Remaining Life (Years)	8 years 6 months 15 days
Weighted Average Exercise Price (in dollars per share)	$ 71.41
Options Exercisable
Number Exercisable (in shares) | shares	173
Weighted Average Exercise Price (in dollars per share)	$ 70.78
Exercise prices, low end of range (in dollars per share)	55.01
Exercise prices, high end of range (in dollars per share)	$ 73.22