Stock Option and Compensation Plans - Options Outstanding and Exercisable by Exercise Price and Options Exercised (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Options Outstanding
Total Options Outstanding (in shares) | shares	5,903
Weighted Average Remaining Life (Years)	7 years 10 months 24 days
Weighted Average Exercise Price (in dollars per share)	$ 13.72
Aggregate Intrinsic Value of Options Outstanding | $	$ 3
Options Exercisable
Number Exercisable (in shares) | shares	2,709
Weighted Average Exercise Price (in dollars per share)	$ 24.07
Aggregate Intrinsic Value of Options Exercisable | $	$ 3
$0.12-$10.03
Options Outstanding
Total Options Outstanding (in shares) | shares	4,231
Weighted Average Remaining Life (Years)	8 years 9 months 18 days
Weighted Average Exercise Price (in dollars per share)	$ 3.07
Options Exercisable
Number Exercisable (in shares) | shares	1,174
Weighted Average Exercise Price (in dollars per share)	$ 4.20
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	133
Weighted Average Remaining Life (Years)	4 years 6 months
Weighted Average Exercise Price (in dollars per share)	$ 13.68
Options Exercisable
Number Exercisable (in shares) | shares	133
Weighted Average Exercise Price (in dollars per share)	$ 13.68
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	114
Weighted Average Remaining Life (Years)	4 years 4 months 24 days
Weighted Average Exercise Price (in dollars per share)	$ 24.69
Options Exercisable
Number Exercisable (in shares) | shares	114
Weighted Average Exercise Price (in dollars per share)	$ 24.69
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	680
Weighted Average Remaining Life (Years)	4 years 4 months 24 days
Weighted Average Exercise Price (in dollars per share)	$ 33.12
Options Exercisable
Number Exercisable (in shares) | shares	680
Weighted Average Exercise Price (in dollars per share)	$ 33.12
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	508
Weighted Average Remaining Life (Years)	6 years 7 months 6 days
Weighted Average Exercise Price (in dollars per share)	$ 46.61
Options Exercisable
Number Exercisable (in shares) | shares	420
Weighted Average Exercise Price (in dollars per share)	$ 46.48
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	237
Weighted Average Remaining Life (Years)	7 years
Weighted Average Exercise Price (in dollars per share)	$ 72.32
Options Exercisable
Number Exercisable (in shares) | shares	188
Weighted Average Exercise Price (in dollars per share)	$ 72.09
Exercise prices, low end of range (in dollars per share)	55.01
Exercise prices, high end of range (in dollars per share)	$ 73.22