Stock-Based Compensation - Range of Exercise Prices (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Common stock options
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Total intrinsic value of stock options exercised during the period	$ 16.5	$ 5.6	$ 4.3
Unrecognized compensation expense related to unvested stock options	$ 31.1
Expected weighted average period for recognizing unrecognized compensation expense	2 years 7 months 6 days
$3.03 to $10.85
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	$ 3.03
Range of Exercise Prices upper range limit (in dollars per share)	$ 10.85
Number of Options outstanding (in shares)	1,419,872
Weighted Average Remaining Contractual Term (in Years)	4 years 7 months 17 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 7.55
Number of Options exercisable (in shares)	1,311,142
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 7.27
$11.14 to $13.67
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	11.14
Range of Exercise Prices upper range limit (in dollars per share)	$ 13.67
Number of Options outstanding (in shares)	1,547,063
Weighted Average Remaining Contractual Term (in Years)	5 years 5 months 8 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 12.91
Number of Options exercisable (in shares)	1,237,855
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 12.76
$13.91 to $13.91
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	13.91
Range of Exercise Prices upper range limit (in dollars per share)	$ 13.91
Number of Options outstanding (in shares)	2,661,040
Weighted Average Remaining Contractual Term (in Years)	9 years 3 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 13.91
Number of Options exercisable (in shares)	0
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 0
$13.94 to $16.16
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	13.94
Range of Exercise Prices upper range limit (in dollars per share)	$ 16.16
Number of Options outstanding (in shares)	1,394,176
Weighted Average Remaining Contractual Term (in Years)	5 years 6 months 25 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 15.59
Number of Options exercisable (in shares)	1,180,091
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 15.56
$16.44 to $19.47
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	16.44
Range of Exercise Prices upper range limit (in dollars per share)	$ 19.47
Number of Options outstanding (in shares)	1,112,775
Weighted Average Remaining Contractual Term (in Years)	7 years 1 month 28 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 17.75
Number of Options exercisable (in shares)	696,563
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 17.88
$19.65 to $24.22
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	19.65
Range of Exercise Prices upper range limit (in dollars per share)	$ 24.22
Number of Options outstanding (in shares)	1,139,884
Weighted Average Remaining Contractual Term (in Years)	6 years 14 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 22.29
Number of Options exercisable (in shares)	892,465
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 22.25
$24.21 to $30.46
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	24.41
Range of Exercise Prices upper range limit (in dollars per share)	$ 30.46
Number of Options outstanding (in shares)	1,058,332
Weighted Average Remaining Contractual Term (in Years)	8 years 2 months 12 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 29.12
Number of Options exercisable (in shares)	339,295
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 29.46
$30.86 to $31.73
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	30.86
Range of Exercise Prices upper range limit (in dollars per share)	$ 31.73
Number of Options outstanding (in shares)	131,180
Weighted Average Remaining Contractual Term (in Years)	8 years 1 month 2 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 30.94
Number of Options exercisable (in shares)	48,407
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 30.96
$31.78 to $31.78
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	31.78
Range of Exercise Prices upper range limit (in dollars per share)	$ 31.78
Number of Options outstanding (in shares)	21,794
Weighted Average Remaining Contractual Term (in Years)	7 years 5 months 23 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 31.78
Number of Options exercisable (in shares)	11,439
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 31.78
$32.46 to $32.46
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	32.46
Range of Exercise Prices upper range limit (in dollars per share)	$ 32.46
Number of Options outstanding (in shares)	6,830
Weighted Average Remaining Contractual Term (in Years)	8 years
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 32.46
Number of Options exercisable (in shares)	2,561
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 32.46