Stock-Based Compensation - Restricted Stock Units (Details) - Restricted stock units - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested in period, fair value	$ 8.8	$ 7.7	$ 3.6
Number of Shares (in shares)
Unvested at beginning of period (in shares)	2,359,261
Granted (in shares)	1,157,679
Forfeited (in shares)	(75,349)
Vested (in shares)	(402,571)
Unvested at end of period (in shares)	3,039,020	2,359,261
Weighted- Average Grant Date Fair Value (in dollars per share)
Unvested at beginning of period (in dollars per share)	$ 23.95
Granted (in dollars per share)	43.26
Forfeited (in dollars per share)	32.16
Vested (in dollars per share)	21.75
Unvested at end of period (in dollars per share)	$ 31.39	$ 23.95
Number of vested shares recipient elected to defer settlement (in shares)	256,660
Number of vested shares recipients elected to defer settlement, released during period (in shares)	274,079
Number of deferred shares vested and outstanding (in shares)	537,202
Unrecognized compensation expense	$ 60.3
Unrecognized compensation expense, period for recognition (years)	2 years 4 months 24 days
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (years)	3 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (years)	4 years
Cliff-vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (years)	3 years
Cliff-vesting | Board of Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (years)	1 year