Stock-Based Compensation - Restricted Stock Units (Details) - Restricted stock units - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested in period, fair value	$ 21.5	$ 6.3
Number of Shares (in shares)
Unvested at beginning of period (in shares)	3,039,020
Granted (in shares)	882,672
Forfeited (in shares)	(243,540)
Vested (in shares)	(671,435)
Unvested at end of period (in shares)	3,006,717
Weighted- Average Grant Date Fair Value (in dollars per share)
Unvested at beginning of period (in dollars per share)	$ 31.39
Granted (in dollars per share)	43.00
Forfeited (in dollars per share)	37.02
Vested (in dollars per share)	31.90
Unvested at end of period (in dollars per share)	$ 35.09
Number of vested shares recipient elected to defer settlement (in shares)	409,302
Number of vested shares recipients elected to defer settlement, released during period (in shares)	7,420
Number of deferred shares vested and outstanding (in shares)	939,084
Unrecognized compensation expense	$ 69.9
Unrecognized compensation expense, period for recognition (years)	2 years 7 months 6 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