Stock-Based Compensation - Restricted Stock Units (Details) - Restricted stock units - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested in period, fair value	$ 7.8	$ 4.3
Number of Shares (in shares)
Unvested at beginning of period (in shares)	3,039,020
Granted (in shares)	636,445
Forfeited (in shares)	(53,456)
Vested (in shares)	(286,338)
Unvested at end of period (in shares)	3,335,671
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)	45.69
Forfeited (in dollars per share)	32.91
Vested (in dollars per share)	27.23
Unvested at end of period (in dollars per share)	$ 34.47
Number of vested shares recipient elected to defer settlement (in shares)	168,966
Number of vested shares recipients elected to defer settlement, released during period (in shares)	0
Number of deferred shares vested and outstanding (in shares)	706,168
Unrecognized compensation expense	$ 79.0
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