Stock Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended			16 Months Ended	20 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 08, 2018	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum exercise price to fair market value on the date of grant (as a percent)	100.00%
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period				5 years	10 years
Stock Option Activity Roll Forward, Number of Shares
Options exercised (in shares)	(388,174)	(243,502)	(386,300)
Summary of intrinsic value
Intrinsic value for the options outstanding	$ 1.2				$ 1.2
Intrinsic value for the options exercisable	$ 0.7				$ 0.7
Employee nonstatutory stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 17.94	$ 12.30	$ 13.00
Stock Option Activity Roll Forward, Number of Shares
Options outstanding at the beginning of the period (in shares)	1,873,795	1,813,450	1,940,785	1,940,785
Options exercised (in shares)	(388,174)	(243,502)	(386,300)
Options forfeited (in shares)	(35,216)	(90,862)	(34,545)
Options terminated (in shares)	(74,583)	(33,481)	(23,320)
Options granted (in shares)	189,787	428,190	316,830
Options outstanding at the end of the period (in shares)	1,565,609	1,873,795	1,813,450		1,565,609
Stock Option Activity Roll Forward, Average Exercise Price
Average exercise price at the beginning of the period (in dollars per share)	$ 72.34	$ 72.04	$ 66.83	$ 66.83
Options exercised (in dollars per share)	74.33	61.92	45.21
Options forfeited (in dollars per share)	71.21	69.82	72.97
Options terminated (in dollars per share)	77.30	75.07	75.60
Options granted (in dollars per share)	78.11	67.36	71.37
Average exercise price at the end of the period (in dollars per share)	$ 72.30	$ 72.34	$ 72.04		$ 72.30
Stock Option Activity Roll Forward, Non-vested, Number of Shares
Nonvested options outstanding at the beginning of the period (in shares)	506,593	664,363			506,593
Options granted (in shares)	189,787	428,190	316,830
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares	(237,758)
Forfeited (in shares)	(109,799)
Stock Option Activity Roll Forward, Non-vested, Weighted-Average Grant Date Fair Value
Share-based Compensation Arrangement by Share-based Payment Award, Option, Nonvested, Weighted Average Exercise Price	$ 14.81	$ 12.88			$ 14.81
Vested/Exercised (in dollars per share)	16.98
Forfeited (in dollars per share)	$ 19.25
Summary of intrinsic value
Total intrinsic value of all options exercised	$ 0.8	$ 1.6	$ 10.3
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan vesting period	1 year
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan vesting period	3 years