Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Accounting for Stock Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
	Apr. 04, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Allocated share-based compensation expense		$ 4.0	$ 5.9
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				166,051
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period, weighted average grant date fair value				$ 57.82
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized		17.9		$ 17.9
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition				2 years 2 months 12 days
Cash Settled RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				112,479
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period, weighted average grant date fair value				$ 57.85
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized		9.4		$ 9.4
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition				1 year 10 months 24 days
Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				55,264
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period, weighted average grant date fair value				$ 58.76
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized		$ 3.8		$ 3.8
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition				1 year 7 months 6 days
Omnibus Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares grants	1,185,000			107,141
Share-based compensation arrangement by share-based payment award, number of additional awards				0
Share-based compensation arrangement by share-based payment award, number of shares available for grant		1,095,772		1,095,772