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		9 Months Ended
	Apr. 04, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Allocated share-based compensation expense		$ 4.5	$ 6.5
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				166,807
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period, weighted average grant date fair value				$ 57.89
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized		15.1		$ 15.1
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition				1 year 10 months 24 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				129,179
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period, weighted average grant date fair value				$ 59.69
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized		8.4		$ 8.4
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition				2 years
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		$ 3.0		$ 3.0
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition				1 year 3 months 18 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	1,600,000			101,901
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		1,112,118		1,112,118