Stock-Based Compensation - Summary of Certain Data for Stock-Based Compensation Plans (Details) - USD ($) $ in Millions	3 Months Ended	4 Months Ended	5 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2019	Jun. 02, 2019	Sep. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based compensation expense	$ 1.7	$ 1.6	$ 1.8	$ 0.0	$ 5.9
Tax (expense) benefit for stock-based compensation	0.4	0.4	0.4	0.0	1.1
Fair value of vested awards	$ 2.1	$ 2.0	$ 2.2	$ 0.0	$ 7.0

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

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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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