Goodwill and Other Intangible Assets - Changes in Carrying Amount of Definite-Lived Intangible Assets (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross carrying value		$ 112.8	$ 93.8
Accumulated amortization		(22.1)	(13.4)
Net carrying value		90.7	80.4
Total intangible assets (excluding goodwill), gross carrying value		185.0	156.5
Total intangible assets (excluding goodwill), net		$ 162.9	143.1
Definite-lived intangible asset, useful life		12 years
Amortization expense		$ 8.8	8.0	$ 4.8
Estimated amortization of intangibles, year one		9.6
Estimated amortization of intangibles, year two		9.6
Estimated amortization of intangibles, year three		9.5
Estimated amortization of intangibles, year four		9.3
Estimated amortization of intangibles, year five		9.3
Estimated amortization of intangibles, thereafter		43.4
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	[1]	108.6	90.9
Accumulated amortization	[1]	(20.5)	(12.1)
Net carrying value	[1]	88.1	78.8
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	[1]	4.2	2.9
Accumulated amortization	[1]	(1.6)	(1.3)
Net carrying value	[1]	$ 2.6	$ 1.6
Definite-lived intangible asset, useful life		8 years

[1] Average useful life of customer relationships and other definite-lived intangible assets are estimated to be approximately 12 years and eight years, respectively. The average useful life across all definite-lived intangible assets is estimated to be approximately 12 years.