Basis of Preparation - Operating Lease Future Payments (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Future minimum lease payments
2019	$ 5.8
2020	6.3
2021	5.6
2022	5.3
2023	4.6
Thereafter	9.1
Total future minimum lease payments	$ 36.7
Future minimum lease payments
2019		$ 7.9
2020		6.9
2021		5.7
2022		5.3
2023		4.6
Thereafter		9.2
Total future minimum lease payments		$ 39.6

Amount of lessee's undiscounted obligation for lease payments for operating lease.

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Amount of lessee's undiscounted obligation for lease payments for operating lease having an initial or remaining lease term in excess of one year due in remainder of fiscal year following latest fiscal year.

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Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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