Discontinued Operations - Reconciliation of Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses:
Loss from discontinued operations	$ 0.0	$ (2.5)	$ 0.0	$ (4.8)
T-System Holdings, Inc. | Discontinued Operations, Held-for-sale
Revenues:
Other operating revenue		12.9		25.1
Total operating revenues		12.9		25.1
Operating expenses:
Personnel costs		7.8		16.1
Depreciation and amortization		3.4		6.9
Other operating expenses		4.8		8.7
Total operating expenses		16.0		31.7
Operating loss		(3.1)		(6.6)
Realized loss		(0.5)		(0.5)
Total other expense		(0.5)		(0.5)
Loss from discontinued operations before income taxes		(3.6)		(7.1)
Income tax benefit		(1.1)		(2.3)
Loss from discontinued operations		$ (2.5)		$ (4.8)