Employee Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income:
Net actuarial loss (gain)	$ 1.6	$ 2.1	$ 4.8
Settlement charge	(1.3)	(1.6)	0.0
Amortization of actuarial (loss) gain	(0.6)	(0.6)	(0.3)
Total net loss (gain) recognized in other comprehensive income	(0.3)	(0.1)	4.5
Pension Benefits
Net Periodic Benefit Cost:
Interest cost	1.2	1.7	1.8
Expected return on plan assets	(1.8)	(2.1)	(2.5)
Amortization of net actuarial loss (gain)	0.6	0.6	0.4
Settlement charge	1.3	1.6	0.0
Net periodic benefit cost (income)	1.3	1.8	(0.3)
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income:
Net actuarial loss (gain)	2.1	1.9	5.2
Settlement charge	(1.3)	(1.6)	0.0
Amortization of actuarial (loss) gain	(0.6)	(0.6)	(0.4)
Total net loss (gain) recognized in other comprehensive income	0.2	(0.3)	4.8
Other Post-retirement Benefits
Net Periodic Benefit Cost:
Interest cost	0.2	0.1	0.1
Expected return on plan assets	0.0	0.0	0.0
Amortization of net actuarial loss (gain)	0.0	0.0	(0.1)
Settlement charge	0.0	0.0	0.0
Net periodic benefit cost (income)	0.2	0.1	0.0
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income:
Net actuarial loss (gain)	(0.5)	0.2	(0.4)
Settlement charge	0.0	0.0	0.0
Amortization of actuarial (loss) gain	0.0	0.0	0.1
Total net loss (gain) recognized in other comprehensive income	$ (0.5)	$ 0.2	$ (0.3)