Pension Plans and Other Postretirement Benefit Plans - Components of Net Periodic Benefit Cost (Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined contribution retirement plan
Percentage that the employer contributes of employee contributions under 401(k) plan			100.00%
Maximum percentage of employee compensation match by employer to defined contribution plan			6.00%
Costs related to defined contribution retirement plan	$ 3.5	$ 3.3	$ 10.4	$ 9.4