Other Assets - Restricted Investments (Details) - Restricted - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Investments
Expense for fair value of assets, less expenses, allocated to participants			$ 1.1	$ 1.1
Maximum
Investments
Expense period			2 years
Gain (loss) on assets	$ 0.1	$ 0.1	$ 0.1	$ 0.1