Income Taxes (Deferred Tax Assets (Liabilities) Classification) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Other assets	$ 162.1	$ 172.8
Total deferred tax assets	162.1	172.8
Deferred tax liabilities:
Long-term income taxes	(22.2)	(22.2)
Total deferred tax liabilities	(22.2)	(22.2)
Net deferred tax assets	$ 139.9	$ 150.6