Recent Accounting Standards Recent Accounting Standards (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Postretirement costs/(benefits)	$ 0.8	$ (0.5)	$ 1.6
Restricted cash	$ 2.3	$ 3.1	$ 2.3	$ 2.5	$ 3.2