Bradley Agreement - Schedule of Deficiency Payments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Balance at beginning of year	$ 11.6	$ 13.3	$ 14.6
Deficiency payments made	0.2	0.1	0.0
Deficiency repayment received	(1.9)	(1.8)	(1.3)
Balance at end of year	$ 9.9	$ 11.6	$ 13.3