Debt (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Preferred stock, shares issued		104,574
Preferred stock, liquidation preference per share		$ 1,000
Cash paid in exchange	$ 27.6
Long-term debt, carrying amount		$ 163.7	$ 234.6
Gain on early extinguishment of debt	33.6	33.6	16.7
Transaction costs	9.0
Write off of deferred financing cost	0.4
Long-term debt, current		6.1	0.0
Subordination to credit facility, facility total		50.0
Subordination to credit facility, facility maximum net borrowing		40.0
Interest payable, cash portion		$ 0.2	1.5
Payment in Kind (PIK) Note [Member]
Repurchase of debt	$ 204.9
Debt instrument interest rate		5.50%
Interest payable		$ 0.6	4.7
Interest payable, cash portion		0.2	1.5
Interest payable, PIK portion		$ 0.4	$ 3.2
Senior Notes [Member]
Debt instrument interest rate		8.25%
Long-term debt, face amount		$ 74.3
Long-term debt, carrying amount		$ 132.4