Debt and Credit Facility, Additional Information Regarding Convertible Notes (Details) - Convertible Notes Payable - Convertible Notes - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Contractual coupon interest	$ 2.0	$ 7.9	$ 7.9
Amortization of discount	2.4	9.1	8.2
Amortization of deferred financing costs	0.3	1.1	1.2
Total interest expense	$ 4.7	$ 18.1	$ 17.3