Deferred Charges (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Deferred Charges [Abstract]
Amortization expense for deferred charges	$ 3.2	$ 4.8
Gross deferred charges	44.2		$ 48.5
Accumulated amortization of deferred charges	$ 21.2		$ 25.5