Long-term Equity-based Compensation -Schedule of Share-based Compensation, Nonemployee Director Deferred Stock Unit Award Plan (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Schedule of Share-based Compensation, Nonemployee Director Deferred Stock Unit Award Plan [Abstract]
Total fair value of DSUs that vested during the years	$ 0.2	$ 0.1
Deferred Stock Units, Outstanding, Number, Period Start	4,000
Deferred Stock Units, Outstanding, Weighted Average Exercise Price, Period Start (per share)	$ 31.50
Deferred Stock Units, Granted and Vested in Period	4,000
Deferred Stock Units, Granted and Vested in Period, Weighted Average Exercise Price (per share)	$ 37.53
Deferred Stock Units, Outstanding, Number, Period End	8,000	4,000
Deferred Stock Units, Outstanding, Weighted Average Exercise Price, Period End (per share)	$ 34.52	$ 31.50