Fair Value Measurements (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
EBITDA Volatility	20.00%
Equity Volatility	30.00%
9.25% Senior Notes due 2020 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of Senior Notes	$ 333.6
Class B Units [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number units to be distributed for GP Buyout
Maximum [Member] | GP Buyout Transaction [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Period of time to distribute units	6 years
Maximum [Member] | GP Buyout Transaction [Member] | Class B Units [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number units to be distributed for GP Buyout	11,600,000