Investments in Unconsolidated Affiliate (Details) (USD $) In Millions, unless otherwise specified		1 Months Ended	9 Months Ended	12 Months Ended	5 Months Ended	12 Months Ended
	Dec. 31, 2012	Sep. 30, 2013 Four Star	Dec. 31, 2012 Four Star	Dec. 31, 2013 Four Star	May 24, 2012 Four Star Predecessor	Dec. 31, 2011 Four Star Predecessor
Investments in Unconsolidated Affiliate
Net proceeds from sale of equity investment		$ 183		$ 183
Impairment on investment		20		20
Investment in unconsolidated affiliate	220		220
Excess of investment relative to the underlying equity in the net assets			125
Operating results:
Operating revenues			105	142	75	257
Operating expenses			87	94	58	167
Net income			11	30	11	60
Financial position data:
Current assets			64
Non-current assets			241
Current liabilities			51
Non-current liabilities			133
Equity in net assets			121
Amortization of investment in unconsolidated affiliates			7	8	12	34
Dividend received			$ 13	$ 24	$ 8	$ 46