Summary of Significant Accounting Policies - Capital Leased Assets (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Capital Leased Assets [Line Items]
Capital Leased Assets, Accumulated Amortization	$ (48)	$ (39)
Capital Leased Assets, Net of Amortization	164	80
Office Building [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	61	61
Nitrogen Plant [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	83	0
Computer-Related Equipment [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	62	58
Gas Pipeline [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	$ 6	$ 0