Fair Value Measurements (Schedule of Carrying Values and Estimated Fair Values of Senior Notes) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Senior Notes	$ 11.4	$ 11.4
Long-term Debt	2,391.3	2,266.0
Notes Payable, Fair Value Disclosure	11.6	11.6
Nrgm Credit Facility
Debt Instrument [Line Items]
Senior Notes		500.0
CMLP \| Crestwood Midstream Senior Notes
Debt Instrument [Line Items]
Notes Payable, Fair Value Disclosure	624.0	617.3
CMLP \| Senior Notes
Debt Instrument [Line Items]
Senior Notes	351.2	351.2
Notes Payable, Fair Value Disclosure	381.5	379.3
CMLP \| Nrgm Credit Facility
Debt Instrument [Line Items]
Senior Notes	504.5	504.7
Notes Payable, Fair Value Disclosure	$ 528.4	$ 513.8

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents notes payable as of the balance sheet date.

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