Long-Term Debt (Components Of Long-Term Debt) (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Deferred Finance Costs, Net	$ 33.8	$ 34.0	$ 40.9
Total debt	1,565.1	1,523.7
Less: current portion	14.8	1.0	1.1
Total long-term debt, less current portion	1,550.3	1,522.7	2,501.8
Crestwood Midstream Partners LP
Debt Instrument [Line Items]
Total debt		1,523.7	2,502.7
Less: current portion	14.8	1.0	0.9
Total long-term debt, less current portion	1,550.3	1,522.7	2,501.8
Crestwood Equity Partners LP
Debt Instrument [Line Items]
Total debt		1,523.7	2,502.9
Obligations under noncompetition agreements and notes to former owners of businesses acquired		0.0	0.2
Senior Notes, 2020 \| Crestwood Midstream Partners LP
Debt Instrument [Line Items]
Senior notes	13.9	340.6	503.3
Senior Notes, 2022
Debt Instrument [Line Items]
Deferred Finance Costs, Net	6.8
Senior Notes, 2022 \| Crestwood Midstream Partners LP
Debt Instrument [Line Items]
Senior notes	0.0	429.3	588.4
Senior Notes, 2023 \| Crestwood Midstream Partners LP
Debt Instrument [Line Items]
Senior notes	691.0	690.6	689.4
Senior Notes, 2025 \| Crestwood Midstream Partners LP
Debt Instrument [Line Items]
Senior notes	491.6	0.0
Senior Notes \| Senior Notes, 2020
Debt Instrument [Line Items]
Senior notes	13.8	338.8	500.0
Senior Notes \| Senior Notes, 2022
Debt Instrument [Line Items]
Senior notes	0.0	436.4	600.0
Senior Notes \| Senior Notes, 2023
Debt Instrument [Line Items]
Senior notes	700.0	700.0	700.0
Senior Notes \| Senior Notes, 2025
Debt Instrument [Line Items]
Senior notes	500.0	0.0
Fair value adjustment of 2020 Senior Notes \| Senior Notes, 2020
Debt Instrument [Line Items]
Fair value adjustment	0.1	1.8	3.3
Other
Debt Instrument [Line Items]
Other	3.3	3.7	5.3
Revolving Credit Facility \| Crestwood Midstream Revolver
Debt Instrument [Line Items]
Credit agreement outstanding carrying value	$ 381.7	$ 77.0	$ 735.0

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Obligations under noncompetition agreements and notes to former owners of businesses acquired

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Represents the aggregate of total long-term debt, including current maturities and short-term debt.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount of long-term debt classified as other.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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