Fair Value Measurements (Schedule of Carrying Values and Estimated Fair Values of Senior Notes) (Detail) - Crestwood Midstream Partners LP - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Senior Notes, 2020
Debt Instrument [Line Items]
Carrying amount	$ 13.9	$ 340.6	$ 503.3
Fair value	14.2	350.2	382.3
Senior Notes, 2022
Debt Instrument [Line Items]
Carrying amount	0.0	429.3	588.4
Fair value	0.0	447.3	437.4
Senior Notes, 2023
Debt Instrument [Line Items]
Carrying amount	691.0	690.6	689.4
Fair value	728.6	722.6	$ 491.8
Senior Notes, 2025
Debt Instrument [Line Items]
Carrying amount	491.6	0.0
Fair value	$ 511.3	$ 0.0

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13476-108611

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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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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16(a))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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