Business Segments - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) Segment Project	Mar. 31, 2015 USD ($) Project		Dec. 31, 2015
Segment Reporting Information [Line Items]
Total operating revenues	$ 379	$ 568
Number of reporting segments | Segment	3
Ownership interest percentage				100.00%
Number of owned and operated rail terminals | Project	6
Number of owned marine import terminals | Project	1
Number of leased marine terminals | Project	1
Pipeline Terminals | Project		1
Gross margin	$ 148	$ 166	[1]
Other Cost and Expense, Operating	(48)	(47)
Depreciation, Depletion and Amortization, Nonproduction	(32)	(29)
General and Administrative Expense	(21)	(21)
Earnings from unconsolidated affiliates	49	23
Interest expense	(24)	(22)
Income tax expense	0	(1)
Net income	72	69
Net income attributable to noncontrolling interests	0	0
Net Income (Loss) Attributable to Parent	72	69
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(45)	(43)
Capital expenditures	10	65
Investments in unconsolidated affiliates, net	$ 8	25
Sand Hills Pipeline [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	33.33%
Natural Gas Services [Member]
Segment Reporting Information [Line Items]
Total operating revenues	$ 305	440
Gross margin	111	119
Other Cost and Expense, Operating	(40)	(40)
Depreciation, Depletion and Amortization, Nonproduction	(29)	(26)
General and Administrative Expense	0	0
Earnings from unconsolidated affiliates	15	(2)
Interest expense	0	0
Income tax expense		0
Net income	57	51
Net income attributable to noncontrolling interests	0	0
Net Income (Loss) Attributable to Parent	57	51
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(45)	(45)
Capital expenditures	9	50
Investments in unconsolidated affiliates, net	$ 0	12
Colorado [Member]
Segment Reporting Information [Line Items]
Ownership interest percentage	75.00%
Discovery Producer Services LLC [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	40.00%
Mont Belvieu 1 Fractionator [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	20.00%
Mont Belvieu Enterprise Fractionator [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	12.50%
Southern Hills Pipeline [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	33.33%
Texas Express [Member]
Segment Reporting Information [Line Items]
Ownership interest percentage in subsidiary	10.00%
Panola [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	15.00%
NGL Logistics [Member]
Segment Reporting Information [Line Items]
Total operating revenues	$ 21	18
Gross margin	21	18
Other Cost and Expense, Operating	(5)	(4)
Depreciation, Depletion and Amortization, Nonproduction	(2)	(2)
General and Administrative Expense	0	0
Earnings from unconsolidated affiliates	34	25
Interest expense	0	0
Income tax expense		0
Net income	48	37
Net income attributable to noncontrolling interests	0	0
Net Income (Loss) Attributable to Parent	48	37
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	0	0
Capital expenditures	0	13
Investments in unconsolidated affiliates, net	8	13
Wholesale Propane Logistics [Member]
Segment Reporting Information [Line Items]
Total operating revenues	53	110
Gross margin	16	29
Other Cost and Expense, Operating	(3)	(3)
Depreciation, Depletion and Amortization, Nonproduction	(1)	(1)
General and Administrative Expense	0	0
Earnings from unconsolidated affiliates	0	0
Interest expense	0	0
Income tax expense		0
Net income	12	25
Net income attributable to noncontrolling interests	0	0
Net Income (Loss) Attributable to Parent	12	25
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	0	3
Capital expenditures	1	2
Investments in unconsolidated affiliates, net	0	0
Other [Member]
Segment Reporting Information [Line Items]
Total operating revenues	0	0
Gross margin	0	0	[1]
Other Cost and Expense, Operating	0	0
Depreciation, Depletion and Amortization, Nonproduction	0	0
General and Administrative Expense	(21)	(21)
Earnings from unconsolidated affiliates	0	0
Interest expense	(24)	(22)
Income tax expense		(1)
Net income	(45)	(44)
Net income attributable to noncontrolling interests	0	0
Net Income (Loss) Attributable to Parent	(45)	(44)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	0	(1)
Capital expenditures	0	0
Investments in unconsolidated affiliates, net	$ 0	$ 0
Front Range Pipeline [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	33.33%

[1] Gross margin consists of total operating revenues, including commodity derivative activity, less purchases of natural gas, propane and NGLs. Gross margin is viewed as a non-GAAP measure under the rules of the SEC, but is included as a supplemental disclosure because it is a primary performance measure used by management as it represents the results of product sales versus product purchases. As an indicator of our operating performance, gross margin should not be considered an alternative to, or more meaningful than, net income or cash flow as determined in accordance with GAAP. Our gross margin may not be comparable to a similarly titled measure of another company because other entities may not calculate gross margin in the same manner.