Supplementary Information - Condensed Consolidating Financial Information - Condensed Consolidating Statements of Cash Flows (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	$ 188	$ 188
Payments for (Proceeds from) Other Investing Activities	0	0
INVESTING ACTIVITIES:
Capital expenditures	(10)	(65)
Investments in unconsolidated affiliates, net	8	25
Net cash used in investing activities	(18)	(90)
Proceeds from (Payments for) Other Financing Activities	0	0
FINANCING ACTIVITIES:
Proceeds from long-term debt	394	162
Repayments of Long-term Debt	442	(162)
Proceeds from issuance of common units, net of offering cost	0	31
Payments of Ordinary Dividends	(121)	(120)
Distributions to noncontrolling interests	(2)	(1)
Payments of Capital Distribution	(121)	(120)
Net cash used in financing activities	(171)	(90)
Net change in cash and cash equivalents	(1)	8
Cash and cash equivalents, beginning of period	2	25
Cash and cash equivalents, end of period	1	33
Parent Guarantor [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	0	0
Payments for (Proceeds from) Other Investing Activities	121	89
INVESTING ACTIVITIES:
Capital expenditures	0	0
Investments in unconsolidated affiliates, net	0	0
Net cash used in investing activities	121	89
Proceeds from (Payments for) Other Financing Activities	0	0
FINANCING ACTIVITIES:
Proceeds from long-term debt	0	0
Repayments of Long-term Debt	0	0
Proceeds from issuance of common units, net of offering cost		31
Payments of Ordinary Dividends	(121)	(120)
Distributions to noncontrolling interests	0	0
Net cash used in financing activities	(121)	(89)
Net change in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Subsidiary Issuer [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	(11)	(8)
Payments for (Proceeds from) Other Investing Activities	59	16
INVESTING ACTIVITIES:
Capital expenditures	0	0
Investments in unconsolidated affiliates, net	0	0
Net cash used in investing activities	59	16
Proceeds from (Payments for) Other Financing Activities	0	0
FINANCING ACTIVITIES:
Proceeds from long-term debt	394	162
Repayments of Long-term Debt	442	(162)
Proceeds from issuance of common units, net of offering cost		0
Payments of Ordinary Dividends	0	0
Distributions to noncontrolling interests	0	0
Net cash used in financing activities	(48)	0
Net change in cash and cash equivalents	0	8
Cash and cash equivalents, beginning of period	0	24
Cash and cash equivalents, end of period	0	32
Non-Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	199	196
Payments for (Proceeds from) Other Investing Activities	0	0
INVESTING ACTIVITIES:
Capital expenditures	(10)	(65)
Investments in unconsolidated affiliates, net	8	25
Net cash used in investing activities	(18)	(90)
Proceeds from (Payments for) Other Financing Activities	(180)	(105)
FINANCING ACTIVITIES:
Proceeds from long-term debt	0	0
Repayments of Long-term Debt	0	0
Proceeds from issuance of common units, net of offering cost		0
Payments of Ordinary Dividends	0	0
Distributions to noncontrolling interests	(2)	(1)
Net cash used in financing activities	(182)	(106)
Net change in cash and cash equivalents	(1)	0
Cash and cash equivalents, beginning of period	2	1
Cash and cash equivalents, end of period	1	1
Consolidating Adjustments [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	0	0
Payments for (Proceeds from) Other Investing Activities	(180)	(105)
INVESTING ACTIVITIES:
Capital expenditures	0	0
Investments in unconsolidated affiliates, net	0	0
Net cash used in investing activities	(180)	(105)
Proceeds from (Payments for) Other Financing Activities	180	105
FINANCING ACTIVITIES:
Proceeds from long-term debt	0	0
Repayments of Long-term Debt	0	0
Proceeds from issuance of common units, net of offering cost		0
Payments of Ordinary Dividends	0	0
Distributions to noncontrolling interests	0	0
Net cash used in financing activities	180	105
Net change in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	$ 0	$ 0