Supplementary Information - Condensed Consolidating Financial Information - Condensed Consolidating Statement of Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net income	$ 72	$ 69
Other comprehensive income (loss):
Reclassification of cash flow hedge losses into earnings	0	1
Other comprehensive income from consolidated subsidiaries	0	0
Total other comprehensive income	0	1
Total comprehensive income	72	70
Total comprehensive income (loss) attributable to noncontrolling interests	0	0
Total comprehensive income attributable to partners	72	70
Parent Guarantor [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	72	69
Other comprehensive income (loss):
Reclassification of cash flow hedge losses into earnings	0	0
Other comprehensive income from consolidated subsidiaries	0	1
Total other comprehensive income	0	1
Total comprehensive income	72	70
Total comprehensive income (loss) attributable to noncontrolling interests	0	0
Total comprehensive income attributable to partners	72	70
Subsidiary Issuer [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	72	69
Other comprehensive income (loss):
Reclassification of cash flow hedge losses into earnings	0	1
Other comprehensive income from consolidated subsidiaries	0	0
Total other comprehensive income	0	1
Total comprehensive income	72	70
Total comprehensive income (loss) attributable to noncontrolling interests	0	0
Total comprehensive income attributable to partners	72	70
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	96	91
Other comprehensive income (loss):
Reclassification of cash flow hedge losses into earnings	0	0
Other comprehensive income from consolidated subsidiaries	0	0
Total other comprehensive income	0	0
Total comprehensive income	96	91
Total comprehensive income (loss) attributable to noncontrolling interests	0	0
Total comprehensive income attributable to partners	96	91
Consolidating Adjustments [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	(168)	(160)
Other comprehensive income (loss):
Reclassification of cash flow hedge losses into earnings	0	0
Other comprehensive income from consolidated subsidiaries	0	(1)
Total other comprehensive income	0	(1)
Total comprehensive income	(168)	(161)
Total comprehensive income (loss) attributable to noncontrolling interests	0	0
Total comprehensive income attributable to partners	$ (168)	$ (161)