QUARTERLY OPERATIONS Quarterly Operations (Details) - USD ($) $ in Millions	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash and Cash Equivalents, at Carrying Value	$ 3	$ 30	$ 65	$ 47	$ 32	$ 55	$ 32	$ 74	$ 65	$ 32	$ 30	$ 55	$ 3	$ 32	$ 17	$ 49
Gas Domestic Regulated Revenue	135	121	123	149	138	125	122	170					528	555	576
Operating revenues	139	126	128	155	143	132	128	178					548	581	1,085
Operating income	43	26	31	53	38	31	34	90					153	193	(382)
Income Tax Expense (Benefit)	17	23	0	12	47	8	23	104	12	127	35	135	52	182	98
Net income (loss)	30	25	19	31	(36)	23	7	(33)	50	(26)	75	(3)	105	(39)	(535)
Net income (loss) attributable to partners	30	25	19	31	(36)	23	7	(39)	50	(32)	75	(9)	105	(45)	(499)
Other Revenue, Net	4	5	5	6	5	7	6	8					20	26	293
Cost of Goods Sold	0	1	1	2	0	1	2	0					4	3	228
Operating Costs and Expenses	57	56	50	53	58	55	49	47					216	209	248
General and Administrative Expense	7	12	11	12	13	12	11	10					42	46	113
Depreciation, Depletion and Amortization, Nonproduction	32	31	35	35	34	33	32	31					133	130	189
Costs and Expenses	96	100	97	102	105	101	94	88					395	388	1,467
Interest Expense	(12)	(13)	(12)	(13)	(20)	(15)	(19)	(12)					(50)	(66)	(111)
Income (Loss) from Equity Method Investments	0	28	(6)	4	(19)	9	6	(8)					26	(12)	15
Interest Income, Related Party	16	6	1	0	6	5	7	5					23	23	9
Other Nonoperating Income (Expense)	0	1	5	(1)	6	1	2	(4)					5	5	(3)
Nonoperating Income (Expense)	4	22	(12)	(10)	(27)	0	(4)	(19)					4	(50)	(90)
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	47	48	19	43	11	31	30	71					157	143	(472)
Net Income (Loss) Attributable to Noncontrolling Interest	0	0	0	0	0	0	0	6					0	6	(36)
Accounts Receivable, Net, Current	48	41	40	51	58	51	51	55	40	51	41	51	48	58
Due from Related Parties, Current	172	120	54	42	128	30	57	33	54	57	120	30	172	128
Gas Balancing Asset (Liability)	5	9	10	12	11	17	45	62	10	45	9	17	5	11
Inventory, Net	113	99	106	83	119	115	147	160	106	147	99	115	113	119
Other Assets, Current	9	15	13	13	10	48	20	15	13	20	15	48	9	10
Assets, Current	350	314	288	248	358	316	352	399	288	352	314	316	350	358
Property, Plant and Equipment, Gross	3,338	3,456	3,428	3,403	3,395	3,360	3,331	3,316	3,428	3,331	3,456	3,360	3,338	3,395
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	286	342	319	292	269	243	215	192	319	215	342	243	286	269
Property, Plant and Equipment, Net	3,052	3,114	3,109	3,111	3,126	3,117	3,116	3,124	3,109	3,116	3,114	3,117	3,052	3,126
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	15	15	1,404	1,428	1,443	1,480	1,488	1,502	1,404	1,488	15	1,480	15	1,443
Other Assets, Noncurrent	122	127	116	110	109	106	105	95	116	105	127	106	122	109
Due from Related Parties, Noncurrent	258	0	40	40	0	0	0	0	40	0	0	0	258	0
NOTE RECEIVABLE FROM RELATED PARTY	574	1,369	40	40	0	386	386	386	40	386	1,369	386	574	0
Goodwill	923	923	1,152	1,152	1,152	1,152	1,152	1,152	1,152	1,152	923	1,152	923	1,152	1,336
Assets	5,294	5,862	6,149	6,129	6,188	6,557	6,599	6,658	6,149	6,599	5,862	6,557	5,294	6,188
Long-term Debt, Current Maturities	1	1	1	1	1	1	1	1	1	1	1	1	1	1
Accounts Payable and Accrued Liabilities, Current	3	4	4	2	6	4	5	2	4	5	4	4	3	6
Accounts Payable, Related Parties, Current	125	63	34	39	43	463	452	467	34	452	63	463	125	43
Gas Balancing Payable, Current	94	83	91	76	114	117	179	214	91	179	83	117	94	114
Interest Payable, Current	12	24	12	24	12	24	12	24	12	12	24	24	12	12
Customer Advances and Deposits, Current	9	9	11	8	10	13	21	16	11	21	9	13	9	10
Other Liabilities, Current	55	60	59	54	56	66	57	52	59	57	60	66	55	56
Liabilities, Current	299	244	212	204	242	688	727	776	212	727	244	688	299	242
Long-term Debt and Capital Lease Obligations	1,165	1,172	1,178	1,184	1,189	1,195	1,201	1,203	1,178	1,201	1,172	1,195	1,165	1,189
Deferred Tax Liabilities, Net, Noncurrent	725	779	1,534	1,542	1,539	1,458	1,467	1,467	1,534	1,467	779	1,458	725	1,539
Due to Affiliate	0	566	0	0	51	0	0	0	0	0	566	0	0	51
Other Liabilities, Noncurrent	222	289	284	279	278	296	294	282	284	294	289	296	222	278
Commitments and Contingencies
General Partners' Capital Account	2,881	2,812	2,940	2,920	2,889	2,918	2,908	2,928	2,940	2,908	2,812	2,918	2,881	2,889
Accumulated Other Comprehensive Income (Loss), Net of Tax	2	1	1	0	0	2	2	2	1	2	1	2	2	0
Partners' Capital	2,883	2,813	2,941	2,920	2,889	2,920	2,910	2,930	2,941	2,910	2,813	2,920	2,883	2,889	$ 3,068	$ 4,028
Liabilities and Equity	$ 5,294	$ 5,862	$ 6,149	$ 6,129	$ 6,188	$ 6,557	$ 6,599	$ 6,658	$ 6,149	$ 6,599	$ 5,862	$ 6,557	$ 5,294	$ 6,188