CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Cash Flows [Abstract]
Proceeds from SUGS Contribution	$ 0	$ 0	$ 482
OPERATING ACTIVITIES:
Net income (loss)	105	(39)	(535)
Reconciliation of net income to net cash provided by operating activities:
Depreciation and amortization	133	130	189
Goodwill Impairment	0	0	689
Deferred income taxes	31	(108)	181
Amortization of deferred financing fees	(23)	(22)	(30)
Unrealized gain on derivatives	0	(25)	(52)
(Income) loss from unconsolidated affiliates	(26)	12	(15)
Distributions of earnings received from unconsolidated affiliates	9	6	15
Other non-cash	13	6	33
Changes in operating assets and liabilities	(66)	197	(159)
Net cash flows provided by operating activities	176	157	316
INVESTING ACTIVITIES:
Proceeds from SUGS Contribution	0	20	0
Proceeds from sale of MGE assets, net of transaction costs	0	0	1,008
Proceeds from affiliates	40	0	0
Increase (Decrease) in Notes Receivable, Related Parties, Current	(40)	0	0
Capital expenditures	(128)	(109)	(250)
Distributions from unconsolidated affiliates in excess of cumulative earnings	46	65	39
Other	2	(16)	5
Net cash flows (used in) provided by investing activities	(80)	(40)	1,284
FINANCING ACTIVITIES:
Distribution Made to Limited Partner, Cash Distributions Paid	125	102	313
Issuance of loans from affiliates	0	0	1,669
Repayments of loans from affiliates	0	0	(975)
Repayment of long-term debt	0	0	(1,795)
Net change in revolving credit facilities	0	0	(210)
Other	0	0	(8)
Net cash flows used in financing activities	(125)	(102)	(1,632)
NET CHANGE IN CASH AND CASH EQUIVALENTS	(29)	15	(32)
CASH AND CASH EQUIVALENTS, beginning of period	32	17	49
CASH AND CASH EQUIVALENTS, end of period	$ 3	$ 32	$ 17