Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Cash Flow from Operating Activities:
Net Income	$ 239	$ 212
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	197	205
Accretion expenses	3	3
Regulatory assets/liabilities amortization	19	41
Regulatory assets/liabilities carrying cost	10	10
Pension cost	28	33
Stock-based compensation	1	1
Earnings from equity method investments	(2)	(2)
Amortization of debt cost (premium)	2	(7)
Gain on disposal of property and equity method investment		(31)
Unrealized (gain) loss on marked-to-market derivative contracts	(27)	29
Deferred taxes	95	106
Other non-cash items	(22)	(3)
Changes in operating assets and liabilities:
Accounts receivable and unbilled revenues	11	16
Inventories	11	75
Other assets/liabilities	64	(129)
Cash distribution from equity method investments	3	3
Accounts payable and accrued liabilities	(155)	(108)
Taxes accrued	9	9
Regulatory assets/liabilities	(45)	(67)
Net Cash Provided by Operating Activities	441	396
Cash Flow from Investing Activities:
Capital expenditures	(525)	(276)
Contributions in aid of construction	6	8
Government grants		1
Proceeds from sale of property, plant and equipment	1
Proceeds from sale of equity method and other investment		54
Receipts from affiliates		6
Cash distribution from equity method investments	2	2
Other investments and equity method investments, net	2	4
Net Cash Used in Investing Activities	(514)	(201)
Cash Flow from Financing Activities:
Repayments of non-current debt	(4)	(42)
Receipts (repayments) of other short-term debt, net	205	(160)
Payments on tax equity financing arrangements	(27)	(17)
Repayments of capital leases	(27)	(1)
Issuance of common stock	(1)
Dividends paid	(134)
Net Cash Provided by (Used in) Financing Activities	12	(220)
Net Decrease in Cash, Cash Equivalents and Restricted Cash	(61)	(25)
Cash, Cash Equivalents and Restricted Cash, Beginning of Period	96	434	$ 434
Cash, Cash Equivalents and Restricted Cash, End of Period	35	409	$ 96
Supplemental Cash Flow Information
Cash paid for interest, net of amounts capitalized	45	57
Cash paid for income taxes	$ 3	$ 5