CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities
Net income	$ 133,722	$ 111,546
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	122,802	115,803
Demand side management program amortization	0	336
Deferred income taxes	13,168	61,726
Amortization of investment tax credits	(700)	(701)
Allowance for equity funds used during construction	(10,944)	(4,608)
Net realized and unrealized hedging and derivative transactions	1,807	1,679
Changes in operating assets and liabilities:
Accounts receivable	(19,358)	1,086
Accrued unbilled revenues	58,369	91,100
Inventories	60,563	43,667
Prepayments and other	1,330	659
Accounts payable	(25,773)	(65,886)
Net regulatory assets and liabilities	31,072	14,345
Other current liabilities	465	17,860
Pension and other employee benefit obligations	(22,803)	(16,506)
Change in other noncurrent assets	2,465	936
Change in other noncurrent liabilities	(7,435)	479
Net cash provided by operating activities	338,750	373,521
Investing activities
Utility capital/construction expenditures	(426,730)	(272,927)
Allowance for equity funds used during construction	10,944	4,608
Investments in utility money pool arrangement	(36,000)	(38,000)
Repayments from utility money pool arrangement	56,000	38,000
Net cash used in investing activities	(395,786)	(268,319)
Financing activities
Repayments of short-term borrowings, net	95,000	(98,000)
Borrowings under utility money pool arrangement	158,000	40,000
Repayments under utility money pool arrangement	(110,000)	(40,000)
Capital contributions from parent	6,508	67,475
Dividends paid to parent	(76,195)	(74,208)
Other	(117)	(110)
Net cash provided by (used in) financing activities	73,196	(104,843)
Net change in cash and cash equivalents	16,160	359
Cash and cash equivalents at beginning of period	7,513	5,926
Cash and cash equivalents at end of period	23,673	6,285
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(60,064)	(61,252)
Cash paid for income taxes, net	(46,482)	(4,804)
Supplemental disclosure of non-cash investing transactions:
Property, plant and equipment additions in accounts payable	$ 128,493	$ 69,885