CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities
Net income	$ 239,277	$ 241,312
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	368,880	323,761
Conservation and demand side management program amortization	755	1,162
Nuclear fuel amortization	30,852	25,750
Deferred income taxes	193,740	160,379
Amortization of investment tax credits	(1,278)	(1,307)
Allowance for equity funds used during construction	(14,313)	(13,113)
Equity earnings of unconsolidated subsidiaries	(7,875)	(13,182)
Dividends from unconsolidated subsidiaries	11,754	11,481
Share-based compensation expense	17,953	13,099
Net realized and unrealized hedging and derivative transactions	4,177	5,576
Other	0	(388)
Changes in operating assets and liabilities:
Accounts receivable	(4,959)	(4,780)
Accrued unbilled revenues	174,387	129,444
Inventories	88,355	88,570
Other current assets	(76,758)	(16,635)
Accounts payable	(121,390)	(22,063)
Net regulatory assets and liabilities	17,863	34,404
Other current liabilities	(42,270)	(32,442)
Pension and other employee benefit obligations	(148,565)	(118,774)
Change in other noncurrent assets	263	(1,196)
Change in other noncurrent liabilities	(12,693)	(8,508)
Net cash provided by operating activities	718,155	802,550
Investing activities
Utility capital/construction expenditures	(749,073)	(700,319)
Allowance for equity funds used during construction	14,313	13,113
Purchases of investment securities	(172,738)	(109,373)
Proceeds from the sale of investment securities	167,645	104,280
Investments in WYCO Development LLC and other	(2,571)	(260)
Other, net	(5,315)	(1,548)
Net cash used in investing activities	(747,739)	(694,107)
Financing activities
Proceeds from (repayments of) short-term borrowings, net	213,000	(663,000)
Proceeds from issuance of long-term debt	0	747,127
Repayments of long-term debt	(217)	(333)
Purchase of common stock for settlement of equity awards	(2,943)	(789)
Dividends paid	(172,456)	(162,410)
Proceeds from (Payments for) Other Financing Activities	(18,291)	(12,487)
Net cash provided by (used in) financing activities	19,093	(91,892)
Net change in cash and cash equivalents	(10,491)	16,551
Cash and cash equivalents at beginning of period	84,476	84,940
Cash and cash equivalents at end of period	73,985	101,491
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(174,381)	(164,511)
Cash received for income taxes, net	0	7,414
Supplemental disclosure of non-cash investing and financing transactions:
Property, plant and equipment additions in accounts payable	185,617	192,818
Issuance of common stock for reinvested dividends and equity awards	$ 11,673	$ 7,703