CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net income	$ 984,485	$ 1,021,306	$ 948,234
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	1,142,966	1,036,515	1,001,843
Conservation and demand side management program amortization	5,225	6,033	6,531
Nuclear fuel amortization	106,424	114,542	98,089
Deferred income taxes	535,868	569,378	515,062
Amortization of investment tax credits	(5,277)	(5,543)	(5,753)
Allowance for equity funds used during construction	(55,936)	(89,750)	(87,683)
Equity earnings of unconsolidated subsidiaries	(34,390)	(30,151)	(30,020)
Dividends from unconsolidated subsidiaries	40,128	36,707	36,416
Provision for bad debts	36,074	42,765	37,627
Share-based compensation expense	44,928	32,189	24,613
Gain on sale of transmission assets	0	0	(13,661)
Loss on Monticello life cycle management/extended power uprate project	129,463	0	0
Net realized and unrealized hedging and derivative transactions	21,919	5,506	(4,704)
Other, net	(1,326)	0	0
Changes in operating assets and liabilities:
Accounts receivable	65,826	(125,146)	(108,911)
Accrued unbilled revenues	73,625	(41,262)	(23,867)
Inventories	(11,240)	(20,558)	(43,588)
Other current assets	9,273	(111,300)	(18,071)
Accounts payable	(120,002)	(53,242)	132,441
Net regulatory assets and liabilities	102,465	195,823	141,325
Other current liabilities	66,134	137,147	126,555
Pension and other employee benefit obligations	(69,256)	(101,457)	(156,369)
Change in other noncurrent assets	10,553	44,364	(9,998)
Change in other noncurrent liabilities	(52,090)	(15,674)	17,925
Net cash provided by operating activities	3,025,839	2,648,192	2,584,036
Investing activities
Utility capital/construction expenditures	(3,683,359)	(3,199,791)	(3,395,325)
Allowance for equity funds used during construction	55,936	89,750	87,683
Proceeds from sale of transmission assets	0	0	37,118
Proceeds from insurance recoveries	27,237	6,000	90,000
Purchases of investments in external decommissioning fund	(1,257,924)	(595,569)	(1,481,881)
Proceeds from the sale of investments in external decommissioning fund	1,236,873	588,430	1,461,291
Investments in WYCO Development LLC and other	(1,392)	(2,376)	(7,504)
Other, net	(145)	(3,695)	(4,766)
Net cash used in investing activities	(3,622,774)	(3,117,251)	(3,213,384)
Financing activities
(Repayments of) proceeds from short-term borrowings, net	(173,500)	260,500	157,000
Proceeds from issuance of long-term debt	1,626,212	837,584	1,431,895
Repayments of long-term debt	(250,882)	(275,948)	(652,451)
Proceeds from issuance of common stock	7,011	180,798	231,767
Dividends paid	(606,574)	(561,411)	(514,042)
Net cash provided by financing activities	602,267	441,523	654,169
Net change in cash and cash equivalents	5,332	(27,536)	24,821
Cash and cash equivalents at beginning of period	79,608	107,144	82,323
Cash and cash equivalents at end of period	84,940	79,608	107,144
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(542,860)	(512,602)	(514,911)
Cash received (paid) for income taxes, net	58,287	(4,542)	17,188
Supplemental disclosure of non-cash investing and financing transactions:
Property, plant and equipment additions in accounts payable	321,969	417,473	452,453
Issuance of common stock for reinvested dividends and 401(k) plans	$ 52,911	$ 62,078	$ 56,950