Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating Activities:
Net income	$ 90,729	$ 88,317
Non-cash items included in net income:
Depreciation and amortization	139,738	130,803
Provision for deferred income taxes	10,575	58,242
Power and natural gas cost amortizations (deferrals), net	6,315	8,416
Amortization of debt expense	2,327	2,440
Amortization of investment in exchange power	1,838	1,838
Stock-based compensation expense	5,215	5,809
Equity-related AFUDC	(4,406)	(5,012)
Pension and other postretirement benefit expense	23,980	27,816
Other regulatory assets and liabilities and deferred debits and credits	20,953	(12,683)
Change in decoupling regulatory deferral	5,436	20,193
Other	3,962	(190)
Contributions to defined benefit pension plan	(22,000)	(22,000)
Cash paid for settlement of interest rate swap agreements	(32,174)	(11,302)
Cash received for settlement of interest rate swap agreements	5,594	2,479
Changes in certain current assets and liabilities:
Accounts and notes receivable	75,878	52,534
Materials and supplies, fuel stock and natural gas stored	(4,691)	(12,653)
Collateral posted for derivative instruments	47,150	(1,896)
Income taxes receivable	(5,994)	(4,254)
Other current assets	2,123	(16)
Accounts payable	(16,392)	(29,992)
Other current liabilities	9,639	8,624
Net cash provided by operating activities	365,795	307,513
Investing Activities:
Utility property capital expenditures (excluding equity-related AFUDC)	(296,216)	(287,853)
Issuance of notes receivable at subsidiaries	(2,930)	(2,800)
Equity and property investments made by subsidiaries	(8,629)	(10,899)
Distributions from investments	1,946	1,915
Other	(1,858)	(2,714)
Net cash used in investing activities	(307,687)	(302,351)
Financing Activities:
Net increase (decrease) in short-term borrowings	(70,398)	75,000
Proceeds from issuance of long-term debt	374,621	0
Maturity of long-term debt and capital leases	(276,804)	(2,465)
Issuance of common stock	1,224	1,490
Cash dividends paid	(73,569)	(69,220)
Other	(8,184)	(3,758)
Net cash provided by (used in) financing activities	(53,110)	1,047
Net increase in cash and cash equivalents	4,998	6,209
Cash and cash equivalents at beginning of period	16,172	8,507
Cash and cash equivalents at end of period	$ 21,170	$ 14,716