Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Activities:
Net income	$ 62,137	$ 57,665
Non-cash items included in net income:
Depreciation and amortization	43,084	40,291
Provision for deferred income taxes	17,614	34,030
Power and natural gas cost amortizations (deferrals), net	3,091	5,379
Amortization of debt expense	813	876
Amortization of investment in exchange power	613	613
Stock-based compensation expense	832	2,313
Equity-related AFUDC	(1,650)	(2,261)
Pension and other postretirement benefit expense	9,348	9,475
Amortization of Spokane Energy contract	0	3,558
Other regulatory assets and liabilities and deferred debits and credits	(6,878)	(7,127)
Change in decoupling regulatory deferral	14,857	(11,456)
Other	(116)	(9)
Contributions to defined benefit pension plan	(7,400)	(4,000)
Changes in certain current assets and liabilities:
Accounts and notes receivable	(668)	18,364
Materials and supplies, fuel stock and natural gas stored	6,129	10,263
Collateral posted for derivative instruments	(2,620)	(42,871)
Income taxes receivable	14,106	11,210
Other current assets	(116)	(4,106)
Accounts payable	(20,239)	(30,804)
Other current liabilities	16,778	15,752
Net cash provided by operating activities	149,715	107,155
Investing Activities:
Utility property capital expenditures (excluding equity-related AFUDC)	(86,763)	(88,878)
Other capital expenditures	(35)	(119)
Issuance of notes receivable at subsidiaries	(400)	(1,076)
Investments made by subsidiaries	(2,627)	(1,358)
Other	(102)	(223)
Net cash used in investing activities	(89,927)	(91,654)
Financing Activities:
Net decrease in borrowings from committed line of credit	(15,000)	(15,000)
Maturity of long-term debt and capital leases	(822)	(792)
Issuance of common stock	315	27,150
Cash dividends paid	(23,167)	(21,545)
Other	(3,442)	(3,031)
Net cash used in financing activities	(42,116)	(13,218)
Net increase in cash and cash equivalents	17,672	2,283
Cash and cash equivalents at beginning of period	8,507	10,484
Cash and cash equivalents at end of period	$ 26,179	$ 12,767