Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Operating Activities:
Net income	$ 68,831	$ 56,745
Non-cash items included in net income:
Depreciation and amortization	64,890	61,647
Provision for deferred income taxes	(1,404)	6,522
Power and natural gas cost amortizations (deferrals), net	(430)	8,822
Amortization of debt expense	1,895	1,926
Amortization of investment in exchange power	1,225	1,225
Stock-based compensation expense	3,080	3,158
Equity-related AFUDC	(2,746)	(1,748)
Pension and other postretirement benefit expense	21,478	19,758
Amortization of Spokane Energy contract	5,587	5,136
Write-off of Reardan wind generation capitalized costs	2,534	0
Other	(3,893)	(4,071)
Contributions to defined benefit pension plan	(29,340)	(29,400)
Changes in working capital components:
Accounts and notes receivable	43,443	55,719
Materials and supplies, fuel stock and natural gas stored	2,133	869
Other current assets	(11,365)	15,694
Accounts payable	(27,106)	(3,456)
Other current liabilities	9,197	(6,971)
Net cash provided by operating activities	155,795	199,717
Investing Activities:
Utility property capital expenditures (excluding equity-related AFUDC)	(145,344)	(120,476)
Other capital expenditures	(1,344)	(2,266)
Federal grant payments received	2,297	4,483
Cash paid by subsidiaries for acquisitions, net of cash received	0	(50,310)
Decrease (increase) in funds held for clients	10,675	(16,424)
Purchase of securities available for sale	(31,949)	(64,850)
Sale and maturity of securities available for sale	15,130	71,492
Other	(4,369)	(4,158)
Net cash used in investing activities	(154,904)	(182,509)
Financing Activities:
Net increase in short-term borrowings	43,500	30,000
Borrowings from Ecova line of credit	3,000	25,000
Repayment of borrowings from Ecova line of credit	(5,000)	0
Redemption and maturity of long-term debt	(359)	(11,264)
Maturity of nonrecourse long-term debt of Spokane Energy	(7,329)	(6,694)
Long-term debt and short-term borrowing issuance costs	(21)	(130)
Cash received (paid) for settlement of interest rate swap agreements	2,901	(18,547)
Issuance of common stock	3,017	3,575
Cash dividends paid	(36,667)	(34,101)
Purchase of subsidiary noncontrolling interest	(325)	(784)
Increase in client fund obligations	6,220	9,764
Issuance of subsidiary noncontrolling interest	0	3,714
Other	119	1,013
Net cash provided by financing activities	9,056	1,546
Net cash provided by financing activities	9,947	18,754
Cash and cash equivalents at beginning of period	75,464	74,662
Cash and cash equivalents at end of period	85,411	93,416
Cash paid during the year:
Interest	36,960	36,277
Income taxes	29,005	12,217
Non-cash financing and investing activities:
Accounts payable for capital expenditures	2,860	4,381
Redeemable noncontrolling interests	$ 2,931	$ (3,031)