Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Operating Activities:
Net income	$ 77,568	$ 68,698
Non-cash items included in net income:
Depreciation and amortization	84,273	79,192
Provision for deferred income taxes	30,783	10,490
Power and natural gas cost amortizations (deferrals), net	9,470	(16,804)
Amortization of debt expense and premium	3,186	3,214
Equity-related AFUDC	(1,655)	(1,436)
Other	32,958	36,524
Contributions to defined benefit pension plan	(26,000)	(21,000)
Changes in working capital components:
Accounts and notes receivable	76,285	50,944
Materials and supplies, fuel stock and natural gas stored	(16,260)	(19,146)
Other current assets	(28,167)	13,746
Accounts payable	(11,994)	(10,064)
Other current liabilities	9,977	7,351
Net cash provided by operating activities	240,424	201,709
Investing Activities:
Utility property capital expenditures (excluding equity-related AFUDC)	(169,598)	(138,083)
Other capital expenditures	(2,730)	(1,300)
Federal grant payments received	13,398	4,634
Cash paid by subsidiary for acquisition, net of cash received	(199)
Decrease (increase) in funds held for customers	43,321	(16,366)
Purchase of securities available for sale	(47,299)
Other	(4,604)	(1,296)
Net cash used in investing activities	(167,711)	(152,411)
Financing Activities:
Net decrease in short-term borrowings	(13,500)	(12,000)
Borrowings from Ecova line of credit		2,300
Repayment of borrowings from Ecova line of credit		(8,000)
Redemption and maturity of long-term debt	(204)	(10,236)
Maturity of nonrecourse long-term debt of Spokane Energy	(9,258)	(8,447)
Long-term debt and short-term borrowing issuance costs	(2,362)	(258)
Cash paid for settlement of interest rate swap agreements	(10,557)
Issuance of common stock	21,216	34,677
Cash dividends paid	(47,685)	(41,385)
Purchase of subsidiary noncontrolling interest	(6,179)	(2,593)
Increase in customer fund obligations	3,978	16,366
Other	528	(75)
Net cash used in financing activities	(64,023)	(29,651)
Net increase in cash and cash equivalents	8,690	19,647
Cash and cash equivalents at beginning of period	69,413	37,035
Cash and cash equivalents at end of period	78,103	56,682
Cash paid during the period:
Interest	41,582	44,985
Income taxes	24,506	11,161
Non-cash financing and investing activities:
Accounts payable for capital expenditures	2,642	6,279
Utility property acquired under capital leases		5,300
Redeemable noncontrolling interests	$ 5,147	$ 7,458