Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Operating Activities:
Net income	$ 38,213	$ 42,403
Non-cash items included in net income:
Depreciation and amortization	30,322	27,719
Provision (benefit) for deferred income taxes	(303)	966
Power and natural gas cost amortizations, net	4,098	3,950
Amortization of debt expense and premium	965	1,236
Equity-related AFUDC	(843)	(842)
Other	14,348	12,650
Contributions to defined benefit pension plan	(14,700)	(8,500)
Changes in working capital components:
Accounts and notes receivable	16,079	12,505
Materials and supplies, fuel stock and natural gas stored	15,652	10,222
Other current assets	21,265	10,509
Accounts payable	(16,112)	(16,674)
Other current liabilities	12,315	7,118
Net cash provided by operating activities	121,299	103,262
Investing Activities:
Utility property capital expenditures (excluding equity-related AFUDC)	(57,771)	(49,654)
Other capital expenditures	(1,144)	(474)
Federal grant payments received	2,855	4,353
Cash paid by subsidiaries for acquisitions, net of cash received	(50,310)	(199)
Decrease (increase) in funds held for clients	(35,857)	47,635
Purchase of securities available for sale	(36,461)
Sale of securities available for sale	27,000
Other	(2,628)	(1,502)
Net cash provided by (used in) investing activities	(154,316)	159
Financing Activities:
Net decrease in short-term borrowings	(24,000)	(45,000)
Borrowings from Ecova line of credit	25,000
Redemption and maturity of long-term debt	(65)	(95)
Maturity of nonrecourse long-term debt of Spokane Energy	(3,307)	(3,016)
Long-term debt and short-term borrowing issuance costs	(33)	(2,303)
Issuance of common stock	1,437	8,458
Cash dividends paid	(17,073)	(15,780)
Purchase of subsidiary noncontrolling interest	(134)	(5,639)
Increase (decrease) in client fund obligations	45,169	(47,635)
Issuance of subsidiary noncontrolling interests	3,714
Other	350	13
Net cash provided by (used in) financing activities	31,058	(110,997)
Net decrease in cash and cash equivalents	(1,959)	(7,576)
Cash and cash equivalents at beginning of period	74,662	69,413
Cash and cash equivalents at end of period	72,703	61,837
Cash paid during the year:
Interest	6,680	6,433
Income taxes	1,322	2,200
Non-cash financing and investing activities:
Accounts payable for capital expenditures	2,677	3,963
Redeemable noncontrolling interests	$ 1,764	$ (2,429)