Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Escrow receivable included in investing activities	$ 13,567	$ 0
Stock Issued During Period, Value, Acquisitions	150,075	0
Operating Activities:
Net income	160,034	80,762
Non-cash items included in net income:
Depreciation and amortization	102,899	98,793
Provision for deferred income taxes	111,335	16,512
Power and natural gas cost amortizations (deferrals), net	(17,956)	(10,149)
Amortization of debt expense	2,799	2,841
Amortization of investment in exchange power	1,838	1,838
Stock-based compensation expense	6,261	4,718
Equity-related AFUDC	(6,426)	(4,341)
Pension and other postretirement benefit expense	17,381	31,894
Amortization of Spokane Energy contract	9,214	8,470
Other Asset Impairment Charges	0	2,534
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax	(161,100)	0
Other	14,568	6,889
Contributions to defined benefit pension plan	(32,000)	(44,000)
Changes in working capital components:
Accounts and notes receivable	64,761	50,681
Materials and supplies, fuel stock and natural gas stored	(22,979)	(9,388)
Other current assets	3,447	(23,165)
Accounts payable	(22,450)	(23,756)
Increase (Decrease) in Income Taxes Payable	6,885	303
Other current liabilities	27,203	10,966
Net cash provided by operating activities	265,714	202,402
Investing Activities:
Utility property capital expenditures (excluding equity-related AFUDC)	(229,764)	(220,712)
Other capital expenditures	(6,316)	(1,725)
Federal grant payments received	2,191	2,631
Payments to Acquire Businesses, Gross	15,007	0
Decrease (increase) In Money Market Funds Held For Clients	(18,931)	11,723
Purchase of securities available for sale	(12,267)	(35,949)
Sale and maturity of securities available for sale	14,612	16,955
Proceeds from Divestiture of Businesses, Net of Cash Divested	229,903	0
Other	(1,194)	(6,481)
Net cash used in investing activities	(6,759)	(233,558)
Financing Activities:
Net increase (decrease) in short-term borrowings	(136,000)	14,000
Borrowings from Ecova line of credit	0	3,000
Repayment of borrowings from Ecova line of credit	(46,000)	(7,000)
Proceeds from Issuance of Long-term Debt	75,000	90,000
Redemption and maturity of long-term debt	(39,367)	(415)
Maturity of nonrecourse long-term debt of Spokane Energy	(12,172)	(11,115)
Payments for (Proceeds from) Derivative Instrument, Financing Activities	0	2,901
Issuance of common stock	3,425	4,479
Payments for Repurchase of Common Stock	(60,963)	0
Cash dividends paid	(58,552)	(54,963)
Increase in client fund obligations	16,216	7,375
Payments to Noncontrolling Interests	(54,179)	0
Payments for Repurchase of Redeemable Noncontrolling Interest	(20,871)	0
Other	2,325	(591)
Net cash provided by (used in) financing activities	(331,138)	47,671
Net increase (decrease) in cash and cash equivalents	(72,183)	16,515
Cash and cash equivalents at beginning of period	82,574	75,464
Cash and cash equivalents at end of period	10,391	91,979
Cash paid during the year:
Interest	44,886	45,633
Income taxes	22,451	33,522
Non-cash financing and investing activities:
Accounts payable for capital expenditures	6,945	4,313
Redeemable noncontrolling interests	$ (15,873)	$ 3,246