Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating Activities:
Net income	$ 83,859	$ 84,952
Non-cash items included in net income:
Depreciation and amortization	86,790	81,071
Provision for deferred income taxes	36,169	56,652
Power and natural gas cost amortizations (deferrals), net	6,366	9,958
Amortization of debt expense	1,627	1,742
Amortization of investment in exchange power	1,225	1,225
Stock-based compensation expense	2,643	4,236
Equity-related AFUDC	(3,292)	(4,368)
Pension and other postretirement benefit expense	18,539	19,315
Amortization of Spokane Energy contract	0	7,192
Other regulatory assets and liabilities and deferred debits and credits	(8,831)	(13,169)
Change in decoupling regulatory deferral	10,365	(24,787)
Other	420	5,032
Contributions to defined benefit pension plan	(14,800)	(8,000)
Changes in certain current assets and liabilities:
Accounts and notes receivable	45,375	50,062
Materials and supplies, fuel stock and natural gas stored	(7,879)	2,510
Collateral posted for derivative instruments	(5,460)	(83,499)
Income taxes receivable	12,457	(1,450)
Other current assets	(3,825)	(4,436)
Accounts payable	(29,435)	(31,484)
Other current liabilities	(3,787)	3,197
Net cash provided by operating activities	228,526	155,951
Investing Activities:
Utility property capital expenditures (excluding equity-related AFUDC)	(177,714)	(182,815)
Issuance of notes receivable at subsidiaries	(2,500)	(9,668)
Equity and property investments made by subsidiaries	(10,347)	(6,988)
Distributions received from investments	1,915	0
Other	(943)	(7,153)
Net cash used in investing activities	(189,589)	(206,624)
Financing Activities:
Net increase in short-term borrowings	16,000	55,000
Maturity of long-term debt and capital leases	(1,643)	(1,583)
Issuance of common stock	1,247	47,173
Cash dividends paid	(46,193)	(43,267)
Other	(3,445)	(3,612)
Net cash provided by (used in) financing activities	(34,034)	53,711
Net increase in cash and cash equivalents	4,903	3,038
Cash and cash equivalents at beginning of period	8,507	10,484
Cash and cash equivalents at end of period	$ 13,410	$ 13,522