Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Assets
Cash and cash equivalents	$ 269,120	$ 220,036
Accounts receivable and unbilled revenues, net	324,433	346,785
Available-for-sale investment and mortgage-related securities	517,534	529,007
Investment in stock of Federal Home Loan Bank of Seattle	86,697	92,546
Loans receivable held for investment, net	4,147,537	4,110,113
Loans held for sale, at lower of cost or fair value	4,363	5,302
Property, plant and equipment, net of accumulated depreciation of $2,206,650 and $2,192,422 at the respective dates	3,908,392	3,865,514
Regulatory assets	579,963	575,924
Other	537,841	512,627
Goodwill	82,190	82,190
Total assets	10,458,070	10,340,044
Liabilities
Accounts payable	210,511	212,331
Interest and dividends payable	28,520	26,716
Deposit liabilities	4,477,987	4,372,477
Short-term borrowings—other than bank	136,369	105,482
Other bank borrowings	244,642	244,514
Long-term debt, net—other than bank	1,492,945	1,492,945
Deferred income taxes	538,321	529,260
Regulatory liabilities	350,916	349,299
Contributions in aid of construction	438,020	432,894
Defined benefit pension and other postretirement benefit plans liability	284,043	288,539
Other	475,575	524,224
Total liabilities	8,677,849	8,578,681
Preferred stock of subsidiaries - not subject to mandatory redemption	34,293	34,293
Commitments and contingencies (Notes 3 and 4)
Shareholders' equity
Preferred stock, no par value, authorized 10,000,000 shares; issued: none	0	0
Common stock, no par value, authorized 200,000,000 shares; issued and outstanding: 101,477,616 shares and 101,259,800 shares at the respective dates	1,491,338	1,488,126
Retained earnings	270,173	255,694
Accumulated other comprehensive loss, net of tax benefits
Net unrealized losses on securities	(2,858)	(3,663)
Unrealized losses on derivatives	(466)	(525)
Retirement benefit plans	(12,259)	(12,562)
Accumulated other comprehensive income (loss), net of taxes	(15,583)	(16,750)
Common stock equity	1,745,928	1,727,070
Total liabilities and shareholders’ equity	$ 10,458,070	$ 10,340,044