Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Assets
Cash and cash equivalents	$ 153,712	$ 219,662
Accounts receivable and unbilled revenues, net	359,259	362,823
Available-for-sale investment and mortgage-related securities	560,172	671,358
Investment in stock of Federal Home Loan Bank of Seattle	94,281	96,022
Loans receivable held for investment, net	3,912,630	3,737,233
Loans held for sale, at lower of cost or fair value	34,073	26,005
Property, plant and equipment, net of accumulated depreciation of $2,161,681 in 2013 and $2,125,286 in 2012	3,701,905	3,594,829
Regulatory assets	885,025	864,596
Other	454,898	494,414
Goodwill	82,190	82,190
Total assets	10,238,145	10,149,132
Liabilities
Accounts payable	175,038	212,379
Interest and dividends payable	25,503	26,258
Deposit liabilities	4,276,243	4,229,916
Short-term borrowings-other than bank	125,786	83,693
Other bank borrowings	187,884	195,926
Long-term debt, net-other than bank	1,422,877	1,422,872
Deferred income taxes	474,197	439,329
Regulatory liabilities	336,065	322,074
Contributions in aid of construction	419,337	405,520
Defined benefit pension and other postretirement benefit plans liability	639,898	656,394
Other	496,375	526,613
Total liabilities	8,579,203	8,520,974
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
Common stock, no par value, authorized 200,000,000 shares; issued and outstanding: 99,044,053 shares in 2013 and 97,928,403 shares in 2012	1,429,371	1,403,484
Retained earnings	230,067	216,804
Accumulated other comprehensive income (loss), net of taxes
Net unrealized gains on securities	888	10,761
Unrealized losses on derivatives	(642)	(760)
Retirement benefit plans	(35,035)	(36,424)
Accumulated other comprehensive income (loss), net of taxes	(34,789)	(26,423)
Total shareholders' equity	1,624,649	1,593,865
Total liabilities and shareholders' equity	$ 10,238,145	$ 10,149,132