Income Taxes Components of Deferred Tax Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Deferred Tax Assets, Advances and Contributions	$ 15,214	$ 14,954
Deferred tax assets:
Unamortized investment tax credit	773	805
Pensions and postretirement benefits	4,757	4,644
California franchise tax	1,193	1,429
Net operating loss	6,439	2,495
Other	1,272	1,181
Total deferred tax assets	29,648	25,508
Deferred tax liabilities:
Utility plant	110,983	96,349
Pension and postretirement benefits	46,315	43,199
Investment in stock	2,487	2,488
Deferred gain and other-property related	14,440	15,287
Debt reacquisition costs	545	595
Other	2,457	1,131
Total deferred tax liabilities	177,227	159,049
Net deferred tax liabilities	147,579	133,541
Federal
Deferred tax liabilities:
Net operating loss carryforward	$ 18,397