Equity (Narrative) (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015
Common Stock Value	$ 12,083,000	$ 12,083,000	$ 11,282,000
Pacific Gas And Electric Company [Member]
Common Stock Value	$ 1,322,000	$ 1,322,000	$ 1,322,000
Equity Contract [Member]
Equity Distribution Agreement, shares issued	400,000	2,600,000
Remaining equity distribution agreement amount	$ 275,000	$ 275,000
Fees and commissions	200	1,300
Stock Issued During Period Value Under Equity Distribution Agreement	$ 26,000	$ 149,000
401K Plan, DRSPP, and Shared Based Compensation Plans [Member]
Stock issued during period for stock options exercised and under 401(K) plan and DRSPP, shares		5,700,000
Stock Issued During Period Value Stock Options Exercised		$ 269,000
Underwritten Public Offering [Member]
Common Stock Shares Issued	4,900,000	4,900,000
Common Stock Value	$ 309,000	$ 309,000