Equity (Narrative) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Common Stock Value	$ 12,292,000	$ 12,198,000
Pacific Gas And Electric Company [Member]
Common Stock Value	$ 1,322,000	$ 1,322,000
Equity Contract [Member]
Equity Distribution Agreement, shares issued	400,000
Remaining equity distribution agreement amount	$ 246,000
Fees and commissions	200
Stock Issued During Period Value Under Equity Distribution Agreement	28,000
Equity Distribution Agreement Total Contract Value	$ 275,000
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	3,300,000
Stock Issued During Period Value Stock Options Exercised	$ 117,000