Commitments And Contingencies (Legal And Regulatory Contingencies) (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Unrecognized Tax Benefits	$ 60,000
Charge for disallowed capital	$ 0	$ 87,000
Butte Fire [Member]
Loss Contingencies [Line Items]
Number of plaintiffs	2,000
Utility liability insurance for damages	$ 900,000
Number of Damaged Structures	44
Loss Contingency Range Of Possible Loss Minimum	$ 750,000
Number of complaints filed against utility	55
Fire Fighting Costs Recovery Requested By Cal Fire	$ 87,000
Expected recovery of costs through insurance	$ 632,000
Number Of Acres Burned	70,868
Number Of Fatalities Caused By Fire	2
Number Of Homes Burned By Fire	549
Number Of Outbuildings Burned By Fire	368
Number Of Commerical Properties Burned By Fire	4
Number Of Households Represented In Court	1,150
Number Of Master Complaints	2
Cumulative Legal Expenses	$ 37,000
Insurance Settlements Receivable Current	$ 50,000
Vegetation Management Contractors	2
Number Of Preference Households	6
Potential Safety Citations [Member]
Loss Contingencies [Line Items]
Number of violations	2
SED Maximum Statutory Penalty Per Violaiton	$ 50
SED Administrative Limit Per Citation	8,000
Citation For Failing To Maintain Electric Line	8,000
Citation For Failure To Timely Report	250
Citation For Failing To Maintain Minimum Clearance	$ 50
Number Of Days To Pay Or Appeal The Citations	30 days
Minimum Clearance From Electric Line	18
Number Of Issued Citations	2
Number Of Gray Pine Trees	2
Minimum [Member] | Potential Safety Citations [Member]
Loss Contingencies [Line Items]
SED fines for self-reported violations	$ 50
Maximum [Member] | Potential Safety Citations [Member]
Loss Contingencies [Line Items]
SED fines for self-reported violations	16,800
Ex Parte Communications [Member]
Loss Contingencies [Line Items]
Payment To State General Fund	1,000
Payment To City Of San Bruno	6,000
Payment To City Of San Carlos	6,000
Revenue Requirement Reduction In Next GRC Cycle	10,000
2018 GT&S Revenue Requirement Reduction	31,750
2019 GT&S Revenue Requirement Reduction	31,750
Ex parte disallowance in 2015 GT&S rate case recognized in 2016	57,000
Ex Parte Disallowance In Twenty Fifteen GTandS Recognized In Twenty Seventeen	$ 15,000
Shareholder Derivative Lawsuits [Member]
Loss Contingencies [Line Items]
Number Of Consolidated Shareholder Derivative Lawsuits	4
Number Of Unconsolidated Cases In Derivative Lawsuits	3
Number Of Days To Make Payment From Decision	11 days
Estimated Cost Of Corporate Governance Therapeutics	$ 32,000
Maximum Amount Of Fees Paid to Plaintiffs Counsel	25,000
Maximum Amount Of Expenses Paid To Plaintiffs Counsel	500
Payment Of Individual Defendant Costs	18,300
Payment To The Corporation From Liability Insurance Carriers	90,000
Gain Contingency Unrecorded Amount	$ 64,500
Number Of Years Of Corporate Governance Therapeutics	5 years
Number Of Years Of Gas Operations Therapeutics	3 years
Loss Accrual [Member] | Butte Fire [Member]
Loss Contingencies [Line Items]
Accrued Losses	$ 0		$ 750,000
Loss Contingency Accrual At Carrying Value	646,000		690,000	$ 0
Payments For Claims	44,000		60,000
Insurance Receivable [Member] | Butte Fire [Member]
Loss Contingencies [Line Items]
Insurance Reimbursement	0		50,000
Insurance Settlements Receivable	582,000		575,000	$ 0
Accrued Insurance Recoveries	7,000		625,000
Q1 Legal Expenses [Member]
Loss Contingencies [Line Items]
Cumulative Legal Expenses	10,000
Pacific Gas And Electric Company [Member]
Loss Contingencies [Line Items]
Charge for disallowed capital	0	$ 87,000
Utility [Member]
Loss Contingencies [Line Items]
Accrued legal liabilities	$ 48,000		$ 45,000