Retirement Plans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Capitalization of pension and OPEB expense related to engineering and plant construction		$ 13	$ 13
Plan contributions		156
Plan distributions		558
Waiver amount		196
Pension and other postretirement benefits		2,438		$ 1,896
Other comprehensive income (loss) before reclassifications		522
Pension plan liability		127
Increase due to remeasurement	$ 395
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Settlements, Benefit Obligation		464
Defined Benefit Plan, Settlements Benefit obligation threshold		211
Estimated plan contributions		193
Plan contributions		37
Plan assets		2,210		$ 2,730
Increase (decrease) in pension assets		(520)
Pension settlement costs		$ 159
Discount rate - used at year end to value obligation		2.80%		3.40%
Pension and other postretirement benefits		$ 1,518		$ 996
Other comprehensive income (loss) before reclassifications		(525)
Pension Benefits [Member] | Northwest Operations [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Positive investment returns		58
Benefit payments		500
Postretirement Costs [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other comprehensive income (loss) before reclassifications		(15)
PBO		3,728		$ 3,726
Increased in PBO		$ 2