Employee Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2017

Retirement Benefits [Abstract]

Schedule of Net Benefit Costs [Table Text Block]

Net periodic benefit cost (credit) is as follows:

	Pension Benefits
	Three Months Ended   September 30,						Nine Months Ended   September 30,
	2017			2016			2017			2016
	(Millions)
Components of net periodic benefit cost (credit):
Service cost	$	13		$	13		$	38		$	40
Interest cost	15			16			44			47
Expected return on plan assets	(21		)	(22		)	(62		)	(64		)
Amortization of net actuarial loss	6			8			20			23
Net actuarial loss from settlements	—			—			—			1
Net periodic benefit cost (credit)	$	13		$	15		$	40		$	47

	Other Postretirement Benefits
	Three Months Ended   September 30,						Nine Months Ended   September 30,
	2017			2016			2017			2016
	(Millions)
Components of net periodic benefit cost (credit):
Service cost	$	—		$	—		$	1		$	1
Interest cost	2			2			6			6
Expected return on plan assets	(3		)	(3		)	(9		)	(9		)
Amortization of prior service credit	(3		)	(3		)	(10		)	(11		)
Reclassification to regulatory liability	1			1			3			3
Net periodic benefit cost (credit)	$	(3	)	$	(3	)	$	(9	)	$	(10	)