Employee Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2017

Compensation and Retirement Disclosure [Abstract]

Schedule of Net Benefit Costs [Table Text Block]

Net periodic benefit cost (credit) is as follows:

	Pension Benefits
	Three Months Ended   June 30,						Six Months Ended   June 30,
	2017			2016			2017			2016
	(Millions)
Components of net periodic benefit cost (credit):
Service cost	$	12		$	13		$	25		$	27
Interest cost	14			16			29			31
Expected return on plan assets	(21		)	(21		)	(41		)	(42		)
Amortization of net actuarial loss	7			7			14			15
Net actuarial loss from settlements	—			1			—			1
Net periodic benefit cost (credit)	$	12		$	16		$	27		$	32

	Other Postretirement Benefits
	Three Months Ended   June 30,						Six Months Ended   June 30,
	2017			2016			2017			2016
	(Millions)
Components of net periodic benefit cost (credit):
Service cost	$	1		$	1		$	1		$	1
Interest cost	2			2			4			4
Expected return on plan assets	(3		)	(3		)	(6		)	(6		)
Amortization of prior service credit	(4		)	(5		)	(7		)	(8		)
Reclassification to regulatory liability	1			1			2			2
Net periodic benefit cost (credit)	$	(3	)	$	(4	)	$	(6	)	$	(7	)