Employee Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2018

Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]

Components of Net Periodic Benefit Cost

The components of net periodic benefit cost (credit) for the Corporation's qualified pension plan, non-qualified pension plan and postretirement benefit plan are as follows.

Qualified Defined Benefit Pension Plan	Three Months Ended September 30,						Nine Months Ended September 30,
(in millions)	2018			2017			2018			2017
Service cost	$	7		$	7		$	22		$	21
Other components of net benefit credit:
Interest cost	19			19			56			58
Expected return on plan assets	(41		)	(39		)	(123		)	(118		)
Amortization of prior service credit	(5		)	(5		)	(14		)	(14		)
Amortization of net loss	13			11			38			32
Total other components of net benefit credit	(14		)	(14		)	(43		)	(42		)
Net periodic defined benefit credit	$	(7	)	$	(7	)	$	(21	)	$	(21	)

Non-Qualified Defined Benefit Pension Plan	Three Months Ended September 30,						Nine Months Ended September 30,
(in millions)	2018			2017			2018			2017
Service cost	$	—		$	—		$	1		$	1
Other components of net benefit cost:
Interest cost	2			2			6			6
Amortization of prior service credit	(1		)	(2		)	(6		)	(6		)
Amortization of net loss	2			2			7			6
Total other components of net benefit cost	3			2			7			6
Net periodic defined benefit cost	$	3		$	2		$	8		$	7

Postretirement Benefit Plan	Three Months Ended September 30,					Nine Months Ended September 30,
(in millions)	2018		2017			2018			2017
Other components of net benefit credit:
Interest cost	$	—	$	1		$	1		$	2
Expected return on plan assets	—		(1		)	(2		)	(2		)
Net periodic defined benefit credit	$	—	$	—		$	(1	)	$	—