Employee Benefit Plans (Tables)

3 Months Ended

Mar. 31, 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 March 31,
(in millions)	2018			2017
Service cost	$	7		$	7
Other components of net benefit credit:
Interest cost	19			20
Expected return on plan assets	(41		)	(40		)
Amortization of prior service credit	(5		)	(5		)
Amortization of net loss	13			11
Total other components of net benefit credit	(14		)	(14		)
Net periodic defined benefit credit	$	(7	)	$	(7	)

Non-Qualified Defined Benefit Pension Plan	Three Months Ended March 31,
(in millions)	2018			2017
Service cost	$	—		$	1
Other components of net benefit cost:
Interest cost	2			2
Amortization of prior service credit	(2		)	(2		)
Amortization of net loss	2			2
Total other components of net benefit cost	2			2
Net periodic defined benefit cost	$	2		$	3

Postretirement Benefit Plan	Three Months Ended March 31,
(in millions)	2018			2017
Other components of net benefit cost:
Interest cost	$	1		$	1
Expected return on plan assets	(1		)	(1		)
Net periodic defined benefit cost	$	—		$	—