Employee Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2015

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

Components of Net Periodic Benefit Cost

The components of net periodic benefit cost 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 June 30,						Six Months Ended June 30,
(in millions)	2015			2014			2015			2014
Service cost	$	9		$	8		$	18		$	15
Interest cost	22			22			44			44
Expected return on plan assets	(40		)	(33		)	(80		)	(66		)
Amortization of prior service cost	1			2			2			3
Amortization of net loss	15			7			29			15
Net periodic defined benefit cost	$	7		$	6		$	13		$	11

Non-Qualified Defined Benefit Pension Plan	Three Months Ended June 30,						Six Months Ended June 30,
(in millions)	2015			2014			2015			2014
Service cost	$	1		$	1		$	2		$	2
Interest cost	3			3			5			5
Amortization of prior service credit	(1		)	(1		)	(2		)	(2		)
Amortization of net loss	2			1			5			3
Net periodic defined benefit cost	$	5		$	4		$	10		$	8

Postretirement Benefit Plan	Three Months Ended June 30,						Six Months Ended June 30,
(in millions)	2015			2014			2015			2014
Interest cost	$	—		$	1		$	1		$	2
Expected return on plan assets	(1		)	(1		)	(2		)	(2		)
Amortization of net loss	1			—			1			—
Net periodic postretirement benefit cost	$	—		$	—		$	—		$	—