Employee Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2016

Compensation and Retirement Disclosure [Abstract]

Schedule of Net Benefit Costs

Following are the components of our pension costs for the periods indicated.

	Three Months Ended June 30,						Six Months Ended June 30,
In millions	2016			2015			2016			2015
Service cost (1)	$	7		$	7		$	13		$	14
Interest cost (1)	11			12			21			23
Expected return on plan assets	(17		)	(17		)	(33		)	(33		)
Net amortization of prior service credit	(1		)	—			(1		)	(1		)
Recognized actuarial loss	7			7			13			15
Net periodic pension benefit cost	$	7		$	9		$	13		$	18

(1) Effective January 1, 2016, we use a spot rate approach to estimate the service cost and interest cost components. Historically, we estimated these components using a single weighted-average discount rate.

Following are the components of our welfare costs for the periods indicated.

	Three Months Ended June 30,						Six Months Ended June 30,
In millions	2016			2015			2016			2015
Service cost (1)	$	—		$	—		$	1		$	1
Interest cost (1)	2			3			5			6
Expected return on plan assets	(1		)	(2		)	(3		)	(4		)
Net amortization of prior service credit	—			(1		)	(1		)	(1		)
Recognized actuarial loss	1			2			2			3
Net periodic welfare benefit cost	$	2		$	2		$	4		$	5

(1) Effective January 1, 2016, we use a spot rate approach to estimate the service cost and interest cost components. Historically, we estimated these components using a single weighted-average discount rate.