Employee Benefits (Tables)

12 Months Ended

Dec. 31, 2016

Compensation and Retirement Disclosure [Abstract]

Net Pension Cost and Amount Recognized in OCI for All Funded and Unfunded Plans

The components of net pension cost and the amount recognized in OCI for all funded and unfunded plans are as follows:

Year ended December 31, in millions	2016			2015			2014
Interest cost on PBO	$	44		$	41		$	46
Expected return on plan assets	(58		)	(56		)	(66		)
Amortization of losses	17			18			16
Settlement loss	18			23			23
Net pension cost	$	21		$	26		$	19
Other changes in plan assets and benefit obligations recognized in OCI:
Net (gain) loss	$	(9	)	$	47		$	97
Amortization of gains	(35		)	(41		)	(39		)
Total recognized in comprehensive income	$	(44	)	$	6		$	58
Total recognized in net pension cost and comprehensive income	$	(23	)	$	32		$	77

Changes in PBO Related to Pension Plans

The following table summarizes changes in the PBO related to our pension plans.

Year ended December 31, in millions	2016			2015
PBO at beginning of year	$	1,136		$	1,206
Interest cost	44			41
Actuarial losses (gains)	(25		)	(24		)
Benefit payments	(85		)	(87		)
Plan acquisitions	268			—
PBO at end of year	$	1,338		$	1,136

Changes in FVA

The following table summarizes changes in the FVA.

Year ended December 31, in millions	2016			2015
FVA at beginning of year	$	869		$	957
Actual return on plan assets	42			(15		)
Employer contributions	14			14
Benefit payments	(85		)	(87		)
Plan acquisitions	293			—
FVA at end of year	$	1,133		$	869

Funded Status of Pension Plans Recognized in Balance Sheets

The following table summarizes the funded status of the pension plans, which equals the amounts recognized in the balance sheets at December 31, 2016, and December 31, 2015.

December 31, in millions	2016			2015
Funded status (a)	$	(205	)	$	(267	)
Net prepaid pension cost recognized consists of:
Current liabilities	$	(16	)	$	(14	)
Noncurrent liabilities	(189		)	(253		)
Net prepaid pension cost recognized (b)	$	(205	)	$	(267	)

(a) The shortage of the FVA under the PBO.

(b) Represents the accrued benefit liability of the pension plans.

Plans ABO in Excess of Plan Assets

As indicated in the table below, collectively our plans had an ABO in excess of plan assets as follows:

December 31,
in millions	2016		2015
PBO	$	1,338	$	1,136
ABO	1,338		1,136
Fair value of plan assets	1,133		869

Weighted-Average Rates to Determine Actuarial Present Value of Benefit Obligations

To determine the actuarial present value of benefit obligations, we assumed the following weighted-average rates.

December 31,	2016		2015
Discount rate	3.75	%	3.75	%
Compensation increase rate	N/A		N/A

Weighted-Average Rates to Determine Net Pension Cost

To determine net pension cost, we assumed the following weighted-average rates.

Year ended December 31,	2016		2015		2014
Discount rate	3.75	%	3.50	%	4.25	%
Compensation increase rate	N/A		N/A		N/A
Expected return on plan assets	6.00		6.25		7.25

Asset Target Allocations Prescribed by Pension Funds' Investment Policies

The following table shows the asset target allocations prescribed by the pension fund’s investment policies based on the plan’s funded status at December 31, 2016.

	Target Allocation
Asset Class	2016
Equity securities:
U.S.	20	%
International	16
Fixed income securities	40
Convertible securities	5
Real assets	13
Other assets	6
Total	100	%

Fair Values of Pension Plan Assets by Asset Category

The following tables show the fair values of our pension plan assets by asset class at December 31, 2016, and December 31, 2015.

December 31, 2016
in millions	Level 1		Level 2		Level 3	Total
ASSET CLASS
Cash and cash equivalents	$	14	—		—	$	14
Equity securities:
Common — U.S.	133		—		—	133
Common — International	15		—		—	15
Preferred — U.S.	2		—		—	2
Debt securities:
Corporate bonds — U.S.	—		$	90	—	90
Corporate bonds — International	—		26		—	26
Government and agency bonds — U.S.	—		101		—	101
Government bonds — International	—		1		—	1
State and municipal bonds	—		5		—	5
Mutual funds:
Equity — U.S.	118		—		—	118
Equity — International	35		—		—	35
Fixed income — U.S.	152		—		—	152
Fixed income — International	19		—		—	19
Real assets	9		—		—	9
Collective investment funds:
Equity — U.S.	—		15		—	15
Equity — International	—		97		—	97
Convertible securities	—		43		—	43
Fixed income securities	—		79		—	79
Short-term investments	—		18		—	18
Real assets	—		95		—	95
Insurance investment contracts and pooled separate accounts (measured at NAV) (a)	—		—		—	14
Other assets (measured at NAV) (a)	—		—		—	52
Total net assets at fair value	$	497	$	570	—	$	1,133

(a) Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the fair value of plan assets presented elsewhere within this footnote.

December 31, 2015
in millions	Level 1		Level 2		Level 3	Total
ASSET CLASS
Equity securities:
Common — U.S.	$	128	—		—	$	128
Common — International	20		—		—	20
Preferred — U.S.	2		—		—	2
Debt securities:
Corporate bonds — U.S.	—		$	97	—	97
Corporate bonds — International	—		26		—	26
Government and agency bonds — U.S.	—		95		—	95
Government bonds — International	—		1		—	1
State and municipal bonds	—		6		—	6
Mutual funds:
Equity — U.S.	16		—		—	16
Equity — International	24		—		—	24
Fixed Income — U.S.	5		—		—	5
Fixed Income — International	2		—		—	2
Collective investment funds:
Equity — U.S.	—		26		—	26
Equity — International	—		106		—	106
Convertible securities	—		41		—	41
Fixed income securities	—		86		—	86
Short-term investments	—		21		—	21
Real assets	—		101		—	101
Insurance investment contracts and pooled separate accounts (measured at NAV) (a)	—		—		—	14
Other assets (measured at NAV) (a)	—		—		—	52
Total net assets at fair value	$	197	$	606	—	$	869

(a) Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the fair value of plan assets presented elsewhere within this footnote.

Pre-tax AOCI Not Yet Recognized as Net Postretirement Benefit Cost

The components of pre-tax AOCI not yet recognized as net postretirement benefit cost are shown below.

December 31,
in millions	2016			2015
Net unrecognized losses (gains)	$	(9	)	$	(5	)
Net unrecognized prior service credit	(2		)	(3		)
Total unrecognized AOCI	$	(11	)	$	(8	)

Net Postretirement Benefit Cost and Amount Recognized in OCI for All Funded and Unfunded Plans

The components of net postretirement benefit cost and the amount recognized in OCI for all funded and unfunded plans are as follows:

December 31,
in millions	2016			2015			2014
Service cost of benefits earned	$	1		$	1		$	1
Interest cost on APBO	2			3			3
Expected return on plan assets	(2		)	(3		)	(3		)
Amortization of prior service credit	(1		)	(1		)	(1		)
Amortization of gains	—			—			(1		)
Net postretirement benefit	—			—			$	(1	)
Other changes in plan assets and benefit obligations recognized in OCI:
Net (gain) loss	$	(4	)	$	(6	)	$	13
Amortization of prior service credit	1			1			1
Amortization of losses	—			—			1
Total recognized in comprehensive income	$	(3	)	$	(5	)	$	15
Total recognized in net postretirement benefit cost and comprehensive income	$	(3	)	$	(5	)	$	14

Changes in APBO

The following table summarizes changes in the APBO.

Year ended December 31,
in millions	2016			2015
APBO at beginning of year	$	67		$	79
Service cost	1			1
Interest cost	2			3
Plan participants’ contributions	2			2
Actuarial losses (gains)	(1		)	(12		)
Benefit payments	(6		)	(6		)
Plan acquisition	4			—
APBO at end of year	$	69		$	67

Change in FVA (Other Post Retirement Benefit Plan Assets)

The following table summarizes changes in FVA.

Year ended December 31,
in millions	2016			2015
FVA at beginning of year	$	49		$	56
Employer contributions	—			—
Plan participants’ contributions	2			2
Benefit payments	(6		)	(6		)
Actual return on plan assets	5			(3		)
FVA at end of year	$	50		$	49

Funded Status of Postretirement Plans Recognized in Balance Sheets

The following table summarizes the funded status of the postretirement plans, which corresponds to the amounts recognized in the balance sheets at December 31, 2016, and December 31, 2015.

December 31,
in millions	2016			2015
Funded status (a)	$	(19	)	$	(18	)
Accrued postretirement benefit cost recognized (b)	(19		)	(18		)

(a) The shortage of the FVA under the APBO.

(b) Consists entirely of noncurrent liabilities.

Weighted-Average Rates to Determine Net Postretirement Benefit Cost

To determine net postretirement benefit cost, we assumed the following weighted-average rates.

Year ended December 31,	2016		2015		2014
Discount rate	4.00	%	3.75	%	4.50	%
Expected return on plan assets	4.50		4.50		5.25

Asset Target Allocations Prescribed by Trusts' Investment Policies

The following table shows the asset target allocations prescribed by the trust’s investment policy.

	Target Allocation
Asset Class	2016
Equity securities	80	%
Fixed income securities	10
Convertible securities	5
Cash equivalents	5
Total	100	%

Fair Values of Pension Plan Assets by Asset Category

The following tables show the fair values of our postretirement plan assets by asset class at December 31, 2016, and December 31, 2015.

December 31, 2016
in millions	Level 1		Level 2		Level 3	Total
ASSET CLASS
Mutual funds:
Equity — U.S.	$	23	—		—	$	23
Equity — International	5		—		—	5
Fixed income — U.S.	5		—		—	5
Common investment funds:
Equity — U.S.	—		$	10	—	10
Short-term investments	—		7		—	7
Total net assets at fair value	$	33	$	17	—	$	50

December 31, 2015
in millions	Level 1		Level 2		Level 3	Total
ASSET CLASS
Mutual funds:
Equity — U.S.	$	18	—		—	$	18
Equity — International	4		—		—	4
Fixed income — U.S.	4		—		—	4
Common investment funds:
Equity — U.S.	—		$	16	—	16
Equity — International	—		4		—	4
Convertible securities	—		2		—	2
Short-term investments	—		1		—	1
Total net assets at fair value	$	26	$	23	—	$	49