Employee Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Pre-tax AOCI not yet recognized as net pension cost	$ 587	$ 529
Accumulated benefit obligation for all pension plans	1,200	1,200
Maximum limit for vary of market related value	10.00%
Percentage increase or decrease in expected return on plan assets	0.25%
Estimated increase or decrease in net pension cost	2
Percentage increase or decrease in assumed discount rate	0.25%
Estimated change in net pension cost due to discount rate	1
Expected return on plan assets	7.25%	7.25%	7.25%
Expected return on plan assets on estimating 2013 pension cost	6.25%
Discount rates to determine APBO	3.75%	4.50%
Employees minimum contribution to saving plan	1.00%
Employees maximum contribution to saving plan	100.00%
Employer contribution to saving plan	6.00%
Employee contribution to savings plan	10.00%
Increase in employee contribution to savings plan	1.00%
Profit sharing allocation	2.00%	2.00%	2.40%
Total expenses associated with saving plan	70	66	77
Initial Default Percentage [Member]
Defined Benefit Plan Disclosure [Line Items]
Employee contribution to savings plan	2.00%
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Pre-tax accumulated other comprehensive loss expected to be recognized as net pension cost	18
Measurement date	December 31, 2014, and December 31, 2013
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2015	87
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2016	95
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2017	96
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2018	85
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2019	81
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2020 through 2024	365
Accumulated benefit obligation for all pension plans	1,206	1,156
Defined benefit plan, net periodic benefit cost expected in next fiscal year	2
Defined benefit plan, net periodic benefit cost expected	19	21	(7)
Settlement loss	23	27
Expected return on plan assets	7.25%	7.25%	7.25%
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Pre-tax AOCI not yet recognized as net pension cost	(3)	(17)
Pre-tax accumulated other comprehensive loss expected to be recognized as net pension cost	1
Measurement date	December 31, 2014, and December 31, 2013
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2015	5
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2016	5
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2017	5
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2018	5
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2019	5
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2020 through 2024	24
Defined benefit plan, net periodic benefit cost expected	1
Expected return on plan assets	5.25%	5.25%	5.58%
Other Postretirement Benefit Plans [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, net periodic benefit cost expected in next fiscal year	1
Defined benefit plan, net periodic benefit cost expected		$ 1