Employee Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Pre-tax AOCI not yet recognized as net pension cost	$ 681	$ 634
Accumulated benefit obligation for all pension plans	1,300	1,200
Defined benefit plan, net periodic benefit cost expected in next fiscal year	7
Defined benefit plan, net periodic benefit cost expected	7	13
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%	7.75%	8.25%
Expected return on plan assets on estimating 2013 pension cost	7.25%
Weighted-average discount rates to determine APBO	3.50%	4.00%
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%	6.00%
Increase in employee contribution to savings plan	1.00%
Profit sharing allocation	2.40%	3.00%	3.00%
Total expenses associated with Saving Plan	68	79	75
Initial Default Percentage [Member]
Defined Benefit Plan Disclosure [Line Items]
Employee contribution to savings plan	2.00%
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pre-tax accumulated other comprehensive loss expected to be recognized as net pension cost	20
Measurement date	31st December	31st December
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2013	107
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2014	100
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2015	94
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2016	93
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2017	89
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2018 through 2022	393
Accumulated benefit obligation for all pension plans	1,277	1,225
Defined benefit plan, net periodic benefit cost expected	(7)	(13)
Percentage increase/decrease in assumed expected return on plan assets	50.00%
Expected return on plan assets	7.25%	7.75%	8.25%
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pre-tax AOCI not yet recognized as net pension cost	(2)
Pre-tax accumulated other comprehensive loss expected to be recognized as net pension cost	1
Measurement date	31st December	31st December
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2013	5
Benefits expected to be paid from all funded and unfunded pension plans/other postretirement plans in 2014	5
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 through 2022	24
Defined benefit plan, net periodic benefit cost expected
Expected return on plan assets	5.58%	5.45%	5.46%
Expected net periodic benefit cost for next fiscal year	Less than $1 million
Defined benefit plan net periodic benefit costs	Less than $1 million	Less than $1 million