Employee Benefit Plans - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Contribution Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Cost of defined benefit plans	$ 374	$ 371	$ 322
Restoration Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of hours of service required to qualify for the plan	1,000 or more hours
Noncontributory and nonqualified plan, benefit expense	29	20	25
Noncontributory and nonqualified plan, accrued benefits liabilities	137	120
Supplemental Executive Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan cost	43	51	33
Defined benefit plan obligation	214	242
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan cost	37	49	39
Defined benefit plan obligation	$ 81	$ 196
Subsequent to March 31, 2008 [Member] | Defined Contribution Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of employer contribution to match participant contribution in defined contribution plan, net	100.00%
Subsequent to March 31, 2008 [Member] | Defined Contribution Benefit Plans [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of employer contribution to match participant contribution in defined contribution plan	3.00%
Subsequent to March 31, 2008 [Member] | Defined Contribution Benefit Plans [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of employer contribution to match participant contribution in defined contribution plan	9.00%