Employee Benefit Plans - Additional Information (Detail) - USD ($)		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Apr. 22, 2014
Defined Contribution Plan, Employer Matching Contribution, Percent of Match		6.00%	6.00%		6.00%
Deferred Compensation Arrangement with Individual, Requisite Service Period		3 years
Deferred Compensation Arrangement with Individual, Compensation Expense		$ 245,000,000	$ 203,000,000		$ 150,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		16,000,000						17,000,000
Document Period End Date		Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period							574,257
Fair Value Per Unit of Restricted Stock Units							$ 21.67
Restricted Stock or Unit Expense		$ 16,000,000	27,000,000		$ 32,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value					$ 7.37
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options		$ 54,000,000	61,000,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition		1 year 10 months
Personal Pension Account Interest Crediting Rate		3.00%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year		7.25%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate		5.00%
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation		$ 1,000,000
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation		1,000,000
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components		1,000,000
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components		1,000,000
Defined Benefit Plan, Effect of 25 Basis Point Change in Expected Long-Term Return on Plan Assets		8,000,000
Defined Benefit Plan, Effect of 25 Basis Point Change in the Discount Rate		1,000,000
Defined Contribution Plan, Employer Discretionary Contribution Amount		19,000,000	19,000,000	[1]	$ 19,000,000	[1]
Defined Contribution Plan, Cost Recognized		$ 102,000,000	$ 98,000,000		$ 96,000,000
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	[1]	1.00%	1.00%		1.00%
Pension Plan [Member]
Defined Benefit Plan, Future Amortization of Gain (Loss)		$ 25,000,000
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan, Future Amortization of Prior Service Cost (Credit)		(6,000,000)
Liability [Member]
Restricted Stock or Unit Expense		$ 23,000,000	$ 21,000,000

[1] Contributions for each of these performance years are paid in the first quarter of the following performance year.