Exit and Disposal Costs - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Restructuring Cost And Reserve [Line Items]
Accrued restructuring costs	$ 102
Percentage of accrued employee severance to be paid in 2015	95.00%
Percentage of accrued facility and other exit costs to be paid in 2015	45.00%
Employee Severance [Member]
Restructuring Cost And Reserve [Line Items]
Accrued restructuring costs	77	171
Facility and Other Exit Costs [Member]
Restructuring Cost And Reserve [Line Items]
Accrued restructuring costs	$ 25	$ 118