Fixed Assets - Depreciation Expense Relating to Fixed Assets (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Property Plant And Equipment [Abstract]
Depreciation expense relating to fixed assets	$ 819	$ 800	$ 1,646	$ 1,593