Employee Benefits - Funded Status of Pension and Other Postretirement Benefit Plans (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 2,946	$ 2,717
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation, beginning of year	2,777	2,894
Service cost	86	95	88
Interest cost	140	125	124
Actuarial loss (gain)	536	(261)
Benefits paid	(85)	(75)
Foreign currency translation effect	(19)	(1)
Benefit obligation, end of year	3,435	2,777	2,894
Plan assets at fair value, beginning of year	2,717	2,305
Actual return on plan assets	240	409
Employer contributions	92	82
Benefits paid	(85)	(75)
Foreign currency translation effect	(18)	(4)
Plan assets at fair value, end of year	2,946	2,717	2,305
Funded status at end of year, included in other liabilities	489	60
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation, beginning of year	394	470
Service cost	10	13	12
Interest cost	19	19	20
Actuarial loss (gain)	74	(97)
Benefits paid	(10)	(11)
Foreign currency translation effect	(2)
Benefit obligation, end of year	485	394	470
Plan assets at fair value, beginning of year	130	96
Actual return on plan assets	12	27
Employer contributions	11	18
Benefits paid	(10)	(11)
Plan assets at fair value, end of year	143	130	96
Funded status at end of year, included in other liabilities	$ 342	$ 264