Commitments and Contingent Liabilities - Rent Expense (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Rent expense	$ 80	$ 84	$ 82
Office Facilities [Member]
Property, Plant and Equipment [Line Items]
Rent expense	67	71	71
Equipment [Member]
Property, Plant and Equipment [Line Items]
Rent expense	$ 13	$ 13	$ 11