Pension and Other Postretirement Benefits - Schedule of Fair Value of Pension Plan Assets (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Sale Of Subsidiary [Abstract]
Net payable which represents assets related to divested businesses to be transferred to the buyers	$ 116
Net receivable which represents securities sold not yet settled plus interest and dividends earned on various investments		$ 159