Segment Information - Schedule of Segment Reporting Information, by Segment (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Interest expense included in the segment results	$ 369	$ 391	$ 340
Interest Income Excluded From Segment Information
Segment Reporting Information [Line Items]
Interest income included in the segment results	20	11
Interest Expense Excluded From Segment Information
Segment Reporting Information [Line Items]
Interest expense included in the segment results	$ 22	$ 22	$ 9