Discontinued Operations - Summarized Results of Operations for Discontinued Operations (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended	9 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Discontinued Operations And Disposal Groups [Abstract]
Revenue			$ 15	$ 103
Operating income				35
Interest expense	0			(8)
Income from operations before income taxes				27
Provision for income taxes				(11)
Income from operations				16
Gain on sale, net of tax		303		303
Income from discontinued operations				$ 319