Sale of Trust Accounts - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended
	Apr. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2014	Dec. 31, 2014
Discontinued Operations and Disposal Groups [Abstract]
Gain on sale of business net of tax	$ 23
Gain on sale of business before tax	45
Goodwill recorded	$ 11
Revenue on sale of business		$ 9	$ 8	$ 26	$ 34