Schedule of Details of Dividend Payments (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Record Date	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Payment Date	Jul. 31, 2015	Apr. 24, 2015	Jan. 30, 2015	Oct. 31, 2014	Jul. 25, 2014	Apr. 25, 2014	Jan. 31, 2014
Amount per Share	$ 0.29	$ 0.28	$ 0.28	$ 0.28	$ 0.28	$ 0.27	$ 0.27
Total Amount	$ 43	$ 42	$ 42	$ 43	$ 43	$ 42	$ 42
Maximum dividend allowed prior to merger	$ 0.29