Schedule Of Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Net revenues	$ 1,902	$ 2,577	$ 2,173	$ 1,850	$ 1,887	$ 2,542	$ 2,194	$ 1,862
Net income (loss)	$ (5)	$ 184	$ 143	$ (9)	$ 23	$ 192	$ 26	$ 4
Basic Net income (loss) (in dollars per share)	$ (0.06)	$ 1.80	$ 1.36	$ (0.09)	$ 0.22	$ 1.84	$ 0.25	$ 0.03	$ 3.02	$ 2.32	$ 0.15
Basic weighted average shares outstanding	99.5	102.7	105.5	106.1	106.2	103.9	105.1	106.6	103.4	105.4	107.6
Diluted Net income (loss) (in dollars per share)	$ (0.06)	$ 1.77	$ 1.34	$ (0.09)	$ 0.21	$ 1.74	$ 0.24	$ 0.03	$ 2.98	$ 2.22	$ 0.15
Diluted weighted average shares outstanding	99.5	104.0	106.7	106.1	108.3	109.9	111.0	108.6	105.0	110.6	111.4