Schedule Of Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Line Items]
Deferred Income Tax Expense (Benefit)									$ (14)	$ 192	$ (51)
Revenues	$ 2,050	$ 2,778	$ 2,328	$ 1,968	$ 2,019	$ 2,752	$ 2,238	$ 1,839	$ 9,124	$ 8,848	$ 8,659
Net income (loss)	$ 13	$ 213	$ 26	$ (87)	$ 220	$ 245	$ 3	$ (107)
Basic Net income (loss) (in dollars per share)	$ 0.16	$ 2.71	$ 0.33	$ (1.08)	$ 2.70	$ 2.96	$ 0.04	$ (1.25)	$ 2.08	$ 4.32	$ 1.78
Basic weighted average shares outstanding	76.9	78.8	80.7	81.0	81.3	82.6	84.0	85.7	79.3	83.4	92.0
Diluted Net income (loss) (in dollars per share)	$ 0.16	$ 2.68	$ 0.32	$ (1.08)	$ 2.65	$ 2.91	$ 0.04	$ (1.25)	$ 2.06	$ 4.25	$ 1.75
Diluted weighted average shares outstanding	77.6	79.5	81.5	81.0	82.7	84.0	85.2	85.7	80.1	84.8	93.3
Provision adjustment due to anticipated repatriation of foreign earnings [Member]
Income Tax Disclosure [Line Items]
Deferred Income Tax Expense (Benefit)		$ (30)								$ (104)
Provision adjustment due to corporate tax rate change [Member]
Income Tax Disclosure [Line Items]
Deferred Income Tax Expense (Benefit)									$ (30)	$ 317