Income Taxes - Components of U.S. and Foreign Income and Reconciliation between Federal Income Tax Expense at Statutory Rates and Actual Income Tax Expense (Benefit) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income before income tax:
Income before income tax, U.S.	$ 1,207	$ 543	$ 1,499
Income before income tax, Foreign	(271)	(299)	311
Income before income tax	936	244	1,810
Income tax expense at statutory rate	328	86	633
Increase (decrease) in income tax expense resulting from:
Exempt investment income	(126)	(126)	(121)
Foreign related tax differential	40	(18)	(48)
Amortization of deferred charges associated with intercompany rig sales to other tax jurisdictions		38	44
Taxes related to domestic affiliate	(14)	(10)	14
Partnership earnings not subject to taxes	(52)	(38)	(39)
Allowance for foreign tax credits	62
Unrecognized tax positions, including foreign currency revaluation	(42)	1	(42)
Other	24	24	16
Income tax expense (benefit)	$ 220	$ (43)	$ 457