Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Undistributed earning related to foreign subsidiaries	$ 1,800
Reductions for tax positions related to a prior year	20	$ 3	$ 35
Income tax expense related to penalties		2
Income tax benefit related to penalties	23		22
Reductions in penalties related to uncertain tax positions	(23)
Net operating loss carryforwards	178	245
Valuation allowance	210	147
Other deferred tax assets	246	282
Federal [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 76
Net operating loss carryforwards expiration year	2034 and 2036
Tax credit carryforwards	$ 157
Foreign [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards expiration year	2020 and 2025
Net operating loss carryforwards in foreign tax jurisdictions	$ 59
Tax credit carryforwards	$ 98
Tax credit carryforwards expiration year	2024 and 2026
Net operating loss carryforwards indefinitely	$ 36
CNA Financial [Member]
Income Tax Contingency [Line Items]
Equity ownership percentage	80.00%
Diamond Offshore [Member]
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would affect effective tax rate upon recognition	$ 36	$ 49	51
Reduction to income tax expense			$ 17
Potential tax expense related to income tax examination	22
Net operating loss carryforwards	91
Valuation allowance	210
Foreign tax credits	62
Other deferred tax assets	57
Diamond Offshore [Member] | Foreign [Member]
Income Tax Contingency [Line Items]
Foreign tax credit carrybacks	$ 33