Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Dec. 31, 2013	Sep. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2013	Dec. 31, 2014
Income Tax Contingency [Line Items]
Undistributed earning related to foreign subsidiaries				$ 2,000
Income tax expense related to penalties				2	$ 38
Income tax benefit related to penalties						$ 22
Reduction to income tax expense				28
Reversal of reserves and accrual for uncertain tax positions		$ 36		11
Reversal of reserves and accrual for uncertain tax positions, interest		6		4
Reversal of reserves and accrual for uncertain tax positions, penalties		$ 11		1
Net operating loss carryforwards				245		321
Federal [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards				$ 138
Net operating loss carryforwards expiration year				2034 and 2035
Tax credit carryforwards				$ 83
Foreign [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards expiration year				2020 and 2025
Net operating loss carryforwards in foreign tax jurisdictions				$ 66
Tax credit carryforwards				$ 46
Tax credit carryforwards expiration year				2024 and 2025
Net operating loss carryforwards indefinitely				$ 32
CNA Financial [Member]
Income Tax Contingency [Line Items]
Equity ownership percentage				80.00%
Diamond Offshore [Member]
Income Tax Contingency [Line Items]
Amount of unrecognized tax benefits would affect the effective tax rate if recognized	$ 76			$ 49	76	$ 51
Reduction to income tax expense			$ 17
Potential tax expense related to income tax examination				$ 53
Diamond Offshore [Member] | Egyptian Tax Authorities [Member]
Income Tax Contingency [Line Items]
Proposed increase to taxable income					$ 1,200
Potential tax expense related to income tax examination	$ 57