Property, Plant and Equipment - Depreciation Expense and Capital Expenditures (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Depreciation	$ 841	$ 955	$ 861
Capital Expend.	1,572	1,718	2,813
CNA Financial [Member]
Property, Plant and Equipment [Line Items]
Depreciation	67	74	69
Capital Expend.	128	123	72
Diamond Offshore [Member]
Property, Plant and Equipment [Line Items]
Depreciation	384	494	457
Capital Expend.	629	812	2,050
Boardwalk Pipeline [Member]
Property, Plant and Equipment [Line Items]
Depreciation	321	327	292
Capital Expend.	648	390	378
Loews Hotels [Member]
Property, Plant and Equipment [Line Items]
Depreciation	63	54	37
Capital Expend.	164	389	289
Corporate [Member]
Property, Plant and Equipment [Line Items]
Depreciation	6	6	6
Capital Expend.	$ 3	$ 4	$ 24