Consolidating Financial Information - Consolidating Balance Sheet Information (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Investments	$ 52,644	$ 52,945
Cash	637	294	257	228
Receivables	8,185	9,338
Property, plant and equipment	14,411	13,524
Goodwill	353	357
Assets of discontinued operations		1,041
Other assets	1,672	1,635
Deferred acquisition costs of insurance subsidiaries	627	624
Separate account business		181
Total assets	78,529	79,939
Insurance reserves	36,095	38,394
Payable to brokers	663	134
Short term debt	850	819
Long term debt	10,051	9,525
Deferred income taxes	1,030	716
Liabilities of discontinued operations		632
Other liabilities	4,724	4,632
Separate account business		181
Total liabilities	53,413	55,033
Total shareholders' equity	19,657	19,458
Noncontrolling interests	5,459	5,448
Total equity	25,116	24,906	24,821	24,676
Total liabilities and equity	78,529	79,939
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Receivables	(88)	(25)
Deferred income taxes	(281)	(247)
Assets of discontinued operations		(637)
Investments in capital stocks of subsidiaries	(16,779)	(17,264)
Other assets	14	39
Total assets	(17,134)	(18,134)
Deferred income taxes	(241)	(725)
Other liabilities	(114)	(565)
Total liabilities	(355)	(1,290)
Total shareholders' equity	(16,779)	(16,844)
Total equity	(16,779)	(16,844)
Total liabilities and equity	(17,134)	(18,134)
CNA Financial [Member] | Operating Segments [Member]
Condensed Financial Statements, Captions [Line Items]
Investments	46,320	46,107
Cash	247	195
Receivables	7,313	8,666
Property, plant and equipment	271	282
Deferred income taxes		244
Goodwill	118	119
Other assets	783	741
Deferred acquisition costs of insurance subsidiaries	627	624
Separate account business		181
Total assets	55,679	57,159
Insurance reserves	36,095	38,394
Payable to brokers	135	85
Short term debt	549	549
Long term debt	2,559	2,011
Deferred income taxes	38
Other liabilities	3,300	3,323
Separate account business		181
Total liabilities	42,676	44,543
Total shareholders' equity	11,673	11,354
Noncontrolling interests	1,330	1,262
Total equity	13,003	12,616
Total liabilities and equity	55,679	57,159
Diamond Offshore [Member] | Operating Segments [Member]
Condensed Financial Statements, Captions [Line Items]
Investments	1,043	2,061
Cash	26	36
Receivables	543	498
Property, plant and equipment	6,076	5,472
Goodwill	20	20
Other assets	329	305
Total assets	8,037	8,392
Payable to brokers	4	1
Short term debt	250	250
Long term debt	1,981	2,230
Deferred income taxes	504	516
Other liabilities	803	734
Total liabilities	3,542	3,731
Total shareholders' equity	2,309	2,362
Noncontrolling interests	2,186	2,299
Total equity	4,495	4,661
Total liabilities and equity	8,037	8,392
Boardwalk Pipeline [Member] | Operating Segments [Member]
Condensed Financial Statements, Captions [Line Items]
Cash	7	29
Receivables	84	97
Property, plant and equipment	7,391	7,296
Goodwill	215	215
Other assets	326	360
Total assets	8,023	7,997
Long term debt	3,410	3,424
Deferred income taxes	691	689
Other liabilities	418	427
Total liabilities	4,519	4,540
Total shareholders' equity	1,561	1,570
Noncontrolling interests	1,943	1,887
Total equity	3,504	3,457
Total liabilities and equity	8,023	7,997
Loews Hotels [Member] | Operating Segments [Member]
Condensed Financial Statements, Captions [Line Items]
Investments	76	43
Cash	7	10
Receivables	39	28
Property, plant and equipment	611	430
Deferred income taxes	3	3
Goodwill		3
Other assets	202	183
Total assets	938	700
Short term debt	51	20
Long term debt	422	182
Deferred income taxes	38	41
Other liabilities	32	23
Total liabilities	543	266
Total shareholders' equity	395	434
Total equity	395	434
Total liabilities and equity	938	700
Corporate and Other [Member]
Condensed Financial Statements, Captions [Line Items]
Investments	5,205	4,734
Cash	350	24
Receivables	294	74
Property, plant and equipment	62	44
Deferred income taxes	278
Assets of discontinued operations		1,678
Investments in capital stocks of subsidiaries	16,779	17,264
Other assets	18	7
Total assets	22,986	23,825
Payable to brokers	524	48
Long term debt	1,679	1,678
Deferred income taxes		195
Liabilities of discontinued operations		632
Other liabilities	285	690
Total liabilities	2,488	3,243
Total shareholders' equity	20,498	20,582
Total equity	20,498	20,582
Total liabilities and equity	$ 22,986	$ 23,825