Segment Information (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Other revenues	$ 2	$ 1
Total revenues	2,159	1,224
Investment gains and losses, net	663	(191)
ERROR in label resolution.	867	(50)
Earned premiums	1,333	1,260
Investment income, net of expenses	157	150
ERROR in label resolution.	23,352		$ 21,935
Fee revenues	4	4
Consolidated Property and Casualty Insurance Entity
Segment Reporting Information [Line Items]
ERROR in label resolution.	3,308		3,285
Life Insurance Segment
Segment Reporting Information [Line Items]
ERROR in label resolution.	1,472		1,424
Investments Segment
Segment Reporting Information [Line Items]
ERROR in label resolution.	17,738		16,741
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Other revenues	2	1
Total revenues	52	30
ERROR in label resolution.	(11)	(11)
ERROR in label resolution.	834		$ 485
Corporate, Non-Segment [Member] \| Reinsurance assumed and other non segment [Member]
Segment Reporting Information [Line Items]
Earned premiums	50	29
Operating Segments \| Commercial Lines
Segment Reporting Information [Line Items]
Total revenues	811	792
ERROR in label resolution.	76	15
Earned premiums	810	790
Fee revenues	1	2
Operating Segments \| Personal Lines
Segment Reporting Information [Line Items]
Total revenues	345	326
ERROR in label resolution.	(4)	(9)
Earned premiums	344	325
Fee revenues	1	1
Operating Segments \| Excess and Surplus Lines Insurance
Segment Reporting Information [Line Items]
Total revenues	64	56
ERROR in label resolution.	11	18
Earned premiums	63	56
Fee revenues	1	0
Operating Segments \| Life Insurance Segment
Segment Reporting Information [Line Items]
Total revenues	67	61
ERROR in label resolution.	(1)	2
Earned premiums	66	60
Fee revenues	1	1
Operating Segments \| Investments Segment
Segment Reporting Information [Line Items]
Total revenues	820	(41)
Investment gains and losses, net	663	(191)
ERROR in label resolution.	796	(65)
Investment income, net of expenses	157	150
Commercial Casualty \| Operating Segments \| Commercial Lines
Segment Reporting Information [Line Items]
Earned premiums	268	265
Commercial Property \| Operating Segments \| Commercial Lines
Segment Reporting Information [Line Items]
Earned premiums	234	228
Commercial Auto \| Operating Segments \| Commercial Lines
Segment Reporting Information [Line Items]
Earned premiums	170	161
Workers' Compensation \| Operating Segments \| Commercial Lines
Segment Reporting Information [Line Items]
Earned premiums	77	80
Other Commercial Lines \| Operating Segments \| Commercial Lines
Segment Reporting Information [Line Items]
Earned premiums	61	56
Personal Auto \| Operating Segments \| Personal Lines
Segment Reporting Information [Line Items]
Earned premiums	155	151
Home Owner Segment \| Operating Segments \| Personal Lines
Segment Reporting Information [Line Items]
Earned premiums	147	136
Other Personal Lines \| Operating Segments \| Personal Lines
Segment Reporting Information [Line Items]
Earned premiums	$ 42	$ 38

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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