Investments - Amortized Cost and Fair Values of Securities (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	$ 38,171	$ 40,307
Gross Unrealized Gains	3,520	2,579
Gross Unrealized Losses	242	695
Estimated Fair Value	41,449	42,191
Unrealized OTTI Losses (Gains)	(54)	(40)
Fixed Maturity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	37,346	39,426
Gross Unrealized Gains	3,382	2,450
Gross Unrealized Losses	143	556
Estimated Fair Value	40,585	41,320
Unrealized OTTI Losses (Gains)	(54)	(40)
Corporate and Other Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	17,276	19,352
Gross Unrealized Gains	1,852	1,645
Gross Unrealized Losses	30	135
Estimated Fair Value	19,098	20,862
States, Municipalities and Political Subdivisions [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	11,215	11,281
Gross Unrealized Gains	1,178	548
Gross Unrealized Losses	70	272
Estimated Fair Value	12,323	11,557
Residential Mortgage-Backed [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	4,882	4,940
Gross Unrealized Gains	202	123
Gross Unrealized Losses	14	92
Estimated Fair Value	5,070	4,971
Unrealized OTTI Losses (Gains)	(51)	(37)
Commercial Mortgage-Backed [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	1,999	1,995
Gross Unrealized Gains	107	90
Gross Unrealized Losses	7	22
Estimated Fair Value	2,099	2,063
Unrealized OTTI Losses (Gains)	(3)	(3)
Other Asset-Backed [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	1,172	945
Gross Unrealized Gains	16	13
Gross Unrealized Losses	3	3
Estimated Fair Value	1,185	955
Total Asset-Backed [Member] | Fixed Maturity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	8,053	7,880
Gross Unrealized Gains	325	226
Gross Unrealized Losses	24	117
Estimated Fair Value	8,354	7,989
Unrealized OTTI Losses (Gains)	(54)	(40)
U.S. Treasury and Obligations of Government-Sponsored Enterprises [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	61	139
Gross Unrealized Gains	6	6
Gross Unrealized Losses	1	1
Estimated Fair Value	66	144
Foreign Government [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	533	531
Gross Unrealized Gains	18	15
Gross Unrealized Losses	1	3
Estimated Fair Value	550	543
Redeemable Preferred Stock [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	39	92
Gross Unrealized Gains	3	10
Estimated Fair Value	42	102
Total Fixed Maturities Available-for-Sale [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	37,177	39,275
Gross Unrealized Gains	3,382	2,450
Gross Unrealized Losses	126	528
Estimated Fair Value	40,433	41,197
Unrealized OTTI Losses (Gains)	(54)	(40)
Fixed Maturities, Trading [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	169	151
Gross Unrealized Losses	17	28
Estimated Fair Value	152	123
Common Stock [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	46	36
Gross Unrealized Gains	14	9
Estimated Fair Value	60	45
Preferred Stock [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	129	143
Gross Unrealized Gains	5	1
Gross Unrealized Losses		4
Estimated Fair Value	134	140
Total Equity Securities Available-for-Sale [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	175	179
Gross Unrealized Gains	19	10
Gross Unrealized Losses		4
Estimated Fair Value	194	185
Unrealized OTTI Losses (Gains)
Equity Securities, Trading [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	650	702
Gross Unrealized Gains	119	119
Gross Unrealized Losses	99	135
Estimated Fair Value	670	686
Equity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or Amortized Cost	825	881
Gross Unrealized Gains	138	129
Gross Unrealized Losses	99	139
Estimated Fair Value	864	871
Unrealized OTTI Losses (Gains)