Investments (tables)

3 Months Ended

Mar. 31, 2017

Investments disclosure

Amortized cost and fair value of investments in fixed maturities [Table Text Block]

	Amortized		Gross Unrealized				Fair
(at March 31, 2017, in millions)	Cost		Gains		Losses		Value
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities	$	2,043	$	10	$	4	$	2,049
Obligations of states, municipalities and political subdivisions:
Local general obligation	14,082		303		159		14,226
Revenue	11,349		238		134		11,453
State general obligation	1,653		36		20		1,669
Pre-refunded	4,428		184		—		4,612
Total obligations of states, municipalities and political subdivisions	31,512		761		313		31,960
Debt securities issued by foreign governments	1,559		33		2		1,590
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	1,690		97		7		1,780
All other corporate bonds	23,378		528		111		23,795
Redeemable preferred stock	87		7		—		94
Total	$	60,269	$	1,436	$	437	$	61,268

	Amortized		Gross Unrealized				Fair
(at December 31, 2016, in millions)	Cost		Gains		Losses		Value
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities	$	2,031	$	9	$	5	$	2,035
Obligations of states, municipalities and political subdivisions:
Local general obligation	13,955		271		182		14,044
Revenue	10,910		215		147		10,978
State general obligation	1,717		36		22		1,731
Pre-refunded	4,968		190		1		5,157
Total obligations of states, municipalities and political subdivisions	31,550		712		352		31,910
Debt securities issued by foreign governments	1,631		34		3		1,662
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	1,614		100		6		1,708
All other corporate bonds	22,737		508		138		23,107
Redeemable preferred stock	87		6		—		93
Total	$	59,650	$	1,369	$	504	$	60,515

Cost and fair value of investments in equity securities [Table Text Block]

			Gross Unrealized				Fair
(at March 31, 2017, in millions)	Cost		Gains		Losses		Value
Public common stock	$	398	$	223	$	2	$	619
Non-redeemable preferred stock	114		23		5		132
Total	$	512	$	246	$	7	$	751

			Gross Unrealized				Fair
(at December 31, 2016, in millions)	Cost		Gains		Losses		Value
Public common stock	$	390	$	216	$	3	$	603
Non-redeemable preferred stock	114		20		5		129
Total	$	504	$	236	$	8	$	732

Unrealized investment losses [Table Text Block]

	Less than 12 months				12 months or longer				Total
(at March 31, 2017, in millions)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Fixed maturities
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities	$	1,275	$	4	$	—	$	—	$	1,275	$	4
Obligations of states, municipalities and political subdivisions	9,185		313		44		—		9,229		313
Debt securities issued by foreign governments	243		2		—		—		243		2
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	529		6		40		1		569		7
All other corporate bonds	5,718		96		343		15		6,061		111
Total fixed maturities	16,950		421		427		16		17,377		437
Equity securities
Public common stock	35		—		16		2		51		2
Non-redeemable preferred stock	—		—		60		5		60		5
Total equity securities	35		—		76		7		111		7
Total	$	16,985	$	421	$	503	$	23	$	17,488	$	444

	Less than 12 months				12 months or longer				Total
(at December 31, 2016, in millions)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Fixed maturities
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities	$	1,124	$	5	$	—	$	—	$	1,124	$	5
Obligations of states, municipalities and political subdivisions	9,781		352		12		—		9,793		352
Debt securities issued by foreign governments	360		3		—		—		360		3
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	528		5		43		1		571		6
All other corporate bonds	6,470		115		437		23		6,907		138
Total fixed maturities	18,263		480		492		24		18,755		504
Equity securities
Public common stock	45		2		10		1		55		3
Non-redeemable preferred stock	2		—		59		5		61		5
Total equity securities	47		2		69		6		116		8
Total	$	18,310	$	482	$	561	$	30	$	18,871	$	512