Investments (Tables)

3 Months Ended

Mar. 31, 2018

Investments [Abstract]

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

The amortized cost and fair value of investments in fixed maturities classified as available for sale were as follows:

	Amortized		Gross Unrealized				Fair
(at March 31, 2018, in millions)	Cost		Gains		Losses		Value
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities	$	2,051	$	2	$	19	$	2,034
Obligations of states, municipalities and political subdivisions:
Local general obligation	13,593		215		127		13,681
Revenue	10,512		177		91		10,598
State general obligation	1,391		21		12		1,400
Pre-refunded	3,638		123		—		3,761
Total obligations of states, municipalities and political subdivisions	29,134		536		230		29,440
Debt securities issued by foreign governments	1,326		9		8		1,327
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	2,495		76		40		2,531
All other corporate bonds	27,000		231		389		26,842
Redeemable preferred stock	87		5		—		92
Total	$	62,093	$	859	$	686	$	62,266

	Amortized		Gross Unrealized				Fair
(at December 31, 2017, in millions)	Cost		Gains		Losses		Value
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities	$	2,080	$	4	$	8	$	2,076
Obligations of states, municipalities and political subdivisions:
Local general obligation	13,488		444		26		13,906
Revenue	11,307		338		19		11,626
State general obligation	1,443		44		3		1,484
Pre-refunded	3,758		142		1		3,899
Total obligations of states, municipalities and political subdivisions	29,996		968		49		30,915
Debt securities issued by foreign governments	1,505		14		10		1,509
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	2,334		87		11		2,410
All other corporate bonds	25,311		478		100		25,689
Redeemable preferred stock	90		5		—		95
Total	$	61,316	$	1,556	$	178	$	62,694

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

							Fair
(at March 31, 2018, in millions)	Cost		Gross Gains		Gross Losses		Value
Public common stock	$	330	$	4	$	10	$	324
Non-redeemable preferred stock	101		11		6		106
Total	$	431	$	15	$	16	$	430

Cost and fair value of investments in equity securities classified as available for sale [Table Text Block]

							Fair
(at December 31, 2017, in millions)	Cost		Gross Gains		Gross Losses		Value
Public common stock	$	332	$	8	$	1	$	339
Non-redeemable preferred stock	108		12		6		114
Total	$	440	$	20	$	7	$	453

Unrealized investment losses [Table Text Block]

The following tables summarize, for all investments in an unrealized loss position at March 31, 2018 and December 31, 2017, the aggregate fair value and gross unrealized loss by length of time those securities have been continuously in an unrealized loss position.  The fair value amounts reported in the tables are estimates that are prepared using the process described in note 4 herein and in note 4 of notes to the consolidated financial statements in the Company’s 2017 Annual Report.  The Company also relies upon estimates of several factors in its review and evaluation of individual investments, using the process described in note 1 of notes to the consolidated financial statements in the Company’s 2017 Annual Report in determining whether such investments are other-than-temporarily impaired.

	Less than 12 months				12 months or longer				Total
(at March 31, 2018, 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	$	1,332	$	15	$	549	$	4	$	1,881	$	19
Obligations of states, municipalities and political subdivisions	5,823		94		2,863		136		8,686		230
Debt securities issued by foreign governments	431		7		32		1		463		8
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	1,474		32		235		8		1,709		40
All other corporate bonds	14,816		294		1,910		95		16,726		389
Total fixed maturities	$	23,876	$	442	$	5,589	$	244	$	29,465	$	686

	Less than 12 months				12 months or longer				Total
(at December 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	$	1,150	$	5	$	470	$	3	$	1,620	$	8
Obligations of states, municipalities and political subdivisions	505		2		2,959		47		3,464		49
Debt securities issued by foreign governments	394		6		111		4		505		10
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	1,021		7		250		4		1,271		11
All other corporate bonds	6,062		48		1,990		52		8,052		100
Total fixed maturities	9,132		68		5,780		110		14,912		178
Equity securities
Public common stock	18		—		34		1		52		1
Non-redeemable preferred stock	3		—		56		6		59		6
Total equity securities	21		—		90		7		111		7
Total	$	9,153	$	68	$	5,870	$	117	$	15,023	$	185