Investments (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Available-for-sale securities
Amortized cost, fixed maturities	$ 8,986
Amortized cost	9,863	9,147
Gross unrealized gains	579	492
Gross unrealized losses	35	82
Estimated fair value, fixed maturities	9,465	8,688
Estimated fair value, equity securities	942	869
Estimated fair value	10,407	9,557
Indemnity
Available-for-sale securities
Amortized cost, fixed maturities	551	518
Amortized cost, equity securities	24	50
Amortized cost	575	568
Gross unrealized gains	15	11
Gross unrealized losses	2	3
Estimated fair value, fixed maturities	563	526
Estimated fair value, equity securities	25	50
Estimated fair value	588	576
Indemnity \| Fixed maturities
Available-for-sale securities
Amortized cost, fixed maturities	551	518
Gross unrealized gains, fixed maturities	14	9
Gross unrealized losses, fixed maturities	2	1
Estimated fair value, fixed maturities	563	526
Indemnity \| States & political subdivisions
Available-for-sale securities
Amortized cost, fixed maturities	219	237
Gross unrealized gains, fixed maturities	12	7
Gross unrealized losses, fixed maturities	0	1
Estimated fair value, fixed maturities	231	243
Indemnity \| Corporate debt securities
Available-for-sale securities
Amortized cost, fixed maturities	241	280
Gross unrealized gains, fixed maturities	2	2
Gross unrealized losses, fixed maturities	1	0
Estimated fair value, fixed maturities	242	282
Indemnity \| Residential mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	10
Gross unrealized gains, fixed maturities	0
Gross unrealized losses, fixed maturities	0
Estimated fair value, fixed maturities	10
Indemnity \| Commercial mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	50
Gross unrealized gains, fixed maturities	0
Gross unrealized losses, fixed maturities	1
Estimated fair value, fixed maturities	49
Indemnity \| Collateralized debt obligations
Available-for-sale securities
Amortized cost, fixed maturities	24	1
Gross unrealized gains, fixed maturities	0	0
Gross unrealized losses, fixed maturities	0	0
Estimated fair value, fixed maturities	24	1
Indemnity \| Other debt securities
Available-for-sale securities
Amortized cost, fixed maturities	7
Gross unrealized gains, fixed maturities	0
Gross unrealized losses, fixed maturities	0
Estimated fair value, fixed maturities	7
Indemnity \| Nonredeemable preferred stock
Available-for-sale securities
Amortized cost, equity securities	11	24
Gross unrealized gains, equity securities	1	2
Gross unrealized losses, equity securities	0	1
Estimated fair value, equity securities	12	25
Indemnity \| Common stock
Available-for-sale securities
Amortized cost, equity securities	13	26
Gross unrealized gains, equity securities	0	0
Gross unrealized losses, equity securities	0	1
Estimated fair value, equity securities	13	25
Exchange
Available-for-sale securities
Amortized cost, fixed maturities	8,435	7,801
Amortized cost, equity securities	853	778
Amortized cost	9,288	8,579
Gross unrealized gains	564	481
Gross unrealized losses	33	79
Estimated fair value, fixed maturities	8,902	8,162
Estimated fair value, equity securities	917	819
Estimated fair value	9,819	8,981
Exchange \| Fixed maturities
Available-for-sale securities
Amortized cost, fixed maturities	8,435	7,801
Gross unrealized gains, fixed maturities	496	426
Gross unrealized losses, fixed maturities	29	65
Estimated fair value, fixed maturities	8,902	8,162
Exchange \| U.S. government & agencies
Available-for-sale securities
Amortized cost, fixed maturities		171
Gross unrealized gains, fixed maturities		1
Gross unrealized losses, fixed maturities		0
Estimated fair value, fixed maturities		172
Exchange \| U.S. treasury
Available-for-sale securities
Amortized cost, fixed maturities	6
Gross unrealized gains, fixed maturities	0
Gross unrealized losses, fixed maturities	0
Estimated fair value, fixed maturities	6
Exchange \| Government sponsored enterprises
Available-for-sale securities
Amortized cost, fixed maturities	3
Gross unrealized gains, fixed maturities	1
Gross unrealized losses, fixed maturities	0
Estimated fair value, fixed maturities	4
Exchange \| States & political subdivisions
Available-for-sale securities
Amortized cost, fixed maturities	1,400	1,430
Gross unrealized gains, fixed maturities	84	55
Gross unrealized losses, fixed maturities	1	15
Estimated fair value, fixed maturities	1,483	1,470
Exchange \| Foreign government securities
Available-for-sale securities
Amortized cost, fixed maturities	15	15
Gross unrealized gains, fixed maturities	0	0
Gross unrealized losses, fixed maturities	0	0
Estimated fair value, fixed maturities	15	15
Exchange \| Corporate debt securities
Available-for-sale securities
Amortized cost, fixed maturities	6,788	5,902
Gross unrealized gains, fixed maturities	399	354
Gross unrealized losses, fixed maturities	26	45
Estimated fair value, fixed maturities	7,161	6,211
Exchange \| Residential mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	117	157
Gross unrealized gains, fixed maturities	3	3
Gross unrealized losses, fixed maturities	1	4
Estimated fair value, fixed maturities	119	156
Exchange \| Commercial mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	31	45
Gross unrealized gains, fixed maturities	2	2
Gross unrealized losses, fixed maturities	0	0
Estimated fair value, fixed maturities	33	47
Exchange \| Collateralized debt obligations
Available-for-sale securities
Amortized cost, fixed maturities	6	8
Gross unrealized gains, fixed maturities	5	8
Gross unrealized losses, fixed maturities	0	0
Estimated fair value, fixed maturities	11	16
Exchange \| Other debt securities
Available-for-sale securities
Amortized cost, fixed maturities	69	73
Gross unrealized gains, fixed maturities	2	3
Gross unrealized losses, fixed maturities	1	1
Estimated fair value, fixed maturities	70	75
Exchange \| Nonredeemable preferred stock
Available-for-sale securities
Amortized cost, equity securities	657	577
Gross unrealized gains, equity securities	66	55
Gross unrealized losses, equity securities	3	11
Estimated fair value, equity securities	720	621
Exchange \| Common stock
Available-for-sale securities
Amortized cost, equity securities	196	201
Gross unrealized gains, equity securities	2	0
Gross unrealized losses, equity securities	1	3
Estimated fair value, equity securities	$ 197	$ 198

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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