Investments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Available-for-sale securities
Amortized cost, fixed maturities	$ 9,095
Amortized cost	9,907	9,147
Gross unrealized gains	584	492
Gross unrealized losses	45	82
Estimated fair value, fixed maturities	9,571	8,688
Estimated fair value, equity securities	875	869
Estimated fair value	10,446us-gaap_AvailableForSaleSecurities	9,557us-gaap_AvailableForSaleSecurities
Indemnity
Available-for-sale securities
Amortized cost, fixed maturities	555	518
Amortized cost, equity securities	24	50
Amortized cost	579	568
Gross unrealized gains	14	11
Gross unrealized losses	4	3
Estimated fair value, fixed maturities	564	526
Estimated fair value, equity securities	25	50
Estimated fair value	589	576
Indemnity \| Fixed maturities
Available-for-sale securities
Amortized cost, fixed maturities	555	518
Gross unrealized gains, fixed maturities	13	9
Gross unrealized losses, fixed maturities	4	1
Estimated fair value, fixed maturities	564	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	236	280
Gross unrealized gains, fixed maturities	1	2
Gross unrealized losses, fixed maturities	3	0
Estimated fair value, fixed maturities	234	282
Indemnity \| Residential mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	8
Gross unrealized gains, fixed maturities	0
Gross unrealized losses, fixed maturities	0
Estimated fair value, fixed maturities	8
Indemnity \| Commercial mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	52
Gross unrealized gains, fixed maturities	0
Gross unrealized losses, fixed maturities	1
Estimated fair value, fixed maturities	51
Indemnity \| Collateralized debt obligations
Available-for-sale securities
Amortized cost, fixed maturities	33	1
Gross unrealized gains, fixed maturities	0	0
Gross unrealized losses, fixed maturities	0	0
Estimated fair value, fixed maturities	33	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	8,540	7,801
Amortized cost, equity securities	788	778
Amortized cost	9,328	8,579
Gross unrealized gains	570	481
Gross unrealized losses	41	79
Estimated fair value, fixed maturities	9,007	8,162
Estimated fair value, equity securities	850	819
Estimated fair value	9,857	8,981
Exchange \| Fixed maturities
Available-for-sale securities
Amortized cost, fixed maturities	8,540	7,801
Gross unrealized gains, fixed maturities	503	426
Gross unrealized losses, fixed maturities	36	65
Estimated fair value, fixed maturities	9,007	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	1,394	1,430
Gross unrealized gains, fixed maturities	84	55
Gross unrealized losses, fixed maturities	1	15
Estimated fair value, fixed maturities	1,477	1,470
Exchange \| Foreign government securities
Available-for-sale securities
Amortized cost, fixed maturities	10	15
Gross unrealized gains, fixed maturities	0	0
Gross unrealized losses, fixed maturities	0	0
Estimated fair value, fixed maturities	10	15
Exchange \| Corporate debt securities
Available-for-sale securities
Amortized cost, fixed maturities	6,918	5,902
Gross unrealized gains, fixed maturities	405	354
Gross unrealized losses, fixed maturities	34	45
Estimated fair value, fixed maturities	7,289	6,211
Exchange \| Residential mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	109	157
Gross unrealized gains, fixed maturities	3	3
Gross unrealized losses, fixed maturities	1	4
Estimated fair value, fixed maturities	111	156
Exchange \| Commercial mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	28	45
Gross unrealized gains, fixed maturities	2	2
Gross unrealized losses, fixed maturities	0	0
Estimated fair value, fixed maturities	30	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	66	73
Gross unrealized gains, fixed maturities	3	3
Gross unrealized losses, fixed maturities	0	1
Estimated fair value, fixed maturities	69	75
Exchange \| Nonredeemable preferred stock
Available-for-sale securities
Amortized cost, equity securities	650	577
Gross unrealized gains, equity securities	64	55
Gross unrealized losses, equity securities	4	11
Estimated fair value, equity securities	710	621
Exchange \| Common stock
Available-for-sale securities
Amortized cost, equity securities	138	201
Gross unrealized gains, equity securities	3	0
Gross unrealized losses, equity securities	1	3
Estimated fair value, equity securities	$ 140	$ 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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