Fair Value (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended																																																																													6 Months Ended	12 Months Ended																																																																																																													6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 Fair value measurements on a recurring basis	Dec. 31, 2013 Fair value measurements on a recurring basis	Jun. 30, 2014 Fair value measurements on a recurring basis Level 1	Dec. 31, 2013 Fair value measurements on a recurring basis Level 1	Jun. 30, 2014 Fair value measurements on a recurring basis Level 2	Dec. 31, 2013 Fair value measurements on a recurring basis Level 2	Jun. 30, 2014 Fair value measurements on a recurring basis Level 3	Dec. 31, 2013 Fair value measurements on a recurring basis Level 3	Jun. 30, 2014 Fair value measurements on a recurring basis Level 3 Real estate fund	Dec. 31, 2013 Fair value measurements on a recurring basis Level 3 Real estate fund	Jun. 30, 2014 Indemnity	Dec. 31, 2013 Indemnity	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Fixed maturities	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Fixed maturities	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis States & political subdivisions	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis States & political subdivisions	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Corporate debt securities	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Corporate debt securities	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Collateralized debt obligations	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Collateralized debt obligations	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Nonredeemable preferred stock	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Nonredeemable preferred stock	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Common stock	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Common stock	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Real estate	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Real estate	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 1	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 1	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 1 Fixed maturities	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 1 Fixed maturities	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 1 States & political subdivisions	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 1 States & political subdivisions	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 1 Corporate debt securities	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 1 Corporate debt securities	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 1 Collateralized debt obligations	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 1 Collateralized debt obligations	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 1 Nonredeemable preferred stock	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 1 Nonredeemable preferred stock	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 1 Common stock	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 1 Common stock	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 1 Real estate	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 1 Real estate	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 2	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 2	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 2 Fixed maturities	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 2 Fixed maturities	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 2 States & political subdivisions	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 2 States & political subdivisions	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 2 Corporate debt securities	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 2 Corporate debt securities	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 2 Collateralized debt obligations	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 2 Collateralized debt obligations	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 2 Nonredeemable preferred stock	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 2 Nonredeemable preferred stock	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 2 Common stock	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 2 Common stock	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 2 Real estate	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 2 Real estate	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 3	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 3	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 3 Fixed maturities	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 3 Fixed maturities	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 3 States & political subdivisions	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 3 States & political subdivisions	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 3 Corporate debt securities	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 3 Corporate debt securities	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 3 Collateralized debt obligations	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 3 Collateralized debt obligations	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 3 Nonredeemable preferred stock	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 3 Nonredeemable preferred stock	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 3 Common stock	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 3 Common stock	Jun. 30, 2014 Indemnity Fair value measurements on a recurring basis Level 3 Real estate	Dec. 31, 2013 Indemnity Fair value measurements on a recurring basis Level 3 Real estate	Jun. 30, 2014 Exchange	Dec. 31, 2013 Exchange	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Fixed maturities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Fixed maturities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis U.S. government & agencies	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis U.S. treasury	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Government sponsored enterprises	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis States & political subdivisions	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis States & political subdivisions	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Foreign government securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Foreign government securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Corporate debt securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Corporate debt securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Residential mortgage-backed securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Residential mortgage-backed securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Commercial mortgage-backed securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Commercial mortgage-backed securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Collateralized debt obligations	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Collateralized debt obligations	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Other debt securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Other debt securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Nonredeemable preferred stock	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Nonredeemable preferred stock	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Common stock	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Common stock	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Real estate	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Real estate	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 Fixed maturities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1 Fixed maturities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1 U.S. government & agencies	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 U.S. treasury	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 Government sponsored enterprises	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 States & political subdivisions	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1 States & political subdivisions	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 Foreign government securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1 Foreign government securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 Corporate debt securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1 Corporate debt securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 Residential mortgage-backed securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1 Residential mortgage-backed securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 Commercial mortgage-backed securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1 Commercial mortgage-backed securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 Collateralized debt obligations	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1 Collateralized debt obligations	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 Other debt securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1 Other debt securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 Nonredeemable preferred stock	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1 Nonredeemable preferred stock	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 Common stock	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1 Common stock	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 1 Real estate	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 1 Real estate	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 Fixed maturities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2 Fixed maturities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2 U.S. government & agencies	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 U.S. treasury	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 Government sponsored enterprises	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 States & political subdivisions	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2 States & political subdivisions	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 Foreign government securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2 Foreign government securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 Corporate debt securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2 Corporate debt securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 Residential mortgage-backed securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2 Residential mortgage-backed securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 Commercial mortgage-backed securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2 Commercial mortgage-backed securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 Collateralized debt obligations	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2 Collateralized debt obligations	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 Other debt securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2 Other debt securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 Nonredeemable preferred stock	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2 Nonredeemable preferred stock	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 Common stock	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2 Common stock	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 2 Real estate	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 2 Real estate	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 Fixed maturities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3 Fixed maturities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3 U.S. government & agencies	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 U.S. treasury	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 Government sponsored enterprises	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 States & political subdivisions	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3 States & political subdivisions	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 Foreign government securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3 Foreign government securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 Corporate debt securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3 Corporate debt securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 Residential mortgage-backed securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3 Residential mortgage-backed securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 Commercial mortgage-backed securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3 Commercial mortgage-backed securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 Collateralized debt obligations	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3 Collateralized debt obligations	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 Other debt securities	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3 Other debt securities	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 Nonredeemable preferred stock	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3 Nonredeemable preferred stock	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 Common stock	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3 Common stock	Jun. 30, 2014 Exchange Fair value measurements on a recurring basis Level 3 Real estate	Dec. 31, 2013 Exchange Fair value measurements on a recurring basis Level 3 Real estate	Jun. 30, 2014 Minimum Fair value measurements on a recurring basis Level 3 Real estate	Dec. 31, 2013 Minimum Fair value measurements on a recurring basis Level 3 Real estate	Jun. 30, 2014 Maximum Fair value measurements on a recurring basis Level 3 Real estate	Dec. 31, 2013 Maximum Fair value measurements on a recurring basis Level 3 Real estate
Fair value measurements on a recurring basis by asset class and level of input
Available-for-sale securities	$ 10,138		$ 9,557											$ 523	$ 576	$ 523	$ 576	$ 497	$ 526	$ 241	$ 243	$ 256	$ 282	$ 0	$ 1	$ 14	$ 25	$ 12	$ 25			$ 14	$ 27	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 2	$ 2	$ 12	$ 25			$ 508	$ 547	$ 496	$ 524	$ 241	$ 243	$ 255	$ 281	$ 0	$ 0	$ 12	$ 23	$ 0	$ 0			$ 1	$ 2	$ 1	$ 2	$ 0	$ 0	$ 1	$ 1	$ 0	$ 1	$ 0	$ 0	$ 0	$ 0			$ 9,615	$ 8,981	$ 9,615	$ 8,981	$ 8,701	$ 8,162	$ 172	$ 31	$ 4	$ 1,519	$ 1,470	$ 15	$ 15	$ 6,866	$ 6,211	$ 146	$ 156	$ 34	$ 47	$ 14	$ 16	$ 72	$ 75	$ 717	$ 621	$ 197	$ 198			$ 500	$ 440	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 303	$ 242	$ 197	$ 198			$ 9,089	$ 8,510	$ 8,676	$ 8,131	$ 172	$ 31	$ 4	$ 1,519	$ 1,470	$ 15	$ 15	$ 6,841	$ 6,185	$ 146	$ 156	$ 34	$ 47	$ 14	$ 11	$ 72	$ 75	$ 413	$ 379	$ 0	$ 0			$ 26	$ 31	$ 25	$ 31	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 25	$ 26	$ 0	$ 0	$ 0	$ 0	$ 0	$ 5	$ 0	$ 0	$ 1	$ 0	$ 0	$ 0
Trading securities																																																																																		3,377	3,202																						3,377	3,202			3,362	3,187																						3,362	3,187			0	0																						0	0			15	15																						15	15
Other investments																														18	18															0	0															0	0															18	18																												102	98																										0	0																										0	0																										102	98
Total				13,635	12,875	3,876	3,654	9,597	9,057	162	164					541	594															14	27															508	547															19	20																	13,094	12,281																										3,862	3,627																										9,089	8,510																										143	144
Other investments:
Number of real estate funds reported under fair value option												4	4
Underlying assets, liquidation period from inception of fund																																																																																																																																																																																														5 years	5 years	10 years	10 years
Contributions made to the funds	46.0	52.0																																																																												0	0																																																																																																													0	0
Distributions received from the funds	70.0	86.0																																																																												1.8	2.4																																																																																																													6.9	21.7
Unfunded commitments																																																																														$ 1.5	$ 1.5																																																																																																													$ 4.5	$ 4.5