Fair Value (Details 3) (USD $) In Millions, unless otherwise specified	Sep. 30, 2011 holding
Adjustments to pricing service valuations
Number of holdings	7
Value of securities using pricing service	$ 26.8
Value of securities used in the financial statements	26.1
Indemnity | Total
Fair value by pricing source
Total available-for-sale securities and trading securities	565
Indemnity | Total | Fixed maturities
Fair value by pricing source
Total available-for-sale securities and trading securities	517
Indemnity | Total | Fixed maturities | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	512
Indemnity | Total | Fixed maturities | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	1
Indemnity | Total | Fixed maturities | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	4
Indemnity | Total | Preferred stock
Fair value by pricing source
Total available-for-sale securities and trading securities	22
Indemnity | Total | Preferred stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	20
Indemnity | Total | Preferred stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	2
Indemnity | Total | Preferred stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Total | Common stock
Fair value by pricing source
Total available-for-sale securities and trading securities	26
Indemnity | Total | Common stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	26
Indemnity | Total | Common stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Total | Common stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Total
Fair value by pricing source
Total available-for-sale securities and trading securities	10,007
Exchange | Total | Fixed maturities
Fair value by pricing source
Total available-for-sale securities and trading securities	7,331
Exchange | Total | Fixed maturities | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	7,192
Exchange | Total | Fixed maturities | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	89
Exchange | Total | Fixed maturities | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	50
Exchange | Total | Preferred stock
Fair value by pricing source
Total available-for-sale securities and trading securities	591
Exchange | Total | Preferred stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	560
Exchange | Total | Preferred stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	31
Exchange | Total | Preferred stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Total | Common stock
Fair value by pricing source
Total available-for-sale securities and trading securities	2,085
Exchange | Total | Common stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	2,072
Exchange | Total | Common stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Total | Common stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	13
Total
Fair value by pricing source
Total available-for-sale securities and trading securities	10,572
Indemnity | Level 1
Fair value by pricing source
Total available-for-sale securities and trading securities	33
Indemnity | Level 1 | Fixed maturities
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 1 | Fixed maturities | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 1 | Fixed maturities | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 1 | Fixed maturities | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 1 | Preferred stock
Fair value by pricing source
Total available-for-sale securities and trading securities	7
Indemnity | Level 1 | Preferred stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	7
Indemnity | Level 1 | Preferred stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 1 | Preferred stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 1 | Common stock
Fair value by pricing source
Total available-for-sale securities and trading securities	26
Indemnity | Level 1 | Common stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	26
Indemnity | Level 1 | Common stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 1 | Common stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 1
Fair value by pricing source
Total available-for-sale securities and trading securities	2,274
Exchange | Level 1 | Fixed maturities
Fair value by pricing source
Total available-for-sale securities and trading securities	21
Exchange | Level 1 | Fixed maturities | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	21
Exchange | Level 1 | Fixed maturities | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 1 | Fixed maturities | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 1 | Preferred stock
Fair value by pricing source
Total available-for-sale securities and trading securities	181
Exchange | Level 1 | Preferred stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	181
Exchange | Level 1 | Preferred stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 1 | Preferred stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 1 | Common stock
Fair value by pricing source
Total available-for-sale securities and trading securities	2,072
Exchange | Level 1 | Common stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	2,072
Exchange | Level 1 | Common stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 1 | Common stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Level 1
Fair value by pricing source
Total available-for-sale securities and trading securities	2,307
Indemnity | Level 2
Fair value by pricing source
Total available-for-sale securities and trading securities	528
Indemnity | Level 2 | Fixed maturities
Fair value by pricing source
Total available-for-sale securities and trading securities	513
Indemnity | Level 2 | Fixed maturities | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	512
Indemnity | Level 2 | Fixed maturities | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	1
Indemnity | Level 2 | Fixed maturities | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 2 | Preferred stock
Fair value by pricing source
Total available-for-sale securities and trading securities	15
Indemnity | Level 2 | Preferred stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	13
Indemnity | Level 2 | Preferred stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	2
Indemnity | Level 2 | Preferred stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 2 | Common stock
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 2 | Common stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 2 | Common stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 2 | Common stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 2
Fair value by pricing source
Total available-for-sale securities and trading securities	7,664
Exchange | Level 2 | Fixed maturities
Fair value by pricing source
Total available-for-sale securities and trading securities	7,260
Exchange | Level 2 | Fixed maturities | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	7,171
Exchange | Level 2 | Fixed maturities | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	89
Exchange | Level 2 | Fixed maturities | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 2 | Preferred stock
Fair value by pricing source
Total available-for-sale securities and trading securities	404
Exchange | Level 2 | Preferred stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	373
Exchange | Level 2 | Preferred stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	31
Exchange | Level 2 | Preferred stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 2 | Common stock
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 2 | Common stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 2 | Common stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 2 | Common stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Level 2
Fair value by pricing source
Total available-for-sale securities and trading securities	8,192
Indemnity | Level 3
Fair value by pricing source
Total available-for-sale securities and trading securities	4
Indemnity | Level 3 | Fixed maturities
Fair value by pricing source
Total available-for-sale securities and trading securities	4
Indemnity | Level 3 | Fixed maturities | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 3 | Fixed maturities | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 3 | Fixed maturities | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	4
Indemnity | Level 3 | Common stock
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 3 | Common stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 3 | Common stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 3 | Common stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 3 | Preferred stock
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 3 | Preferred stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 3 | Preferred stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Indemnity | Level 3 | Preferred stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 3
Fair value by pricing source
Total available-for-sale securities and trading securities	69
Exchange | Level 3 | Fixed maturities
Fair value by pricing source
Total available-for-sale securities and trading securities	50
Exchange | Level 3 | Fixed maturities | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 3 | Fixed maturities | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 3 | Fixed maturities | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	50
Exchange | Level 3 | Common stock
Fair value by pricing source
Total available-for-sale securities and trading securities	13
Exchange | Level 3 | Common stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 3 | Common stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 3 | Common stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	13
Exchange | Level 3 | Preferred stock
Fair value by pricing source
Total available-for-sale securities and trading securities	6
Exchange | Level 3 | Preferred stock | Priced via pricing services
Fair value by pricing source
Total available-for-sale securities and trading securities	6
Exchange | Level 3 | Preferred stock | Priced via market comparables/non-binding broker quote
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Exchange | Level 3 | Preferred stock | Priced via internal modeling
Fair value by pricing source
Total available-for-sale securities and trading securities	0
Level 3
Fair value by pricing source
Total available-for-sale securities and trading securities	73
Exchange
Adjustments to pricing service valuations
Number of holdings	7
Value of securities using pricing service	26.8
Value of securities used in the financial statements	$ 26.1
Fixed maturities | Priced via internal modeling
Fair value by pricing source
Number of securities	11
Common stock | Priced via internal modeling
Fair value by pricing source
Number of securities	3
Priced via internal modeling
Fair value by pricing source
Securities priced via internal modeling as a percentage of total portfolio (as a percent)	0.60%