Schedule IV - Reinsurance (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Total premiums earned:
Gross Amount	$ 4,604,327		$ 4,624,557		$ 4,535,626
Ceded to Other Companies	1,263,157		1,509,308		1,374,243
Assumed from Other Companies	2,749,271		2,574,881		2,252,678
Net Amount	6,090,441		5,690,130		5,414,061
Percentage of Amount Assumed to Net	45.10%		45.30%		41.60%
Life Insurance in Force
Total premiums earned:
Gross Amount	0	[1]	0	[1]	0	[1]
Ceded to Other Companies	443,798	[1]	559,676	[1]	559,674	[1]
Assumed from Other Companies	82,099,647	[1]	88,646,215	[1]	100,908,397	[1]
Net Amount	81,655,849	[1]	88,086,539	[1]	100,348,723	[1]
Percentage of Amount Assumed to Net	100.50%	[1]	100.60%	[1]	100.60%	[1]
Property and casualty operations
Total premiums earned:
Gross Amount	4,604,327		4,624,557		4,535,626
Ceded to Other Companies	1,231,835		1,477,000		1,342,017
Assumed from Other Companies	2,393,490		2,179,555		1,837,528
Net Amount	5,765,982		5,327,112		5,031,137
Percentage of Amount Assumed to Net	41.50%		40.90%		36.50%
Life operations
Total premiums earned:
Gross Amount	0		0		0
Ceded to Other Companies	31,322		32,308		32,226
Assumed from Other Companies	355,781		395,326		415,150
Net Amount	$ 324,459		$ 363,018		$ 382,924
Percentage of Amount Assumed to Net	109.70%		108.90%		108.40%

[1] Represents the sum face value outstanding of the in force life reinsurance policies.