Schedule IV - Reinsurance (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Life reinsurance in force:
Gross amount, life reinsurance in force	[1]	$ 0	$ 0	$ 0
Ceded to other companies, life reinsurance in force	[1]	51,176,725	62,290,992	46,947,677
Assumed from other companies, life reinsurance in force	[1]	51,971,475	63,158,304	68,854,340
Net amount, life reinsurance in force	[1]	794,750	867,312	21,906,663
Total premiums earned:
Gross amount, premiums earned		9,142,690	7,717,173	5,173,403
Ceded to other companies, premiums earned		3,704,888	3,266,085	1,955,098
Assumed from other companies, premiums earned		4,340,132	3,775,337	2,676,765
Net amount, premiums earned		$ 9,777,934	$ 8,226,425	$ 5,895,070
Percentage of amount assumed to net		44.40%	45.90%	45.40%
Property and casualty operations
Total premiums earned:
Gross amount, premiums earned		$ 9,142,690	$ 7,717,173	$ 5,173,403
Ceded to other companies, premiums earned		3,451,620	3,018,410	1,799,294
Assumed from other companies, premiums earned		4,074,817	3,465,421	2,343,329
Net amount, premiums earned		$ 9,765,887	$ 8,164,184	$ 5,717,438
Percentage of amount assumed to net		41.70%	42.40%	41.00%
Life operations
Total premiums earned:
Gross amount, premiums earned		$ 0	$ 0	$ 0
Ceded to other companies, premiums earned		253,268	247,675	155,804
Assumed from other companies, premiums earned		265,315	309,916	333,436
Net amount, premiums earned		$ 12,047	$ 62,241	$ 177,632

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