Schedule IV - Reinsurance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Life insurance in-force, direct amount	$ 117,886,265	$ 110,125,270	$ 102,843,372
Life insurance in-force, ceded to other companies	24,913,905	26,601,422	29,646,646
Life insurance in-force, assumed from other companies	218,020	230,845	257,552
Life insurance in-force, net amount	$ 93,190,380	$ 83,754,693	$ 73,454,278
Life insurance in-force, percentage of amount assumed to net	0.20%	0.30%	0.40%
Premiums earned, direct amount	$ 2,464,870	$ 2,499,584	$ 2,341,088
Premiums earned, ceded to other companies	518,580	557,556	500,939
Premiums earned, assumed from other companies	236,504	286,165	227,053
Net premiums	$ 2,182,794	$ 2,228,193	$ 2,067,202
Premiums earned, percentage of amount assumed to net	10.80%	12.80%	11.00%
Life and Annuity
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Premiums earned, direct amount	$ 605,796	$ 684,399	$ 654,086
Premiums earned, ceded to other companies	99,856	103,749	104,599
Premiums earned, assumed from other companies	618	389	1,290
Net premiums	$ 506,558	$ 581,039	$ 550,777
Premiums earned, percentage of amount assumed to net	0.10%	0.10%	0.20%
Health
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Premiums earned, direct amount	$ 209,200	$ 209,109	$ 194,516
Premiums earned, ceded to other companies	269,487	303,623	253,110
Premiums earned, assumed from other companies	225,322	274,928	215,030
Net premiums	$ 165,035	$ 180,414	$ 156,436
Premiums earned, percentage of amount assumed to net	136.50%	152.40%	137.50%
Property & Casualty
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Premiums earned, direct amount	$ 1,649,874	$ 1,606,076	$ 1,492,486
Premiums earned, ceded to other companies	149,237	150,184	143,230
Premiums earned, assumed from other companies	10,564	10,848	10,733
Net premiums	$ 1,511,201	$ 1,466,740	$ 1,359,989
Premiums earned, percentage of amount assumed to net	0.70%	0.70%	0.80%