Deferred Policy Acquisition Costs - Deferred Policy Acquisition Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	$ 1,497,261	$ 1,373,844	$ 1,294,443
Additions	543,258	551,654	525,835
Amortization	(530,509)	(480,157)	(444,351)
Effect of change in unrealized gains on available-for-sale debt securities	(87,003)	51,920	(2,083)
Net change	(74,254)	123,417	79,401
Ending balance	1,423,007	1,497,261	1,373,844
Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	839,133	791,276	745,840
Additions	139,336	131,156	123,854
Amortization	(113,300)	(97,263)	(74,068)
Effect of change in unrealized gains on available-for-sale debt securities	(12,269)	13,964	(4,350)
Net change	13,767	47,857	45,436
Ending balance	852,900	839,133	791,276
Annuity
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	499,588	426,497	394,208
Additions	70,272	92,603	104,772
Amortization	(79,746)	(57,468)	(74,750)
Effect of change in unrealized gains on available-for-sale debt securities	(74,734)	37,956	2,267
Net change	(84,208)	73,091	32,289
Ending balance	415,380	499,588	426,497
Health
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	33,960	36,806	40,620
Additions	19,940	12,590	11,413
Amortization	(21,322)	(15,436)	(15,227)
Effect of change in unrealized gains on available-for-sale debt securities	0	0	0
Net change	(1,382)	(2,846)	(3,814)
Ending balance	32,578	33,960	36,806
Property & Casualty
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	124,580	119,265	113,775
Additions	313,710	315,305	285,796
Amortization	(316,141)	(309,990)	(280,306)
Effect of change in unrealized gains on available-for-sale debt securities	0	0	0
Net change	(2,431)	5,315	5,490
Ending balance	$ 122,149	$ 124,580	$ 119,265