Deferred Policy Acquisition Costs - Deferred Policy Acquisition Costs (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	$ 1,497,261
Additions	277,260
Amortization	(253,321)
Effect of change in unrealized gains on available-for-sale debt securities	(34,853)
Net change	(10,914)
Ending balance	1,486,347
Life
Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	839,133
Additions	64,419
Amortization	(50,379)
Effect of change in unrealized gains on available-for-sale debt securities	(9,809)
Net change	4,231
Ending balance	843,364
Annuity
Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	499,588
Additions	48,168
Amortization	(40,779)
Effect of change in unrealized gains on available-for-sale debt securities	(25,044)
Net change	(17,655)
Ending balance	481,933
Health
Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	33,960
Additions	6,544
Amortization	(7,205)
Effect of change in unrealized gains on available-for-sale debt securities	0
Net change	(661)
Ending balance	33,299
Property & Casualty
Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	124,580
Additions	158,129
Amortization	(154,958)
Effect of change in unrealized gains on available-for-sale debt securities	0
Net change	3,171
Ending balance	$ 127,751