Deferred Policy Acquisition Costs - Deferred Policy Acquisition Costs (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	$ 1,497,261
Additions	404,005
Amortization	(381,614)
Effect of change in unrealized gains on available-for-sale debt securities	(82,452)
Net change	(60,061)
Ending balance	1,437,200
Life
Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	839,133
Additions	98,812
Amortization	(79,692)
Effect of change in unrealized gains on available-for-sale debt securities	(12,799)
Net change	6,321
Ending balance	845,454
Annuity
Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	499,588
Additions	61,779
Amortization	(61,396)
Effect of change in unrealized gains on available-for-sale debt securities	(69,653)
Net change	(69,270)
Ending balance	430,318
Health
Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	33,960
Additions	7,629
Amortization	(8,548)
Effect of change in unrealized gains on available-for-sale debt securities	0
Net change	(919)
Ending balance	33,041
Property & Casualty
Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	124,580
Additions	235,785
Amortization	(231,978)
Effect of change in unrealized gains on available-for-sale debt securities	0
Net change	3,807
Ending balance	$ 128,387