Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net realized investment (gains) losses	$ (3,590)	$ (3,201)	$ (15,877)	$ (2,885)
Total before tax	(15,849)	(5,793)	(39,743)	(10,241)
Income tax expense (benefit)	1,186	(1,399)	5,480	(2,652)
Net loss	(14,663)	(7,192)	(34,263)	(12,893)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	(3,740)	611	(1,818)	686
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains and Losses on Available for Sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net realized investment (gains) losses	(4,083)	361	(3,785)	454
Other than temporary impairment losses on investments	0	371	1,897	371
Total before tax	(4,083)	732	(1,888)	825
Income tax expense (benefit)	343	(121)	70	(139)
Net loss	(3,740)	611	(1,818)	686
Reclassification out of Accumulated Other Comprehensive Income | Foreign Currency Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net realized investment (gains) losses	0	0	0	0
Income tax expense (benefit)	0	0	0	0
Net loss	$ 0	$ 0	$ 0	$ 0