Deferred Policy Acquisition Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of year	$ 233,166	$ 215,131	$ 198,151
Policy acquisition costs deferred	641,616	620,120	589,144
Amortization	(627,788)	(602,085)	(572,164)
Balance, end of year	$ 246,994	$ 233,166	$ 215,131