Deferred Policy Acquisition Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of year	$ 201,762	$ 197,202	$ 194,466
Policy acquisition costs deferred	561,610	543,791	528,944
Amortization	(562,546)	(539,231)	(526,208)
Balance, end of year	$ 200,826	$ 201,762	$ 197,202