Summary of Significant Accounting Policies Deferred Acquisition Costs and Cost of Customer Relationships Acquired (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Policy Acquisition Costs and Cost of Customer Relationship Acquired [Abstract]
First year commissions, percentage of capitalized deferred acquisition costs	95.00%
New business expense, percentage of capitalized deferred acquisition costs	5.00%
Number of years of available premiums	50 years
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance at beginning of period	$ 167,790	$ 163,692	$ 155,859
Capitalization of deferred policy acquisition costs	29,120	32,732	31,104
Amortization of deferred policy acquisition costs	(29,690)	(28,515)	(23,400)
Effect of Unrealized (gains) losses	(157)	(119)	129
Balance at end of period	$ 167,063	$ 167,790	$ 163,692