Summary of Investments - Other-than-temporary impairment table (Details) - Fixed maturities - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	$ 52,775	$ 80,359	$ 62,231	$ 83,665
Due to sales, maturities or payoffs during the period	0	0	(1,510)	0
Due to increases in cash flows expected to be collected that are recognized over the remaining life of the security	(3,092)	(2,948)	(11,038)	(6,254)
Ending balance	$ 49,683	$ 77,411	$ 49,683	$ 77,411