Investments Gains and Losses by Security Type (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains	$ 1,115	$ 1,875	$ 2,622
Available-for-sale, Gross Realized Gains, Fair Value at Sale	37,457	69,737	94,931
Available-for-sale Securities, Gross Realized Losses	(1,048)	(1,328)	(1,795)
Available-for-sale, Gross Realized Losses, Fair Value at Sale	54,943	62,254	42,657
Available-for-sale Securities, Gross Realized Gain (Loss)	67	547	827
Available-for-sale, Gross Realized Gains (Losses), Fair Value at Sale	92,400	131,991	137,588
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains	268	1,811	727
Available-for-sale, Gross Realized Gains, Fair Value at Sale	35,248	56,484	87,141
Available-for-sale Securities, Gross Realized Losses	(890)	(1,136)	(595)
Available-for-sale, Gross Realized Losses, Fair Value at Sale	53,194	24,464	38,485
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains	847	64	1,895
Available-for-sale, Gross Realized Gains, Fair Value at Sale	2,209	13,253	7,790
Available-for-sale Securities, Gross Realized Losses	(158)	(192)	(1,200)
Available-for-sale, Gross Realized Losses, Fair Value at Sale	$ 1,749	$ 37,790	$ 4,172