Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets
Unpaid loss discount	$ 20,368	$ 39,746
Unearned premium adjustment	14,449	22,847
Compensation related	11,467	20,190
Intangibles	514	1,001
Foreign NOL	4,116	1,962
Total gross deferred tax assets	50,914	85,746
Valuation allowance	(4,116)	(1,962)
Total deferred tax assets, net of valuation allowance	46,798	83,784
Deferred tax liabilities
Deferred policy acquisition costs	(6,333)	(9,754)
Unrealized gains on investments, net	(5,166)	(9,797)
Fixed assets	(826)	(1,291)
Basis differentials–investments	(10,397)	(25,512)
Intangibles	(12,548)	(22,067)
Other	(1,598)	(5,107)
Total deferred tax liabilities	(36,868)	(73,528)
Net deferred tax assets (liabilities)	$ 9,930	$ 10,256