Investments - Realized Gains (Losses) on Investment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Gain (Loss) on Investments [Line Items]
Gross gains	$ 7,690	$ 3,041	$ 1,773
Gross losses	(916)	(543)	(610)
Net	6,774	2,498	1,163
Proceeds from sales of fixed maturities classified as available-for-sale	129,306	129,152	171,216
Total net unrealized (losses) gains	(20,632)	(54,028)	78,749
Deferred income tax	(84)	(84)	(170)
Net unrealized (losses) gains, net of deferred income tax	(20,716)	(54,112)	78,579
Change, net of deferred income tax	33,396	(132,691)	43,851
Other investments
Gain (Loss) on Investments [Line Items]
Gross gains	550	192	439
Gross losses	0	0	0
Net	550	192	439
Total net unrealized (losses) gains	3,003	996	1,709
Fixed maturities | Available-for-sale securities
Gain (Loss) on Investments [Line Items]
Gross gains	7,140	2,849	1,334
Gross losses	(916)	(543)	(610)
Net	6,224	2,306	724
Total net unrealized (losses) gains	$ (23,635)	$ (55,024)	$ 77,040