Liability for Unpaid Claims - Reconciliation of Net Incurred and Paid Claims Development to Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration products	$ 597,715
Insurance lines other than short duration—life	186,429	$ 156,437
Total policy claims and other benefits payable	333,294	299,565
Health Insurance Product Line [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration products	24,707	26,721
Insurance lines other than short duration—health	122,158	116,407
Total policy claims and other benefits payable	$ 146,865	$ 143,128