Reserves for Unpaid Losses and Loss Adjustment Expenses Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves	$ (1,284)	$ (5,104)
Accident Year 2017 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves	(2,500)
Accident Year 2016 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves	(1,200)	(3,300)
Accident Year 2015 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves		(2,500)
Accident Year 2013 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves		$ 900
Accident Years 2011 to 2015 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves	$ 2,400