Reserves for Unpaid Losses and Loss Adjustment Expenses Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves	$ (5,722)	$ (11,831)
Accident Year 2017 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves	(4,800)
Accident Year 2016 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves	(3,300)	(8,600)
Accident Year 2015 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves		(4,800)
Accident Year 2014 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves		(1,800)
Accident Years 2011 to 2015 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves	$ 2,400
Accident Years 2011 to 2013 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves		$ 3,400