Reserves for Unpaid Losses and Loss Adjustment Expenses Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves	$ (3,523)	$ (8,936)
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	(3,000)	(5,800)
Accident Year 2015 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves	(800)	(3,700)
Accident Year 2013 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves		$ 1,100
Accident Years 2011 to 2014 [Member]
Claims Development [Line Items]
Adverse (favorable) development on prior year loss reserves	$ 2,800