Summary of Significant Accounting Policies (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred Policy Acquisition Costs
Policy acquisition costs deferred	$ 7.7	$ 6.6	$ 6.6
Other underwriting and operating expenses
Deferred Policy Acquisition Costs
Amortization of deferred policy acquisition costs	$ 5.8	$ 4.7	$ 3.2