Schedule II - Valuation and Qualifying Accounts - Summary of Valuation and Qualifying Accounts (Details) - Accrued Risk Reserves [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Beginning Balance	$ 93,275	$ 91,162	$ 98,508
Charged to Costs and Expenses	75,052	71,229	63,596
Charged to other Accounts
Deductions	72,303	69,116	70,942
Accrued risk reserves	$ 96,024	$ 93,275	$ 91,162