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, 2019	Dec. 31, 2018	Dec. 31, 2017
Beginning Balance	$ 96,024	$ 93,275	$ 91,162
Charged to Costs and Expenses	79,959	75,052	71,229
Charged to other Accounts	0	0	0
Deductions	79,972	72,303	69,116
Accrued risk reserves	$ 96,011	$ 96,024	$ 93,275