SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Benefit (charge) within operating expense	$ (1,000)	$ 9,000	$ (9,000)
Accounts receivable allowance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	13,847	14,915	15,560
Charged to Earnings	10,890	12,335	13,118
Transferred from (to) Other Accounts	0	0	0
Deductions	7,555	13,403	13,763
Balance at End of Period	17,182	13,847	14,915
Self-insurance accruals
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	348,612	336,901	311,821
Charged to Earnings	359,528	327,306	324,673
Transferred from (to) Other Accounts	82,904	74,153	71,703
Deductions	433,518	389,748	371,296
Balance at End of Period	357,526	348,612	336,901
Valuation allowance on deferred tax assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	18,667	16,387	14,991
Charged to Earnings	(534)	2,213	98
Transferred from (to) Other Accounts	0	0	0
Deductions	1,947	(67)	(1,298)
Balance at End of Period	$ 16,186	$ 18,667	$ 16,387