Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Movement in Valuation Allowances and Reserves [Roll Forward]
Benefit (charge) within operating expense	$ (4,000)	$ 14,000	$ 5,000
Accounts receivable allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	16,388	16,955	15,429
Charged to Earnings	11,172	7,086	7,561
Transferred from (to) Other Accounts	0	0	0
Deductions	12,000	7,653	6,035
Balance at End of Period	15,560	16,388	16,955
Direct finance lease allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	288	501	703
Charged to Earnings	1,495	47	205
Transferred from (to) Other Accounts	0	0	0
Deductions	1,540	260	407
Balance at End of Period	243	288	501
Self-insurance accruals
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	300,994	290,255	279,157
Charged to Earnings	308,026	273,509	266,314
Transferred from (to) Other Accounts	68,999	62,548	60,235
Deductions	366,198	325,318	315,451
Balance at End of Period	311,821	300,994	290,255
Valuation allowance on deferred tax assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	24,742	33,793	38,182
Charged to Earnings	(1,150)	(976)	1,627
Transferred from (to) Other Accounts	0	0	0
Deductions	8,601	8,075	6,016
Balance at End of Period	$ 14,991	$ 24,742	$ 33,793