Valuation and Qualifying Accounts (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Movement in Valuation Allowances and Reserves [Roll Forward]
Benefit (charge) within operating expense	$ 14,000,000	$ 5,000,000	$ 1,000,000
Accounts receivable allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	16,955,000	15,429,000	14,489,000
Charged to Earnings	7,086,000	7,561,000	10,478,000
Transferred from (to) Other Accounts	0	0	0
Deductions	(7,653,000)	(6,035,000)	(9,538,000)
Balance at End of Period	16,388,000	16,955,000	15,429,000
Direct finance lease allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	501,000	703,000	903,000
Charged to Earnings	47,000	205,000	812,000
Transferred from (to) Other Accounts	0	0	0
Deductions	(260,000)	(407,000)	(1,012,000)
Balance at End of Period	288,000	501,000	703,000
Self-insurance accruals [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	290,255,000	279,157,000	253,424,000
Charged to Earnings	273,509,000	266,314,000	272,357,000
Transferred from (to) Other Accounts	62,548,000	60,235,000	57,285,000
Deductions	(325,318,000)	(315,451,000)	(303,909,000)
Balance at End of Period	300,994,000	290,255,000	279,157,000
Reserve For Residual Value Guarantees [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	239,000	1,635,000	4,218,000
Charged to Earnings	(11,000)	(413,000)	179,000
Transferred from (to) Other Accounts	0	0	0
Deductions	0	(983,000)	(2,762,000)
Balance at End of Period	228,000	239,000	1,635,000
Valuation allowance on deferred tax assets [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	33,793,000	38,182,000	41,324,000
Charged to Earnings	(976,000)	1,627,000	1,061,000
Transferred from (to) Other Accounts	0	0	0
Deductions	(8,075,000)	(6,016,000)	(4,203,000)
Balance at End of Period	$ 24,742,000	$ 33,793,000	$ 38,182,000