Segment Information Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 region	Jun. 30, 2013
Segment Reporting Information [Line Items]
Number of operating regions			11
Operating revenues	$ 414,563	$ 400,648	$ 790,842	$ 775,598
Income from operations	110,109	107,417	184,984	183,617
Depreciation and amortization	38,212	34,161	75,853	68,384
Interest expense	17,814	17,203	31,455	37,323
Interest income	241	950	1,275	1,993
(Provision for)/benefit from income taxes	(32,567)	(25,218)	(55,467)	(286)
Expenditures for additions to property & equipment, net of grants from outside parties	88,459	72,773	147,277	106,326
North American & European Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues	331,444	317,216	631,431	616,311
Income from operations	84,528	82,122	140,218	136,916
Depreciation and amortization	31,040	27,388	61,619	54,799
Interest expense	14,280	13,282	23,725	29,093
Interest income	192	915	1,094	1,804
(Provision for)/benefit from income taxes	(26,007)	(19,379)	(44,464)	10,670
Expenditures for additions to property & equipment, net of grants from outside parties	85,412	59,215	139,397	73,926
Australian Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues	83,119	83,432	159,411	159,287
Income from operations	25,581	25,295	44,766	46,701
Depreciation and amortization	7,172	6,773	14,234	13,585
Interest expense	3,534	3,921	7,730	8,230
Interest income	49	35	181	189
(Provision for)/benefit from income taxes	(6,560)	(5,839)	(11,003)	(10,956)
Expenditures for additions to property & equipment, net of grants from outside parties	$ 3,047	$ 13,558	$ 7,880	$ 32,400