Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Number of Operating Regions	11
Operating revenues	$ 375,208	$ 207,436
Income from operations	76,200	41,314
Depreciation and amortization	34,223	17,633
Interest expense	(20,120)	(8,616)
Interest income	1,043	867
Benefit from/(provision for) income taxes	24,932	(12,305)
Expenditures for additions to property & equipment, net of grants from outside parties	33,553	41,881
North American & European Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues	299,095	144,073
Income from operations	54,794	31,313
Depreciation and amortization	27,411	12,318
Interest expense	(15,811)	(4,765)
Interest income	888	805
Benefit from/(provision for) income taxes	30,049	(10,539)
Expenditures for additions to property & equipment, net of grants from outside parties	14,711	12,804
Australian Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues	76,113	63,363
Income from operations	21,406	10,001
Depreciation and amortization	6,812	5,315
Interest expense	(4,309)	(3,851)
Interest income	155	62
Benefit from/(provision for) income taxes	(5,117)	(1,766)
Expenditures for additions to property & equipment, net of grants from outside parties	$ 18,842	$ 29,077