Segment Information Segments (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) reportable_segment region	Jun. 30, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of operating regions | region			11
Number of reportable segments | reportable_segment			3
Operating revenues	$ 542,219,000	$ 414,563,000	$ 939,249,000	$ 790,842,000
Income/(loss) from operations	99,451,000	110,109,000	172,071,000	184,984,000
Depreciation and amortization	48,048,000	38,212,000	90,265,000	75,853,000
Interest expense, net	17,648,000	17,573,000	31,130,000	30,180,000
Foreign Currency Forward Purchase Contracts Not Designated as Hedging Instruments, Gain (Loss), Net	0	0	18,686,000	0
Provision for/(benefit from) income taxes	29,300,000	32,567,000	46,162,000	55,467,000
Expenditures for additions to property & equipment, net of grants from outside parties	87,627,000	88,459,000	137,525,000	147,277,000
North American Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues	310,980,000	325,742,000	628,604,000	621,384,000
Income/(loss) from operations	76,621,000	85,387,000	133,702,000	141,979,000
Depreciation and amortization	34,936,000	30,629,000	70,241,000	60,824,000
Interest expense, net	9,588,000	13,863,000	20,361,000	22,230,000
Foreign Currency Forward Purchase Contracts Not Designated as Hedging Instruments, Gain (Loss), Net			16,374,000
Provision for/(benefit from) income taxes	24,939,000	26,707,000	39,226,000	45,865,000
Expenditures for additions to property & equipment, net of grants from outside parties	73,440,000	85,315,000	118,710,000	138,899,000
Australian Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues	66,808,000	83,119,000	126,750,000	159,411,000
Income/(loss) from operations	15,131,000	25,331,000	29,367,000	44,266,000
Depreciation and amortization	7,394,000	7,172,000	13,620,000	14,234,000
Interest expense, net	2,271,000	3,485,000	4,604,000	7,549,000
Foreign Currency Forward Purchase Contracts Not Designated as Hedging Instruments, Gain (Loss), Net			2,312,000
Provision for/(benefit from) income taxes	3,829,000	6,560,000	6,757,000	11,003,000
Expenditures for additions to property & equipment, net of grants from outside parties	9,159,000	3,047,000	13,774,000	7,880,000
U.K./European Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues	164,431,000	5,702,000	183,895,000	10,047,000
Income/(loss) from operations	7,699,000	(609,000)	9,002,000	(1,261,000)
Depreciation and amortization	5,718,000	411,000	6,404,000	795,000
Interest expense, net	5,789,000	225,000	6,165,000	401,000
Foreign Currency Forward Purchase Contracts Not Designated as Hedging Instruments, Gain (Loss), Net			0
Provision for/(benefit from) income taxes	532,000	(700,000)	179,000	(1,401,000)
Expenditures for additions to property & equipment, net of grants from outside parties	$ 5,028,000	$ 97,000	$ 5,041,000	$ 498,000