Segment Information Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 region reportable_segment	Sep. 30, 2013
Segment Reporting Information [Line Items]
Number of operating regions			11
Number of reportable segments			2
Operating revenues	$ 432,543	$ 401,377	$ 1,223,385	$ 1,176,975
Income from operations	123,116	101,741	308,100	285,358
Depreciation and amortization	40,277	37,334	116,130	105,718
Interest expense	12,654	16,029	44,109	53,352
Interest income	82	992	1,357	2,985
Provision for income taxes	36,945	22,231	92,412	22,517
Expenditures for additions to property & equipment, net of grants from outside parties	80,901	40,231	228,178	146,557
North American & European Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues	351,065	319,079	982,496	935,390
Income from operations	100,507	77,024	240,725	213,940
Depreciation and amortization	33,205	30,704	94,824	85,503
Interest expense	10,118	12,473	33,843	41,566
Interest income	32	926	1,126	2,730
Provision for income taxes	31,001	17,287	75,465	6,617
Expenditures for additions to property & equipment, net of grants from outside parties	73,240	31,277	212,637	105,203
Australian Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues	81,478	82,298	240,889	241,585
Income from operations	22,609	24,717	67,375	71,418
Depreciation and amortization	7,072	6,630	21,306	20,215
Interest expense	2,536	3,556	10,266	11,786
Interest income	50	66	231	255
Provision for income taxes	5,944	4,944	16,947	15,900
Expenditures for additions to property & equipment, net of grants from outside parties	$ 7,661	$ 8,954	$ 15,541	$ 41,354