Segment and Geographic Area Information Segments (Details) $ in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 AUD ($) reportable_segment region	Dec. 31, 2018 USD ($) reportable_segment region	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of operating regions | region									9	9
Number of reportable segments | reportable_segment									3	3
Noncontrolling Interest, Ownership Percentage by Parent	51.10%								51.10%	51.10%
Operating Revenues										$ 2,348,550	$ 2,208,044	$ 2,001,527
Operating income/(loss)	$ 105,654	$ 127,820	$ 103,125	$ 86,913	$ 106,506	$ 109,842	$ 99,733	$ 75,900		423,512	391,981	286,362
Depreciation and amortization										263,216	250,457	205,188
Interest expense, net										104,463	105,209	74,534
Provision for/(benefit from) income taxes										64,535	(261,259)	74,395
Cash expenditures for additions to property & equipment, net of grants from outside parties										263,575	208,223	183,450
Payments of Ordinary Dividends									$ 65.0
Payments of Ordinary Dividends, Parent									33.2	24,600
Payments of Ordinary Dividends, Noncontrolling Interest									$ 31.8	$ 23,583	0	0
MIRA [Member]
Segment Reporting Information [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	48.90%								48.90%	48.90%
North American Operations [Member]
Segment Reporting Information [Line Items]
Number of operating regions | region									7	7
Operating Revenues										$ 1,358,870	1,274,285	1,236,764
Operating income/(loss)										343,112	304,252	319,661
Depreciation and amortization										165,625	158,006	147,527
Interest expense, net										40,827	38,547	40,985
Provision for/(benefit from) income taxes										43,531	(266,063)	80,701
Cash expenditures for additions to property & equipment, net of grants from outside parties										182,645	166,685	137,334
Australian Operations [Member]
Segment Reporting Information [Line Items]
Operating Revenues										301,678	307,510	222,586
Operating income/(loss)										80,277	77,251	4,810
Depreciation and amortization										60,766	61,142	30,863
Interest expense, net										51,358	54,718	13,958
Provision for/(benefit from) income taxes										8,694	6,110	988
Cash expenditures for additions to property & equipment, net of grants from outside parties										42,722	16,076	11,285
U.K./European Operations [Member]
Segment Reporting Information [Line Items]
Operating Revenues										688,002	626,249	542,177
Operating income/(loss)										123	10,478	(38,109)
Depreciation and amortization										36,825	31,309	26,798
Interest expense, net										12,278	11,944	19,591
Provision for/(benefit from) income taxes										12,310	(1,306)	(7,294)
Cash expenditures for additions to property & equipment, net of grants from outside parties										$ 38,208	$ 25,462	$ 34,831