Segment Information Segments (Details) $ in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) reportable_segment provinces region	Sep. 30, 2018 AUD ($) reportable_segment provinces region	Sep. 30, 2017 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%
Payments of Ordinary Dividends				$ 40.0
Payments of Ordinary Dividends, Parent			$ 15,600	20.4
Payments of Ordinary Dividends, Noncontrolling Interest			14,898	$ 19.6	$ 0
Operating revenue	$ 603,304	$ 576,927	1,772,955		1,636,468
Operating income/(loss)	127,820	109,842	317,858		285,475
Depreciation and amortization	65,392	64,222	197,127		186,509
Interest expense, net	26,012	27,818	79,106		79,160
Provision for/(benefit from) income taxes	31,013	30,507	41,569		82,032
Expenditures for Additions to Property and Equipment Net of Grants From Outside Parties	57,009	53,239	$ 177,436		133,107
North American Operations [Member]
Segment Reporting Information [Line Items]
Number of operating regions | provinces			7	7
Operating revenue	355,709	318,927	$ 1,020,896		954,077
Operating income/(loss)	102,484	82,203	255,918		229,545
Depreciation and amortization	41,388	40,036	123,266		117,822
Interest expense, net	10,339	9,817	30,572		29,928
Provision for/(benefit from) income taxes	26,323	28,270	26,930		78,133
Expenditures for Additions to Property and Equipment Net of Grants From Outside Parties	42,120	41,713	129,607		105,940
Australia Operations [Member]
Segment Reporting Information [Line Items]
Operating revenue	76,703	81,270	230,566		231,986
Operating income/(loss)	20,713	22,276	62,585		59,685
Depreciation and amortization	14,937	15,753	46,232		45,915
Interest expense, net	12,780	13,678	38,914		41,500
Provision for/(benefit from) income taxes	2,398	2,013	7,120		4,805
Expenditures for Additions to Property and Equipment Net of Grants From Outside Parties	8,185	4,545	27,936		9,721
U.K./European Operations [Member]
Segment Reporting Information [Line Items]
Operating revenue	170,892	176,730	521,493		450,405
Operating income/(loss)	4,623	5,363	(645)		(3,755)
Depreciation and amortization	9,067	8,433	27,629		22,772
Interest expense, net	2,893	4,323	9,620		7,732
Provision for/(benefit from) income taxes	2,292	224	7,519		(906)
Expenditures for Additions to Property and Equipment Net of Grants From Outside Parties	$ 6,704	$ 6,981	$ 19,893		$ 17,446
MIRA [Member]
Segment Reporting Information [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	48.90%		48.90%	48.90%