Restructuring Charges - By segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring charges
Restructuring charges	$ 2,900	$ 0	$ 7,036	$ 0
Organizational Restructuring
Restructuring charges
Restructuring charges	(33)		1,695
Pandemic Restructuring
Restructuring charges
Restructuring charges	1,435		3,843
Property Restructuring
Restructuring charges
Impairment loss	583		583
Loss on sale	915		915
Restructuring charges	1,498		1,498
Corporate
Restructuring charges
Restructuring charges	1,730		3,090
Corporate | Organizational Restructuring
Restructuring charges
Restructuring charges	(13)		612
Corporate | Pandemic Restructuring
Restructuring charges
Restructuring charges	245		980
Corporate | Property Restructuring
Restructuring charges
Impairment loss	583		583
Loss on sale	915		915
Restructuring charges	1,498		1,498
Contract Operations | Operating Segments
Restructuring charges
Restructuring charges	526		2,390
Contract Operations | Operating Segments | Organizational Restructuring
Restructuring charges
Restructuring charges	(20)		458
Contract Operations | Operating Segments | Pandemic Restructuring
Restructuring charges
Restructuring charges	546		1,932
Aftermarket Services | Operating Segments
Restructuring charges
Restructuring charges	644		1,556
Aftermarket Services | Operating Segments | Organizational Restructuring
Restructuring charges
Restructuring charges			625
Aftermarket Services | Operating Segments | Pandemic Restructuring
Restructuring charges
Restructuring charges	$ 644		$ 931