Revenue from contracts with customers - disaggregation of revenue (Details) - USD ($)
$ in Millions |
3 Months Ended |
Mar. 31, 2018 |
Mar. 31, 2017 |
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
$ 879.1
|
$ 788.4
|
| Core services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
419.7
|
371.9
|
| High-value services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
402.1
|
368.7
|
| Other security services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
57.3
|
47.8
|
| Reportable segments |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
853.3
|
740.3
|
| Reportable segments | Core services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
409.0
|
347.8
|
| Reportable segments | High-value services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
387.0
|
344.7
|
| Reportable segments | Other security services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
57.3
|
47.8
|
| Reportable segments | North America |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
320.1
|
304.6
|
| Reportable segments | North America | Core services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
190.0
|
172.3
|
| Reportable segments | North America | High-value services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
130.1
|
132.3
|
| Reportable segments | North America | Other security services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
0.0
|
0.0
|
| Reportable segments | South America |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
254.8
|
202.2
|
| Reportable segments | South America | Core services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
125.4
|
96.8
|
| Reportable segments | South America | High-value services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
126.5
|
101.4
|
| Reportable segments | South America | Other security services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
2.9
|
4.0
|
| Reportable segments | Rest of World |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
278.4
|
233.5
|
| Reportable segments | Rest of World | Core services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
93.6
|
78.7
|
| Reportable segments | Rest of World | High-value services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
130.4
|
111.0
|
| Reportable segments | Rest of World | Other security services |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
54.4
|
43.8
|
| Other items not allocated to segments | Venezuela |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
25.8
|
48.1
|
| Other items not allocated to segments | Core services | Venezuela |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
10.7
|
24.1
|
| Other items not allocated to segments | High-value services | Venezuela |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
15.1
|
24.0
|
| Other items not allocated to segments | Other security services | Venezuela |
|
|
| Disaggregation of Revenue [Line Items] |
|
|
| Revenue disaggregated by reportable segment and type of service |
$ 0.0
|
$ 0.0
|