Debt - Guarantees (Details) £ in Millions, CAD in Millions, AUD in Millions	6 Months Ended
	Jun. 30, 2015 ZAR	Jun. 30, 2015 GBP (£) guarantee	Jun. 30, 2015 ZAR guarantee	Jun. 30, 2015 USD ($) guarantee	Jun. 30, 2015 CAD guarantee	Sep. 30, 2014 AUD	Sep. 30, 2014 USD ($)
Geo Amey
Line of Credit Facility [Line Items]
Ownership percentage in South African Custodial Services Pty. Limited	50.00%
Working capital line of credit issued to GEOAmey | £		£ 12.0
Note receivable for GEOAmey		£ 10.5		$ 16,500,000
Ravenhall
Line of Credit Facility [Line Items]
Number of letters of guarantee outstanding under separate international facilities relating to performance guarantees | guarantee		10	10	10	10
Letters of credit outstanding relating to performance guarantees				$ 14,000,000
Ravenhall | Letter of Credit | Revolver
Line of Credit Facility [Line Items]
Guaranteed obligations						AUD 215.0	$ 164,600,000
SACS
Line of Credit Facility [Line Items]
Guaranteed obligations			ZAR 21,000,000	1,700,000
Remaining guarantee under letter of credit | ZAR	ZAR 21,000,000
Maximum loan amount under standby facility			ZAR 20,000,000	1,630,000
Canada Facility
Line of Credit Facility [Line Items]
Potential estimated exposure of tax obligations				2,000,000	CAD 2.5
Liability related to potential tax exposure				$ 2,000,000