Debt - Guarantees (Details) £ in Millions, CAD in Millions, AUD in Millions	9 Months Ended
	Sep. 30, 2015 ZAR	Sep. 30, 2015 GBP (£) guarantee	Sep. 30, 2015 USD ($) guarantee	Sep. 30, 2015 ZAR guarantee	Sep. 30, 2015 CAD guarantee	Sep. 30, 2014 AUD	Sep. 30, 2014 USD ($)
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		£ 9.5	$ 14,400,000
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			$ 12,800,000
Ravenhall | Letter of Credit | Revolver
Line of Credit Facility [Line Items]
Guaranteed obligations						AUD 215.0	$ 150,000,000
SACS
Line of Credit Facility [Line Items]
Guaranteed obligations			1,200,000	ZAR 16,700,000
Remaining guarantee under letter of credit | ZAR	ZAR 16,700,000
Maximum loan amount under standby facility			1,400,000.0	ZAR 20,000,000
Amount funded			0
Canada Facility
Line of Credit Facility [Line Items]
Potential estimated exposure of tax obligations			$ 1,100,000		CAD 1.5