Exit activities (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Realized loss from sale of a business		$ 3.3	$ (3.8)
Disposed of by Sale
Restructuring Cost and Reserve [Line Items]
Realized loss from sale of a business	$ 3.3
Disposed of by Sale | Quality Control Services Business
Restructuring Cost and Reserve [Line Items]
Consideration received	1.8	1.8
Disposed of by Sale | Government Services Business
Restructuring Cost and Reserve [Line Items]
Consideration received	1.6	1.6
Exit Plan Out Of Delinquent Loan Servicing Operations
Restructuring Cost and Reserve [Line Items]
Cumulative exit-related charges	6.4	6.4
Exit Plan Out Of Delinquent Loan Servicing Operations | Employee Severance
Restructuring Cost and Reserve [Line Items]
Cumulative exit-related charges	1.6	1.6
Exit-related charges		0.4
Exit Plan Out Of Delinquent Loan Servicing Operations | Contract Termination
Restructuring Cost and Reserve [Line Items]
Cumulative exit-related charges	2.3	2.3
Exit-related charges		1.4
Exit Plan Out Of Delinquent Loan Servicing Operations | Accelerated Depreciation of Assets
Restructuring Cost and Reserve [Line Items]
Cumulative exit-related charges	$ 2.5	2.5
Exit-related charges		$ 1.1