Exit activities - Additional Information (Details) - Exit Plan Out Of Delinquent Loan Servicing Operations $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Restructuring Cost and Reserve [Line Items]
Total cumulative charges incurred	$ 6.4
Employee Termination Benefits
Restructuring Cost and Reserve [Line Items]
Total cumulative charges incurred	1.6
Costs recorded in period	0.4
Early Lease Termination
Restructuring Cost and Reserve [Line Items]
Total cumulative charges incurred	2.3
Costs recorded in period	1.3
Accelerated Depreciation of Assets
Restructuring Cost and Reserve [Line Items]
Total cumulative charges incurred	2.5
Costs recorded in period	$ 1.1