Exit activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restructuring Cost and Reserve [Line Items]
Employee termination benefits	$ 658,266	$ 624,326	$ 571,026
Payments for employee termination benefits	300
Early lease termination costs	1,000
Accelerated depreciation of assets	30,298	$ 24,226	$ 17,920
Exit Plan Out Of Delinquent Loan Servicing Operations
Restructuring Cost and Reserve [Line Items]
Restructuring costs recorded	3,500
Employee Severance | Exit Plan Out Of Delinquent Loan Servicing Operations
Restructuring Cost and Reserve [Line Items]
Employee termination benefits	1,100
Accelerated Depreciation of Assets | Exit Plan Out Of Delinquent Loan Servicing Operations
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation of assets	1,400
Minimum | Exit Plan Out Of Delinquent Loan Servicing Operations
Restructuring Cost and Reserve [Line Items]
Delinquent loan servicing exit, estimated total charge to be incurred	5,000
Maximum | Exit Plan Out Of Delinquent Loan Servicing Operations
Restructuring Cost and Reserve [Line Items]
Delinquent loan servicing exit, estimated total charge to be incurred	$ 7,000