Borrowings - Line of Credit and other disclosures (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Long-term borrowings
Unused line of credit	$ 270,440
FHLB
Long-term borrowings
Unused line of credit	97,040
FRB
Long-term borrowings
Unused line of credit	13,430
Federal Funds Agreements
Long-term borrowings
Unused line of credit	65,000
Repurchase Lines of Credit
Long-term borrowings
Unused line of credit	50,000
Non-Recourse Revolving Bank Line of Credit
Long-term borrowings
Unused line of credit	$ 44,970