Bank segment - Credit risk profile - assigned grades (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Commercial real estate
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	$ 790,191	$ 800,395
Commercial real estate | Pass
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	669,117	701,657
Commercial real estate | Special mention
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	89,370	65,541
Commercial real estate | Substandard
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	31,704	33,197
Commercial real estate | Doubtful
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	0	0
Commercial real estate | Loss
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	0	0
Commercial construction
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	130,808	126,768
Commercial construction | Pass
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	84,495	102,955
Commercial construction | Special mention
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	22,500	0
Commercial construction | Substandard
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	23,813	23,813
Commercial construction | Doubtful
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	0	0
Commercial construction | Loss
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	0	0
Commercial loans
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	661,016	692,051
Commercial loans | Pass
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	605,256	614,139
Commercial loans | Special mention
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	22,568	25,229
Commercial loans | Substandard
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	33,192	52,683
Commercial loans | Doubtful
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	0	0
Commercial loans | Loss
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	$ 0	$ 0