Bank segment - Credit risk profile - assigned grades (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Commercial real estate
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	$ 808,900	$ 800,395
Commercial real estate | Pass
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	660,015	701,657
Commercial real estate | Special mention
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	95,656	65,541
Commercial real estate | Substandard
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	53,229	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	116,548	126,768
Commercial construction | Pass
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	92,069	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	1,979	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	649,657	692,051
Commercial loans | Pass
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	602,903	614,139
Commercial loans | Special mention
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	19,429	25,229
Commercial loans | Substandard
Credit risk profile by internally assigned grade for loans
Loans and leases receivable before fees, gross	27,325	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