Debt Trust preferred debt instruments (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2016	Jul. 14, 2016
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 180,000,000
Connecticut Statutory Trust I [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 15,000
Issue date of trust	Dec. 04, 2002
Redemption date		Dec. 04, 2032
Connecticut Statutory Trust II [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 17,500
Issue date of trust	May 15, 2003
Redemption date		May 15, 2033
Connecticut Statutory Trust III [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 20,000
Issue date of trust	Oct. 29, 2003
Redemption date		Oct. 29, 2033
Delaware Statutory Trust III [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 15,000
Issue date of trust	May 22, 2003
Redemption date		May 22, 2033
Delaware Statutory Trust IV [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 10,000
Issue date of trust	Sep. 30, 2003
Redemption date		Sep. 30, 2033
Delaware Statutory Trust VI [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 13,000
Issue date of trust	Dec. 16, 2003
Redemption date		Jan. 08, 2034