FEDERAL HOME LOAN BANK OF BOSTON ADVANCES - Certain information concerning short-term FHLBB advances (Details) (Short-term FHLBB advances Information, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Short-term FHLBB advances Information
Highest month-end balance during period	$ 5,545
Ending balance
Average balance during period	$ 664	$ 52
Weighted average rate during period	0.29%	0.29%