CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common stock amount	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income	Treasury stock
Balance at beginning of period at Dec. 31, 2016	$ 156,740	$ 13,577	$ 23,027	$ 130,489	$ (4,326)	$ (6,027)
Comprehensive income:
Net income	10,767			10,767
Other comprehensive income (loss)	2,621				2,621
Total comprehensive income	13,388			10,767	2,621
Cash dividends declared	(5,744)			(5,744)
Acquisition of Lake Sunapee Bank Group	181,919	8,328	173,591
Treasury stock purchased	(86)					(86)
Net issuance to employee stock plans, including related tax effects	365		(68)	(40)		473
Three-for-two stock split	(16)	10,952	(10,952)	(16)
Recognition of stock based compensation	556		556
Balance at end of period at Jun. 30, 2017	347,122	32,857	186,154	135,456	(1,705)	(5,640)
Balance at beginning of period at Mar. 31, 2017					(3,662)
Comprehensive income:
Net income	6,556
Other comprehensive income (loss)	1,957
Total comprehensive income	8,513
Balance at end of period at Jun. 30, 2017	347,122	32,857	186,154	135,456	(1,705)	(5,640)
Comprehensive income:
Modified retrospective basis adoption of Revenue Recognition Accounting Codification Standard 606 | Accounting Standards Update 2014-09	(184)			(184)
Balance at beginning of period at Dec. 31, 2017	354,641	32,857	186,702	144,977	(4,554)	(5,341)
Comprehensive income:
Net income	16,347			16,347
Other comprehensive income (loss)	(9,813)				(9,813)
Total comprehensive income	6,534			16,347	(9,813)
Cash dividends declared	(5,981)			(5,981)
Treasury stock purchased	(278)					(278)
Net issuance to employee stock plans, including related tax effects	604		(131)			735
Reclassification of the income tax effects of the Tax Cuts and Jobs Act from accumulated other comprehensive income for adoption of ASU 2018-02	0			980	(980)
Recognition of stock based compensation	627		627
Balance at end of period at Jun. 30, 2018	355,963	32,857	187,198	156,139	(15,347)	(4,884)
Balance at beginning of period at Mar. 31, 2018					(13,163)
Comprehensive income:
Net income	8,535
Other comprehensive income (loss)	(2,184)
Total comprehensive income	6,351
Balance at end of period at Jun. 30, 2018	$ 355,963	$ 32,857	$ 187,198	$ 156,139	$ (15,347)	$ (4,884)