CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - UNAUDITED - USD ($) $ in Thousands	Total	Revision of Prior Period, Accounting Standards Update, Adjustment [Member]	Common stock	Common stock Revision of Prior Period, Accounting Standards Update, Adjustment [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] Revision of Prior Period, Accounting Standards Update, Adjustment [Member]	Retained Earnings [Member]	Retained Earnings [Member] Revision of Prior Period, Accounting Standards Update, Adjustment [Member]	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Balance at at Dec. 31, 2018	$ 1,067,903		$ 35,531		$ 606,573		$ 441,553		$ (15,754)
Net income/ (loss)	58,593		0		0		58,593		0
Other comprehensive income, net of tax	12,189		0		0		0		12,189
Common stock dividends - $0.30 and $0.30 per share for 2nd quarter; $0.60 and $0.58 per share for YTD June 30 2020 and 2019 respectively	(20,757)		0		0		(20,757)		0
Stock compensation expense	1,473		0		1,473		0		0
Common stock issued pursuant to:
Director's stock purchase plan 867 shares 2nd quarter and YTD June 30, 2019 respectively	30		1		29		0		0
Stock option plan - 2,625; 4,142 for the 2nd quarter; 8,638; 10,897 shares YTD June 2020 and 2019 respectively	224		11		213		0		0
Employee stock purchase plan - shares of 20,198; 10,004 2nd quarter; 28,815; 17,666 shares YTD June 2020, 2019 respectively	492		17		475		0		0
Restricted stock - Restricted stock, net - shares of 44,578; 42,830 for 2nd quarter and 44,578; 54,789 YTD June 30, 2020, 2019 respectively	(702)		55		(757)		0		0
Balance at at Jun. 30, 2019	1,119,445		35,615		608,006		479,389		(3,565)
Balance at at Mar. 31, 2019	1,095,848		35,557		607,479		461,862		(9,050)
Net income/ (loss)	28,276		0		0		28,276		0
Other comprehensive income, net of tax	5,485		0		0		0		5,485
Common stock dividends - $0.30 and $0.30 per share for 2nd quarter; $0.60 and $0.58 per share for YTD June 30 2020 and 2019 respectively	(10,749)		0		0		(10,749)		0
Stock compensation expense	783		0		783		0		0
Common stock issued pursuant to:
Director's stock purchase plan 867 shares 2nd quarter and YTD June 30, 2019 respectively	30		1		29		0		0
Stock option plan - 2,625; 4,142 for the 2nd quarter; 8,638; 10,897 shares YTD June 2020 and 2019 respectively	95		4		91		0		0
Employee stock purchase plan - shares of 20,198; 10,004 2nd quarter; 28,815; 17,666 shares YTD June 2020, 2019 respectively	278		10		268		0		0
Restricted stock - Restricted stock, net - shares of 44,578; 42,830 for 2nd quarter and 44,578; 54,789 YTD June 30, 2020, 2019 respectively	(601)		43		(644)		0		0
Balance at at Jun. 30, 2019	1,119,445		35,615		608,006		479,389		(3,565)
Balance at at Dec. 31, 2019	1,132,974		34,970		586,622		515,714		(4,332)
Net income/ (loss)	(4,351)		0		0		(4,351)		0
Other comprehensive income, net of tax	19,156		0		0		0		19,156
Common stock dividends - $0.30 and $0.30 per share for 2nd quarter; $0.60 and $0.58 per share for YTD June 30 2020 and 2019 respectively	(24,748)		0		0		(24,748)		0
Stock compensation expense	1,792		0		1,792		0		0
Common stock issued pursuant to:
Revere Bank acquisition - 12,768,949 shares for the qarter and year to date June 30, 2020 respectively	289,089		12,769		276,320		0		0
Stock option plan - 2,625; 4,142 for the 2nd quarter; 8,638; 10,897 shares YTD June 2020 and 2019 respectively	147		9		138		0		0
Conversion of Revere stock options - 395,298 options for 2nd quarter and year to date June 30, 2020	3,611		0		3,611		0		0
Employee stock purchase plan - shares of 20,198; 10,004 2nd quarter; 28,815; 17,666 shares YTD June 2020, 2019 respectively	785		29		756		0		0
Restricted stock - Restricted stock, net - shares of 44,578; 42,830 for 2nd quarter and 44,578; 54,789 YTD June 30, 2020, 2019 respectively	(437)		44		(481)		0		0
Adoption of ASC 326 - Financial Instruments - Credit Losses		$ (2,223)		$ 0		$ 0		$ (2,223)		$ 0
Repurchase of treasury shares - 820,328 shares	(25,702)		(820)		(24,882)		0		0
Balance at at Jun. 30, 2020	1,390,093		47,001		843,876		484,392		14,824
Balance at at Mar. 31, 2020	1,116,334		34,165		562,891		512,934		6,344
Net income/ (loss)	(14,338)		0		0		(14,338)		0
Other comprehensive income, net of tax	8,480		0		0		0		8,480
Common stock dividends - $0.30 and $0.30 per share for 2nd quarter; $0.60 and $0.58 per share for YTD June 30 2020 and 2019 respectively	(14,204)		0		0		(14,204)		0
Stock compensation expense	1,038		0		1,038		0		0
Common stock issued pursuant to:
Revere Bank acquisition - 12,768,949 shares for the qarter and year to date June 30, 2020 respectively	289,089		12,769		276,320		0		0
Stock option plan - 2,625; 4,142 for the 2nd quarter; 8,638; 10,897 shares YTD June 2020 and 2019 respectively	25		3		22		0		0
Conversion of Revere stock options - 395,298 options for 2nd quarter and year to date June 30, 2020	3,611		0		3,611		0		0
Employee stock purchase plan - shares of 20,198; 10,004 2nd quarter; 28,815; 17,666 shares YTD June 2020, 2019 respectively	495		20		475		0		0
Restricted stock - Restricted stock, net - shares of 44,578; 42,830 for 2nd quarter and 44,578; 54,789 YTD June 30, 2020, 2019 respectively	(437)		44		(481)		0		0
Balance at at Jun. 30, 2020	$ 1,390,093		$ 47,001		$ 843,876		$ 484,392		$ 14,824
Common stock issued pursuant to:
Accounting Standards Update [Extensible List]	u-sgaap:AccountingStandardsUpdate201613Member