CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Acquisition of Connecticut Bank and Trust Company	Common stock	Common stock Acquisition of Connecticut Bank and Trust Company	Additional paid-in capital	Additional paid-in capital Acquisition of Connecticut Bank and Trust Company	Unearned compensation	Retained earnings	Accumulated other comprehensive loss	Treasury stock	Comprehensive income
Balance at Dec. 31, 2011	$ 553,365		$ 229		$ 494,304		$ (2,790)	$ 109,477	$ (4,885)	$ (42,970)
Balance (in shares) at Dec. 31, 2011			21,148
Comprehensive income:
Net income	13,830							13,830			13,830
Other comprehensive income (loss)	549								549		549
Total comprehensive income	14,379										14,379
Acquisition		21,990		9		21,981
Acquisition (in shares)				965
Cash dividends declared $0.36 and $0.34 for the period ended June 30, 2013 and 2012, respectively	(7,372)							(7,372)
Forfeited shares					11		169			(180)
Forfeited shares (in shares)			(8)
Exercise of stock options	271							(64)		335
Exercise of stock options (in shares)			13
Restricted stock grants					(148)		(1,476)			1,624
Restricted stock grants (in shares)			64
Stock-based compensation	897						897
Net tax benefit related to stock-based compensation	35				35
Other, net	(295)									(295)
Other, net (in shares)			(13)
Balance at Jun. 30, 2012	583,270		238		516,183		(3,200)	115,871	(4,336)	(41,486)
Balance (in shares) at Jun. 30, 2012			22,169
Balance at Dec. 31, 2012	667,265		265		585,360		(3,035)	122,014	(2,979)	(34,360)
Balance (in shares) at Dec. 31, 2012			25,148
Comprehensive income:
Net income	22,502							22,502			22,502
Other comprehensive income (loss)	(3,231)								(3,231)		(3,231)
Total comprehensive income	19,271										19,271
Cash dividends declared $0.36 and $0.34 for the period ended June 30, 2013 and 2012, respectively	(9,068)							(9,068)
Treasury stock purchased	(8,868)									(8,868)
Treasury stock purchased (in shares)			(348)
Forfeited shares					10		140			(150)
Forfeited shares (in shares)			(6)
Exercise of stock options	2,582							(2,518)		5,100
Exercise of stock options (in shares)			195
Restricted stock grants					(690)		(3,717)			4,407
Restricted stock grants (in shares)			155
Stock-based compensation	1,812				585		1,227
Net tax benefit related to stock-based compensation	1,150				1,150
Other, net	(1,174)				(14)					(1,160)
Other, net (in shares)			(48)
Balance at Jun. 30, 2013	$ 672,970		$ 265		$ 586,401		$ (5,385)	$ 132,930	$ (6,210)	$ (35,031)
Balance (in shares) at Jun. 30, 2013			25,096