Consolidated Statements of Cash Flows	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Cash flow from operating activities
Net income	$ 76,648,000	$ 64,960,000	$ 59,845,000
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	14,354,000	12,307,000	12,108,000
Provision for loan losses	6,075,000	1,500,000	10,403,000
Deferred income tax expense (benefit)	(5,000)	10,220,000	2,840,000
Loss on write-down of investments in securities available for sale	26,000	405,000	(191,000)
Net loss on bank premises and equipment	114,000	221,000	469,000
Loss on extinguishment of debt	437,000	122,000	0
Loss on termination of derivatives	0	0	1,122,000
Net loss on other real estate owned and foreclosed assets	29,000	1,152,000	723,000
Realized gain on sale leaseback transaction	(1,034,000)	(1,034,000)	(1,034,000)
Stock based compensation	2,965,000	2,490,000	2,712,000
Excess tax benefit related to equity award activity	(476,000)	(1,042,000)	(704,000)
Increase in cash surrender value of life insurance policies	(4,089,000)	(3,692,000)	(3,128,000)
Gain on life insurance benefits	0	0	(1,964,000)
Change in fair value on loans held for sale	(87,000)	22,000	(18,000)
Net change in:
Trading assets	(448,000)	(356,000)	0
Loans held for sale	(62,000)	876,000	2,012,000
Other assets	7,627,000	3,842,000	(1,907,000)
Other liabilities	(8,738,000)	(2,450,000)	7,017,000
Total adjustments	16,688,000	24,583,000	30,460,000
Net cash provided by operating activities	93,336,000	89,543,000	90,305,000
Cash flows used in investing activities
Proceeds from sales of securities available for sale	618,000	14,199,000	5,438,000
Proceeds from maturities and principal repayments of securities available for sale	69,775,000	78,497,000	47,720,000
Purchases of securities available for sale	(69,671,000)	(73,064,000)	(37,047,000)
Proceeds from maturities and principal repayments of securities held to maturity	90,991,000	60,168,000	44,710,000
Purchases of securities held to maturity	(100,198,000)	(162,021,000)	(69,544,000)
Redemption of Federal Home Loan Bank stock	5,229,000	23,054,000	6,693,000
Investments in low income housing projects	(7,626,000)	(15,055,000)	(16,452,000)
Purchases of life insurance policies	(163,000)	(162,000)	(10,161,000)
Proceeds from life insurance policies	0	0	6,310,000
Net increase in loans	(227,838,000)	(114,550,000)	(266,961,000)
Cash Acquired in Excess of Payments to Acquire Business	8,668,000
Cash provided by (used in) business combinations		(13,448,000)	0
Purchases of bank premises and equipment	(10,395,000)	(10,488,000)	(7,678,000)
Proceeds from the sale of bank premises and equipment	345,000	1,233,000	1,219,000
Payments on early termination of hedging relationship			(1,122,000)
Proceeds from the sale of other real estate owned and foreclosed assets	1,583,000	7,667,000	7,458,000
Net payments relating to other real estate owned and foreclosed assets	(204,000)	(1,571,000)	(3,255,000)
Net cash used in investing activities	(238,886,000)	(205,541,000)	(292,672,000)
Cash flows provided by financing activities
Net decrease in time deposits	(104,803,000)	(80,726,000)	(94,008,000)
Net increase in other deposits	350,739,000	428,713,000	318,056,000
Net repayments of short-term Federal Home Loan Bank borrowings	(37,000,000)	(10,000,000)	(65,000,000)
Repayments of long-term Federal Home Loan Bank borrowings	(65,791,000)	(9,000,000)	(5,000,000)
Net increase (decrease) in customer repurchase agreements	42,955,000	(13,932,000)	(1,398,000)
Increase (Decrease) in Payables under Repurchase Agreements	0	(50,000,000)	0
Net decrease in other short term borrowings			(5,000,000)
Repayments of Subordinated Debt	0	(30,000,000)
Proceeds from Issuance of Subordinated Long-term Debt			35,000,000
Net proceeds from exercise of stock options	201,000	1,367,000	2,333,000
Restricted stock awards issued, net of awards surrendered	(696,000)	(657,000)	(641,000)
Excess tax benefit from stock based compensation	476,000	1,042,000	704,000
Tax benefit from deferred compensation distribution	187,000	179,000	138,000
Proceeds from shares issued under the direct stock purchase plan	2,323,000	2,695,000	1,555,000
Common dividends paid	(29,711,000)	(26,172,000)	(22,443,000)
Net cash provided by financing activities	158,880,000	213,509,000	164,296,000
Net increase (decrease) in cash and cash equivalents	13,330,000	97,511,000	(38,071,000)
Cash and cash equivalents at beginning of year	275,765,000	178,254,000	216,325,000
Cash and cash equivalents at end of period	289,095,000	275,765,000	178,254,000
Supplemental schedule of noncash investing and financing activities
Interest on deposits and borrowings	18,963,000	20,773,000	20,257,000
Income taxes	33,473,000	11,841,000	14,547,000
Transfer of loans to other real estate owned and foreclosed assets	1,322,000	1,522,000	5,248,000
Real Estate Owned, Transfer to Real Estate Owned	0	142,000
Capital commitment relating to Low Income Housing Project investments, noncash	5,180,000	1,658,000	38,839,000
In conjunction with the Company's acquisitions, assets were acquired and liabilities were assumed as follows
Common stock issued for acquisition	40,730,000	86,415,000	0
Fair value of assets acquired, net of cash acquired	266,242,000	598,376,000	$ 0
Fair value of liabilities assumed		$ 498,513,000
New England Bancorp, Inc. [Member]
In conjunction with the Company's acquisitions, assets were acquired and liabilities were assumed as follows
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities	$ 234,180,000