Reportable Segments (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011		Dec. 31, 2011
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	$ 46,366,000		$ 45,059,000		$ 137,730,000		$ 134,804,000
Noninterest Income	28,604,000		29,724,000		84,067,000		88,832,000
Revenues	74,970,000		74,783,000		221,797,000		223,636,000
Noninterest Expense	58,150,000	[1]	54,916,000	[1]	169,112,000	[1]	175,887,000	[1]
Income tax expense/(benefit)	5,124,000		4,542,000		14,215,000		8,559,000
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	15,696,000		10,825,000		36,770,000		23,530,000
Net income/ (loss) attributable to noncontrolling interests	855,000		740,000		2,407,000		2,265,000
Net Income (Loss) Attributable to Parent	16,513,000	[2]	11,679,000	[2]	40,179,000	[2]	26,075,000	[2]
Amortization of intangibles	1,082,000		1,124,000		3,263,000		3,679,000
Total assets	6,272,784,000		6,024,321,000		6,272,784,000		6,024,321,000		6,049,372,000
Assets under Management, Carrying Amount	20,114,000,000	[3]	17,276,000,000	[3]	20,114,000,000	[3]	17,276,000,000	[3]
Depreciation	1,704,000		1,538,000		4,970,000		4,678,000
Restructuring Charges	3,581,000		1,116,000		4,280,000		7,402,000
Net income from discontinued operations	1,672,000		1,594,000		5,816,000		4,810,000
Private Banking Segment [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	47,812,000	[4]	46,814,000	[4]	142,467,000	[4]	140,163,000	[4]
Noninterest Income	7,937,000	[4]	11,014,000	[4]	24,233,000	[4]	29,507,000	[4]
Revenues	55,749,000	[4]	57,828,000	[4]	166,700,000	[4]	169,670,000	[4]
Noninterest Expense	36,785,000	[1],[4]	35,680,000	[1],[4]	108,030,000	[1],[4]	114,672,000	[1],[4]
Income tax expense/(benefit)	8,133,000	[4]	6,160,000	[4]	19,312,000	[4]	12,452,000	[4]
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	14,831,000	[4]	11,488,000	[4]	37,658,000	[4]	26,886,000	[4]
Net income/ (loss) attributable to noncontrolling interests	0	[4]	0	[4]	0	[4]	0	[4]
Net Income (Loss) Attributable to Parent	14,831,000	[2],[4]	11,488,000	[2],[4]	37,658,000	[2],[4]	26,886,000	[2],[4]
Amortization of intangibles	26,000	[4]	26,000	[4]	79,000	[4]	377,000	[4]
Total assets	6,071,302,000	[4]	5,812,215,000	[4]	6,071,302,000	[4]	5,812,215,000	[4]
Assets under Management, Carrying Amount	3,784,000,000	[4]	3,427,000,000	[4]	3,784,000,000	[4]	3,427,000,000	[4]
Depreciation	1,496,000		1,341,000		4,364,000		4,074,000
Investment Managers Segment [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	6,000		8,000		21,000		65,000
Noninterest Income	10,043,000		10,276,000		29,110,000		30,730,000
Revenues	10,049,000		10,284,000		29,131,000		30,795,000
Noninterest Expense	7,841,000		7,839,000		23,351,000	[1]	23,715,000	[1]
Income tax expense/(benefit)	748,000		854,000		1,977,000		2,409,000
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	1,460,000		1,591,000		3,803,000		4,671,000
Net income/ (loss) attributable to noncontrolling interests	444,000		400,000		1,184,000		1,196,000
Net Income (Loss) Attributable to Parent	1,016,000	[2]	1,191,000	[2]	2,619,000	[2]	3,475,000	[2]
Amortization of intangibles	800,000		830,000		2,401,000		2,489,000
Total assets	105,349,000		108,767,000		105,349,000		108,767,000
Assets under Management, Carrying Amount	8,553,000,000		7,127,000,000		8,553,000,000		7,127,000,000
Depreciation	59,000		58,000		189,000		192,000
Wealth Advisors Segment [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	6,000	[5]	7,000	[5]	19,000	[5]	17,000	[5]
Noninterest Income	9,494,000	[5]	8,623,000	[5]	27,900,000	[5]	25,672,000	[5]
Revenues	9,500,000	[5]	8,630,000	[5]	27,919,000	[5]	25,689,000	[5]
Noninterest Expense	6,806,000	[5]	6,186,000	[5]	20,334,000	[1],[5]	18,912,000	[1],[5]
Income tax expense/(benefit)	996,000	[5]	910,000	[5]	2,771,000	[5]	2,459,000	[5]
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	1,698,000	[5]	1,534,000	[5]	4,814,000	[5]	4,318,000	[5]
Net income/ (loss) attributable to noncontrolling interests	411,000	[5]	340,000	[5]	1,223,000	[5]	1,069,000	[5]
Net Income (Loss) Attributable to Parent	1,287,000	[2],[5]	1,194,000	[2],[5]	3,591,000	[2],[5]	3,249,000	[2],[5]
Amortization of intangibles	256,000	[5]	268,000	[5]	783,000	[5]	813,000	[5]
Total assets	71,936,000	[5]	68,848,000	[5]	71,936,000	[5]	68,848,000	[5]
Assets under Management, Carrying Amount	7,797,000,000	[3],[5]	6,740,000,000	[3],[5]	7,797,000,000	[3],[5]	6,740,000,000	[3],[5]
Depreciation	91,000		93,000		269,000		267,000
Reportable Segment [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	47,824,000		46,829,000		142,507,000		140,245,000
Noninterest Income	27,474,000		29,913,000		81,243,000		85,909,000
Revenues	75,298,000		76,742,000		223,750,000		226,154,000
Noninterest Expense	51,432,000	[1]	49,705,000	[1]	151,715,000	[1]	157,299,000	[1]
Income tax expense/(benefit)	9,877,000		7,924,000		24,060,000		17,320,000
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	17,989,000		14,613,000		46,275,000		35,875,000
Net income/ (loss) attributable to noncontrolling interests	855,000		740,000		2,407,000		2,265,000
Net Income (Loss) Attributable to Parent	17,134,000	[2]	13,873,000	[2]	43,868,000	[2]	33,610,000	[2]
Amortization of intangibles	1,082,000		1,124,000		3,263,000		3,679,000
Total assets	6,248,587,000		5,989,830,000		6,248,587,000		5,989,830,000
Assets under Management, Carrying Amount	20,134,000,000	[3]	17,294,000,000	[3]	20,134,000,000	[3]	17,294,000,000	[3]
Depreciation	1,646,000		1,492,000		4,822,000		4,533,000
Holding Company and Eliminations Segment [Domain]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	(1,458,000)		(1,770,000)		(4,777,000)		(5,441,000)
Noninterest Income	1,130,000		(189,000)		2,824,000		2,923,000
Revenues	(328,000)		(1,959,000)		(1,953,000)		(2,518,000)
Noninterest Expense	6,718,000	[1]	5,211,000	[1]	17,397,000	[1]	18,588,000	[1]
Income tax expense/(benefit)	(4,753,000)		(3,382,000)		(9,845,000)		(8,761,000)
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	(2,293,000)		(3,788,000)		(9,505,000)		(12,345,000)
Net income/ (loss) attributable to noncontrolling interests	0		0		0		0
Net Income (Loss) Attributable to Parent	(621,000)	[2]	(2,194,000)	[2]	(3,689,000)	[2]	(7,535,000)	[2]
Amortization of intangibles	0		0		0		0
Total assets	24,197,000		34,491,000		24,197,000		34,491,000
Assets under Management, Carrying Amount	(20,000,000)		(18,000,000)		(20,000,000)		(18,000,000)
Depreciation	$ 58,000		$ 46,000		$ 148,000		$ 145,000

[1] Non-interest expense for the three and nine months ended September 30, 2012 includes $3.6 million and $4.3 million, respectively, of restructuring expense. Non-interest expense for the three and nine months ended September 30, 2011 includes $1.1 million and $7.4 million, respectively, of restructuring expense. Restructuring expenses have been incurred in the Private Banking segment as well as at the Holding Company.

[2] Net income from discontinued operations for the three months ended September 30, 2012, and 2011 of $1.7 million, and $1.6 million, respectively, and for the nine months ended September 30, 2012, and 2011, of $5.8 million and $4.8 million, respectively, are included in Holding Company and Eliminations in the calculation of net loss attributable to the Company.

[3] AUM” represents Assets Under Management and Advisory at the affiliates. AUM at DTC have been removed since DTC operations are classified with discontinued operations

[4] In the second quarter of 2011, the Company merged its four Private Banking affiliates into one bank operating under the charter of Boston Private Bank. See Part I. Item 1. “Notes to Unaudited Consolidated Financial Statements - Note 1: Basis of Presentation and Summary of Significant Accounting Policies” for additional details.

[5] In the second quarter of 2012, the Company sold its Wealth Advisory affiliate, DTC. Accordingly, current and prior period results for DTC have been reclassified into discontinued operations and are included with Holding Company and Eliminations in the tables above.