Boston Private Financial Holdings, Inc. (Parent Company Only) Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2016	[1]	Sep. 30, 2016	[1]	Jun. 30, 2016	[1]	Mar. 31, 2016	[1]	Dec. 31, 2015	[1]	Sep. 30, 2015	[1]	Jun. 30, 2015	[1]	Mar. 31, 2015	[1]	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Noninterest Income, Other Operating Income																	$ 3,410		$ 3,722		$ 870
Revenues																	359,225		346,939		320,499
Salaries and employee benefits																	163,767		159,401		146,648
Professional services																	11,576		12,861		12,473
Interest Expense, Junior Subordinated Debentures																	2,427		3,875		3,872
Other																	14,574		16,222		14,128
Income before income taxes	$ 24,762		$ 28,351		$ 23,768		$ 24,325		$ 20,106		$ 21,390		$ 25,327		$ 26,490		101,207		93,313		99,770
Income tax benefit	7,247		8,652		7,626		7,438		5,638		8,182		8,000		8,572		30,963	[2]	30,392	[2]	32,365	[2]
Income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	1,184		1,047		1,245		2,065		1,455		1,316		1,546		2,094		5,541	[3]	6,411	[3]	6,160	[3]
Net income attributable to the Company	$ 17,552		$ 19,636		$ 16,398		$ 18,041		$ 15,002		$ 13,530		$ 17,610		$ 18,783		71,628		64,925		68,815
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Interest Income, Operating																	130		116		115
Noninterest Income, Other Operating Income																	310		236		279
Revenues																	47,184		51,841		47,250
Salaries and employee benefits																	4,620		10,320		11,876
Professional services																	1,337		2,007		2,965
Interest Expense, Junior Subordinated Debentures																	2,427		3,875		3,872
Other																	1,381		2,740		2,966
Operating Expenses																	9,765		18,942		21,679
Income before income taxes																	37,419		32,899		25,571
Income tax benefit																	(3,751)		(6,877)		(8,599)
Income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest																	5,541		6,411		6,160
Net income attributable to the Company																	46,711		46,187		40,330
Parent Company [Member] | Private Banking Segment [Member]
Condensed Financial Statements, Captions [Line Items]
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries																	22,700		22,700		26,500
Net income attributable to the Company																	(58,184)		(57,201)		(62,491)
Parent Company [Member] | Non Banking Segments [Member]
Condensed Financial Statements, Captions [Line Items]
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries																	24,044		28,789		20,356
Net income attributable to the Company																	(13,477)		(13,026)		(12,850)
Private Banking, Wealth Management and Trust, Investment Management, and Wealth Advisory Segments [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income attributable to the Company																	$ 24,917		$ 18,738		$ 28,485

[1] Due to rounding, the sum of the four quarters may not add to the year to date total.

[2] The Company’s effective tax rate for 2016, 2015, and 2014 is not consistent due to earnings from tax-exempt investments, non-deductible compensation, state and local taxes, income tax credits and income attributable to noncontrolling interests having a different impact on the effective tax rate due primarily to the different levels of income before taxes in years 2016, 2015, and 2014. See Part II. Item 8. “Financial Statements and Supplementary Data - Note 17: Income Taxes” for additional details.

[3] The Company presents its EPS based on the treasury stock method. The Company reverted to the treasury stock presentation from the two-class presentation due to the immaterial number of participating shares outstanding as of March 31, 2016. If the EPS presentation had been based on the two-class method, the following adjustments would have been made to the presentation of EPS for the year ended December 31, 2016. Net income attributable to common shareholders would have been reduced by an additional $4 thousand, for the year ended December 31, 2016. The allocation of net income to participating securities would have been $8 thousand for the year ended December 31, 2016, reducing net income attributable to common shareholders by a total of $12 thousand for the same period. Basic EPS would not change. Weighted average diluted shared outstanding would have been reduced by 7,185 shares for the year ended December 31, 2016. Diluted EPS would not change. If the EPS presentation had been based on the two-class method, the following adjustments would have been made to the presentation of EPS for the year ended December 31, 2015. Net income attributable to common shareholders would have been reduced by an additional $90 thousand for the year ended December 31, 2015, and the allocation of net income to participating securities would have been $92 thousand for the same period, reducing net income attributable to common shareholders by a total of $182 thousand, for the same period. Total basic EPS and basic EPS from continuing operations would each decrease by $0.01 per share for the year ended December 31, 2015. Weighted average diluted shares outstanding would have been reduced by 167,937 shares for the same period. Diluted EPS would not change.If the EPS presentation had been based on the two-class method, the following adjustments would have been made to the presentation of EPS for the year ended December 31, 2014. Net income attributable to common shareholders would have been reduced by an additional$228 thousand for the year ended December 31, 2014, and the allocation of net income to participating securities would have been $335 thousand for the same period, reducing net income attributable to common shareholders by a total of $563 thousand, for the same period. Total basic EPS and basic EPS from continuing operations would each decrease by $0.01 per share for the year ended December 31, 2014. Weighted average diluted shares outstanding would have been reduced by 428,913 shares for the same period. Total diluted EPS and diluted EPS from discontinued operations would each decrease by $0.01 per share.