Basis of Presentation and Summary of Significant Accounting Policies	9 Months Ended
Sep. 30, 2012
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Significant Accounting Policies [Text Block]	Basis of Presentation and Summary of Significant Accounting Policies Boston Private Financial Holdings, Inc. (the “Company” or “BPFH”), is a holding company with three reportable segments: Private Banking, Investment Management, and Wealth Advisory. On May 27, 2011, Boston Private Bank & Trust Company (the “Bank” or “Boston Private Bank”), a trust company chartered by The Commonwealth of Massachusetts, whose deposits are insured by the Federal Deposit Insurance Corporation (the “FDIC”), and a wholly-owned subsidiary of the Company, merged, as the surviving bank, with Borel Private Bank & Trust Company (“Borel”), First Private Bank & Trust (“FPB”), and Charter Private Bank (“Charter”), all of which were also wholly-owned subsidiaries of the Company. Boston Private Bank operates primarily in four geographic markets: New England, San Francisco Bay, Southern California, and the Pacific Northwest. The Bank currently conducts business under the name of Boston Private Bank & Trust Company in all markets. In the third quarter of 2012, the San Francisco Bay market switched from conducting business under the name of Borel Private Bank & Trust Company, A Division of Boston Private Bank & Trust Company, to conducting business under the name of Boston Private Bank. The Investment Management segment has two consolidated affiliate partners, consisting of Dalton, Greiner, Hartman, Maher & Co., LLC (“DGHM”) and Anchor Capital Holdings, LLC (“Anchor”) (together, the “Investment Managers”). The Wealth Advisory segment has two consolidated affiliate partners, KLS Professional Advisors Group, LLC (“KLS”) and Bingham, Osborn & Scarborough, LLC (“BOS”) (together, the “Wealth Advisors”). In addition, at December 31, 2010, the Company held an equity interest in Coldstream Holdings, Inc. of approximately 45%, which it sold in January 2011. In the second quarter of 2012, the Company sold its affiliate Davidson Trust Company (“DTC”). The Company recorded a gain of $0.8 million on the DTC transaction, which includes $0.6 million of tax benefits. Accordingly, prior period and current financial information related to DTC is included with discontinued operations. The Company conducts substantially all of its business through its three reportable segments. All significant intercompany accounts and transactions have been eliminated in consolidation. The unaudited interim consolidated financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”), and include all necessary adjustments of a normal recurring nature which, in the opinion of management, are required for a fair presentation of the results of operations and financial condition of the Company. The interim results of consolidated operations are not necessarily indicative of the results for the entire year. The information in this report should be read in conjunction with the consolidated financial statements and accompanying notes included in the Annual Report on Form 10-K for the year ended December 31, 2011, as filed with the Securities and Exchange Commission (“SEC”). Prior period amounts are reclassified whenever necessary to conform to the current period presentation. The Company’s significant accounting policies are described in Part II. Item 8. “Financial Statements and Supplementary Data - Note 1: Basis of Presentation and Summary of Significant Accounting Policies” in the Company’s Annual Report on Form 10-K for the year ended December 31, 2011, as filed with the SEC. For interim reporting purposes, the Company follows the same significant accounting policies, except for earnings per share, as described below. Earnings Per Share (“EPS”) Basic EPS is computed by dividing net income/ (loss) attributable to common shareholders by the weighted average number of common shares outstanding during the year. Diluted EPS reflects the potential dilution that could occur if securities or other contracts to issue common stock (such as stock options, among others) were exercised or converted into additional common shares that would then share in the earnings of the entity. Diluted EPS is computed by dividing net income attributable to common shareholders by the weighted average number of common shares outstanding for the year, plus an incremental number of common-equivalent shares computed using the treasury stock method. Dilutive potential common shares could consist of: stock options, performance-based restricted stock, warrants or other dilutive securities, and conversion of the convertible trust preferred securities. Additionally, when dilutive, interest expense (net of tax) related to the convertible trust preferred securities is added back to net income attributable to common shareholders. The calculation of diluted EPS excludes the potential dilution of common shares and the inclusion of any related expenses if the effect is antidilutive. Unvested time-based restricted stock and Series B Non-Cumulative Perpetual Contingent Convertible Preferred Stock (“Series B Preferred”), both of which include the right to receive non-forfeitable dividends, are considered to participate with common stock in undistributed earnings for purposes of computing EPS. Companies, such as BPFH, that have such participating securities are required to calculate basic EPS using the two-class method and diluted EPS using the more dilutive amount resulting from the application of either the two-class method or the if-converted method. Calculations of EPS under the two-class method (i) exclude from the numerator any dividends paid or owed on participating securities and any undistributed earnings considered to be attributable to participating securities, and (ii) exclude from the denominator the dilutive impact of the participating securities. Calculations of EPS under the if-converted method (i) include in the numerator any dividends paid or owed on participating securities, and (ii) include the dilutive impact of the participating securities using the treasury stock method.

Basis of Presentation and Summary of Significant Accounting Policies

Boston Private Financial Holdings, Inc. (the “Company” or “BPFH”), is a holding company with three reportable segments: Private Banking, Investment Management, and Wealth Advisory.

On May 27, 2011, Boston Private Bank & Trust Company (the “Bank” or “Boston Private Bank”), a trust company chartered by The Commonwealth of Massachusetts, whose deposits are insured by the Federal Deposit Insurance Corporation (the “FDIC”), and a wholly-owned subsidiary of the Company, merged, as the surviving bank, with Borel Private Bank & Trust Company (“Borel”), First Private Bank & Trust (“FPB”), and Charter Private Bank (“Charter”), all of which were also wholly-owned subsidiaries of the Company.

Boston Private Bank operates primarily in four geographic markets: New England, San Francisco Bay, Southern California, and the Pacific Northwest. The Bank currently conducts business under the name of Boston Private Bank & Trust Company in all markets. In the third quarter of 2012, the San Francisco Bay market switched from conducting business under the name of Borel Private Bank & Trust Company, A Division of Boston Private Bank & Trust Company, to conducting business under the name of Boston Private Bank.

The Investment Management segment has two consolidated affiliate partners, consisting of Dalton, Greiner, Hartman, Maher & Co., LLC (“DGHM”) and Anchor Capital Holdings, LLC (“Anchor”) (together, the “Investment Managers”).

The Wealth Advisory segment has two consolidated affiliate partners, KLS Professional Advisors Group, LLC (“KLS”) and Bingham, Osborn & Scarborough, LLC (“BOS”) (together, the “Wealth Advisors”). In addition, at December 31, 2010, the Company held an equity interest in Coldstream Holdings, Inc. of approximately 45%, which it sold in January 2011. In the second quarter of 2012, the Company sold its affiliate Davidson Trust Company (“DTC”). The Company recorded a gain of $0.8 million on the DTC transaction, which includes $0.6 million of tax benefits. Accordingly, prior period and current financial information related to DTC is included with discontinued operations.

The Company conducts substantially all of its business through its three reportable segments. All significant intercompany accounts and transactions have been eliminated in consolidation.

The unaudited interim consolidated financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”), and include all necessary adjustments of a normal recurring nature which, in the opinion of management, are required for a fair presentation of the results of operations and financial condition of the Company. The interim results of consolidated operations are not necessarily indicative of the results for the entire year.

The information in this report should be read in conjunction with the consolidated financial statements and accompanying notes included in the Annual Report on Form 10-K for the year ended December 31, 2011, as filed with the Securities and Exchange Commission (“SEC”). Prior period amounts are reclassified whenever necessary to conform to the current period presentation.

The Company’s significant accounting policies are described in Part II. Item 8. “Financial Statements and Supplementary Data - Note 1: Basis of Presentation and Summary of Significant Accounting Policies” in the Company’s Annual Report on Form 10-K for the year ended December 31, 2011, as filed with the SEC. For interim reporting purposes, the Company follows the same significant accounting policies, except for earnings per share, as described below.

Earnings Per Share (“EPS”)

Basic EPS is computed by dividing net income/ (loss) attributable to common shareholders by the weighted average number of common shares outstanding during the year. Diluted EPS reflects the potential dilution that could occur if securities or other contracts to issue common stock (such as stock options, among others) were exercised or converted into additional common shares that would then share in the earnings of the entity. Diluted EPS is computed by dividing net income attributable to common shareholders by the weighted average number of common shares outstanding for the year, plus an incremental number of common-equivalent shares computed using the treasury stock method. Dilutive potential common shares could consist of: stock options, performance-based restricted stock, warrants or other dilutive securities, and conversion of the convertible trust preferred securities. Additionally, when dilutive, interest expense (net of tax) related to the convertible trust preferred securities is added back to net income attributable to common shareholders. The calculation of diluted EPS excludes the potential dilution of common shares and the inclusion of any related expenses if the effect is antidilutive.

Unvested time-based restricted stock and Series B Non-Cumulative Perpetual Contingent Convertible Preferred Stock (“Series B Preferred”), both of which include the right to receive non-forfeitable dividends, are considered to participate with common stock in undistributed earnings for purposes of computing EPS. Companies, such as BPFH, that have such participating securities are required to calculate basic EPS using the two-class method and diluted EPS using the more dilutive amount resulting from the application of either the two-class method or the if-converted method. Calculations of EPS under the two-class method (i) exclude from the numerator any dividends paid or owed on participating securities and any undistributed earnings considered to be attributable to participating securities, and (ii) exclude from the denominator the dilutive impact of the participating securities. Calculations of EPS under the if-converted method (i) include in the numerator any dividends paid or owed on participating securities, and (ii) include the dilutive impact of the participating securities using the treasury stock method.