Basis of Presentation and Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2015
Basis of Presentation and Summary of Significant Accounting Policies [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 bank holding company (the “Holding Company”) with four reportable segments: Private Banking, Wealth Management and Trust, Investment Management, and Wealth Advisory. The Private Banking segment is comprised of the banking operations of Boston Private Bank & Trust Company (the “Bank” or “Boston Private Bank”), a trust company chartered by The Commonwealth of Massachusetts, insured by the Federal Deposit Insurance Corporation (the “FDIC”), and a wholly-owned subsidiary of the Company. Boston Private Bank currently operates in three geographic markets: New England, San Francisco Bay, and Southern California. The Wealth Management and Trust segment is comprised for purposes of this segment of Boston Private Bank's existing trust business and Boston Private Wealth, LLC (“BP Wealth”). BP Wealth was formed in the first quarter of 2015 and combines Boston Private Bank's existing wealth management business and the business of Banyan Partners, LLC (“Banyan”), which Boston Private Bank purchased in the fourth quarter of 2014. The segment offers investment management, wealth management, family office, and trust services to individuals, families, and institutions. The Wealth Management and Trust segment operates in New England; South Florida; Texas; California; Atlanta, Georgia; and Madison, Wisconsin. For comparative purposes, the Wealth Management and Trust data that was previously included within the Private Banking segment has been reclassified into the Wealth Management and Trust segment. The Investment Management segment has two consolidated affiliates, consisting of Dalton, Greiner, Hartman, Maher & Co., LLC (“DGHM”) and Anchor Capital Advisors, LLC (“Anchor”) (together, the “Investment Managers”). The Wealth Advisory segment has two consolidated affiliates, consisting of KLS Professional Advisors Group, LLC (“KLS”) and Bingham, Osborn & Scarborough, LLC (“BOS”) (together, the “Wealth Advisors” and, together with the Wealth Management and Trust and Investment Management segments, the “Wealth and Investment businesses”). The Company conducts substantially all of its business through its four 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, 2014, 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, 2014, as filed with the SEC. For interim reporting purposes, the Company follows the same significant accounting policies.

Basis of Presentation and Summary of Significant Accounting Policies

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

The Private Banking segment is comprised of the banking operations of Boston Private Bank & Trust Company (the “Bank” or “Boston Private Bank”), a trust company chartered by The Commonwealth of Massachusetts, insured by the Federal Deposit Insurance Corporation (the “FDIC”), and a wholly-owned subsidiary of the Company. Boston Private Bank currently operates in three geographic markets: New England, San Francisco Bay, and Southern California.

The Wealth Management and Trust segment is comprised for purposes of this segment of Boston Private Bank's existing trust business and Boston Private Wealth, LLC (“BP Wealth”). BP Wealth was formed in the first quarter of 2015 and combines Boston Private Bank's existing wealth management business and the business of Banyan Partners, LLC (“Banyan”), which Boston Private Bank purchased in the fourth quarter of 2014. The segment offers investment management, wealth management, family office, and trust services to individuals, families, and institutions. The Wealth Management and Trust segment operates in New England; South Florida; Texas; California; Atlanta, Georgia; and Madison, Wisconsin. For comparative purposes, the Wealth Management and Trust data that was previously included within the Private Banking segment has been reclassified into the Wealth Management and Trust segment.

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

The Wealth Advisory segment has two consolidated affiliates, consisting of KLS Professional Advisors Group, LLC (“KLS”) and Bingham, Osborn & Scarborough, LLC (“BOS”) (together, the “Wealth Advisors” and, together with the Wealth Management and Trust and Investment Management segments, the “Wealth and Investment businesses”).

The Company conducts substantially all of its business through its four 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, 2014, 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, 2014, as filed with the SEC. For interim reporting purposes, the Company follows the same significant accounting policies.