Boston Private Financial Holdings, Inc. (Parent Company Only) Cash Flow (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net Income Attributable to Parent	$ 17,668	[1]	$ 18,336	[1]	$ 21,328	[1]	$ 13,203	[1]	$ 13,092	[1]	$ 16,513	[1]	$ 14,161	[1]	$ 9,505	[1]	$ 70,535	$ 53,271	$ 39,137
Net income from discontinued operations	1,968	[1]	1,321	[1]	2,781	[1]	1,722	[1]	1,819	[1]	1,672	[1]	2,590	[1]	1,554	[1]	7,792	7,635	6,184
Net income from continuing operations																	66,691	48,758	36,101
Gain on repurchase of debt																	(620)	(3,444)	(4,230)
Deferred income tax expense/(benefit)																	10,313	3,648	7,798
Depreciation and amortization																	19,107	18,888	18,051
Net decrease/(increase) in other operating activities																	5,861	6,094	6,202
Net Cash Provided by (Used in) Operating Activities, Continuing Operations																	106,383	57,378	78,840
Cash Provided by (Used in) Operating Activities, Discontinued Operations																	7,792	(5,566)	7,506
Net Cash Provided by (Used in) Operating Activities																	114,175	51,812	86,346
Payments for (Proceeds from) Other Investing Activities																	224	1,561
Net Cash Provided by (Used in) Investing Activities, Continuing Operations																	(295,908)	(310,122)	(225,041)
Net cash provided by/(used in) investing activities - discontinued operations																	0	(21)	(1,126)
Net Cash Provided by (Used in) Investing Activities																	(295,908)	(310,143)	(226,167)
Repurchase of debt																	(35,536)	(33,749)	(6,988)
Proceeds from issuance of Series D preferred stock, net																	47,753	0	0
Dividends paid to common share holders																	(19,129)	(3,125)	(3,089)
Dividends paid to preferred shareholders																	(2,660)	(290)	(290)
Tax deficiency from certain stock compensation awards																	(663)	(1,588)	(1,706)
Repurchase of Warrants																	0	15,000	0
Repurchase of Series B preferred stock, including deemed dividend at repurchase																	69,827	0	0
Proceeds from stock option exercises																	2,332	738	205
Proceeds from issuance of common stock, net																	1,230	1,215	1,244
Other equity adjustments																	238	(1,183)	492
Net Cash Provided by (Used in) Financing Activities, Continuing Operations																	64,870	363,721	(150,258)
Net cash provided by/(used in) financing activities - discontinued operations																	0	0	0
Net Cash Provided by (Used in) Financing Activities																	64,870	363,721	(150,258)
Cash and Cash Equivalents, Period Increase (Decrease)																	(116,863)	105,390	(290,079)
Cash and cash equivalents at beginning of year							308,744								203,354		308,744	203,354	493,433
Cash and cash equivalents at end of period	191,881								308,744								191,881	308,744	203,354
Parent Company [Member]
Net Income Attributable to Parent																	46,572	21,744	20,973
Net income from discontinued operations																	7,792	7,635	6,184
Net income from continuing operations																	62,743	45,636	32,953
Gain on repurchase of debt																	(620)	(3,444)	(4,230)
Deferred income tax expense/(benefit)																	4,873	3,963	(4,279)
Depreciation and amortization																	3,187	5,613	3,288
Net decrease/(increase) in other operating activities																	(6,630)	(11,075)	(1,557)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations																	39,590	9,166	7,926
Cash Provided by (Used in) Operating Activities, Discontinued Operations																	7,792	7,635	6,184
Net Cash Provided by (Used in) Operating Activities																	47,382	16,801	14,110
Payments to Acquire Businesses, Net of Cash Acquired																	0	0	(217)
Proceeds from Divestiture of Businesses																	747	5,964	2,752
Payments for (Proceeds from) Other Investing Activities																	(115)	897	0
Net Cash Provided by (Used in) Investing Activities, Continuing Operations																	276	1,670	2,535
Net cash provided by/(used in) investing activities - discontinued operations																	0	0	0
Net Cash Provided by (Used in) Investing Activities																	276	1,670	2,535
Repurchase of debt																	(35,536)	(33,749)	(6,988)
Proceeds from issuance of Series D preferred stock, net																	47,753	0	0
Dividends paid to common share holders																	(19,129)	(3,125)	(3,089)
Dividends paid to preferred shareholders																	(2,660)	(290)	(290)
Tax deficiency from certain stock compensation awards																	(663)	(1,588)	(1,706)
Repurchase of Warrants																	0	(15,000)	0
Repurchase of Series B preferred stock, including deemed dividend at repurchase																	(69,827)	0	0
Proceeds from stock option exercises																	2,332	738	205
Proceeds from issuance of common stock, net																	4,583	3,198	5,288
Other equity adjustments																	(3,178)	(4,305)	(1,657)
Net Cash Provided by (Used in) Financing Activities, Continuing Operations																	(76,325)	(54,121)	(8,237)
Net cash provided by/(used in) financing activities - discontinued operations																	0	0	0
Net Cash Provided by (Used in) Financing Activities																	(76,325)	(54,121)	(8,237)
Cash and Cash Equivalents, Period Increase (Decrease)																	(28,667)	(35,650)	8,408
Cash and cash equivalents at beginning of year							61,221								96,871		61,221	96,871	88,463
Cash and cash equivalents at end of period	32,554								61,221								32,554	61,221	96,871
Private Banking Segment [Member] | Parent Company [Member]
Net Income Attributable to Parent																	(64,628)	(51,212)	(40,119)
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries																	27,900	10,300	7,400
Non Banking Segments [Member] | Parent Company [Member]
Net Income Attributable to Parent																	(11,280)	(8,174)	(8,777)
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries																	24,045	17,559	23,247
Private Banking Segment [Member]
Net Income Attributable to Parent																	64,628	51,212	40,119	[2]
Net income from continuing operations																	64,628	51,212	40,119	[2]
Private Banking Segment [Member] | Parent Company [Member]
Payments of Distributions to Affiliates																	0	0	0
Non Banking Segments [Member] | Parent Company [Member]
Payments of Distributions to Affiliates																	$ (356)	$ (5,191)	$ 0

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

[2] 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 II. Item 8. “Financial Statements and Supplementary Data-Note 2: Restructuring” for additional details.