Regulatory Matters (Tables)

12 Months Ended

Dec. 31, 2018

Regulatory Capital Requirements [Abstract]

Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations

	Actual				For capital adequacy purposes (at least)				To be well capitalized under prompt corrective action provisions (at least)				Basel III minimum capital ratio with capital conservation buffer (1)
	Amount		Ratio		Amount		Ratio		Amount		Ratio
	(In thousands)
As of December 31, 2018
Common equity tier 1 risk-based capital
Company	$	702,728	11.40	%	$	277,275	4.5	%	n/a		n/a		7.0	%
Boston Private Bank	745,051		12.13		276,352		4.5		$	399,175	6.5	%	7.0
Tier 1 risk-based capital
Company	803,311		13.04		369,701		6.0		n/a		n/a		8.5
Boston Private Bank	745,051		12.13		368,469		6.0		491,292		8.0		8.5
Total risk-based capital
Company	879,927		14.28		492,934		8.0		n/a		n/a		10.5
Boston Private Bank	821,584		13.38		491,292		8.0		614,115		10.0		10.5
Tier 1 leverage capital
Company	803,311		9.54		336,648		4.0		n/a		n/a		4.0
Boston Private Bank	745,051		8.92		334,029		4.0		417,537		5.0		4.0
As of December 31, 2017
Common equity tier 1 risk-based capital
Company	$	607,800	10.32	%	$	265,153	4.5	%	n/a		n/a		7.0	%
Boston Private Bank	694,201		11.83		264,028		4.5		$	381,373	6.5%		7.0
Tier 1 risk-based capital
Company	758,089		12.87		353,537		6.0		n/a		n/a		8.5
Boston Private Bank	694,201		11.83		352,037		6.0		469,382		8.0		8.5
Total risk-based capital
Company	832,182		14.12		471,383		8.0		n/a		n/a		10.5
Boston Private Bank	767,576		13.08		469,382		8.0		586,728		10.0		10.5
Tier 1 leverage capital
Company	758,089		9.34		324,725		4.0		n/a		n/a		4.0
Boston Private Bank	694,201		8.63		321,920		4.0		402,400		5.0		4.0

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n/a = not applicable

(1) Required capital ratios under the Basel III capital rules with the fully phased-in capital conservation buffer added to the minimum risk-based capital ratios. The fully phased-in ratios are effective for 2019, with lower requirements during the transition years 2016 through 2018.