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Acquisitions (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Business Acquisition [Line Items] |  |  |
Goodwill acquired | $ 2,604 | $ 2,047 |
Downeast Pension Services, Inc.[Member] |  |  |
Business Acquisition [Line Items] |  |  |
Total consideration paid | 5,700 |  |
Goodwill acquired | 2,600 |  |
Contingent consideration, liability | $ 1,700 |  |
Actuarial Designs & Solutions, Inc. [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Total consideration paid |  | 3,000 |
Goodwill acquired |  | 1,300 |
Columbia Ridge Capital Management, Inc. [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Total consideration paid |  | 1,300 |
Goodwill acquired |  | $ 800 |
Third Party Administrators, Inc. [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Total consideration paid |  |  | $ 4,100
Goodwill acquired |  |  | $ 2,300

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