Acquisitions, Asset Sales, and Divestitures Asset Sales and Divestitures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Liabilities, Deposits Included in Sale	$ 104,000
Gain on sale of offices	$ 2,862	$ 0	$ 0
Westfield Capital Management Company LLC [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Nature of Activities Having Continuing Cash Flows after Disposal	12.5% share in Westfield’s revenues (up to an annual maximum of $11.6 million)
Discontinued Operation, Period of Continuing Cash Flows after Disposal	1 year