Acquisitions and Divestitures - Disposals (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and cash equivalents	$ 19,508	$ 10,000	$ 0	$ 0
Disposal Group, Held-for-sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and cash equivalents	19,508	10,000
Fees receivable, net	49,191	50,928
Goodwill	246,661	212,994
Intangible assets, net	264,145	250,472
Other assets	23,849	18,571
Total assets held-for-sale	603,354	542,965
Accounts payable and accrued liabilities	26,467	32,388
Deferred revenues	65,846	61,450
Other liabilities	51,644	52,007
Total liabilities held-for-sale	$ 143,957	$ 145,845