Intangible Assets and Goodwill - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Pretax impairment charge recorded during the period for intangible assets related to our credit hedge funds			$ 0	$ 0
Intangible asset amortization expense, excluding impairment losses	$ 2,500,000	$ 8,900,000	$ 5,000,000	$ 19,300,000