Fair Value of Financial Instruments - Unrealized Gains Included in Earnings Attributable to Level 3 Assets Held (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total unrealized gains, net	$ 34,469	$ 37,724
Unrealized (losses) gains attributable to noncontrolling interests	(199)	143
Venture capital and private equity funds | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total unrealized gains, net	(222)	160
Equity warrant assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total unrealized gains, net	$ 34,691	$ 37,564