Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Total Capital Commitments, Unfunded Capital Commitments, and Our Ownership in Each Fund (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Other Commitments [Line Items]
Unfunded Commitments	$ 5,849
Strategic Investors Fund, LP
Other Commitments [Line Items]
Unfunded Commitments	1,338
Capital Preferred Return Fund, LP
Other Commitments [Line Items]
Unfunded Commitments	1,936
Growth Partners, LP
Other Commitments [Line Items]
Unfunded Commitments	2,575
Parent Company
Other Commitments [Line Items]
Capital Commitments	457,670
Unfunded Commitments	15,252
Parent Company | CP I, LP
Other Commitments [Line Items]
Capital Commitments	6,000
Unfunded Commitments	$ 270
Ownership interest percentage	10.70%
Parent Company | CP II, LP
Other Commitments [Line Items]
Capital Commitments	$ 1,200
Unfunded Commitments	$ 162
Ownership interest percentage	5.10%
Parent Company | Shanghai Yangpu Venture Capital Fund (LP)
Other Commitments [Line Items]
Capital Commitments	$ 843
Unfunded Commitments	$ 0
Ownership interest percentage	6.80%
Parent Company | Strategic Investors Fund, LP
Other Commitments [Line Items]
Capital Commitments	$ 15,300
Unfunded Commitments	$ 688
Ownership interest percentage	12.60%
Parent Company | Strategic Investors Fund II, LP
Other Commitments [Line Items]
Capital Commitments	$ 15,000
Unfunded Commitments	$ 1,050
Ownership interest percentage	8.60%
Parent Company | Strategic Investors Fund III, LP
Other Commitments [Line Items]
Capital Commitments	$ 15,000
Unfunded Commitments	$ 1,275
Ownership interest percentage	5.90%
Parent Company | Strategic Investors Fund IV, LP
Other Commitments [Line Items]
Capital Commitments	$ 12,239
Unfunded Commitments	$ 2,325
Ownership interest percentage	5.00%
Parent Company | Strategic Investors Fund V funds
Other Commitments [Line Items]
Capital Commitments	$ 515
Unfunded Commitments	131
Parent Company | Capital Preferred Return Fund, LP
Other Commitments [Line Items]
Capital Commitments	12,688
Unfunded Commitments	$ 0
Ownership interest percentage	20.00%
Parent Company | Growth Partners, LP
Other Commitments [Line Items]
Capital Commitments	$ 24,670
Unfunded Commitments	$ 1,340
Ownership interest percentage	33.00%
Parent Company | Debt funds (equity method accounting)
Other Commitments [Line Items]
Capital Commitments	$ 58,493
Unfunded Commitments	0
Parent Company | Other fund investments
Other Commitments [Line Items]
Capital Commitments	295,722
Unfunded Commitments	$ 8,011