Summary of Significant Accounting Policies - Summary of Ownership Interests in Investments Held Under Fair Value Accounting (Detail) - Fair value accounting	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Venture capital and private equity fund investments | Strategic Investors Fund, L.P.
Schedule of Investments [Line Items]
Company Direct and Indirect Ownership in Limited Partnership	12.60%	12.60%
Venture capital and private equity fund investments | Capital Preferred Return Fund, L.P.
Schedule of Investments [Line Items]
Company Direct and Indirect Ownership in Limited Partnership	20.00%	20.00%
Venture capital and private equity fund investments | Growth Partners, L.P.
Schedule of Investments [Line Items]
Company Direct and Indirect Ownership in Limited Partnership	33.00%	33.00%
Venture capital and private equity fund investments | Other private equity fund
Schedule of Investments [Line Items]
Company Direct and Indirect Ownership in Limited Partnership	58.20%	58.20%
Other venture capital investments | CP I, L.P.
Schedule of Investments [Line Items]
Company Direct and Indirect Ownership in Limited Partnership	10.70%	10.70%