Fair Value of Financial Instruments - Summary of Estimated Fair Values of Investments and Remaining Unfunded Commitments for Each Major Category of Investments (Textual) (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 507,306
Unfunded Commitments	22,388
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	145,649
Unfunded Commitments	$ 6,610
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments | Lower Limit
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Period distributions from fund investments to be received	10 years
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments | Upper Limit
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Period distributions from fund investments to be received	13 years
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments | Noncontrolling Interests
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 103,000
Unfunded Commitments	5,000
Non-marketable securities | Equity method accounting | Venture capital and private equity fund investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	83,555
Unfunded Commitments	$ 4,954
Non-marketable securities | Equity method accounting | Venture capital and private equity fund investments | Lower Limit
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Period distributions from fund investments to be received	10 years
Non-marketable securities | Equity method accounting | Venture capital and private equity fund investments | Upper Limit
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Period distributions from fund investments to be received	13 years
Non-marketable securities | Equity method accounting | Other investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 22,352
Unfunded Commitments	886
Non-marketable securities | Cost method accounting | Venture capital and private equity fund investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	232,684
Unfunded Commitments	$ 9,938