Fair Value of Financial Instruments - Summary of Estimated Fair Values of Investments and Remaining Unfunded Commitments for Each Major Category of Investments (Textual) (Detail) - Jun. 30, 2015 - USD ($) $ in Thousands	Total
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 517,544
Unfunded Commitments	27,976
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	156,730
Unfunded Commitments	$ 10,949
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	$ 112,000
Unfunded Commitments	8,000
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	78,574
Unfunded Commitments	$ 4,990
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	$ 22,705
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	236,031
Unfunded Commitments	$ 11,151