Fair Value of Financial Instruments - Summary of Estimated Fair Values of Investments and Remaining Unfunded Commitments for Each Major Category of Investments (Detail) $ in Thousands	Jun. 30, 2015 USD ($)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Carrying Amount	$ 407,395
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]
Carrying Amount	156,730
Fair Value	156,730
Unfunded Commitments	10,949
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]
Carrying Amount	78,574
Fair Value	78,574
Unfunded Commitments	4,990
Non-marketable securities | Equity method accounting | Debt funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Carrying Amount	22,313
Fair Value	23,504
Unfunded Commitments	0
Non-marketable securities | Equity method accounting | Other investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Carrying Amount	22,705
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]
Carrying Amount	127,073
Fair Value	236,031
Unfunded Commitments	$ 11,151