Fair Value of Financial Instruments - Summary of Estimated Fair Values of Investments and Remaining Unfunded Commitments for Each Major Category of Investments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Carrying Amount	$ 914,126
Fair Value	954,259
Unfunded Commitments	516,747
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	701,076	[1]
Fair Value	701,076	[1]
Unfunded Commitments	448,482	[1]
Non-marketable securities | Equity method accounting | Other investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Carrying Amount	52,180	[2]
Fair Value	53,679	[2]
Unfunded Commitments	17,258	[2]
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	160,870	[3]
Fair Value	199,504	[3]
Unfunded Commitments	$ 51,007	[3]

[1] Venture capital and private equity fund investments within non-marketable securities (fair value accounting) include investments made by our managed funds of funds and one of our direct venture funds. These investments represent investments in venture capital and private equity funds that invest primarily in U.S. and global technology and life sciences companies. Included in the fair value and unfunded commitments of fund investments under fair value accounting are $624 million and $440 million, respectively, attributable to noncontrolling interests. It is estimated that we will receive distributions from the fund investments over the next 10 to 13 years, depending on the age of the funds and any potential extensions of terms of the funds.

[2] Other investments within non-marketable securities (equity method accounting) include investments in debt funds and venture capital and private equity fund investments that invest in or lend money to primarily U.S. and global technology and life sciences companies. It is estimated that we will receive distributions from the fund investments over the next 10 to 13 years, depending on the age of the funds.

[3] Venture capital and private equity fund investments within non-marketable securities (cost method accounting) include investments in venture capital and private equity fund investments that invest primarily in U.S. and global technology and life sciences companies. It is estimated that we will receive distributions from the fund investments over the next 10 to 13 years, depending on the age of the funds and any potential extensions of the terms of the funds.