Fair Value of Financial Instruments - Summary of Estimated Fair Values of Investments and Remaining Unfunded Commitments for Each Major Category of Investments (Textual) (Details) $ in Thousands	3 Months Ended
Jun. 30, 2019 USD ($)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value	$ 494,024
Unfunded commitments	24,002
Non-marketable securities \| Venture capital and private equity fund investments \| Fair value accounting
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value	302,852
Unfunded commitments	$ 12,259
Non-marketable securities \| Venture capital and private equity fund investments \| Fair value accounting \| 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 \| Venture capital and private equity fund investments \| Fair value accounting \| 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 \| Venture capital and private equity fund investments \| Equity method accounting
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value	$ 169,219
Unfunded commitments	10,857
Non-marketable securities \| Venture capital and private equity fund investments \| Noncontrolling Interests \| Fair value accounting
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value	81,100
Unfunded commitments	4,100
Non-marketable securities \| Other investments \| Equity method accounting
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value	14,785
Unfunded commitments	$ 886
Non-marketable securities \| Other investments \| Equity method accounting \| Lower Limit
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Period distributions from fund investments to be received	5 years
Non-marketable securities \| Other investments \| Equity method accounting \| Upper Limit
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Period distributions from fund investments to be received	8 years

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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- Definition

Remaining period of expected liquidation by investee of underlying asset of investment measured at net asset value per share or unit. In 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=SL6742756-110258

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- Definition

The total fair value for all investments, comprising or included in the major category, of those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments) for which the entity has intentions to sell or liquidate, but the specific assets for sale or liquidation have not been identified (for example, the entity intends to sell $10,000,000 of its investments in private equity funds, but the individual investments to be sold have not been identified).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=SL6742756-110258

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- Definition

The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=SL6742756-110258

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