Investment Securities - Components of Gains and Losses (Realized and Unrealized) on Investment Securities (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($) Investment	Dec. 31, 2015 USD ($) Investment		Dec. 31, 2014 USD ($) Investment
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	$ 87,500,000	$ 107,886,000		$ 551,681,000
Gross losses on investment securities	(35,760,000)	(18,441,000)		(284,658,000)
Gains on investment securities, net	51,740,000	89,445,000	[1],[2]	267,023,000
Other than Temporary Impairment Losses, Investments	$ 0	$ 0		$ 0
Cost method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Number of other-than-temporary impaired investments | Investment	26	22		27
Number of investments | Investment	252	267		281
Cost-method Investments, Other than Temporary Impairment	$ 600,000	$ 600,000		$ 800,000
Available-for-sale Securities
Gain (Loss) on Investments [Line Items]
Available-for-sale Securities, Gross Realized Gains	15,051,000	2,971,000		657,000
Available-for-sale Securities, Gross Realized Losses	(2,856,000)	(1,770,000)		(19,255,000)
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	25,041,000	32,399,000		349,747,000
Gross losses on investment securities	(19,077,000)	(9,210,000)		(86,263,000)
Non-marketable securities | Fair value accounting | Other venture capital investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	17,000	1,512,000		17,309,000
Gross losses on investment securities	(38,000)	(320,000)		(4,516,000)
Non-marketable securities | Fair value accounting | Other securities
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	691,000	9,180,000		151,007,000
Gross losses on investment securities	(781,000)	(1,559,000)		(170,890,000)
Non-marketable securities | Equity method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	10,834,000	26,415,000		1,661,000
Gross losses on investment securities	(6,764,000)	(909,000)		(231,000)
Non-marketable securities | Equity method accounting | Debt Securities
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	1,406,000	4,111,000		4,749,000
Gross losses on investment securities	(458,000)	(774,000)		(1,558,000)
Non-marketable securities | Equity method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	15,739,000	2,791,000		4,755,000
Gross losses on investment securities	(4,857,000)	(3,146,000)		(759,000)
Non-marketable securities | Cost method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	18,428,000	25,908,000		16,001,000
Gross losses on investment securities	(591,000)	(729,000)		(827,000)
Non-marketable securities | Cost method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	293,000	2,599,000		5,795,000
Gross losses on investment securities	$ (338,000)	$ (24,000)		$ (359,000)

[1] During the second quarter of 2015 we adopted new accounting guidance related to our consolidated variable interest entities (ASU 2015-02). Amounts prior to January 1, 2015 have not been revised for the adoption of this guidance. See Note 2— "Summary of Significant Accounting Policies” of the “Notes to the Consolidated Financial Statements” under Part II, Item 8 of this report for additional details.

[2] During the second quarter of 2015 we adopted new accounting guidance related to our consolidated variable interest entities (ASU 2015-02). Amounts prior to January 1, 2015 have not been revised for the adoption of this guidance. See Note 2— "Summary of Significant Accounting Policies” of the “Notes to the Consolidated Financial Statements” under Part II, Item 8 of this report for additional details.