Fair Value of Financial Instruments - Additional Information about Level 3 Assets Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 125,651	$ 478,435	$ 117,989	$ 451,979
Total Realized and Unrealized Gains Included in Income	23,249	15,433	43,464	144,343
Purchases	0	15,826	0	16,496
Sales	(27,393)	(17,569)	(42,190)	(107,916)
Issuances	2,467	2,749	4,550	6,166
Distributions and Other Settlements	344	573	748	1,089
Transfers Out of Level 3	(891)	(358,741)	(1,134)	(375,451)
Ending Balance	123,427	136,706	123,427	136,706
Equity warrant assets | Other assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	122,261	87,642
Total Realized and Unrealized Gains Included in Income	23,249	13,141
Purchases	0	0
Sales	(27,393)	(16,644)
Issuances	2,467	2,749
Distributions and Other Settlements	344	583
Transfers Out of Level 3	(891)	(320)
Ending Balance	120,037	87,151	120,037	87,151
Non-marketable securities | Fair value accounting
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	3,390	390,793	3,291	352,088
Total Realized and Unrealized Gains Included in Income	0	2,292	131	106,824
Purchases	0	15,826	0	16,496
Sales	0	(925)	(32)	(51,279)
Issuances	0	0	0	0
Distributions and Other Settlements	0	(10)	0	(120)
Transfers Out of Level 3	0	(358,421)	0
Ending Balance	3,390	49,555	3,390	49,555
Non-marketable securities | Fair value accounting | Other venture capital investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	3,390	28,306
Total Realized and Unrealized Gains Included in Income	0	676
Purchases	0	15,826
Sales	0	(925)
Issuances	0	0
Distributions and Other Settlements	0	(10)
Transfers Out of Level 3	0	(126)		(374,454)
Ending Balance	$ 3,390	43,747	3,390	43,747
Non-marketable securities | Fair value accounting | Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		362,487
Total Realized and Unrealized Gains Included in Income		1,616
Purchases		0
Sales		0
Issuances		0
Distributions and Other Settlements		0
Transfers Out of Level 3		(358,295)
Ending Balance		$ 5,808		5,808
Fair Value, Measurements, Recurring | Equity warrant assets | Other assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance			114,698	99,891
Total Realized and Unrealized Gains Included in Income			43,333	37,519
Purchases			0	0
Sales			(42,158)	(56,637)
Issuances			4,550	6,166
Distributions and Other Settlements			748	1,209
Transfers Out of Level 3			(1,134)	(997)
Fair Value, Measurements, Recurring | Non-marketable securities | Fair value accounting | Other venture capital investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance			3,291	32,839
Total Realized and Unrealized Gains Included in Income			131	2,514
Purchases			0	16,496
Sales			(32)	(4,439)
Issuances			0	0
Distributions and Other Settlements			0	(3,537)
Transfers Out of Level 3			$ 0	(126)
Fair Value, Measurements, Recurring | Non-marketable securities | Fair value accounting | Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance				319,249
Total Realized and Unrealized Gains Included in Income				104,310
Purchases				0
Sales				(46,840)
Issuances				0
Distributions and Other Settlements				3,417
Transfers Out of Level 3				$ (374,328)