Fair Value of Financial Instruments - Additional Information about Level 3 Assets Measured at Fair Value on a Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended				6 Months Ended		3 Months Ended				6 Months Ended		12 Months Ended			6 Months Ended	12 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Equity warrant assets Other assets	Jun. 30, 2013 Equity warrant assets Other assets	Jun. 30, 2014 Non-marketable securities Fair value accounting	Jun. 30, 2013 Non-marketable securities Fair value accounting	Jun. 30, 2014 Non-marketable securities Fair value accounting	Jun. 30, 2013 Non-marketable securities Fair value accounting	Jun. 30, 2014 Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Jun. 30, 2013 Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Jun. 30, 2014 Non-marketable securities Fair value accounting Other venture capital investments	Jun. 30, 2013 Non-marketable securities Fair value accounting Other venture capital investments	Jun. 30, 2013 Non-marketable securities Fair value accounting Other venture capital investments	Jun. 30, 2014 Level 3 Equity warrant assets Other assets	Dec. 31, 2013 Level 3 Equity warrant assets Other assets	Jun. 30, 2014 Level 3 Fair value accounting Other venture capital investments	Dec. 31, 2013 Level 3 Fair value accounting Other venture capital investments	Jun. 30, 2014 Level 3 Fair value accounting Other securities	Dec. 31, 2013 Level 3 Fair value accounting Other securities	Jun. 30, 2014 Fair Value, Measurements, Recurring Equity warrant assets Other assets	Jun. 30, 2013 Fair Value, Measurements, Recurring Equity warrant assets Other assets	Jun. 30, 2014 Fair Value, Measurements, Recurring Fair value accounting Other securities	Jun. 30, 2014 Fair Value, Measurements, Recurring Fair value accounting Other securities	Jun. 30, 2014 Fair Value, Measurements, Recurring Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Jun. 30, 2013 Fair Value, Measurements, Recurring Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Jun. 30, 2014 Fair Value, Measurements, Recurring Non-marketable securities Fair value accounting Other venture capital investments	Jun. 30, 2013 Fair Value, Measurements, Recurring Non-marketable securities Fair value accounting Other venture capital investments	Jun. 30, 2014 Lower Limit Level 3 Equity warrant assets	Jun. 30, 2014 Upper Limit Level 3 Equity warrant assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Inputs, Weighted Average Discount for Sales Restrictions																14.80%	13.70%			10.00%	12.00%									1000.00%	2000.00%
Beginning Balance	$ 1,455,357	$ 891,908	$ 1,314,951	$ 859,141	$ 87,642	$ 66,046	$ 1,367,715	$ 825,862	$ 1,215,060	$ 793,012	$ 976,922	$ 701,076	$ 28,306	$ 124,786				$ 43,747	$ 32,839	$ 319,249		$ 99,891	$ 66,129	$ 362,487	$ 319,249	$ 862,972	$ 665,921	$ 32,839	$ 127,091
Total Realized and Unrealized Gains (Losses) Included in Income	(52,878)	(39,257)	(293,123)	(65,414)	(13,141)	(6,468)	(39,737)	(32,789)	(255,604)	(57,487)	(37,445)	(33,728)	(676)	939								(37,519)	(7,927)	(1,616)	(104,310)	(148,780)	(56,238)	(2,514)	(1,249)
Purchases	81,782	35,602	126,907	65,512	0	0	81,782	35,602	126,907	65,512	65,956	35,574	15,826	28								0	0	0	0	110,411	65,318	16,496	194
Sales	(17,569)	(2,553)	(107,916)	(4,824)	(16,644)	(2,189)	(925)	(364)	(51,279)	(385)	0	0	(925)	(364)								(56,637)	(4,439)	0	(46,840)	0	0	(4,439)	(385)
Issuances	2,749	2,388	6,166	4,314	2,749	2,388	0	0	0	0	0	0	0	0								6,166	4,314	0	0	0	0	0	0
Distributions and Other Settlements	(39,228)	(27,860)	(80,552)	(45,672)	583	1,014	(39,811)	(28,874)	(81,761)	(47,050)	(39,801)	(28,856)	(10)	(18)								1,209	1,378	0	3,417	(81,641)	(45,955)	(3,537)	(1,095)
Transfers Into Level 3	0	0	0	0	0	0	0	0	0	0	0	0	0	0								0	0	0	0	0	0	0	0
Transfers Out of Level 3	(358,741)	(498)	(375,451)	(5,641)	(320)	(498)	(358,421)	0	(374,454)		0	0	(126)	0	(3,561)							(997)	(2,080)	(358,295)	(374,328)	0	0	(126)	(3,561)
Ending Balance	$ 1,177,228	$ 938,244	$ 1,177,228	$ 938,244	$ 87,151	$ 73,229	$ 1,090,077	$ 865,015	$ 1,090,077	$ 865,015	$ 1,040,522	$ 741,522	$ 43,747	$ 123,493	$ 123,493			$ 43,747	$ 32,839	$ 5,808	$ 319,249			$ 5,808	$ 5,808