Fair Value of Financial Instruments Quantitative Information About Significant Unobservable Inputs (Detail) (Significant Unobservable Inputs (Level 3), USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Equity Warrant Asset, Public Portfolio | Other assets
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Valuation Technique	Modified Black-Scholes option pricing model
Sales Restrictions Discount	13.70%	[1]
Volatility	41.30%
Risk-Free interest rate	1.70%
Equity Warrant Asset, Public Portfolio | Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 24,217
Equity Warrant Asset, Private Portfolio | Other assets
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Valuation Technique	Modified Black-Scholes option pricing model		Modified Black-Scholes option pricing model
Volatility	40.10%		45.20%
Risk-Free interest rate	0.80%		0.40%
Marketability Discount	22.50%	[2]	22.50%	[2]
Remaining Life Assumption	45.00%	[3]	45.00%	[3]
Equity Warrant Asset, Private Portfolio | Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	75,674		66,129
Other venture capital investments | Fair value accounting
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	32,839		127,091
Valuation Technique	Private company equity pricing		Private company equity pricing
Other Securities | Fair value accounting
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 319,249
Valuation Technique	Modified stock price
Sales Restrictions Discount	12.00%	[1]

[1] We adjust quoted market prices of public companies which are subject to certain sales restrictions. Sales restriction discounts generally range from 10 percent to 20 percent depending on the duration of the sales restrictions which typically range from 3 to 6 months.

[2] Our marketability discount is applied to all private company warrants to account for a general lack of liquidity due to the private nature of the associated underlying company. The quantitative measure used is based on long-run averages and is influenced over time by various factors, including market conditions. On a quarterly basis, a sensitivity analysis is performed on our marketability discount.

[3] We adjust the contractual remaining term of private company warrants based on our best estimate of the actual remaining life, which we determine by utilizing historical data on cancellations and exercises. At December 31, 2013, the weighted average contractual remaining term was 6.3 years, compared to our estimated remaining life of 2.8 years. On a quarterly basis, a sensitivity analysis is performed on our remaining life assumption.