Fair Value of Financial Instruments Quantitative Information About Significant Unobservable Inputs (Detail) - Significant Unobservable Inputs (Level 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Equity warrant assets | Other Assets
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Valuation Technique	Modified Black-Scholes option pricing model	Modified Black-Scholes option pricing model
Sales Restrictions Discount	18.00%	17.80%
Volatility	38.10%	42.60%
Risk-Free interest rate	2.10%	1.70%
Equity warrant assets | Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 1,786	$ 1,681
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	36.00%	38.30%
Risk-Free interest rate	1.10%	0.90%
Marketability discount	16.60%	20.00%
Remaining Life Assumption	45.00%	45.00%
Equity Warrant Asset, Private Portfolio | Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 133,382	$ 113,017
Other venture capital investments | Fair value accounting
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 2,040	$ 71,204
Valuation Technique	Private company equity pricing	Private company equity pricing