Fair Value of Financial Instruments - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Debt Disclosure [Line Items]
Investments transferred out of Level 3	$ 16,710		$ 5,143
Fair value accounting | Non-marketable securities
Debt Disclosure [Line Items]
Investments transferred out of Level 3	$ 16,033	[1]	$ 3,561	[1]

[1] Realized and unrealized gains (losses) are recorded on the line items “gains on investment securities, net”, and “other noninterest income”, components of noninterest income.