Fair Value Measurements - Change in Fair Value for Financial Instruments (Detail) (Loan Securities Carried at Fair Value [Member], Significant Unobservable Inputs (Level 3) [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Loan Securities Carried at Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value, Beginning balance	$ 11	$ 5,309
Net unrealized gain	215	447
Fair value, Ending balance	226	5,756
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held at September 30, 2013 and 2012, respectively	$ 215	$ 447