Fair Value Measurements - Change in Fair Value for Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value, Ending balance	$ 226
Significant Unobservable Inputs (Level 3) [Member] | Loan Securities Carried at Fair Value [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value, Beginning balance	11	5,309
Net unrealized gain	215	76
Fair value, Ending balance	226	5,385
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 the reporting date	$ 215	$ 76