Fair Value Accounting - Gains and Losses from Fair Value Changes on Securities Measured at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net losses for the period on trading securities included in earnings	$ (2)	$ (52)	$ 16	$ (54)
Less: net gains and (losses) recognized during the period on trading securities sold during the period	0	0	0	0
Change in unrealized gains or (losses) for the period included in earnings for trading securities held at the end of the reporting period	$ (2)	$ (52)	$ 16	$ (54)