Investment Securities - Roll-Forward of Credit Loss Component of Other-than Temporary Impairment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Beginning credit loss amount	$ 1,674	$ 1,240
Add: Initial OTTI credit losses	0	0
Subsequent OTTI credit losses	0	0
Less: Realized losses for securities sold	1,540	0
Securities intended or required to be sold	0	0
Increases in expected cash flows on debt securities	0	0
Ending credit loss amount	$ 134	$ 1,240