Investment Securities - Roll-Forward of Credit Loss Component of Other-than Temporary Impairment (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
Investments, Debt and Equity Securities [Abstract]
Beginning credit loss amount	$ 134	$ 1,240	$ 1,674	$ 1,240
Add: Initial OTTI credit losses	0	0	0	0
Subsequent OTTI credit losses	0	0	0	0
Less: Realized losses for securities sold	134	0	1,674	0
Securities intended or required to be sold	0	0	0	0
Increases in expected cash flows on debt securities	0	0	0	0
Ending credit loss amount	$ 0	$ 1,240	$ 0	$ 1,240