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Investment Securities - Additional Information (Detail) (USD $)
3 Months Ended
Mar. 31, 2014
Investment
Mar. 31, 2013
Dec. 31, 2013
Dec. 31, 2012
Investment Holdings [Line Items]        
Gross realized gain or loss on sale of Investment Securities $ 0 $ 0    
Other-than-temporary impairment losses 0      
Credit losses associated with debt securities 0 187,114,000 0 197,809,000
Number of investment securities with aggregate gross unrealized losses 392      
Unrealized losses on individual investment securities 115,007,000   165,819,000  
Cost method investment securities 299,000,000      
Privately Issued Mortgage-Backed Securities [Member]
       
Investment Holdings [Line Items]        
Pre-tax other-than-temporary impairment losses   $ 10,000,000