Quarterly report pursuant to Section 13 or 15(d)

Accumulated Other Comprehensive Income - Activity in Accumulated Other Comprehensive Income (Loss) (Detail)

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Accumulated Other Comprehensive Income - Activity in Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Balance at beginning of period $ 1,634 $ 3,154 $ 5,418 $ 3,524
Other comprehensive (loss) income before reclassification (5,492) 2,044 (8,964) 2,940
Reclassification from accumulated other comprehensive income (611) 166 (923) (1,100)
Other comprehensive (loss ) income (6,103) 2,210 (9,887) 1,840
Balance at end of period (4,469) 5,364 (4,469) 5,364
Accumulated Net Unrealized Investment Gain (Loss) [Member]
        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Balance at beginning of period 915 3,442 7,348 4,115
Other comprehensive (loss) income before reclassification (10,020) 3,623 (16,141) 4,216
Reclassification from accumulated other comprehensive income (611) 166 (923) (1,100)
Other comprehensive (loss ) income (10,631) 3,789 (17,064) 3,116
Balance at end of period (9,716) 7,231 (9,716) 7,231
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Interest-Only-Strip [Member]
        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Balance at beginning of period 17 14 16 20
Other comprehensive (loss) income before reclassification    2 1 (4)
Reclassification from accumulated other comprehensive income            
Other comprehensive (loss ) income    2 1 (4)
Balance at end of period 17 16 17 16
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Interest Rate Swap [Member]
        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Balance at beginning of period          (9)
Other comprehensive (loss) income before reclassification          9
Reclassification from accumulated other comprehensive income            
Other comprehensive (loss ) income          9
Balance at end of period            
Tax Expense Benefit [Member]
        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Balance at beginning of period 702 (302) (1,946) (602)
Other comprehensive (loss) income before reclassification 4,528 (1,581) 7,176 (1,281)
Reclassification from accumulated other comprehensive income            
Other comprehensive (loss ) income 4,528 (1,581) 7,176 (1,281)
Balance at end of period $ 5,230 $ (1,883) $ 5,230 $ (1,883)