Quarterly report pursuant to Section 13 or 15(d)

Accumulated Other Comprehensive Income - Additional Information (Detail)

v3.3.0.814
Accumulated Other Comprehensive Income - Additional Information (Detail) - USD ($)
 3 Months Ended 9 Months Ended 12 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Dec. 31, 2014
Dec. 31, 2013
Accumulated Other Comprehensive Income [Line Items]                
Net gain on sales of securities     $ 2,048,000 $ 67,000 $ 6,144,000 $ 1,852,000    
Unrealized gain         0 0 $ 0  
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]                
Accumulated Other Comprehensive Income [Line Items]                
Net gain on sales of securities     $ 2,000,000 $ 67,000 $ 6,100,000 $ 1,900,000    
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Other-than-Temporary Impairment [Member]                
Accumulated Other Comprehensive Income [Line Items]                
Unrealized gain $ 1,200,000 $ 23,000         $ 2,000,000 $ 498,000