Annual report pursuant to Section 13 and 15(d)

Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Detail)

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Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]                      
Interest and dividend income $ 61,957 $ 60,036 $ 57,322 $ 55,082 $ 55,784 $ 53,862 $ 51,326 $ 48,349 $ 234,397 $ 209,321 $ 178,471
Interest expense 16,311 14,707 12,208 10,158 9,440 8,936 8,148 5,995 53,384 32,519 18,274
Net interest income before provision for loan and lease losses 45,646 45,329 45,114 44,924 46,344 44,926 43,178 42,354 181,013 176,802 160,197
Loan and lease loss provision (income) 3,041 200 100 649 220 269 422 (80) 3,990 831 (4,339)
Noninterest income 6,299 6,215 5,945 6,061 7,680 8,816 9,702 7,217 24,520 33,415 33,075
Noninterest expense 29,298 29,008 29,510 29,757 29,258 28,660 28,944 27,240 117,573 114,102 108,223
Income before income tax expense 19,606 22,336 21,449 20,579 24,546 24,813 23,514 22,411      
Income tax expense 8,222 6,255 5,901 5,724 13,049 9,890 9,057 8,628 26,102 40,624 32,899
Net income $ 11,384 $ 16,081 $ 15,548 $ 14,855 $ 11,497 $ 14,923 $ 14,457 $ 13,783 $ 57,868 $ 54,660 $ 56,489
Basic earnings per share:                      
Basic earnings per share (in usd per share) $ 0.37 $ 0.50 $ 0.48 $ 0.46 $ 0.36 $ 0.46 $ 0.45 $ 0.43 $ 1.80 $ 1.70 $ 1.76
Diluted earnings per share:                      
Diluted earnings per share (in usd per share) $ 0.37 $ 0.50 $ 0.48 $ 0.46 $ 0.36 $ 0.46 $ 0.45 $ 0.43 $ 1.79 $ 1.69 $ 1.75