Selected Quarterly Financial Data (Unaudited) - Schedule of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Interest income	$ 67,713	$ 63,736	$ 59,683	$ 58,718	$ 57,161	$ 51,298	$ 45,092	$ 36,874	$ 249,850	$ 190,427	$ 128,156
Interest expense	14,245	13,802	13,125	12,388	12,175	11,084	8,162	7,082	53,560	38,504	24,301
Net interest income	53,468	49,934	46,558	46,330	44,986	40,214	36,930	29,792	196,290	151,923	103,855
Provision for loan losses, net of change to FDIC receivable and clawback liability	6,173	2,094	9,335	2,964	2,459	5,035	2,886	4,368	20,566	14,747	2,236
Non-interest income	9,420	6,171	6,393	5,733	5,804	5,102	6,911	7,310	27,717	25,126	22,703
Non-interest expenses	31,514	30,307	25,660	27,465	27,864	24,679	25,205	21,169	114,946	98,914	74,024
Income before income tax expense	25,201	23,704	17,956	21,634	20,467	15,602	15,750	11,565	88,495	63,388	50,298
Provision for income taxes	7,415	8,415	6,400	7,682	7,289	3,940	5,517	3,429	29,912	20,174	17,604
Net income	17,786	15,289	11,556	13,952					58,583	43,214	32,694
Preferred stock dividend	1,006	980	507	0					2,493	0	0
Net income available to common shareholders	$ 16,780	$ 14,309	$ 11,049	$ 13,952	$ 13,178	$ 11,662	$ 10,233	$ 8,136	$ 56,090	$ 43,214	$ 32,694
Earnings per common share:
Basic earnings per share (usd per share)	$ 0.62	$ 0.53	$ 0.41	$ 0.52	$ 0.49	$ 0.44	$ 0.38	$ 0.30	$ 2.09	$ 1.62	$ 1.34
Diluted earnings per share (usd per share)	$ 0.58	$ 0.50	$ 0.39	$ 0.49	$ 0.47	$ 0.42	$ 0.37	$ 0.29	$ 1.96	$ 1.55	$ 1.30