Business Combinations - Schedule of Supplemental Pro Forma Financial Information (Detail) - Sun Bancorp, Inc. - USD ($)	2 Months Ended	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2018	Mar. 31, 2017
Business Acquisition [Line Items]
Net interest income, Actual	$ 12,976,000
Provision for loan losses, Actual	221,000
Non-interest income, Actual	1,409,000
Non-interest expense, Actual	7,994,000
Net income, Actual	$ 4,874,000
Earnings per share, Actual:
Net interest income, Pro forma		$ 62,190,000	$ 59,773,000
Provision for loan losses, Pro forma		1,371,000	700,000
Non-interest income, Pro forma		9,725,000	9,426,000
Non-interest expense, Pro forma		74,101,000	47,180,000
Net income, Pro forma		$ (3,998)	$ 16,104,000
Earnings per share, Pro forma:
Fully diluted, Pro forma		$ (0.08)	$ 0.33