Business Combinations - Schedule of Supplemental Pro Forma Financial Information (Detail) - Sun Bancorp, Inc. - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Earnings per share, Actual:
Net interest income, Pro forma	$ 184,887	$ 181,572
Provision for loan losses, Pro forma	2,984	2,199
Non-interest income, Pro forma	26,894	29,590
Non-interest expense, Pro forma	164,538	146,154
Net income, Pro forma	$ 35,575	$ 45,027
Earnings per share, Pro forma:
Fully diluted, Pro forma (in usd per share)	$ 0.74	$ 0.93