Subsequent Events - Additional Information (Detail) - Bank of Carolinas Corporation [Member] shares in Millions		6 Months Ended
	Aug. 05, 2015 USD ($) Office shares	Jun. 30, 2015 USD ($)
Subsequent Event [Line Items]
Total assets acquired		$ 345,000,000
Total loans acquired		277,000,000
Total deposits acquired		$ 296,000,000
Date of acquisition		Aug. 05, 2015
Number of common stock issued		$ 48,000,000
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of common stock issued | shares	1.4
Total transaction value	$ 65,400,000
Number of bank offices | Office	8