Business Segments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2014 Segment FinancialCenters
Segment Reporting Information [Line Items]
Number of principal reporting segments	2
Bank operated Business Financial Centers, number	40
Bank operated Commercial Banking Centers, number	6
Consideration of Business Financial and Commercial Banking Centers	1
Subsidiary bank [Member]
Segment Reporting Information [Line Items]
Bank operated Business Financial Centers, number	40
Bank operated Commercial Banking Centers, number	6