Mortgage Banking Activities - Key Economic Assumptions in Measuring Value of Mortgage Servicing Rights (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Mortgage Banking [Abstract]
Weighted average prepayment rate	189	182
Weighted average life (in years)	3 years 8 months 9 days	3 years 11 months 9 days
Weighted average discount rate	8.00%	8.00%