Mortgage Banking Activities - Key Economic Assumptions in Measuring Value of Mortgage Servicing Rights (Detail)	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Mortgage Banking [Abstract]
Weighted average prepayment rate	195	219
Weighted average life (in years)	3 years 6 months 15 days	3 years 7 months 10 days
Weighted average discount rate	8.00%	8.00%