Mortgage Banking Activities - Principal Balance of Mortgage Servicing Rights (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Mortgage loan portfolios serviced for:
Mortgage loan portfolios service	$ 1,100,000,000	$ 1,100,000,000
FHLMC [Member]
Mortgage loan portfolios serviced for:
Mortgage loan portfolios service	824,060	827,146
FNMA [Member]
Mortgage loan portfolios serviced for:
Mortgage loan portfolios service	$ 277,211	$ 283,340