Loans - Schedule of Average Recorded Investment in Impaired Loans and Related Interest Income Recognized (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Average recorded investment:
Average recorded investment in impaired loans	$ 12,324	$ 7,794	$ 11,940	$ 8,945
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	74	81	278	282
Commercial [Member]
Average recorded investment:
Average recorded investment in impaired loans	7,148	3,777	6,780	3,917
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	53	41	156	126
Commercial Real Estate [Member]
Average recorded investment:
Average recorded investment in impaired loans	2,811	3,518	3,328	3,730
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	6	40	76	125
Residential Real Estate [Member]
Average recorded investment:
Average recorded investment in impaired loans	1,775	499	1,832	1,270
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	15		46	29
Construction & land development [Member]
Average recorded investment:
Average recorded investment in impaired loans				28
Interest income recognized:
Interest income recognized on a cash basis on impaired loans				$ 2