Balance in Allowance for Loan Losses and Recorded Investment in Loans by Portfolio Segment and Based on Impairment Method (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Dec. 31, 2010
Allowance for loan losses:
Individually evaluated for impairment	$ 2,453,000	$ 3,471,000
Collectively evaluated for impairment	22,962,000	24,653,000
Total ending allowance balance	25,415,000	28,124,000
Loans:
Loans individually evaluated for impairment	122,158,000	149,883,000
Loans collectively evaluated for impairment	560,433,000	559,443,000
Total ending loans balance	682,591,000	709,326,000	1,300,000,000
Commercial
Allowance for loan losses:
Individually evaluated for impairment	452,000	290,000
Collectively evaluated for impairment	3,156,000	2,931,000
Total ending allowance balance	3,608,000	3,221,000
Loans:
Loans individually evaluated for impairment	4,799,000	4,995,000
Loans collectively evaluated for impairment	56,889,000	47,883,000
Total ending loans balance	61,688,000	52,878,000
Commercial Real Estate
Allowance for loan losses:
Individually evaluated for impairment	1,546,000	2,345,000
Collectively evaluated for impairment	12,383,000	14,069,000
Total ending allowance balance	13,929,000	16,414,000
Loans:
Loans individually evaluated for impairment	86,843,000	94,330,000
Loans collectively evaluated for impairment	244,228,000	252,211,000
Total ending loans balance	331,071,000	346,541,000
Residential Real Estate
Allowance for loan losses:
Individually evaluated for impairment	451,000	827,000
Collectively evaluated for impairment	6,620,000	6,935,000
Total ending allowance balance	7,071,000	7,762,000
Loans:
Loans individually evaluated for impairment	29,986,000	49,512,000
Loans collectively evaluated for impairment	219,456,000	225,851,000
Total ending loans balance	249,442,000	275,363,000
Consumer
Allowance for loan losses:
Individually evaluated for impairment	4,000	9,000
Collectively evaluated for impairment	379,000	407,000
Total ending allowance balance	383,000	416,000
Loans:
Loans individually evaluated for impairment	46,000	93,000
Loans collectively evaluated for impairment	13,585,000	14,272,000
Total ending loans balance	13,631,000	14,365,000
Agriculture
Allowance for loan losses:
Collectively evaluated for impairment	415,000	305,000
Total ending allowance balance	415,000	305,000
Loans:
Loans individually evaluated for impairment	299,000	322,000
Loans collectively evaluated for impairment	26,049,000	18,877,000
Total ending loans balance	26,348,000	19,199,000
Other
Allowance for loan losses:
Collectively evaluated for impairment	9,000	6,000
Total ending allowance balance	9,000	6,000
Loans:
Loans individually evaluated for impairment	185,000	631,000
Loans collectively evaluated for impairment	226,000	349,000
Total ending loans balance	$ 411,000	$ 980,000