Fair Value Disclosures - Assets Measured at Fair Value on Non-recurring Basis (Detail) (Fair Value, Measurements, Nonrecurring [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans held for investment	$ 55,193,000	$ 55,370,000
Total assets	55,193,000	55,370,000
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans held for investment	0	0
Total assets	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans held for investment	0	0
Total assets	0	0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans held for investment	55,193,000	55,370,000
Total assets	$ 55,193,000	$ 55,370,000