Securities - Summary of Amortized Cost and Estimated Fair Values of Securities Held for Investment (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 8,281
Gross Unrealized Gains	69
Estimated Fair Value	8,350
Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	439
Gross Unrealized Gains	32
Estimated Fair Value	471
States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	7,842
Gross Unrealized Gains	37
Estimated Fair Value	$ 7,879