Securities - Amortized Cost and Estimated Fair Value of Investment Securities by Contractual Maturity (Detail) $ in Thousands	Jun. 30, 2015 USD ($)
Investments, Debt and Equity Securities [Abstract]
Less than one year, Amortized Cost	$ 34,038
Due after one year through five years, Amortized Cost	71,943
Due after five years through ten years, Amortized Cost	340
Due after ten years, Amortized Cost	55,000
Total Amortized Cost	161,321
Less than one year, Estimated Fair Value	34,076
Due after one year through five years, Estimated Fair Value	72,189
Due after five years through ten years, Estimated Fair Value	338
Due after ten years, Estimated Fair Value	47,250
Total Estimated Fair Value	$ 153,853