Securities - Amortized Cost and Estimated Fair Value of Investment Securities by Contractual Maturity (Detail) $ in Thousands	Dec. 31, 2015 USD ($)
Investments, Debt and Equity Securities [Abstract]
Less than one year, Amortized Cost	$ 40,925
Due after one year through five years, Amortized Cost	54,280
Due after five years through ten years, Amortized Cost	4,190
Due after ten years, Amortized Cost	55,000
Total Amortized Cost	154,395
Less than one year, Estimated Fair Value	40,880
Due after one year through five years, Estimated Fair Value	54,360
Due after five years through ten years, Estimated Fair Value	4,194
Due after ten years, Estimated Fair Value	46,473
Total Estimated Fair Value	$ 145,907