Amortized Cost Basis and Estimated Fair Value of Debt Securities by Contractual Maturity (Detail) - USD ($)
$ in Thousands |
Sep. 30, 2016 |
Dec. 31, 2015 |
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Due within one year, Available-for-sale Securities, Amortized Cost Basis |
$ 0
|
|
| Due after one year through five years, Available-for-sale Securities, Amortized Cost Basis |
17,070
|
|
| Due after five years through ten years, Available-for-sale Securities, Amortized Cost Basis |
5,000
|
|
| Due after ten years, Available-for-sale Securities, Amortized Cost Basis |
0
|
|
| Available-for-sale Securities, Amortized Cost Basis |
22,070
|
$ 22,126
|
| Due within one year, Available-for-sale Securities, Fair Value |
0
|
|
| Due after one year through five years, Available-for-sale Securities, Fair Value |
17,171
|
|
| Due after five years through ten years, Available-for-sale Securities, Fair Value |
5,045
|
|
| Due after ten years, Available-for-sale Securities, Fair Value |
0
|
|
| Available-for-sale Securities, Fair Value |
22,216
|
21,876
|
| Due within one year, Held-to-Maturity, Amortized Cost Basis |
8
|
|
| Due after one year through five years, Held-to-Maturity, Amortized Cost Basis |
8,989
|
|
| Due after five years through ten years, Held-to-Maturity, Amortized Cost Basis |
50,707
|
|
| Due after ten years, Held-to-Maturity, Amortized Cost Basis |
74,782
|
|
| Held-to-maturity securities, Amortized Cost Basis |
134,486
|
137,119
|
| Due within one year, Held-to-Maturity, Fair Value |
8
|
|
| Due after one year through five years, Held-to-Maturity, Fair Value |
9,055
|
|
| Due after five years through ten years, Held-to-Maturity, Fair Value |
52,022
|
|
| Due after ten years, Held-to-Maturity, Fair Value |
75,363
|
|
| Held-to-Maturity, Fair Value |
$ 136,448
|
$ 136,728
|