Summary of Significant Accounting Policies - Customers with Accounts Receivable Greater than 10% (Detail) - Customer Concentration Risk [Member] - Accounts Receivable [Member] |
12 Months Ended | |
|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Walmart Stores, Inc. [Member] | ||
| Entity Wide Accounts Receivable Major Customer | ||
| Customers with accounts receivable greater than 10% | 15.00% | |
| Caterpillar Inc. [Member] | ||
| Entity Wide Accounts Receivable Major Customer | ||
| Customers with accounts receivable greater than 10% | 11.60% | 13.60% |