Schedule II - Valuation and Qualifying Accounts (Detail) - Valuation Allowances for Deferred Tax Assets [Member] - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Valuation And Qualifying Accounts Disclosure [Line Items] | |||
| Balance at beginning of period | $ 43,173 | $ 36,645 | $ 23,964 |
| Additions/charged to expense | 4,803 | 6,528 | 12,681 |
| Balance at end of period | $ 47,976 | $ 43,173 | $ 36,645 |