Condensed Consolidating Financial Information - Guarantor Subsidiaries - Condensed Consolidating Statements of Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2015 |
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2015 |
Dec. 31, 2014 |
Sep. 30, 2014 |
Jun. 30, 2014 |
Mar. 31, 2014 |
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
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| Condensed Financial Statements, Captions [Line Items] | ||||||||||||||
| Net earnings | $ 2,438 | $ 7,669 | $ 6,454 | $ 10,363 | $ 7,392 | $ 17,249 | $ 13,368 | $ (5,321) | $ 26,924 | $ 32,688 | $ 58,956 | |||
| Unrealized gain (loss) on short-term investments | (641) | (285) | 44 | |||||||||||
| Other unrealized gain (loss) | 24 | (24) | ||||||||||||
| Changes in pension plan assets and benefit obligations | 7 | 17 | (2) | |||||||||||
| Tax impact | 254 | 105 | (15) | |||||||||||
| Total Comprehensive Income (Loss) | 26,568 | 32,501 | 58,983 | |||||||||||
| Parent Company Only (issuer) [Member] | ||||||||||||||
| Condensed Financial Statements, Captions [Line Items] | ||||||||||||||
| Net earnings | 26,924 | 32,688 | 58,956 | |||||||||||
| Unrealized gain (loss) on short-term investments | (641) | (285) | 44 | |||||||||||
| Other unrealized gain (loss) | 24 | (24) | ||||||||||||
| Changes in pension plan assets and benefit obligations | 7 | 17 | (2) | |||||||||||
| Tax impact | 254 | 105 | (15) | |||||||||||
| Total Comprehensive Income (Loss) | 26,568 | 32,501 | 58,983 | |||||||||||
| Guarantor Subsidiaries [Member] | ||||||||||||||
| Condensed Financial Statements, Captions [Line Items] | ||||||||||||||
| Net earnings | [1] | 31,225 | 38,740 | 15,567 | ||||||||||
| Total Comprehensive Income (Loss) | [1] | 31,225 | 38,740 | 15,567 | ||||||||||
| Eliminations [Member] | ||||||||||||||
| Condensed Financial Statements, Captions [Line Items] | ||||||||||||||
| Net earnings | (31,225) | (38,740) | (15,567) | |||||||||||
| Total Comprehensive Income (Loss) | $ (31,225) | $ (38,740) | $ (15,567) | |||||||||||
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