Nature of operations and summary of significant accounting policies (Recently Adopted Accounting Pronouncements) (Detail) - USD ($) $ in Thousands |
Mar. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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|---|---|---|---|---|---|---|
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] | ||||||
| Unamortized debt issuance cost | [1] | $ 1,649 | ||||
| Predecessor | ||||||
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] | ||||||
| Unamortized debt issuance cost | [1] | $ 2,303 | $ 23,426 | |||
| Senior Notes | Predecessor | ||||||
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] | ||||||
| Unamortized debt issuance cost | 18,359 | |||||
| Existing Credit Facility | Predecessor | ||||||
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] | ||||||
| Unamortized debt issuance cost | $ 2,303 | $ 5,067 | ||||
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