Nature of operations and summary of significant accounting policies (Cost Reduction Initiatives) (Detail) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | ||||
|---|---|---|---|---|---|---|
Mar. 31, 2017 |
Mar. 21, 2017 |
Mar. 31, 2016 |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Restructuring Cost and Reserve [Line Items] | ||||||
| Cost reduction initiatives expense | $ 6 | |||||
| Predecessor | ||||||
| Restructuring Cost and Reserve [Line Items] | ||||||
| Cost reduction initiatives expense | $ 629 | $ 3,125 | $ 2,879 | $ 10,028 | $ 0 | |
| One-time Severance and Termination Benefits | ||||||
| Restructuring Cost and Reserve [Line Items] | ||||||
| Cost reduction initiatives expense | 1 | |||||
| One-time Severance and Termination Benefits | Predecessor | ||||||
| Restructuring Cost and Reserve [Line Items] | ||||||
| Cost reduction initiatives expense | 608 | 3,036 | 2,772 | 7,757 | ||
| Professional Fees | ||||||
| Restructuring Cost and Reserve [Line Items] | ||||||
| Cost reduction initiatives expense | $ 5 | |||||
| Professional Fees | Predecessor | ||||||
| Restructuring Cost and Reserve [Line Items] | ||||||
| Cost reduction initiatives expense | $ 21 | $ 89 | $ 107 | $ 2,271 | ||