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Earnings (loss) per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Earnings Per Share [Abstract] |  |  |  |  |  |  |  |  |  |  |  |
Net income (loss) | $ (15,139) | $ (168,464) | $ (58,273) | $ (9,515) | $ (16,163) | $ (43,080) | $ (56,112) | $ (33,897) | $ 73,779 | $ (252,415) | $ (59,310) | $ 126,474
Amount allocated to common shareholders (in hundredths) | 100.00% |  |  |  | 100.00% |  |  |  |  | 100.00% | 100.00% | 91.81%
Basic and Diluted EPS: |  |  |  |  |  |  |  |  |  |  |  |
Net loss allocated to common stockholders | $ (15,139) |  |  |  | $ (16,163) |  |  |  |  | $ (252,415) | $ (59,310) |
Shares outstanding, basic and diluted | 87,254 |  |  |  | 87,040 |  |  |  |  | 87,064 | 87,375 |
Basic and Diluted (in dollars per share) | $ (0.17) |  |  |  | $ (0.19) |  |  |  |  | $ (2.90) | $ (0.68) |
Basic EPS: |  |  |  |  |  |  |  |  |  |  |  |
Net income (loss) allocated to common stockholders |  | $ (168,464) | $ (58,273) | $ (9,515) | $ (16,163) | $ (43,080) | $ (56,112) | $ (33,897) | $ 67,813 |  |  | $ 116,116
Shares outstanding, basic |  |  |  |  |  |  |  |  |  |  |  | 88,823
Basic (in dollars per share) |  | $ (1.93) | $ (0.67) | $ (0.11) | $ (0.19) | $ (0.50) | $ (0.65) | $ (0.39) | $ 0.76 | (2.90) | (0.68) | $ 1.31
Effect of Dilutive Securities: |  |  |  |  |  |  |  |  |  |  |  |
Share-based compensation plans (shares) |  |  |  |  |  |  |  |  |  |  |  | 605
Diluted EPS: |  |  |  |  |  |  |  |  |  |  |  |
Net income (loss) allocated to common stockholders |  |  |  |  |  |  |  |  |  |  |  | $ 116,116
Shares outstanding, diluted |  |  |  |  |  |  |  |  |  |  |  | 89,428
Diluted (in dollars per share) |  | $ (1.93) | $ (0.67) | $ (0.11) | $ (0.19) | $ (0.50) | $ (0.65) | $ (0.39) | $ 0.76 | $ (2.90) | $ (0.68) | $ 1.30

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