Earnings Per Share - Computations Of Basic And Diluted EPS (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Basic:
Net income (loss)	$ 17,784	$ (6,403)	$ 15,224	$ (22,818)
Less: Undistributed earnings allocated to participating securities	(171)		(147)
Undistributed earnings allocated to common shares	$ 17,613		$ 15,077
Weighted average number of shares outstanding, basic (in shares)	146,683	145,940	146,668	144,599
Effect of dilutive securities:
Undistributed earnings reallocated to participating securities	$ 0		$ 0
Net income, diluted	$ 17,613		$ 15,077
Share-based awards other than participating securities (in shares)	41		0
Weighted average number of shares outstanding, diluted (in shares)	146,724	145,940	146,668	144,599

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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