Earnings Per Share - Computations Of Basic And Diluted EPS (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic:
Net income (loss)	$ 27,121	$ 2,290	$ 42,345	$ (20,528)
Less: Undistributed earnings allocated to participating securities	(260)	(27)	(407)	0
Undistributed earnings allocated to common shares	$ 26,861	$ 2,263	$ 41,938	$ (20,528)
Weighted average number of shares outstanding, basic (in shares)	146,700	145,958	146,679	145,057
Effect of dilutive securities:
Undistributed earnings reallocated to participating securities	$ 0	$ 0	$ 0	$ 0
Net income, diluted	$ 26,861	$ 2,263	$ 41,938	$ (20,528)
Share-based awards other than participating securities (in shares)	264	0	82	0
Weighted average number of shares outstanding, diluted (in shares)	146,964	145,958	146,761	145,057

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