Earnings (Loss) Per Share ("EPS") - Schedule of Diluted Earnings Per Shares Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								6 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Calculation of net income (loss) per share:
Net income (loss)	$ 14,852	$ 15,534	$ 9,626	$ 6,583	$ 60,595	$ 3,534	$ (80)	$ 2,341	$ 16,209	$ 46,595	$ 66,390	$ (895)
Basic weighted average shares outstanding (in shares)										49,542	49,150	48,807
Basic income (loss) per share (in dollars per share)	$ 0.31	$ 0.31	$ 0.19	$ 0.13	$ 1.23	$ 0.07	$ 0.00	$ 0.05	$ 0.33	$ 0.94	$ 1.35	$ (0.02)
Effect of stock options and awards outstanding:
Basic weighted average shares outstanding (in shares)										49,542	49,150	48,807
Effect from dilutive shares and options outstanding (in shares)										521	876	0
Diluted weighted average shares (in shares)										50,063	50,026	48,807
Diluted income (loss) per share (in dollars per share)	$ 0.30	$ 0.31	$ 0.19	$ 0.13	$ 1.21	$ 0.07	$ 0.00	$ 0.05	$ 0.32	$ 0.93	$ 1.33	$ (0.02)