Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Jun. 30, 2018	$ 318,843	$ 279	$ 132,198	$ 211,494	$ (17,717)	$ (7,411)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	6,237	0	0	6,237	0	0
Other comprehensive income (loss)	(668)	0	0	0	0	(668)
Exercise of stock options	128	0	(126)	0	254	0
Open market purchases of treasury shares	(5,190)	0	0	0	(5,190)	0
Treasury shares sold to Employee Stock Purchase Plan	153	0	19	0	134	0
Issuance of deferred shares	0	0	(5,940)	0	5,940	0
Other Treasury Share Purchases	(1,651)	0	0	0	(1,651)	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2018	323,590	279	131,889	217,731	(18,230)	(8,079)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	5,738	0	5,738	0	0	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2018	322,781	279	129,885	213,799	(14,172)	(7,010)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	3,932	0	0	3,932	0	0
Other comprehensive income (loss)	(1,069)	0	0	0	0	(1,069)
Open market purchases of treasury shares	(5,190)	0	0	0	(5,190)	0
Treasury shares sold to Employee Stock Purchase Plan	75	0	23	0	52	0
Issuance of deferred shares	0	0	(1,172)	0	1,172	0
Other Treasury Share Purchases	(92)	0	0	0	(92)	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2018	323,590	279	131,889	217,731	(18,230)	(8,079)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	3,153	0	3,153	0	0	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Jun. 30, 2019	351,957	279	137,712	239,476	(17,759)	(7,751)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(21,857)	0	0	(21,857)	0	0
Other comprehensive income (loss)	129	0	0	0	0	129
Open market purchases of treasury shares	(9,913)	0	0	0	(9,913)	0
Treasury shares sold to Employee Stock Purchase Plan	157	0	18	0	139	0
Issuance of deferred shares	0	0	(8,486)	0	8,486	0
Other Treasury Share Purchases	(3,491)	0	0	0	(3,491)	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2019	322,795	279	135,057	217,619	(22,538)	(7,622)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	5,813	0	5,813	0	0	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2019	357,427	279	132,936	245,627	(13,270)	(8,145)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(28,008)	0	0	(28,008)	0	0
Other comprehensive income (loss)	523	0	0	0	0	523
Open market purchases of treasury shares	(9,913)	0	0	0	(9,913)	0
Treasury shares sold to Employee Stock Purchase Plan	74	0	5	0	69	0
Issuance of deferred shares	0	0	(673)	0	673	0
Other Treasury Share Purchases	(97)	0	0	0	(97)	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2019	322,795	279	135,057	217,619	(22,538)	(7,622)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	$ 2,789	$ 0	$ 2,789	$ 0	$ 0	$ 0