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Revisions of Prior Period Financial Statements (Revised Consolidated Statements of Stockholders' Equity) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)	$ (1,710)	$ (12,579)	$ 327	$ 98	$ (749)	$ (118)	$ 211	$ 190	$ (13,864)	$ (466)	$ 19,794
Retained earnings	137,478				151,342				137,478	151,342	151,808
Total stockholders' equity	$ 247,693				259,232				247,693	259,232	257,262	$ 232,954
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)		(12,232)	573	357	(282)	236	247	225		426	19,851
Retained earnings					152,291					152,291	151,865
Total stockholders' equity					260,181					260,181	257,319
Revisions | Revision Of Prior Period Financial Statements
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)		$ (347)	$ (246)	$ (259)	(467)	$ (354)	$ (36)	$ (35)	$ 1,130	(892)	(57)
Retained earnings					(949)					(949)	(57)
Total stockholders' equity					$ (949)					$ (949)	$ (57)

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