Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands					12 Months Ended
	Nov. 27, 2019	Jul. 03, 2018	Aug. 09, 2017	Nov. 07, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 08, 2019	Nov. 30, 2018	May 10, 2017
Class of Stock [Line Items]
Common stock shares authorized					100,000,000	100,000,000
Common stock, par value					$ 0.01	$ 0.01
Preferred stock shares authorized					50,000,000	50,000,000
Preferred stock, par value					$ 0.01	$ 0.01
Common stock shares issued					33,350,633	33,067,375
Common stock shares outstanding					33,350,633	33,067,375
Preferred stock shares outstanding					0	0
Gross proceeds from issuances of common stock						$ 79,052	$ 30,947
Number of shares authorized to be repurchased									4,500,000
Common stock shares repurchased, shares					0	83,000
Common stock shares repurchased, value						$ 1,439	$ 10,952
First Amended And Restated 2013 Long-Term Incentive Plan [Member]
Class of Stock [Line Items]
Common stock shares for stock award issuance										1,800,000
2017 Incentive Plan [Member]
Class of Stock [Line Items]
Common stock shares for stock award, available for issuance								1,631,000
Common stock shares issued related to vesting of RSUs					500,000	300,000
Common stock shares rolled into plan										600,000
Amended 2017 Incentive Plan [Member]
Class of Stock [Line Items]
Common stock shares for stock award, available for issuance					1,000,000.0
Distribution Agreement [Member]
Class of Stock [Line Items]
Aggregate offering price				$ 50,000
Common stock shares sold and issued					0	2,700,000
Gross proceeds from issuances of common stock						$ 80,100
Comissions and fees paid to sales agents						$ 600
Second Distribution Agreement [Member]
Class of Stock [Line Items]
Aggregate offering price			$ 100,000
Third Distribution Agreement [Member]
Class of Stock [Line Items]
Aggregate offering price		$ 100,000
Fourth Distribution Agreement [Member]
Class of Stock [Line Items]
Common stock, par value	$ 0.01
Aggregate offering price	$ 100,000