N. STOCKHOLDERS'S EQUITY - NARRATIVE (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended		12 Months Ended			30 Months Ended
	Oct. 17, 2016	Jun. 03, 2015	Mar. 31, 2017	Aug. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Nov. 30, 2015
Common stock shares authorized					45,000,000	45,000,000		45,000,000
Preferred Stock shares authorized					5,000,000	5,000,000		5,000,000
Warrants outstanding					$ 0			$ 0
Public offering of common stock, net of value					21,572	$ 27,237	$ 38,648
Additional paid in capital									$ 6,000
Aggregate share price		$ 140,000
Proceeds from common share					$ 21,572	$ 27,237	$ 38,648
ATM Offering [Member]
Public offering of common stock, net, in shares				1,900,000
Public offering of common stock, net of value				$ 38,600
Weighted average price per share				$ 21.54
Second ATM Offering [Member]
Public offering of common stock, net, in shares			1,600,000
Public offering of common stock, net of value	$ 250,000
Weighted average price per share			$ 31.55
Proceeds from common share			$ 48,800
Raymond James & Associates [Member] | ATM Offering [Member]
Aggregate share price								$ 40,000
Raymond James & Associates [Member] | Second ATM Offering [Member]
Public offering of common stock, net of value	$ 50,000