Changes in Shareholders' Equity and Comprehensive Income: (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance at March 31, 2016:	$ 83,195
Net income	6,594	$ 5,757
Ending balance at June 30, 2016:	86,367
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance at March 31, 2016:	4,871
Share based compensation	463
Dividends declared
Net income
Ending balance at June 30, 2016:	5,334
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance at March 31, 2016:	78,295
Share based compensation
Dividends declared	(3,885)
Net income	6,594
Ending balance at June 30, 2016:	$ 81,004