Changes in Stockholders' Equity and Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Gain	Total
Beginning balance at Mar. 31, 2012		$ 81,108	$ 44	$ 81,181
Changes In Stockholders Equity and Comprehensive Income [Line Items]
Share based compensation	1,496
Dividends declared		(29,079)
Net income		12,563		12,563
Repurchased and retired shares	(3,865)
Deffered tax adjustment related to resticted stock	(168)
Allocation of retirement of additional paid in capital and retained earnings	2,537	(2,537)
Net change in unrealized loss on short term investments			(58)	(58)
Ending balance at Dec. 31, 2012		$ 62,055	$ (14)	$ 62,070