Note 5 - Stockholders' Equity (Details Textual)	1 Months Ended	12 Months Ended
	Mar. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)
Underwritten Offering [Member]
Stock Issued During Period, Shares, New Issues	13,500,000
Share Price | $ / shares	$ 13
Proceeds from Issuance of Common Stock | $	$ 167,300,000
Issuance of Stock, Underwriting Discount | $	7,500,000
Issuance of Stock, Underwriting Expenses | $	$ 900,000
Common Class A [Member]
Common Stock, Shares Authorized		15,000,000	15,000,000
Common Stock, Voting Rights, Votes Per Share		10
Common Stock, Capital Shares Reserved for Future Issuance		476,193	763,706
Blank Check Preferred Stock [Member]
Preferred Stock, Shares Authorized		20,000,000
Proceeds from Issuance of Common Stock | $		$ 167,313,000	$ 0	$ 280,000
Capital Units, Authorized		135,000,000
Common Stock, Shares Authorized		100,000,000	100,000,000
Common Stock, Voting Rights, Votes Per Share		1
Stock Repurchase Program, Number of Shares Authorized to be Repurchased		5,000,000
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased		279,200
Common Stock, Capital Shares Reserved for Future Issuance		5,689,219	5,841,425