Note 9 - Capital Stock (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Feb. 26, 2016	Feb. 28, 2014	Apr. 30, 2013
Share Repurchase Program [Member] | Subsequent Event [Member] | Convertible Debt [Member]
Debt Instrument, Repurchased Face Amount				$ 11,200,000
Debt Instrument, Repurchase Amount				9,200,000
Share Repurchase Program [Member] | Subsequent Event [Member]
Stock Repurchase Program, Remaining Authorized Repurchase Amount				$ 33,500,000
Share Repurchase Program [Member]
Treasury Stock, Shares, Acquired	0	4,317,278	562,341
Stock Repurchase Program, Authorized Amount					$ 100,000,000	$ 50,000,000
Treasury Stock Acquired, Average Cost Per Share		$ 11.72	$ 11.94
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 42,700,000
Restricted Stock [Member]
Treasury Stock, Value, Acquired, Cost Method	$ 2,300,000	$ 2,500,000	$ 2,600,000
Employee Stock Purchase Plan [Member]
Stock Issued During Period, Shares, Treasury Stock Reissued	200,056	155,650	67,622
Treasury Stock, Shares, Acquired	292,168	215,760	222,175
Preferred Stock, Shares Outstanding	0	0	0
Preferred Stock, Shares Authorized	1,000,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01
Treasury Stock, Value, Acquired, Cost Method		$ 50,596,000	$ 6,713,000