Note 4 - Fair Value of Financial Instruments Other Fair Value Disclosure (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes		$ 1,027,875	$ 1,027,074
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost Method Investments	[1]	0	334
Senior Notes		1,027,875	1,027,074
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost Method Investments, Fair Value Disclosure	[1]	0	3,226
Senior Notes, Fair Value		$ 1,056,437	$ 1,093,934

[1] As a result of implementing the update to the standard for the accounting of financial instruments effective January 1, 2018, other invested assets are no longer carried at amortized cost.