Note 6 - Estimated Fair Value of Senior Notes (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Senior Notes 5.625 Due 2020 [Member]
Carrying Amount	$ 246,247	$ 246,032
Fair Value	252,592	257,813
Senior Notes 5.5 Due 2024 [Member]
Carrying Amount	248,254	248,209
Fair Value	239,833	252,188
Senior Notes 6.00 Due January 2043 [Member]
Carrying Amount	346,297	346,283
Fair Value	268,753	276,938
Carrying Amount	840,798	840,524
Fair Value	$ 761,178	$ 786,939

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant