Note 10 - Income Taxes Reconciliation of Taxes from Statutory Rate to Provision (Benefit) for Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Federal Statutory Income Tax Rate	21.00%	35.00%	35.00%
Provision for income taxes computed at the statutory tax rate	$ 143,679,000	$ 121,358,000	$ 169,290,000
Repurchase premium on convertible notes	0	(96,000)	9,988,000
State tax provision (benefit), net of federal impact	5,570,000	(15,641,000)	(8,974,000)
Valuation allowance	(1,856,000)	18,197,000	10,663,000
Remeasurement of net deferred tax assets due to the TCJA	0	102,617,000	0
Effective Income Tax rate Reconciliation, Impact of IRS Settlement	(73,585,000)	0	0
Other, net	4,367,000	(786,000)	(5,534,000)
Income tax (benefit) provision	78,175,000	$ 225,649,000	$ 175,433,000
Tax Adjustments, Settlements, and Unusual Provisions	$ 0