Note 16 - Accumulated Other Comprehensive Income - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Beginning balance			$ 5,522,147	$ 5,402,874
Net current-period other comprehensive income	$ 138	$ (412)	416	307
Ending balance	5,488,978	5,425,602	5,488,978	5,425,602
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Beginning balance			(344)	(975)
Other comprehensive income before reclassifications			416	205
Amounts reclassified from AOCI
Net current-period other comprehensive income			416	205
Ending balance	72	(770)	72	(770)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Beginning balance				6,335
Other comprehensive income before reclassifications				1,721
Amounts reclassified from AOCI
Net current-period other comprehensive income				1,721
Ending balance		8,056		8,056
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Beginning balance				406
Other comprehensive income before reclassifications				(1,619)
Amounts reclassified from AOCI
Net current-period other comprehensive income				(1,619)
Ending balance		(1,213)		(1,213)
AOCI Attributable to Parent [Member]
Beginning balance			(1,480)	5,766
Other comprehensive income before reclassifications				307
Amounts reclassified from AOCI
Net current-period other comprehensive income				307
Ending balance	$ 72	$ 6,073	$ 72	$ 6,073