Note 14 - Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended						9 Months Ended
		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Tax (expense) benefit		$ (2,536)			$ (1,910)			$ (8,095)	$ (9,349)
Net of tax		10,724	$ 10,556	$ 7,068	17,333	$ 13,923	$ 11,412	28,348	42,668
Other expense		30,440			23,965			88,016	62,795
Other expense		3,182			3,718			11,147	12,158
Total before tax		13,260			19,243			36,443	52,017
Reclassification out of Accumulated Other Comprehensive Income [Member]
Tax (expense) benefit		4			38			10	116
Net of tax		(7)			(84)			(22)	(252)
Total before tax		(11)			(122)			(32)	(368)
Reclassification out of Accumulated Other Comprehensive Income [Member] | AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Net loss on sale of securities		0						(15)
Tax (expense) benefit		0						5
Net of tax		0						(10)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] | Interest Rate Swap [Member]
Tax (expense) benefit		(127)			(36)			(389)	74
Net of tax		282			80			868	(161)
Other expense		409			116			1,257	(235)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Other expense	[1]	(33)			(132)			(96)	(396)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Other expense	[1]	$ 22			$ 10			$ 64	$ 28

[1] These accumulated other comprehensive loss components are included in the computation of net periodic pension cost. See Note 10 ("Pension and Other Postretirement Benefit Plans") for additional information.