Note 12 - Employee Benefit and Retirement Plans - Status of the Postretirement Medical and Life Insurance Benefit Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016	Jan. 01, 2017	Dec. 31, 2016
Benefit obligation at beginning of year	$ 169,696	$ 175,233	$ 166,189
Service cost		1,405	2,757
Interest cost	6,077	6,246	7,032
Benefits paid	(6,489)	(6,902)	(6,590)
Actuarial (gain) loss	(10,778)	(1,207)	13,670
Benefit obligation at end of year	159,213	169,696	175,233
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				4.31%	3.77%
Fair value of plan assets at beginning of year	117,778	115,015	122,787
Employer contributions	4,366	5,000	4,482
Benefits paid	(6,489)	(6,902)	(6,590)
Fair value of plan assets at end of year	118,693	117,778	115,015
Current liability	(67)	(63)	(45)
Noncurrent liability	(40,453)	(51,855)	(60,173)
Net amount recognized in balance sheet	(40,520)	(51,918)	(60,218)
Prior service cost
Accumulated loss	(4,038)	(12,131)	(17,849)
Amounts not yet recognized as a component of net periodic benefit cost	(4,038)	(12,131)	(17,849)
Accumulated net periodic benefit cost in excess of contributions	(36,482)	(39,787)	(42,369)
Net periodic benefit cost	963	2,585	21,399
Prior service cost
Net loss	(28)	(26)	(114)
UNITED STATES
Benefit obligation at beginning of year	124,138	130,863	116,398
Service cost		1,405	2,757
Interest cost	4,804	4,994	5,248
Benefits paid	(4,786)	(5,106)	(4,593)
Actuarial (gain) loss	(7,879)	(3,848)	11,053
Benefit obligation at end of year	$ 116,277	$ 124,138	$ 130,863
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.27%	3.92%	3.77%
Fair value of plan assets at beginning of year	$ 81,928	$ 81,910	$ 84,853
Employer contributions	3,353	4,045	3,380
Benefits paid	(4,786)	(5,106)	(4,593)
Fair value of plan assets at end of year	82,140	81,928	81,910
Current liability	(67)	(63)	(45)
Noncurrent liability	(34,070)	(42,147)	(48,908)
Net amount recognized in balance sheet	$ (34,137)	$ (42,210)	$ (48,953)
Discount rate	3.92%	3.77%	4.49%
Prior service cost
Accumulated loss	(2,731)	(8,254)	(13,412)
Amounts not yet recognized as a component of net periodic benefit cost	(2,731)	(8,254)	(13,412)
Accumulated net periodic benefit cost in excess of contributions	(31,406)	(33,956)	(35,541)
Net periodic benefit cost	804	2,460	19,195
Prior service cost
Net loss	(28)	(26)	(114)
Post Retirement Medical and Life Insurance Plan [Member] | UNITED STATES
Benefit obligation at beginning of year	7,086	7,381	6,611
Service cost	85	85	105
Interest cost	270	269	287
Benefits paid	(388)	(483)	(772)
Actuarial (gain) loss	(668)	(166)	1,150
Benefit obligation at end of year	$ 6,385	$ 7,086	$ 7,381
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.27%	3.92%	3.77%
Rate of compensation increase	2.64%	2.64%	2.64%
Fair value of plan assets at beginning of year
Employer contributions	388	483	772
Benefits paid	(388)	(483)	(772)
Fair value of plan assets at end of year
Current liability	(338)	(370)	(396)
Noncurrent liability	(6,047)	(6,716)	(6,985)
Net amount recognized in balance sheet	$ (6,385)	$ (7,086)	$ (7,381)
Discount rate	3.92%	3.77%	4.49%
Rate of compensation increase	2.64%	2.64%	2.64%
Prior service cost	$ 3,314	$ 3,851	$ 4,523
Accumulated loss	(928)	(1,696)	(1,983)
Amounts not yet recognized as a component of net periodic benefit cost	2,386	2,155	2,540
Accumulated net periodic benefit cost in excess of contributions	(8,771)	(9,241)	(9,921)
Prior service cost	(537)	(673)	(781)
Amortization of accumulated loss	99	121	15
Net periodic benefit cost	(83)	(198)	(374)
Prior service cost	537	537	673
Net loss	(30)	(99)	(120)
	$ 507	$ 438	$ 553
Healthcare cost trend rate assumed for next year	6.60%	6.60%	6.90%
Rate to which the cost trend rate gradually declines	4.50%	4.50%	4.50%
Year that the rate reaches the rate at which it is assumed to remain	2037	2037	2037