Note 13 - Employee Retirement Plans - Changes in Fair Value of Level 3 Assets for Defined Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair value of plan assets at beginning of year	$ 3,058,000	$ 3,263,000
Fair value of plan assets at end of year	3,225,000	3,058,000
Private Equity Funds [Member]
Fair value of plan assets at beginning of year	163,000	192,000
Actual return on plan assets relating to assets still held at the reporting date	14,000	16,000
Transfers in and/or out of level 3	(40,000)	(45,000)
Fair value of plan assets at end of year	137,000	163,000
Real Estate [Member]
Fair value of plan assets at beginning of year	61,000	84,000
Actual return on plan assets relating to assets still held at the reporting date	(7,000)	12,000
Transfers in and/or out of level 3	96,000	(35,000)
Fair value of plan assets at end of year	150,000	61,000
Collateralized Mortgage Backed Securities [Member]
Fair value of plan assets at beginning of year	2,000	7,000
Actual return on plan assets relating to assets still held at the reporting date
Transfers in and/or out of level 3	(2,000)	(5,000)
Fair value of plan assets at end of year	0	2,000
Insurance Contracts [Member]
Fair value of plan assets at beginning of year	3,000	5,000
Actual return on plan assets relating to assets still held at the reporting date
Transfers in and/or out of level 3	(1,000)	(2,000)
Fair value of plan assets at end of year	$ 2,000	$ 3,000