Consolidated Statements of Comprehensive Income (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Change in unrealized loss on derivative instruments, net of tax expense	$ 31	$ 6	$ 158
Pension plan adjustments, net of tax expense (benefit)	$ 7,661	$ (2,412)	$ (7,382)