Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]

(in thousands)	As Previously Reported			Adjustment			Upon Adoption
Twelve Months Ended December 31, 2017
Operating expenses	$	1,359,842		$	94,501		$	1,454,343
Selling, general and administrative expenses	909,592			(21,802		)	887,790
Income from Operations	209,102			(72,699		)	136,403
Non-operating pension and postretirement benefit income, net	—			72,699			72,699
Income from Continuing Operations Before Income Taxes	182,789			—			182,789
Twelve Months Ended December 31, 2016
Operating expenses	$	1,180,945		$	89,085		$	1,270,030
Selling, general and administrative expenses	904,517			(8,420		)	896,097
Income from Operations	303,534			(80,665		)	222,869
Non-operating pension and postretirement benefit income, net	—			80,665			80,665
Income from Continuing Operations Before Income Taxes	250,658			—			250,658
Twelve Months Ended December 31, 2015
Operating expenses	$	1,206,153		$	100,710		$	1,306,863
Selling, general and administrative expenses	1,104,163			(23,395		)	1,080,768
Loss from Operations	(80,825		)	(77,315		)	(158,140		)
Non-operating pension and postretirement benefit income, net	—			77,315			77,315
Loss from Continuing Operations Before Income Taxes	(120,890		)	—			(120,890		)