Summary of Significant Accounting Policies (Additional Cash Flow) (Details) - USD ($) $ in Thousands		12 Months Ended
	May 12, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Noncash or Part Noncash Acquisitions [Line Items]
Accrual for purchases of property and equipment		$ 800	$ 2,900	$ 3,600
Gain (Loss) on Disposition of Business, Non Cash		(3,971)	(5,722)	0
Notes Reduction		4,000
Noncash or Part Noncash Divestiture, Amount of Consideration Received		3,100
Notes Issued			2,500
Total net adjustment		8,900	11,600	12,700
Adjustments to other comprehensive income related to underfunding of pension and SERP plans and changes in fair value of derivative financial instruments, tax		2,600	3,700	7,700
Dividends declared but not yet paid		5,600	$ 5,600	5,600
Treasury Stock, Not yet Paid		1,700
Warrant
Noncash or Part Noncash Acquisitions [Line Items]
Options issued in debt conversion (in shares)			114,778
Stock conversion amount			$ 7,600
Bond Hedge Transactions - 2017 Notes [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Value of shares received				7,500
2017 Notes
Noncash or Part Noncash Acquisitions [Line Items]
Stock conversion amount				$ 7,500
Debt Conversion, Converted Instrument, Shares Issued				136,347
2017 Notes
Noncash or Part Noncash Acquisitions [Line Items]
Options issued in debt conversion (in shares)	624,044		114,778
Stock conversion amount				$ 7,500
Debt Conversion, Converted Instrument, Shares Issued				136,347
2017 Notes | Warrant
Noncash or Part Noncash Acquisitions [Line Items]
Options issued in debt conversion (in shares)				624,044
Stock conversion amount				$ 30,300
2017 Notes | Bond Hedge Transactions - 2017 Notes [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Shares received in noncash transaction (in shares)				136,369
Distribution [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Gain (Loss) on Disposition of Business, Non Cash		$ 4,000