Cash Flow Disclosures and Non-Cash Investing and Financing Activities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Interest Costs Capitalized	$ 1,707	$ 2,057
Interest Paid, Excluding Capitalized Interest, Operating Activities	33,500	34,900
Income Taxes Paid, Net		600
Cash Paid for Operating Leases	3,600	3,600
Capital Expenditures Incurred but Not yet Paid	69,600	73,600
Operating Lease, Right-of-Use Asset	173,698		$ 173,796	$ 178,100
Cash and cash equivalents	395,070		102,762
Restricted Cash and Cash Equivalents	664		656
Total Cash, Cash Equivalents, and Restricted Cash shown on our Consolidated Statement of Cash Flows	395,734	$ 135,445	$ 103,418		$ 142,929
Restricted Cash Stipulated by Lenders and Various Agreements [Member]
Restricted Cash and Cash Equivalents	700
Deposit Assets, Foreign [Member]
Restricted Cash and Cash Equivalents	$ 0