Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Income taxes (net of refunds of $21,459, $17,522 and $9,270 in 2018, 2017 and 2016, respectively)	$ 157,758	$ 320,222	$ 143,404
Income taxes, refunds	21,459	17,522	9,270
Interest (net of capitalization)	49,762	61,243	96,948
Capital expenditures included in Accounts payable	$ 134,784	$ 89,188	$ 33,622