Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Amount paid for interest	$ 57,144	$ 45,472	$ 44,063
Amount paid for income taxes, net	9,261	42,003	132,695
Non-cash conversion of convertible notes to common shares	0	0	43,215
Accrued capital expenditures	$ 6,492	$ 13,824	$ 12,391