Revenue (Disaggregation of Revenue by Geographical Areas) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of revenue
Revenues	$ 620,302	$ 590,214	$ 568,959	$ 592,703	$ 621,787	$ 618,264	$ 627,533	$ 596,117	$ 2,372,178	$ 2,463,701	$ 2,457,914
United States
Disaggregation of revenue
Revenues									2,144,105	2,191,560	2,145,098
Mexico
Disaggregation of revenue
Revenues									149,438	197,470	233,116
Other
Disaggregation of revenue
Revenues									$ 78,635	$ 74,671	$ 79,700