Business Segments and Geographic Information - Geographic Information (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
Geographical Information
Total Revenues	$ 578,116	$ 579,136	$ 587,829	$ 605,017	$ 621,710	$ 631,579	$ 613,966	$ 610,667	$ 2,350,098	$ 2,477,922	$ 2,331,386
Property and Equipment, Net	2,122,195				2,144,722				2,122,195	2,144,722	2,158,610
U.S. operations
Geographical Information
Total Revenues									2,123,045	2,216,401	2,073,286
Property and Equipment, Net	2,109,070				2,131,877				2,109,070	2,131,877	2,145,197
Australia operations
Geographical Information
Total Revenues									201,932	235,462	231,164
Property and Equipment, Net	12,908				12,215				12,908	12,215	13,006
South African operations
Geographical Information
Total Revenues									17,044	18,779	19,806
Property and Equipment, Net	127				182				127	182	88
United Kingdom operations
Geographical Information
Total Revenues									8,077	7,280	7,130
Property and Equipment, Net	$ 90				$ 448				$ 90	$ 448	$ 319