Quarterly Financial Information (Unaudited) (Summarized Unaudited Consolidated Quarterly Information) (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 921,165	$ 918,940	$ 943,198	$ 1,012,054	$ 996,004	$ 983,155	$ 950,717	$ 942,874	$ 3,795,357	$ 3,872,750	$ 3,745,810
Income from continuing operations	111,953	13,737	(159,235)	474,730	12,893	86,918	211,898	127,588	441,185	439,297	415,991
Net income	111,953	13,737	(159,235)	474,730	12,893	86,918	211,898	127,588	441,185	439,297	415,981
Comprehensive income attributable to noncontrolling interests	1,502	986	(2,065)	1,613	1,450	1,659	1,369	1,803	2,036	6,281	6,514
Net income attributable to common stockholders	$ 110,451	$ 12,751	$ (157,170)	$ 473,117	$ 11,443	$ 85,259	$ 210,529	$ 125,785	$ 439,149	$ 433,016	$ 409,467
Basic:
Income from continuing operations (USD per share)	$ 0.30	$ 0.04	$ (0.43)	$ 1.27	$ 0.03	$ 0.23	$ 0.59	$ 0.36	$ 1.18	$ 1.20	$ 1.17
Net income attributable to common stockholders (USD per share)	0.29	0.03	(0.42)	1.27	0.03	0.23	0.58	0.35	1.18	1.18	1.15
Diluted:
Income from continuing operations (USD per share)	0.30	0.04	(0.43)	1.26	0.03	0.23	0.58	0.35	1.17	1.19	1.16
Net income attributable to common stockholders (USD per share)	$ 0.29	0.03	(0.42)	1.26	0.03	0.23	0.58	0.35	1.17	1.17	1.14
Dividends declared per common share (in dollars per share)		$ 0.4500	$ 0.4500	$ 0.7925	$ 0.7925	$ 0.7925	$ 0.7925	$ 0.7925	$ 2.14250	$ 3.17000	$ 3.16250