Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 85,520	$ 79,871	$ 136,774	$ 228,840
Cumulative effect adjustment of new accounting standards	0	0	0	(1,541)
Other Comprehensive Income (Loss):
Net unrealized gain on derivatives	0	0	0	1,379
Reclassification adjustment of derivatives and designated hedges into net income	(221)	(221)	(440)	(3,854)
Retirement liability adjustment	299	307	587	578
Total	78	86	147	(1,897)
Comprehensive Income	85,598	79,957	136,921	225,402
Comprehensive Income Attributable to Noncontrolling Interests	(1,711)	(1,582)	(3,299)	(3,727)
Comprehensive Income Adjusted for Noncontrolling Interests	$ 83,887	$ 78,375	$ 133,622	$ 221,675