Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 74,473	$ 61,337	$ 180,062	$ 207,655
Other Comprehensive Income (Loss):
Net unrealized gain on investments, net of taxes	222	197	678	295
Realized loss on derivatives	0	(2,084)	0	(2,084)
Net unrealized gain (loss) on derivatives	77	3,556	(29)	(5,015)
Reclassification adjustment of derivatives and designated hedges into net income	(90)	462	74	1,193
Retirement liability adjustment	365	251	1,111	1,004
Total	574	2,382	1,834	(4,607)
Comprehensive Income	75,047	63,719	181,896	203,048
Comprehensive Income Attributable to Noncontrolling Interests	(1,844)	(9,436)	(12,755)	(12,864)
Comprehensive Income Adjusted for Noncontrolling Interests	$ 73,203	$ 54,283	$ 169,141	$ 190,184