Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 345,343	$ 350,715	$ 276,831
Cumulative effect adjustment of accounting standards (see Note 2)	(1,541)	0	0
Other Comprehensive (Loss) Income:
Net unrealized gain on investments, net of taxes	0	1,228	407
Realized gain on investments	0	(651)	0
Realized loss on derivatives	0	0	(2,084)
Net unrealized gain (loss) on derivatives	1,379
Net unrealized gain (loss) on derivatives		1,063	(1,204)
Reclassification adjustment of derivatives and designated hedges into net income	(4,302)	(42)	1,531
Retirement liability adjustment	85	1,393	(167)
Total	(2,838)	2,991	(1,517)
Comprehensive Income	340,964	353,706	275,314
Comprehensive Income Attributable to Noncontrolling Interests	(17,742)	(15,441)	(37,898)
Comprehensive Income Adjusted for Noncontrolling Interests	$ 323,222	$ 338,265	$ 237,416