Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 148,969,000	$ 36,396,000
Cumulative effect adjustment of new accounting standards (see Note 2)	(1,541,000)	0
Other Comprehensive (Loss) Income:
Net unrealized gain on investments, net of taxes	0	298,000
Net unrealized gain on derivatives	1,379,000	389,000
Reclassification adjustment of derivatives and designated hedges into net income	(3,633,000)	139,000
Retirement liability adjustment	271,000	377,000
Total	(1,983,000)	1,203,000
Comprehensive Income	145,445,000	37,599,000
Comprehensive Income Attributable to Noncontrolling Interests	(2,145,000)	(5,570,000)
Comprehensive Income Adjusted for Noncontrolling Interests	$ 143,300,000	$ 32,029,000