Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 69,193	$ 37,651	$ 105,589	$ 146,318
Other Comprehensive Income (Loss):
Net unrealized gain on investments, net of taxes	158	80	456	98
Net unrealized loss on derivatives	(495)	(4,140)	(106)	(8,571)
Reclassification adjustment of derivatives and designated hedges into net income	25	360	164	731
Retirement liability adjustment	369	376	746	753
Total	57	(3,324)	1,260	(6,989)
Comprehensive Income	69,250	34,327	106,849	139,329
Comprehensive Income Attributable to Noncontrolling Interests	(5,341)	(1,835)	(10,911)	(3,428)
Comprehensive Income Adjusted for Noncontrolling Interests	$ 63,909	$ 32,492	$ 95,938	$ 135,901