Business Segments (Reconciliation of Segment Results to Consolidated Income Before Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Segments [Abstract]
Income from construction operations	$ 49,072	$ 60,919	$ 120,134	$ 149,870
Other income, net	967	2,048	42,373	5,214
Interest expense	(15,643)	(15,041)	(53,726)	(44,655)
INCOME BEFORE INCOME TAXES	$ 34,396	$ 47,926	$ 108,781	$ 110,429