Business Segments (Reconciliation of Segment Results to Consolidated Income Before Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Business Segments [Abstract]
Income from construction operations	$ 34,045	$ 48,829	$ 71,062	$ 88,951
Other income, net	40,990	2,485	41,406	3,166
Interest expense	(22,519)	(15,534)	(38,083)	(29,614)
INCOME BEFORE INCOME TAXES	$ 52,516	$ 35,780	$ 74,385	$ 62,503