Income Taxes (Significant Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Deferred tax assets:
Timing of expense recognition	$ 20,832		$ 22,730
Net operating losses	8,611		8,590
Other, net	18,828		15,618
Deferred tax assets	48,271		46,938
Valuation Allowance	(1,150)		(381)
Net deferred tax assets	47,121		46,557
Deferred tax liabilities:
Intangible assets, due primarily to purchase accounting	(36,862)		(30,019)
Fixed assets, due primarily to purchase accounting	(75,998)		(73,833)
Construction contract accounting	(9,435)		(17,539)
Joint ventures	(9,853)		(11,343)
Other	(20,411)		(22,263)
Deferred tax liabilities	(152,559)		(154,997)
Net deferred tax liabilities	(105,438)		(108,440)
Net Deferred Tax Liabilities
Deferred tax asset	83		64
Deferred tax liabilities	(105,521)	$ (106,967)	(108,504)
Net deferred tax liabilities	$ (105,438)		$ (108,440)