Income Taxes (Significant Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Timing of expense recognition	$ 24,470	$ 44,761
Net operating losses	19,968	23,711
Goodwill	19,315	26,658
Other, net	10,155	17,098
Deferred tax assets	73,908	112,228
Valuation allowance	0	(2,212)
Net deferred tax assets	73,908	110,016
Deferred tax liabilities:
Intangible assets, due primarily to purchase accounting	(15,212)	(15,309)
Fixed assets	(76,567)	(75,461)
Construction contract accounting	(9,769)	(13,464)
Joint ventures	(41,669)	(24,331)
Other	(11,962)	(16,567)
Deferred tax liabilities	(155,179)	(145,132)
Net deferred tax liabilities	(81,271)	(35,116)
Net Deferred Tax Liabilities
Deferred tax assets	1,695	570
Deferred tax liabilities	(82,966)	(35,686)
Net deferred tax liabilities	$ (81,271)	$ (35,116)