CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities
Net income	$ 66,200	$ 68,248	$ 35,876
Adjustments to reconcile net income to net cash provided by operating activities:
Non-cash restructuring and impairment gains	(1,000)	(1,044)	(2,643)
Depreciation, depletion and amortization	64,375	64,309	68,252
Gain on sales of property and equipment	(8,358)	(8,286)	(15,972)
Change in deferred income taxes	9,842	28,258	14,907
Stock-based compensation	13,383	8,763	11,160
Equity in net income from unconsolidated joint ventures	(15,614)	(43,374)	(49,168)
Gain on real estate entity	(2,452)	0	0
Net Income from affiliates	(7,177)	(3,210)	(901)
Changes in assets and liabilities:
Receivables	(75,756)	(32,877)	3,549
Costs and estimated earnings in excess of billings, net	2,100	(22,374)	(13,856)
Inventories	308	13,367	(6,446)
Contributions to unconsolidated construction joint ventures	(11,795)	(69,313)	(37,097)
Distributions from unconsolidated construction joint ventures	19,344	53,367	67,255
Prepaid and other assets, net	(11,421)	(1,078)	5,519
Accounts payable	37,731	8,363	(12,669)
Accrued expenses and other current liabilities	(6,564)	3,859	(24,624)
Net cash provided by operating activities	73,146	66,978	43,142
Investing activities
Purchases of marketable securities	(129,685)	(104,971)	(64,975)
Maturities of marketable securities	50,000	29,260	45,000
Proceeds from called marketable securities	55,000	75,000	35,000
Purchases of property and equipment ($17.8 million, $0 and $3.6 million related to CCJVs)	(90,970)	(44,179)	(43,428)
Proceeds from sales of property and equipment	12,946	13,148	28,614
Distributions from affiliates	2,233	305	494
Collection of notes receivable	4,331	943	468
Other investing activities, net	(245)	(213)	(393)
Net cash (used in) provided by investing activities	(96,390)	(30,707)	780
Financing activities
Proceeds from long-term debt	30,000	30,000	0
Debt principal payments	(45,025)	(46,763)	(1,226)
Cash dividends paid	(20,563)	(20,445)	(20,319)
Purchases of common stock	(5,227)	(3,777)	(5,124)
Contributions from non-controlling partners	5,250	7,462	15,835
Distributions to non-controlling partners	(5,258)	(6,992)	(8,066)
Other financing activities	557	1,119	1,818
Net cash used in financing activities	(40,266)	(39,396)	(17,082)
(Decrease) increase in cash and cash equivalents	(63,510)	(3,125)	26,840
Cash and cash equivalents at beginning of year	252,836	255,961	229,121
Cash and cash equivalents at end of year	189,326	252,836	255,961
Cash paid during the period for:
Interest	13,392	14,601	14,666
Income taxes	29,872	4,298	2,326
Other non-cash activities:
Performance guarantees	17,596	(10,306)	21,332
Non-cash investing and financing activities:
Restricted stock units issued, net of forfeitures (See Note 13)	21,101	6,220	6,514
Accrued cash dividends	5,151	5,124	5,094
Accrued equipment purchases	(3,865)	2,891	(3,704)
Joint Venture Consolidated [Member]
Changes in assets and liabilities:
Net cash provided by operating activities	37,800	16,400	22,500
Joint Venture Consolidated [Member] | Consolidated Construction Joint Venture [Member]
Investing activities
Purchases of property and equipment ($17.8 million, $0 and $3.6 million related to CCJVs)	17,800	0	$ 3,600
Financing activities
Cash and cash equivalents at beginning of year	46,210
Cash and cash equivalents at end of year	$ 73,115	$ 46,210