CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net income	$ 9,462	$ 9,535	$ 16,422	$ 15,745
Adjustments to reconcile net income to net cash flows provided by operating activities -
Depreciation and amortization of property and equipment	7,066	6,047	13,945	11,747
Amortization of intangible assets	83	83	167	167
Stock-based compensation expense	907	647	1,658	1,341
Gain on sale of property and equipment	(336)	(193)	(514)	(320)
Other non-cash items	41	34	75	68
Changes in operating assets and liabilities
Accounts receivable, net	(18,351)	1,158	(10,459)	(27,260)
Costs and estimated earnings in excess of billings on uncompleted contracts	6,438	(293)	24,937	(10,472)
Construction materials inventory		1,542		4,003
Receivable for insurance claims in excess of deductibles	64	61	102	241
Other assets	742	654	1,081	1,244
Accounts payable	2,865	5,544	(20,781)	11,721
Billings in excess of costs and estimated earnings on uncompleted contracts	16,748	113	16,399	3,918
Accrued self insurance	126	135	88	(512)
Other liabilities	(379)	(2,912)	(5,150)	(1,484)
Net cash flows provided by operating activities	25,476	22,155	37,970	10,147
Cash flows from investing activities:
Proceeds from sale of property and equipment	368	224	546	364
Purchases of property and equipment	(9,460)	(12,099)	(21,918)	(20,429)
Net cash flows used in investing activities	(9,092)	(11,875)	(21,372)	(20,065)
Cash flows from financing activities:
Net borrowings on revolving credit facility		10,000
Employee stock option and restricted stock transactions	(157)	219	522	145
Excess tax benefit from stock-based awards	65	15	628	35
Debt issuance costs		(2)		(13)
Other financing activities	56	38	56	38
Net cash flows provided by (used in) financing activities	(36)	10,270	1,206	205
Net increase (decrease) in cash and cash equivalents	16,348	20,550	17,804	(9,713)
Cash and cash equivalents:
Beginning of period	21,281	3,750	19,825	34,013
End of period	$ 37,629	$ 24,300	$ 37,629	$ 24,300

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The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.