DETAIL OF CERTAIN BALANCE SHEET ACCOUNTS:

Activity in Quanta’s current and long-term allowance for doubtful accounts consisted of the following (in thousands):



	December 31,
	2017		2016
Balance at beginning of year	$	2,752	$	5,226
Charged to bad debt expense (recoveries of bad debt expense)	87		(543		)
Deductions for uncollectible receivables written off (recoveries of uncollectible receivables)	1,626		(1,931		)
Balance at end of year	$	4,465	$	2,752

Contracts in progress were as follows (in thousands):



	December 31,
	2017			2016
Costs incurred on contracts in progress	$	7,912,999		$	6,687,484
Estimated earnings, net of estimated losses	1,092,303			766,560
	9,005,302			7,454,044
Less — Billings to date	(8,941,397		)	(7,255,582		)
	$	63,905		$	198,462

Costs and estimated earnings in excess of billings on uncompleted contracts	$	497,292		$	473,308
Less — Billings in excess of costs and estimated earnings on uncompleted contracts	(433,387		)	(274,846		)
	$	63,905		$	198,462

Property and equipment consisted of the following (in thousands):



	Estimated Useful	December 31,
	Lives in Years	2017			2016
Land	N/A	$	48,832		$	45,919
Buildings and leasehold improvements	5-30	155,628			137,515
Operating equipment and vehicles	5-25	1,834,715			1,634,850
Office equipment, furniture and fixtures and information technology systems	3-10	170,115			145,174
Construction work in progress	N/A	60,587			73,461
		2,269,877			2,036,919
Less — Accumulated depreciation and amortization		(981,275		)	(862,825		)
Property and equipment, net		$	1,288,602		$	1,174,094

Accounts payable and accrued expenses consisted of the following (in thousands):



	December 31,
	2017		2016
Accounts payable, trade	$	632,931	$	529,608
Accrued compensation and related expenses	225,193		194,056
Accrued insurance, current portion	64,112		60,880
Deferred revenues, current portion	15,967		15,512
Income and franchise taxes payable	19,635		40,765
Other accrued expenses	99,622		81,998
	$	1,057,460	$	922,819