Revenue

9 Months Ended

Sep. 30, 2019

Revenue from Contract with Customer [Abstract]

Disaggregation of revenue

The following table shows net sales classified by major product category for the three and nine months ended September 30, 2019 and 2018:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Structural components	$	175,344	$	166,919	$	483,575	$	470,365
Lumber & lumber sheet goods	274,908		357,286		798,722		1,013,495
Millwork, doors & windows	285,750		251,606		796,807		730,318
Other building products & services	228,247		214,453		656,925		608,749
Total net sales	$	964,249	$	990,264	$	2,736,029	$	2,822,927

The following table reflects the Company’s estimate of net sales by each customer type for the three and nine months ended September 30, 2019 and 2018. Certain previously reported amounts for the three and nine months ended September 30, 2018 were revised in the table below. The revisions were not material to the previously issued financial statements.



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Single-family homebuilders	$	718,690	$	760,131	$	2,064,382	$	2,163,784
Remodeling contractors	115,756		113,416		314,277		327,700
Multi-family, commercial & other contractors	129,803		116,717		357,370		331,443
Total net sales	$	964,249	$	990,264	$	2,736,029	$	2,822,927

Contract balances

The following table reflects the Company’s contract balances as of September 30, 2019 and December 31, 2018:



(in thousands)	September 30, 2019		December 31, 2018		Change
Receivables, including unbilled receivables presented in prepaid expenses and other current assets	$	353,992	$	306,370	$	47,622
Contract assets	36,759		32,348		4,411
Contract liabilities	$	34,501	$	34,888	$	(387	)

During the nine months ended September 30, 2019, the Company’s contract assets increased by $4.4 million and the Company’s contract liabilities decreased by $0.4 million. The changes in contract assets and liabilities were primarily due to the timing of revenue recognition, as the balances were not materially impacted by any other factors. For the three and nine months ended September 30, 2019, the Company recognized revenue of $0.9 million and $32.0 million, respectively, that was included in contract liabilities as of December 31, 2018. Revenue recognized related to performance obligations that were satisfied or partially satisfied in previous periods was not material for the three and nine months ended September 30, 2019.

As permitted by ASC 606, Revenue from Contracts with Customers, the Company has elected not to disclose the value of unsatisfied performance obligations, as the Company’s contracts generally have an original expected length of one year or less.