We participate in multiple healthcare plans, the largest of which is partially self-funded with an insurance company paying benefits in excess of stop loss limits per individual/family. Our healthcare benefit expense (net of employee contributions) was approximately $6.8 million and $5.7 million for the three months ended June 30, 2021 and 2020, respectively, and $14.1 million and $12.7 million for the six months ended June 30, 2021 and 2020, for all plans. An accrual for estimated healthcare claims incurred but not reported (“IBNR”) is included within accrued compensation on the Condensed Consolidated Balance Sheets and was $3.5 million and $3.1 million as of June 30, 2021 and December 31, 2020, respectively.

Workers’ compensation expense totaled $2.9 million for each of the three months ended June 30, 2021 and 2020, and $7.1 million and $7.3 million for the six months ended June 30, 2021 and 2020. Workers’ compensation known claims and IBNR reserves included on the Condensed Consolidated Balance Sheets were as follows (in thousands):


	June 30, 2021		December 31, 2020
Included in other current liabilities	$	7,591	$	7,703
Included in other long-term liabilities	11,348		11,986
	$	18,939	$	19,689

We also had an insurance receivable for claims that exceeded the stop loss limit under our self-insured policies as well as claims under our fully insured policies included on the Condensed Consolidated Balance Sheets. This receivable offsets an equal liability included within the reserve amounts noted above and was as follows (in thousands):

We participate in multiple 401(k) plans, whereby we provide a matching contribution of wages deferred by employees and can also make discretionary contributions to each plan. Certain plans allow for discretionary employer contributions only. These plans cover substantially all our eligible employees. We recognized 401(k) plan expenses of $0.7 million and $0.6 million during the three months ended June 30, 2021 and 2020, respectively, and $1.4 million and $1.2 million during the six months ended June 30, 2021 and 2020. These expenses are included in administrative expenses on the accompanying Condensed Consolidated Statements of Operations and Comprehensive Income.

We participate in various multiemployer pension plans under collective bargaining agreements in Washington, Oregon and Illinois with other companies in the construction industry. These plans cover our union-represented employees and contributions to these plans are expensed as incurred. These plans generally provide for retirement, death and/or termination benefits for eligible employees within the applicable collective bargaining units, based on specific eligibility/participation requirements, vesting periods and benefit formulas. We do not participate in any multiemployer pension plans that are considered to be individually significant.

We periodically grant shares of our common stock to non-employee members of our board of directors and our employees. During the three and six months ended June 30, 2021 and 2020, we granted approximately 4 thousand and 6 thousand shares of our common stock, respectively, under our 2014 Omnibus Incentive Plan to non-employee members of our board of directors. The stock will vest over a one year service period.

In addition, we granted approximately 39 thousand and 0.2 million shares of our common stock to employees during the three and six months ended June 30, 2021 and 2020, respectively.

During the six months ended June 30, 2021, we issued approximately 0.1 million shares of our common stock to certain officers, which vest in two equal installments on each of April 20, 2022 and April 20, 2023. In addition, during the six months ended June 30, 2021, we established, and our board of directors approved, performance-based targets in connection with common stock awards to be issued to certain officers in 2022 contingent upon achievement of these targets.

In addition, there are long-term performance-based restricted stock awards to be issued to certain employees annually through 2022 contingent upon achievement of certain performance targets. These awards are accounted for as liability-based awards since they represent a predominantly-fixed monetary amount that will be settled with a variable number of common shares in the first quarter of 2022 and as such are included in other current liabilities on the Condensed Consolidated Balance Sheets. During the six months ended June 30, 2021 and 2020, we granted approximately five thousand and seven thousand shares of our common stock, respectively, all of which will vest in 2022.

During 2020, we established, and our board of directors approved, performance-based restricted stock units in connection with common stock awards which were issued to certain employees in 2021 based upon achievement of a performance target. In addition, during the six months ended June 30, 2021, we established, and our board of directors approved, performance-based restricted stock units in connection with common stock awards to be issued to certain employees in 2022 based upon achievement of a performance target. These units will be accounted for as equity-based awards that will be settled with a fixed number of common shares.


	Common Stock Awards			Performance-Based Stock Awards			Performance-Based Restricted Stock Units
	Awards	Weighted Average Grant Date Fair Value Per Share		Awards	Weighted Average Grant Date Fair Value Per Share		Units	Weighted Average Grant Date Fair Value Per Share
Nonvested awards/units at December 31, 2020	231,280	$	48.05	166,961	$	59.97	13,273	$	36.51
Granted	48,673	125.75		42,449	123.32		8,470	126.89
Vested	(83,403)	48.63		(64,525)	52.79		(12,952)	36.51
Forfeited/Cancelled	(1,092)	43.73		—	—		(443)	61.40
Nonvested awards/units at June 30, 2021	195,458	$	67.17	144,885	$	81.73	8,348	$	126.89


	Three months ended June 30,				Six months ended June 30,
	2021		2020		2021		2020
Common Stock Awards	$	1,296	$	1,026	$	2,417	$	2,009
Non-Employee Common Stock Awards	111		92		213		125
Performance-Based Stock Awards	1,187		947		2,334		1,916
Liability Performance-Based Stock Awards	680		538		1,385		1,067
Performance-Based Restricted Stock Units	224		130		344		298
	$	3,498	$	2,733	$	6,693	$	5,415


	Three months ended June 30,				Six months ended June 30,
	2021		2020		2021		2020
Cost of sales	$	63	$	65	$	126	$	161
Selling	38		59		89		109
Administrative	3,397		2,609		6,478		5,145
	$	3,498	$	2,733	$	6,693	$	5,415

Administrative stock compensation expense includes all stock compensation earned by our administrative personnel, while cost of sales and selling stock compensation represents all stock compensation earned by our installation and sales employees, respectively.


	As of June 30, 2021
	Unrecognized Compensation Expense on Unvested Awards		Weighted Average Remaining Vesting Period
Common Stock Awards	$	10,092	2.0 years
Performance-Based Stock Awards	7,210		1.9 years
Performance-Based Restricted Stock Units	800		0.8 years
Total unrecognized compensation expense related to unvested awards	$	18,102

Total unrecognized compensation expense is subject to future adjustments for forfeitures. This expense is expected to be recognized over the remaining weighted-average period shown above on a straight-line basis except for the Performance-Based Stock Awards which uses the graded-vesting method. Shares forfeited are returned as treasury shares and available for future issuances.

During the six months ended June 30, 2021 and 2020, our employees surrendered approximately 43 thousand and 25 thousand shares of our common stock, respectively, to satisfy tax withholding obligations arising in connection with the vesting of common stock awards issued under our 2014 Omnibus Incentive Plan. We recognized windfall tax benefits of $3.0 million for the three and six months ended June 30, 2021 and we recognized a tax shortfall of $0.3 million for the three and six months ended June 30, 2020 within the income tax provision in the Condensed Consolidated Statements of Operations and Comprehensive Income.

As of June 30, 2021, approximately 1.9 million of the 3.0 million shares of common stock authorized for issuance were available for issuance under the 2014 Omnibus Incentive Plan.