Fixed Assets

The following table summarizes our fixed assets by category at December 31:



(in thousands)	2018			2017
Land, buildings, and building improvements	$	—		$	7,627
Leasehold improvements	617			1,375
Software	163,735			129,553
Equipment	15,075			13,858
Projects in progress	10,392			21,898
Construction in progress	66,088			26,312
Total fixed assets, gross	255,907			200,623
Less: Accumulated depreciation and amortization	(125,075		)	(117,474		)
Fixed assets, net	$	130,832		$	83,149

On December 31, 2018, we sold the field offices we owned to the Exchange at the current independent appraised value in order to align the ownership interest of these facilities with the functions being performed at these locations, which are claims-related activities. We recognized a gain on the sale of $3.4 million, which is included in "Other income (expense)" in the Statements of Operations. See Note 14, "Related Party".

Software increased primarily related to an investment in platform technology, as well as internally developed software projects in progress that were completed and placed in production related to providing new quote and application processing capabilities for commercial lines and new web-based system functionality for personal lines.

Projects in progress include certain computer software and software developments costs for internal use that are not yet subject to amortization.

In 2016, we announced the construction of a new office building that will serve as part of our principal headquarters. The costs associated with this project are included in construction in progress. Capitalized interest included in construction in progress was $2.1 million at December 31, 2018 and $0.6 million at December 31, 2017, respectively. The building is expected to be completed in 2020 and is financed using a senior secured draw term loan credit facility. See Note 8, "Borrowing Arrangements".

For the years ended December 31, 2018, 2017 and 2016, depreciation and amortization of fixed assets totaled $13.4 million, $14.8 million and $15.1 million, respectively, and is included in "Cost of operations - policy issuance and renewal services" in the Statements of Operations.