The Company has entered into operating leases for facilities and equipment. These leases are non-cancellable and typically do not contain renewal options, except for certain facility leases. Certain leases contain rent escalation clauses for which the Company recognizes the expense on a straight-line basis. Rent expense under the Company’s operating leases for the years ended December 31, 2018, 2017 and 2016 was approximately $3.5 million, $3.1 million and $3.0 million, respectively.

Future minimum lease payments under operating leases as of December 31, 2018 are as follows:

(U.S. Dollars, in thousands)
2019	$	3,330
2020		2,729
2021		2,946
2022		2,818
2023		1,727
Thereafter		11,372
Total	$	24,922

In January 2019, subsequent to the adoption of ASU 2016-02, the Company entered into an amendment for its corporate headquarters lease. As a result of this amendment, the classification of the lease changed from an operating lease to a finance lease resulting in an increase in both the lease liability and lease asset of approximately $8 million during the first quarter of 2019.

The Company had inventory purchase commitments with third-party manufacturers for $0.1 million and $1.9 million as of December 31, 2018, and 2017, respectively.