Lease Obligations - Summary of lease-related assets and liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Assets
Operating lease right-of-use assets	$ 28,500	$ 30,544
Finance lease right-of-use assets	$ 2,741	3,238
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property and equipment, net of accumulated depreciation of $363,112 and $351,753, respectively
Total right-of-use lease assets	$ 31,241	33,782
Current
Operating lease obligations	9,835	9,711
Finance lease obligations	2,349	1,127
Total current obligations	12,184	10,838
Non-current
Operating lease obligations	18,635	20,845
Finance lease obligations, net of current maturities	575	2,313
Total non-current obligations	19,210	23,158
Total lease obligations	$ 31,394	$ 33,996