Summary of Significant Accounting Policies - Property and Equipment - Tabular Disclosure (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property and Equipment
Property and equipment, gross	$ 870,190	$ 831,127
Accumulated depreciation	(733,451)	(699,415)
Property and equipment, net	136,739	131,712
Building improvements
Property and Equipment
Property and equipment, before depreciation	12,027	17,726
Equipment
Property and Equipment
Property and equipment, before depreciation	188,954	188,611
Finance lease, right-of-use asset, before accumulated amortization	32,568	26,856
Property
Property and Equipment
Finance lease, right-of-use asset, before accumulated amortization	10,455	26,945
Capitalized internal-use software
Property and Equipment
Property and equipment, before depreciation	$ 626,186	$ 570,989

Amount, before accumulated amortization, of right-of-use asset from finance lease.

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Amount of accumulated depreciation and amortization from plant, property, and equipment and right-of-use asset from finance lease.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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