Income Taxes - Components of deferred income tax liabilities and assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2015	Dec. 31, 2019
Deferred income tax liabilities:
Book over tax basis of intangible assets and fixed assets	$ (65,724)		$ (77,088)
Unremitted foreign earnings	(6,063)		(6,339)
Operating lease and finance lease right-of-use assets	(11,597)		(16,981)
Other, net	(2,604)		(2,571)
Total deferred income tax liabilities	(85,988)		(102,979)
Deferred income tax assets:
Allowance for doubtful accounts and receivable adjustments	1,704		1,498
Inventory	1,677		903
Accrued liabilities	15,345		11,608
Net operating loss and tax credit carryforwards	171,148		158,265
Tax deductible goodwill	6,171		8,066
Disallowed Interest Deduction	74,672		56,873
Operating lease and finance lease liabilities	13,004		18,127
Other, net	19,334		15,480
Total deferred income tax assets	303,055		270,820
Valuation allowance	(220,030)		(163,805)
Total net deferred income tax assets			$ 4,036
Total net deferred income tax liabilities	(2,963)
Increase (decrease) in valuation allowance	56,200
Federal
Deferred income tax assets:
Valuation allowance related to disallowed interest deduction	64,700
Valuation allowance related to limitation of utilization of NOL carryforwards	60,500
Increase (decrease) in valuation allowance		$ 3,500
State
Deferred income tax assets:
Valuation allowance related to disallowed interest deduction	9,100
Valuation allowance related to limitation of utilization of NOL carryforwards	4,500
Foreign.
Deferred income tax assets:
Valuation allowance related to disallowed interest deduction	$ 81,300