Acquisitions, Goodwill And Other Intangible Assets (Schedule of Business Acquisitions) (Details) - USD ($) $ in Thousands	1 Months Ended						12 Months Ended
	Dec. 31, 2020	Nov. 30, 2020	Jan. 31, 2020	Dec. 31, 2019	Nov. 30, 2019	Aug. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition
Cash consideration, net of cash acquired							$ 182,130	$ 447,764	$ 184,792
Assets Acquired
Operating lease right-of-use assets	$ 13,200			$ 34,300			13,200	34,300
Liabilities Assumed
Goodwill	454,728			351,114			454,728	351,114	$ 180,168
Measurement Period Adjustments
Goodwill (not tax deductible)							10,362
Veada
Business Acquisition
Cash consideration, net of cash acquired	56,760
Holdback payment	12,219
Total fair value of consideration given	68,979
Assets Acquired
Net tangible assets, excluding pension obligation	8,864						8,864
Liabilities Assumed
Total fair value of net assets acquired	46,114						46,114
Goodwill	22,865						22,865
Challenger
Business Acquisition
Cash consideration, net of cash acquired		$ 30,461
Holdback payment		4,500
Total fair value of consideration given		34,961
Assets Acquired
Identifiable intangible assets		12,900
Net tangible assets, excluding pension obligation		8,983
Liabilities Assumed
Total fair value of net assets acquired		21,883
Goodwill		$ 13,078
Polyplastic
Business Acquisition
Cash consideration, net of cash acquired			$ 95,766
Contingent consideration			2,796
Total fair value of consideration given			98,562
Assets Acquired
Net tangible assets, excluding pension obligation			14,247
Liabilities Assumed
Accrued expenses and other current liabilities			(28,665)
Total fair value of net assets acquired			49,208
Goodwill			49,354
CURT
Business Acquisition
Cash consideration, net of cash acquired				337,640			336,587
Total fair value of consideration given				336,600
Assets Acquired
Accounts receivable	28,611			28,611			28,611	28,611
Inventories	82,117			88,765			82,117	88,765
Fixed assets	24,036			24,036			24,036	24,036
Operating lease right-of-use assets	27,925			27,925			27,925	27,925
Other tangible assets	2,510			4,060			2,510	4,060
Liabilities Assumed
Accounts payable	(18,577)			(18,577)			(18,577)	(18,577)
Current portion of operating lease obligations	(5,360)			(5,360)			(5,360)	(5,360)
Accrued expenses and other current liabilities	(10,002)			(10,002)			(10,002)	(10,002)
Operating lease obligations	(22,565)			(22,565)			(22,565)	(22,565)
Deferred taxes	(30,125)			(31,877)			(30,125)	(31,877)
Total fair value of net assets acquired	220,175			234,721			220,175	234,721
Goodwill	116,412			102,919			116,412	102,919
Cash consideration, net of cash acquired							(1,053)
Measurement Period Adjustments
Cash consideration, net of cash acquired							(1,053)
Inventories							(6,648)
Other tangible assets							(1,550)
Deferred taxes							1,752
Total fair value of net assets acquired							(14,546)
Goodwill (not tax deductible)							13,493
PWR-ARM
Business Acquisition
Holdback payment					$ 5,000
Total fair value of consideration given					$ 45,000
Lewmar Marine Limited
Business Acquisition
Total fair value of consideration given						$ 43,200
Customer relationships | Veada
Assets Acquired
Identifiable intangible assets	30,000						30,000
Customer relationships | Polyplastic
Assets Acquired
Identifiable intangible assets			37,012
Customer relationships | CURT
Assets Acquired
Identifiable intangible assets	104,200			112,000			104,200	112,000
Measurement Period Adjustments
Intangible assets							(7,800)
Other intangible assets | Veada
Assets Acquired
Identifiable intangible assets	7,250						7,250
Other intangible assets | Polyplastic
Assets Acquired
Identifiable intangible assets			$ 26,614
Trade name | CURT
Assets Acquired
Identifiable intangible assets	$ 37,405			$ 37,705			37,405	$ 37,705
Measurement Period Adjustments
Intangible assets							$ (300)