Revenue Recognition (Changes in Contract Balances) (Details) - Contract Liability (Current) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenue recognized that was included in the opening contract liabilities balance	$ (53,226)	$ (58,918)
Cash received or amounts billed in advance and not recognized as revenue	$ 50,836	$ 53,881

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130549-203045

Name:	us-gaap_ContractWithCustomerLiabilityRevenueRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration