Revenues - Impact of Adoption of ASC 606 on Company's Condensed Consolidated Statement of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Revenues:
License, maintenance and related	$ 127,126	$ 131,247
Operating expenses:
Selling and marketing	31,150	$ 30,242
Balance Without Adoption of ASC 606 [Member] \| ASU 2014-09 [Member]
Revenues:
License, maintenance and related	122,128
Operating expenses:
Selling and marketing	31,748
Effect of Change [Member] \| ASU 2014-09 [Member]
Revenues:
License, maintenance and related	4,998
Operating expenses:
Selling and marketing	$ (598)

Revenue from multiple-deliverable arrangements that include licensing fees and maintenance revenue. Licensing revenue is consideration received from another party for the right to use, but not own, certain of the entity's intangible assets. Licensing arrangements include, but are not limited to, rights to use a patent, copyright, technology, manufacturing process, software or trademark. Licensing fees are generally, but not always, fixed as to amount and not dependent upon the revenue generated by the licensing party. An entity may receive licensing fees for licenses that also generate royalty payments to the entity. Maintenance revenue is derived from maintenance services provided under contracts or arrangements with clients. Services may include the maintenance of software, plant and equipment, and facilities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(d),(e))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration