Interest and Other Investment Income, Net (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Interest and Other Investment Income, Net [Abstract]
Dividends on marketable securities	$ 3,230	$ 3,202	$ 6,445	$ 6,405
Mark-to-market income (loss) of investments in our deferred compensation plan	4,359	(609)	2,421	2,250
Interest on loans receivable	748	1,135	1,496	3,959
Other, net	1,899	1,938	3,392	3,844
Interest and other investment income, net	$ 10,236	$ 5,666	$ 13,754	$ 16,458

The net amount of other income and expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income (expense) recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) net gains or losses on securities, (d) unusual costs, (e) gains or losses on foreign exchange transactions, and (f) miscellaneous other income and expense items.

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 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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