Equity-Based Compensation (Management Stock Purchase Plan) (Details) - Management Stock Purchase Plan - USD ($)	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based liabilities paid (in thousands)	$ 4,986,000	$ 2,392,000
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units credited	$ 74,180	$ 90,754

Amount of cash paid related to share-based compensation liabilities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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