Available for Sale Securities and Other Investments (Additional Information) (Details) $ in Millions	Sep. 30, 2018 USD ($)
Investments, Debt and Equity Securities [Abstract]
Other investment not readily marketable, fair value	$ 233.7

Value of the other investment not readily marketable determined by management based upon fair value methods, including pricing of similar securities and valuation techniques, that was used to record the investment for financial reporting purposes.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 820
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=35710923&loc=d3e45360-110995

Name:	us-gaap_OtherInvestmentNotReadilyMarketableFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant