v3.19.2
Document entity information - shares
9 Months Ended
Jun. 30, 2019
Jul. 31, 2019
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2019  
Document Transition Report false  
Entity File Number 001-32686  
Entity Registrant Name VIACOM INC.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 20-3515052  
Entity Address, Address Line One 1515 Broadway  
Entity Address, City or Town New York  
Entity Address, State or Province NY  
Entity Address, Postal Zip Code 10036  
City Area Code 212  
Local Phone Number 258-6000  
Entity Current Reporting Status - Indicate 'Yes' or 'No' whether registrants (1) have filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that registrants were required to file such reports), and (2) have been subject to such filing requirements for the past 90 days. This information should be based on the registrant's current or most recent filing containing the related disclosure. Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Central Index Key 0001339947  
Current Fiscal Year End Date --09-30  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Common Class A    
Title of 12(b) Security Class A common stock, par value $0.001 per share  
Trading Symbol VIA  
Security Exchange Name NASDAQ  
Entity Common Stock, Shares Outstanding   49,430,524
Common Class B    
Title of 12(b) Security Class B common stock, par value $0.001 per share  
Trading Symbol VIAB  
Security Exchange Name NASDAQ  
Entity Common Stock, Shares Outstanding   353,964,838