Cover Page - shares	3 Months Ended
	Dec. 31, 2019	Jan. 24, 2020
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	1-35509
Entity Registrant Name	TD Ameritrade Holding Corporation
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-0543156
Entity Address, Address Line One	200 South 108th Avenue
Entity Address, City or Town	Omaha
Entity Address, State or Province	NE
Entity Address, Postal Zip Code	68154
City Area Code	800
Local Phone Number	669-3900
Title of 12(b) Security	Common stock – $0.01 par value
Trading Symbol	AMTD
Security Exchange Name	NASDAQ
Entity Current Reporting Status	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 Common Stock, Shares Outstanding		540,646,962
Amendment Flag	false
Entity Central Index Key	0001173431
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1