TD Ameritrade Holding 10-Q 8 Feb 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Dec. 31, 2017	Jan. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Trading Symbol	AMTD
Entity Registrant Name	TD AMERITRADE HOLDING CORPORATION
Entity Central Index Key	1,173,431
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		567,369,331

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
ASSETS
Cash and cash equivalents	$ 1,644	$ 1,472
Cash and investments segregated and on deposit for regulatory purposes	10,136	10,446
Receivable from brokers, dealers and clearing organizations	1,291	1,334
Receivable from clients, net	18,578	17,151
Receivable from affiliates	219	137
Other receivables, net	199	174
Securities owned, at fair value	593	503
Investments available-for-sale, at fair value (including $99 million of securities pledged as collateral for repurchase agreements at December 31, 2017 and September 30, 2017)	99	746
Property and equipment at cost, net	780	752
Goodwill	4,197	4,213
Acquired intangible assets, net	1,432	1,470
Other assets	244	229
Total assets	39,412	38,627
Liabilities:
Payable to brokers, dealers and clearing organizations	3,064	2,504
Payable to clients	25,286	25,107
Accounts payable and other liabilities	714	815
Payable to affiliates	55	109
Notes payable	50	0
Securities sold under agreements to repurchase	97	97
Long-term debt	2,531	2,555
Deferred income taxes	182	193
Total liabilities	31,979	31,380
Stockholders' equity:
Preferred stock, $0.01 par value; 100 million shares authorized, none issued	0	0
Common stock, $0.01 par value; one billion shares authorized; 670 million shares issued; 567 million shares outstanding	7	7
Additional paid-in capital	3,375	3,369
Retained earnings	6,189	6,011
Treasury stock, common, at cost: 103 million shares	(2,119)	(2,116)
Deferred compensation	1	1
Accumulated other comprehensive loss	(20)	(25)
Total stockholders' equity	7,433	7,247
Total liabilities and stockholders' equity	$ 39,412	$ 38,627

CONDENSED CONSOLIDATED BALANCE3

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Statement of Financial Position [Abstract]
Securities pledged as collateral for repurchase agreements	$ 99	$ 99
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	670,000,000	670,000,000
Common stock, shares outstanding	567,000,000	567,000,000
Treasury stock, shares	103,000,000	103,000,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Transaction-based revenues:
Commissions and transaction fees	$ 440	$ 355
Asset-based revenues:
Bank deposit account fees	381	245
Net interest revenue	276	151
Investment product fees	133	94
Total asset-based revenues	790	490
Other revenues	27	14
Net revenues	1,257	859
Operating expenses:
Employee compensation and benefits	415	214
Clearing and execution costs	47	36
Communications	53	35
Occupancy and equipment costs	80	44
Depreciation and amortization	34	24
Amortization of acquired intangible assets	38	19
Professional services	74	53
Advertising	64	57
Other	116	24
Total operating expenses	921	506
Operating income	336	353
Other expense:
Interest on borrowings	20	14
Loss on sale of investments	11	0
Other	2	0
Total other expense	33	14
Pre-tax income	303	339
Provision for income taxes	6	123
Net income	$ 297	$ 216
Earnings per share - basic (in USD per share)	$ 0.52	$ 0.41
Earnings per share - diluted (in USD per share)	$ 0.52	$ 0.41
Weighted average shares outstanding - basic (in shares)	567	527
Weighted average shares outstanding - diluted (in shares)	569	530
Dividends declared per share (in USD per share)	$ 0.21	$ 0.18

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 297	$ 216
Investments available-for-sale:
Unrealized loss	(4)	(10)
Reclassification adjustment for realized loss included in net income	11	0
Net change in investments available-for-sale	7	(10)
Cash flow hedging instruments:
Reclassification adjustment for portion of realized loss amortized to net income	1	1
Total other comprehensive income (loss), before tax	8	(9)
Income tax effect	(3)	4
Total other comprehensive income (loss), net of tax	5	(5)
Comprehensive income	$ 302	$ 211

CONDENSED CONSOLIDATED STATEME6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 297	$ 216
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	34	24
Amortization of acquired intangible assets	38	19
Deferred income taxes	(13)	7
Loss on sale of investments	11	0
Stock-based compensation	10	10
Other, net	5	1
Changes in operating assets and liabilities:
Cash and investments segregated and on deposit for regulatory purposes	310	(534)
Receivable from brokers, dealers and clearing organizations	43	231
Receivable from clients, net	(1,428)	(98)
Receivable from/payable to affiliates, net	(101)	(38)
Other receivables, net	(24)	24
Securities owned, at fair value	(90)	154
Other assets	(90)	(21)
Payable to brokers, dealers and clearing organizations	560	(12)
Payable to clients	179	7
Accounts payable and other liabilities	(127)	(71)
Net cash provided by (used in) operating activities	(386)	(81)
Cash flows from investing activities:
Purchase of property and equipment	(63)	(29)
Cash paid in business acquisition	(12)	0
Proceeds from sale of investments available-for-sale, at fair value	643	0
Proceeds from sale and maturity of short-term investments	65	0
Net cash provided by (used in) investing activities	633	(29)
Cash flows from financing activities:
Proceeds from notes payable, net	50	0
Payment of cash dividends	(119)	(95)
Proceeds from exercise of stock options: Three months ended December 31, 2016 – 1.3 million shares	0	23
Purchase of treasury stock for income tax withholding on stock-based compensation: Three months ended December 31, 2017 – 0.2 million shares; 2016 – 0.3 million shares	(8)	(11)
Other	2	0
Net cash provided by (used in) financing activities	(75)	(83)
Net increase (decrease) in cash and cash equivalents	172	(193)
Cash and cash equivalents at beginning of period	1,472	1,855
Cash and cash equivalents at end of period	1,644	1,662
Supplemental cash flow information:
Interest paid	36	19
Income taxes paid	$ 112	$ 99

CONDENSED CONSOLIDATED STATEME7

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (Parenthetical) - shares shares in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Statement of Cash Flows [Abstract]
Proceeds from exercise of stock options, shares	0	1.3
Purchase of treasury stock for income tax withholding on stock-based compensation, shares	0.2	0.3

Basis of Presentation

Basis of Presentation	3 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The condensed consolidated financial statements include the accounts of TD Ameritrade Holding Corporation (the "Parent") and its wholly-owned subsidiaries (collectively, the "Company"). Intercompany balances and transactions have been eliminated. These financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission ("SEC") and, in the opinion of management, reflect all adjustments, which are all of a normal recurring nature, necessary to present fairly the financial position, results of operations and cash flows for the periods presented in conformity with U.S. generally accepted accounting principles ("GAAP"). These financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company's annual report filed on Form 10-K for the fiscal year ended September 30, 2017 . Recently Adopted Accounting Pronouncements ASU 2016-09 — In March 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-09, Improvements to Employee Share-Based Payment Accounting . The guidance in ASU 2016-09 simplified several aspects of the accounting for share-based payment transactions, including: (1) recognize all excess tax benefits and tax deficiencies as income tax expense or benefit in the statement of income; (2) treat tax effects of exercised or vested awards as discrete items in the period in which they occur; (3) recognize excess tax benefits regardless of whether the benefit reduces taxes payable in the current period; (4) classify excess tax benefits with other income tax cash flows as an operating activity; (5) an entity can make an accounting policy election to either estimate the number of awards that are expected to vest or account for forfeitures when they occur; (6) the threshold to qualify for equity classification will permit withholding up to the maximum statutory rates in the applicable jurisdictions; and (7) classify cash paid by an employer when directly withholding shares for tax withholding purposes as a financing activity in the statement of cash flows. The Company adopted the amended accounting guidance as of October 1, 2017, and as a result, the Company's provision for income taxes was reduced by $3 million on its Condensed Consolidated Statement of Income for the three months ended December 31, 2017, due to the inclusion of excess tax benefits applied on a prospective basis. The future effects of excess tax benefits and tax deficiencies recognized in the Company's earnings will depend on the volume of equity compensation during a particular period and on the market price of the Company's common stock at the date the equity awards either vest or are exercised. In addition, the Company elected to retrospectively adopt the amendment to present excess tax benefits on share-based compensation as an operating activity on the statement of cash flows. This resulted in an increase in cash flows from operating activities and a decrease in cash flows from financing activities of $9 million on the Company's Condensed Consolidated Statement of Cash Flows for the three months ended December 31, 2016. For the purpose of recognizing compensation cost associated with share-based awards, the Company has elected to continue to follow its current practice of estimating forfeitures. None of the other provisions in this amended guidance had a significant impact on the Company's condensed consolidated financial statements. Recently Issued Accounting Pronouncements ASU 2016-13 — In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments . The main objective of ASU 2016-13 is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by an entity at each reporting date. To achieve this objective, the amendments in this update replace the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to develop credit loss estimates. ASU 2016-13 is effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years, with early adoption permitted. Therefore, ASU 2016-13 will be effective for the Company's fiscal year beginning on October 1, 2020, using a modified retrospective approach. The Company is currently assessing the impact this ASU will have on its condensed consolidated financial statements. ASU 2016-02 — In February 2016, the FASB issued ASU 2016-02, Leases . This ASU will supersede the guidance in Accounting Standards Codification ("ASC") Topic 840, Leases . Under ASU 2016-02, for lease arrangements exceeding a 12-month term, a lessee will be required to recognize in the balance sheet a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term. ASU 2016-02 will retain a distinction between finance and operating leases; however, the principal difference from the previous guidance is that lease assets and liabilities arising from operating leases will be recognized in the balance sheet. The recognition, measurement and presentation of expenses and cash flows arising from a lease by a lessee will not significantly change from current GAAP. The accounting applied by a lessor will be largely unchanged from that applied under current GAAP. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, and will require an entity to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. Therefore, ASU 2016-02 will be effective for the Company's fiscal year beginning October 1, 2019. Early adoption is permitted. The Company is currently assessing the impact of this ASU, but does not expect the standard to have a material impact on its net income. Upon adoption of ASU 2016-02, the Company expects to recognize right-of-use assets and lease liabilities for its operating leases, with initial measurement as defined by the ASU, in its Condensed Consolidated Balance Sheets. ASU 2014-09 — In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers , to clarify the principles of recognizing revenue from contracts with customers and to improve financial reporting by creating common revenue recognition guidance for U.S. GAAP and International Financial Reporting Standards. This ASU will supersede the revenue recognition requirements in ASC Topic 605, Revenue Recognition, and most industry-specific guidance. Entities are required to apply the following steps when recognizing revenue under ASU 2014-09: (1) identify the contract(s) with a customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when (or as) the entity satisfies a performance obligation. This ASU also requires additional disclosures related to the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. An entity may apply the amendments by using one of the following two methods: (1) retrospective application to each prior reporting period presented or (2) a modified retrospective approach, requiring the standard be applied only to the most current period presented, with the cumulative effect of initially applying the standard recognized at the date of initial application. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period, with early adoption permitted. Subsequent to issuing ASU 2014-09, the FASB has issued additional standards for the purpose of clarifying certain aspects of ASU 2014-09. The subsequently issued ASUs have the same effective date and transition requirements as ASU 2014-09. The Company plans to adopt the revenue recognition standard as of October 1, 2018. The guidance does not apply to revenue associated with financial instruments, such as interest revenue, which is accounted for under other GAAP. Accordingly, the Company does not expect the adoption of this standard to impact net interest revenue. While the Company has not yet identified any material changes in the timing of revenue recognition, its review is ongoing. The Company has not selected a transition method and continues to evaluate the potential impacts that these revenue recognition standards may have on its condensed consolidated financial statements, including the incremental costs of obtaining contracts, gross versus net reporting, and additional disclosure requirements.

Business Acquisition

Business Acquisition	3 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Business Acquisition	Business Acquisition On September 18, 2017 , the Company completed its acquisition of Scottrade Financial Services, Inc. ("Scottrade"), pursuant to an Agreement and Plan of Merger dated October 24, 2016 (the "Acquisition") among the Company, Rodger O. Riney, as Voting Trustee of the Rodger O. Riney Family Voting Trust U/A/D 12/31/2012 (the "Riney Stockholder"), and Alto Acquisition Corp., a wholly-owned subsidiary of the Company. Founded in 1980, Scottrade provides securities brokerage and investment services to retail investors, traders and independent registered investment advisors through its online platform as well as through nearly 500 branch locations. Immediately prior to the closing of the Acquisition, pursuant to the terms and conditions set forth in a separate Agreement and Plan of Merger, TD Bank, N.A., a wholly-owned subsidiary of The Toronto-Dominion Bank ("TD"), acquired Scottrade Bank, which was a wholly-owned subsidiary of Scottrade, from Scottrade (the "Bank Merger") for approximately $1.37 billion in cash (the "Bank Merger Consideration"). Immediately prior to the closing of the Acquisition, the Company also issued 11,074,197 shares of the Company's common stock to TD at a price of $36.12 per share, or approximately $400 million , pursuant to a subscription agreement dated October 24, 2016 between the Company and TD. Immediately following the Bank Merger, the Acquisition was completed. The aggregate consideration paid by the Company for all of the outstanding capital stock of Scottrade consisted of 27,685,493 shares of the Company's common stock and $3.07 billion in cash (the "Cash Consideration"). The Cash Consideration was funded with the Bank Merger Consideration paid by TD Bank, N.A. to Scottrade, the proceeds received from the Company's issuance of the 3.300% Senior Notes on April 27, 2017 , cash on hand and cash proceeds from the sale of the Company's common stock to TD, as described above. At the closing of the Acquisition, 1,736,815 shares of the Company's common stock otherwise payable to the Riney Stockholder were deposited into a third-party custodian account (the “Escrow Account”) pursuant to an escrow agreement to secure certain indemnification obligations of the Riney Stockholder. In connection with the closing of the Acquisition, the Company entered into a registration rights agreement with TD, the Riney Stockholder and the other stockholders described therein (the "Ricketts Stockholders") providing for certain customary registration rights with respect to their shares of the Company's common stock. Additionally, the Company and the Riney Stockholder entered into a stockholders agreement (the "Riney Stockholders Agreement"), which contained various provisions relating to stock ownership, voting, election of directors and other matters. On December 14, 2017 , all of the Company's common stock received as consideration by the Riney Stockholder in the Acquisition, including shares held in the Escrow Account, were sold in a public offering. Prior to the public offering, the Riney Stockholder replaced the shares previously held in the Escrow Account with cash. As a result of the Riney Stockholder no longer owning any shares of the Company's common stock, the registration rights agreement was terminated solely with respect to the Riney Stockholder and the Riney Stockholders Agreement was terminated. The Company accounted for the purchase of Scottrade using the acquisition method of accounting under GAAP and accordingly, the purchase price of the Acquisition was allocated to the assets acquired and liabilities assumed based on their estimated fair values as of the date of acquisition. The estimated fair values of the assets acquired and liabilities assumed are considered provisional and are based on currently available information. The determination of estimated fair values requires management to make significant estimates and assumptions. The Company believes that the information available provides a reasonable basis for estimating the fair values of assets acquired and liabilities assumed; however, these provisional estimates may be adjusted upon the availability of new information regarding facts and circumstances which existed at the date of Acquisition, and such adjustments are not expected to be material to the Company's condensed consolidated financial statements. These provisional amounts consist primarily of estimates related to property acquired and liabilities assumed. The Company expects to finalize the valuation of these assets and liabilities as soon as practicable, but not later than one year from the Acquisition date. Adjustments to the initial estimates of the fair value of the acquired assets and liabilities assumed are recorded as adjustments to the respective assets and liabilities, with the residual amounts allocated to goodwill. During the three months ended December 31, 2017, the Company recorded purchase accounting adjustments, primarily attributable to post-closing adjustments related to the Bank Merger Consideration and liabilities assumed, resulting in a net decrease in goodwill of $16 million . Goodwill associated with the Acquisition was primarily attributable to the anticipated synergies from combining the operations of the Company and Scottrade. Approximately $1.60 billion of the goodwill associated with the Acquisition is expected to be deductible for income tax purposes. The purchase price for Scottrade was comprised of the following (dollars in millions): TD Ameritrade Holding Corporation common stock issued to the Riney Stockholder and the Escrow Account (1) $ 1,261 Cash paid at closing (2) 3,073 Total purchase price $ 4,334 (1) Represents the value of 27,685,493 shares of the Company's common stock at a price of $45.55 per share. The per share value is based on the opening market price of the Company's common stock as of September 18, 2017, the Acquisition date. As discussed above, the shares held in the Escrow Account were sold and replaced with cash. (2) Includes $1.37 billion of Bank Merger Consideration paid by TD Bank, N.A. to Scottrade, which was used to fund a portion of the Acquisition. The provisional purchase price allocation for Scottrade as of December 31, 2017 is summarized as follows (dollars in millions): Cash and cash equivalents (1) $ 1,785 Cash and investments segregated and on deposit for regulatory purposes 3,535 Receivable from brokers, dealers and clearing organizations 167 Receivable from clients, net 3,136 Receivable from affiliates 38 Other receivables 54 Securities owned 37 Property and equipment 133 Goodwill 1,730 Acquired intangible assets 974 Deferred tax assets 76 Other assets 34 Total assets acquired 11,699 Payable to brokers, dealers and clearing organizations (354 ) Payable to clients (6,248 ) Accounts payable and other liabilities (239 ) Payable to affiliates (88 ) Long-term debt (2) (436 ) Total liabilities assumed (7,365 ) Total provisional purchase price allocated $ 4,334 (1) Includes $1.37 billion of Bank Merger Consideration paid by TD Bank, N.A. to Scottrade, which was used to fund a portion of the Acquisition. (2) On the date of Acquisition, amounts owed by Scottrade under its 6.125% senior notes, including a prepayment premium, and the amount owed under its 6.18% secured loan were repaid by the Company. The results of operations for Scottrade are included in the Company's condensed consolidated financial statements from the date of Acquisition. The following unaudited pro forma financial information sets forth the results of operations of the Company as if the Acquisition had occurred on October 1, 2015, the beginning of the comparable fiscal year prior to the year of Acquisition. The unaudited pro forma results include certain adjustments for acquisition-related costs, depreciation, amortization of intangible assets, interest expense on acquisition financing, and related income tax effects, and do not reflect potential revenue enhancements, cost savings or operating synergies that the Company expects to realize after the Acquisition. The unaudited pro forma financial information is based on currently available information, is presented for informational purposes only, and is not indicative of future operations or results had the Acquisition been completed as of October 1, 2015 or any other date. The following table summarizes the unaudited pro forma financial information for the three months ended December 31, 2016, (dollars in millions): Three Months Ended December 31, 2016 (unaudited) Pro forma net revenues $ 1,072 Pro forma net income $ 219 Pro forma basic earnings per share $ 0.39 Pro forma diluted earnings per share $ 0.38

Cash and Cash Equivalents

Cash and Cash Equivalents	3 Months Ended
	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	Cash and Cash Equivalents The Company's cash and cash equivalents is summarized in the following table (dollars in millions): December 31, September 30, Corporate $ 771 $ 279 Broker-dealer subsidiaries 668 997 Futures commission merchant and forex dealer member subsidiary 102 98 Trust company subsidiary 74 79 Investment advisory subsidiaries 29 19 Total $ 1,644 $ 1,472 Capital requirements may limit the amount of cash available for dividend from the broker-dealer, futures commission merchant ("FCM")/forex dealer member ("FDM") and trust company subsidiaries to the Parent.

Cash and Investments Segregated

Cash and Investments Segregated and on Deposit for Regulatory Purposes	3 Months Ended
	Dec. 31, 2017
Restricted Cash and Investments [Abstract]
Cash and Investments Segregated and on Deposit for Regulatory Purposes	Cash and Investments Segregated and on Deposit for Regulatory Purposes Cash and investments segregated and on deposit for regulatory purposes consists of the following (dollars in millions): December 31, September 30, Cash in demand deposit accounts $ 4,131 $ 3,653 U.S. government debt securities 3,544 4,019 U.S. government agency mortgage-backed securities 1,433 1,486 Reverse repurchase agreements (collateralized by U.S. government debt securities) 750 1,004 Cash on deposit with futures commission merchants 228 209 U.S. government debt securities on deposit with futures commission merchant 50 75 Total $ 10,136 $ 10,446

Goodwill

Goodwill	3 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill The Company has recorded goodwill for business acquisitions to the extent the purchase price of each completed acquisition exceeded the fair value of the net identifiable tangible and intangible assets of each acquired company. The following table summarizes changes in the carrying amount of goodwill for the three months ended December 31, 2017 (dollars in millions): Balance as of September 30, 2017 $ 4,213 Purchase accounting adjustments (1) (16 ) Balance as of December 31, 2017 $ 4,197 (1) The purchase accounting adjustments are primarily attributable to post-closing adjustments related to the Bank Merger Consideration and liabilities assumed in the acquisition of Scottrade. The purchase price allocation for the Scottrade acquisition is provisional as of December 31, 2017. The provisional amounts consist primarily of estimates related to property acquired and liabilities assumed. The Company expects to finalize the valuation of assets and liabilities as soon as practicable, but not later than one year from the date of acquisition.

Exit Liabilities

Exit Liabilities	3 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Exit Liabilities	Exit Liabilities As of September 18, 2017, the date of Acquisition, the Company began to incur costs in connection with actions taken to attain synergies from combining the operations of the Company and Scottrade. These costs, collectively referred to as "acquisition-related exit costs," include severance and other costs associated with consolidating facilities and administrative functions. The Company expects to incur total acquisition-related exit costs ranging from approximately $455 million to $545 million , consisting of severance pay and other termination benefits ranging from $300 million to $320 million and contract termination and other costs ranging from $155 million to $225 million . All acquisition-related exit costs are expected to be incurred by the end of fiscal year 2018. The following table summarizes activity in the Company's exit liabilities for the three-month period ended December 31, 2017, which are included in accounts payable and other liabilities on the Condensed Consolidated Balance Sheets (dollars in millions): Severance Pay and Other Termination Benefits Contract Termination and Other Costs Total Balance, September 30, 2017 $ 138 $ — $ 138 Exit liabilities assumed - post closing adjustments — 9 9 Costs incurred and charged to expense 82 (1) 98 (2) 180 Costs paid or otherwise settled (20 ) (95 ) (115 ) Balance, December 31, 2017 $ 200 $ 12 $ 212 (1) Costs incurred for severance pay and other termination benefits are included in employee compensation and benefits on the Condensed Consolidated Statements of Income. (2) Costs incurred for contract termination and other costs are primarily included in other operating expense on the Condensed Consolidated Statements of Income. There were no material non-acquisition related exit costs during the three months ended December 31, 2017 and 2016. The following table summarizes the cumulative amount of acquisition-related exit costs incurred by the Company related to the Scottrade acquisition as of December 31, 2017 (dollars in millions): Severance Pay and Other Termination Benefits Contract Termination and Other Costs Total Exit liabilities assumed in business acquisition $ 100 $ 9 $ 109 Employee compensation and benefits 116 — 116 Communications — 1 1 Occupancy and equipment costs — 2 2 Professional services — 8 8 Other operating expense — 85 85 Other non-operating expense — 2 2 Total $ 216 $ 107 $ 323 The remaining acquisition-related exit costs are expected to be incurred and charged to expense over the course of the Scottrade integration during fiscal year 2018.

Income Taxes

Income Taxes	3 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Tax Cuts and Jobs Act (the "Act") was enacted on December 22, 2017. The Act reduces the U.S. federal corporate income tax rate from 35% to 21% , requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred and creates new taxes on certain foreign sourced earnings. As of December 31, 2017, the Company has not completed its accounting for the tax effects of the Act; however, in certain cases, as described below, the Company has made reasonable estimates as to the impacts on its effective income tax rate, existing deferred income tax balances and unrecognized tax benefits. The estimates recorded are considered provisional and are based on currently available information. The Company believes that the information available provides a reasonable basis for estimating the impact of the Act on its financial statements. The Company may need to make adjustments to the provisional amounts, if it obtains, prepares or analyzes additional information regarding facts and circumstances which existed as of the date of enactment; however, such adjustments are not expected to be material to the Company's condensed consolidated financial statements. Any adjustment to a provisional amount will be recorded in the provision for income taxes on the Company's Condensed Consolidated Statement of Income and treated as a discrete event in the period in which the adjustment is identified. The Company expects to finalize its accounting for the tax effects of the Act as soon as practicable, but not later than one year from the date of enactment. An estimated income tax rate of 27% has been applied to the results of operations before consideration of discrete items for the three months ended December 31, 2017. The Company's effective income tax rate for the three months ended December 31, 2017 and 2016 was 2.0% and 36.3% , respectively. The provision for income taxes for the three months ended December 31, 2017 included an estimated net favorable adjustment of $68 million related to the remeasurement of the Company's deferred income tax balances as it pertains to the Act, a $3 million income tax benefit resulting from the change in accounting for income taxes related to equity-based compensation under ASU 2016-09, $10 million of favorable resolutions of state income tax matters and a $6 million favorable benefit primarily resulting from acquisition-related exit costs. The effective income tax rate was also impacted by a $9 million unfavorable remeasurement of uncertain tax positions related to certain federal incentives. These items had a net favorable impact on the Company's earnings for the three months ended December 31, 2017 of approximately $0.14 per share. The provision for income taxes for the three months ended December 31, 2016 included $7 million of favorable resolutions of state income tax matters. This favorably impacted the Company's earnings for the three months ended December 31, 2016 by approximately $0.01 per share. As a result of the Act, the effective income tax rate for the full fiscal year 2018 is estimated to be approximately 22% , which includes the net favorable adjustment of $68 million described above. As a result of the Act, the Company estimates its effective income tax rate will be approximately 27% for the remainder of fiscal 2018 , excluding the effect of any adjustments related to remeasurement or resolution of uncertain tax positions and federal incentives. This estimate is based on a forecast of income through September 30, 2018 and is subject to change based on actual results. The Company remeasured deferred income tax asset and liability balances as of the date of the Act's enactment based on the income tax rates at which they are expected to reverse in the future, which is estimated to be 24% to 25% . In accordance with Staff Accounting Bulletin 118, the estimated net favorable adjustment of $68 million related to the remeasurement of the Company's deferred income tax balances is considered provisional at December 31, 2017. The Company continues to analyze certain aspects of the Act and refine its calculations, which could potentially affect the measurement of these balances or give rise to new deferred income tax amounts. Deferred tax assets (liabilities) are comprised of the following for the periods indicated (dollars in millions): December 31, 2017 September 30, 2017 Deferred tax assets: Accrued and other liabilities $ 67 $ 131 Stock-based compensation 16 28 Unrecognized loss on cash flow hedging instruments 8 15 Allowance for doubtful accounts 3 6 Intangible assets, state tax benefit 5 5 Operating loss carryforwards 1 1 Gross deferred tax assets 100 186 Less: Valuation allowance (1 ) (1 ) Net deferred tax assets 99 185 Deferred tax liabilities: Acquired intangible assets (219 ) (331 ) Property and equipment (38 ) (35 ) Prepaid expenses (23 ) (11 ) Other deferred tax liabilities (1 ) (1 ) Total deferred tax liabilities (281 ) (378 ) Net deferred tax liabilities $ (182 ) $ (193 ) As of December 31, 2017, the Company has not accumulated and analyzed the necessary information to complete the accounting for the tax effects of the Act related to changes in taxation for international operations, thus no estimates have been recorded for the impact of such changes. Any adjustments related to international taxation will be recorded in the period in which a reasonable estimate can be determined; however, the Company does not expect these adjustments to have a material impact on the Company's condensed consolidated financial statements.

Long-term Debt and Other Borrow

Long-term Debt and Other Borrowings	3 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Long-term Debt and Other Borrowings	Long-term Debt and Other Borrowings Long-term debt and other borrowings consist of the following (dollars in millions): December 31, 2017 Face Value Unamortized Discounts and Debt Issuance Costs Fair Value Adjustment (1) Net Carrying Value Other borrowings: Notes payable $ 50 $ — $ — $ 50 Securities sold under agreements to repurchase 97 — — 97 Subtotal - Other borrowings 147 — — 147 Long-term debt: Senior Notes: 5.600% Notes due 2019 500 (1 ) 11 510 2.950% Notes due 2022 750 (5 ) (7 ) 738 3.625% Notes due 2025 500 (3 ) 5 502 3.300% Notes due 2027 800 (9 ) (10 ) 781 Subtotal - Long-term debt 2,550 (18 ) (1 ) 2,531 Total long-term debt and other borrowings $ 2,697 $ (18 ) $ (1 ) $ 2,678 September 30, 2017 Face Value Unamortized Discounts and Debt Issuance Costs Fair Value Adjustment (1) Net Carrying Value Other borrowings: Securities sold under agreements to repurchase $ 97 $ — $ — $ 97 Long-term debt: Senior Notes: 5.600% Notes due 2019 500 (1 ) 15 514 2.950% Notes due 2022 750 (5 ) — 745 3.625% Notes due 2025 500 (3 ) 11 508 3.300% Notes due 2027 800 (9 ) (3 ) 788 Subtotal - Long-term debt 2,550 (18 ) 23 2,555 Total long-term debt and other borrowings $ 2,647 $ (18 ) $ 23 $ 2,652 (1) Fair value adjustments relate to changes in the fair value of the debt while in a fair value hedging relationship. See " Fair Value Hedging " below. Notes Payable – TD Ameritrade Clearing, Inc. ("TDAC"), a clearing broker-dealer subsidiary of the Company, utilizes secured uncommitted lines of credit for short-term liquidity. As of December 31, 2017, there was $50 million in borrowings outstanding under these credit lines. Securities Sold Under Agreements to Repurchase (repurchase agreements) – At times, the Company enters into repurchase agreements to finance its short-term liquidity and capital needs. Under repurchase agreements, the Company receives cash from the counterparty and provides U.S. Treasury securities as collateral. On December 15, 2017 , the Company's outstanding repurchase agreement matured and the Company entered into another repurchase agreement with the same counterparty. The December 15, 2017 repurchase agreement will mature on March 15, 2018 and its terms are similar to the prior agreement. The applicable interest rate under the December 15, 2017 repurchase agreement is calculated based on one-month LIBOR, plus an interest rate margin of ten basis points . As of December 31, 2017, the effective interest rate was 1.58% . The Company will repurchase the collateral on March 15, 2018 for $97 million , plus accrued interest. Fair Value Hedging – The Company is exposed to changes in the fair value of its fixed-rate Senior Notes resulting from interest rate fluctuations. To hedge this exposure, the Company has entered into fixed-for-variable interest rate swaps on each of the Senior Notes. Each fixed-for-variable interest rate swap has a notional amount and a maturity date matching the aggregate principal amount and maturity date, respectively, for each of the respective Senior Notes. The interest rate swaps effectively change the fixed-rate interest on the Senior Notes to variable-rate interest. Under the terms of the interest rate swap agreements, the Company receives semi-annual fixed-rate interest payments based on the same rates applicable to the Senior Notes, and makes quarterly variable-rate interest payments based on three-month LIBOR plus (a) 2.3745% for the swap on the 2019 Notes, (b) 0.9486% for the swap on the 2022 Notes, (c) 1.1022% for the swap on the 2025 Notes and (d) 1.0340% for the swaps on the 2027 Notes. As of December 31, 2017 , the weighted average effective interest rate on the aggregate principal balance of the Senior Notes was 2.65% . The interest rate swaps are accounted for as fair value hedges and qualify for the shortcut method of accounting. Changes in the payment of interest resulting from the interest rate swaps are recorded in interest on borrowings on the Condensed Consolidated Statements of Income. Changes in fair value of the interest rate swaps are completely offset by changes in fair value of the related notes, resulting in no effect on net income. The following table summarizes gains and losses resulting from changes in the fair value of interest rate swaps designated as fair value hedges and the hedged fixed-rate debt for the periods indicated (dollars in millions): Three Months Ended December 31, 2017 2016 Gain (loss) on fair value of interest rate swaps $ (24 ) $ (49 ) Gain (loss) on fair value of hedged fixed-rate debt 24 49 Net gain (loss) recorded in interest on borrowings $ — $ — Balance Sheet Impact of Hedging Instruments — The following table summarizes the fair value of outstanding derivatives designated as hedging instruments on the Condensed Consolidated Balance Sheets (dollars in millions): December 31, September 30, Pay-variable interest rate swaps designated as fair value hedges: Other assets $ 16 $ 26 Accounts payable and other liabilities $ (17 ) $ (3 ) The interest rate swaps are subject to counterparty credit risk. Credit risk is managed by limiting activity to approved counterparties that meet a minimum credit rating threshold, by entering into credit support agreements, or by utilizing approved central clearing counterparties registered with the Commodity Futures Trading Commission ("CFTC"). The interest rate swaps require daily collateral coverage, in the form of cash or U.S. Treasury securities, for the aggregate fair value of the interest rate swaps (including accrued interest). As of December 31, 2017 and September 30, 2017 , the pay-variable interest rate swap counterparties had pledged $18 million and $40 million of collateral, respectively, to the Company in the form of cash. A liability for collateral pledged to the Company in the form of cash is recorded in accounts payable and other liabilities on the Condensed Consolidated Balance Sheets. As of December 31, 2017 and September 30, 2017, the Company had pledged $16 million and $1 million of collateral, respectively, to the pay-variable interest rate swap counterparties in the form of cash. An asset for collateral pledged to the swap counterparties in the form of cash is recorded in other receivables on the Condensed Consolidated Balance Sheets.

Capital Requirements

Capital Requirements	3 Months Ended
	Dec. 31, 2017
Regulatory Capital Requirements [Abstract]
Capital Requirements	Capital Requirements The Company's broker-dealer subsidiaries are subject to the SEC Uniform Net Capital Rule (Rule 15c3-1 under the Securities Exchange Act of 1934, or the "Exchange Act"), administered by the SEC and the Financial Industry Regulatory Authority ("FINRA"), which requires the maintenance of minimum net capital, as defined. Net capital and the related net capital requirement may fluctuate on a daily basis. TDAC and Scottrade, Inc., the Company's clearing broker-dealer subsidiaries, and TD Ameritrade, Inc., an introducing broker-dealer subsidiary of the Company, compute net capital under the alternative method as permitted by Rule 15c3-1. TDAC is required to maintain minimum net capital of the greater of $1.5 million , which is based on the type of business conducted by the broker-dealer, or 2% of aggregate debit balances arising from client transactions. TD Ameritrade, Inc. and Scottrade, Inc. are required to maintain minimum net capital of the greater of $250,000 or 2% of aggregate debit balances. In addition, under the alternative method, a broker-dealer may not repay any subordinated borrowings, pay cash dividends or make any unsecured advances or loans to its parent company or employees if such payment would result in net capital of less than (a) 5% of aggregate debit balances or (b) 120% of its minimum dollar requirement. TD Ameritrade Futures & Forex LLC ("TDAFF"), the Company's FCM and FDM subsidiary registered with the CFTC, is subject to CFTC Regulations 1.17 and 5.7 under the Commodity Exchange Act, administered by the CFTC and the National Futures Association ("NFA"). As an FCM, TDAFF is required to maintain minimum adjusted net capital under CFTC Regulation 1.17 of the greater of (a) $1.0 million or (b) its futures risk-based capital requirement, equal to 8% of the total risk margin requirement for all futures positions carried by the FCM in client and nonclient accounts. As an FDM, TDAFF is also subject to the net capital requirements under CFTC Regulation 5.7, which requires TDAFF to maintain minimum adjusted net capital of the greater of (a) any amount required under CFTC Regulation 1.17 as described above or (b) $20.0 million plus 5% of all foreign exchange liabilities owed to forex clients in excess of $10.0 million . In addition, an FCM and FDM must provide notice to the CFTC if its adjusted net capital amounts to less than (a) 110% of its risk-based capital requirement under CFTC Regulation 1.17, (b) 150% of its $1.0 million minimum dollar requirement, or (c) 110% of $20.0 million plus 5% of all foreign exchange liabilities owed to forex clients in excess of $10.0 million . Net capital and net capital requirements for the Company's broker-dealer subsidiaries are summarized in the following tables (dollars in millions): TD Ameritrade Clearing, Inc. Date Net Capital Required Net Capital (2% of Aggregate Debit Balances) Net Capital in Excess of Required Net Capital Ratio of Net Capital to Aggregate Debit Balances December 31, 2017 $ 1,704 $ 362 $ 1,342 9.42 % September 30, 2017 $ 1,595 $ 340 $ 1,255 9.39 % TD Ameritrade, Inc. Date Net Capital Required Net Capital (Minimum Dollar Requirement) Net Capital in Excess of Required Net Capital December 31, 2017 $ 186 $ 0.25 $ 186 September 30, 2017 $ 155 $ 0.25 $ 155 Scottrade, Inc. Date Net Capital Required Net Capital (2% of Aggregate Debit Balances) Net Capital in Excess of Required Net Capital Ratio of Net Capital to Aggregate Debit Balances December 31, 2017 $ 367 $ 73 $ 294 10.04 % September 30, 2017 $ 348 $ 70 $ 278 9.99 % Adjusted net capital and adjusted net capital requirements for the Company's FCM and FDM subsidiary are summarized in the following table (dollars in millions): TD Ameritrade Futures & Forex LLC Date Adjusted Net Capital Required Adjusted Net Capital ($20 Million Plus 5% of All Foreign Exchange Liabilities Owed to Forex Clients in Excess of $10 Million) Adjusted Net Capital in Excess of Required Adjusted Net Capital December 31, 2017 $ 84 $ 23 $ 61 September 30, 2017 $ 77 $ 22 $ 55 The Company's non-depository trust company subsidiary, TD Ameritrade Trust Company ("TDATC"), is subject to capital requirements established by the State of Maine, which require TDATC to maintain minimum Tier 1 capital. TDATC's Tier 1 capital was $34 million and $32 million as of December 31, 2017 and September 30, 2017 , respectively, which exceeded the required Tier 1 capital by $14 million and $13 million , respectively.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal and Regulatory Matters Order Routing Matters — Five putative class action complaints were filed between August and October 2014 regarding TD Ameritrade, Inc.'s routing of client orders and one putative class action was filed in December 2014 regarding Scottrade, Inc.'s routing of client orders. The cases against TD Ameritrade were filed in, or transferred to, the U.S. District Court for the District of Nebraska: Jay Zola et al. v. TD Ameritrade, Inc., et al ., Case No. 8:14CV288; Tyler Verdieck v. TD Ameritrade, Inc. , Case No. 8:14CV289; Bruce Lerner v. TD Ameritrade, Inc. , Case No. 8:14CV325; Michael Sarbacker v. TD Ameritrade Holding Corporation, et al. , Case No. 8:14CV341 ; and Gerald Klein v. TD Ameritrade Holding Corporation, et al. , Case No. 8:14CV396. The case against Scottrade, Inc. was transferred to the U.S. District Court for the Eastern District of Missouri: Nicholas Lewis v. Scottrade, Inc., Case No. 4:15CV01255. The complaints in Zola, Klein and Sarbacker allege that the defendants failed to provide clients with best execution and routed orders to the market venue that paid the most for its order flow. The complaints in Verdieck, Lerner and Lewis allege that the defendant routed its clients' non-marketable limit orders to the venue paying the highest rates of maker rebates, and that clients did not receive best execution on these kinds of orders. The complaints variously include claims of breach of contract, breach of fiduciary duty, breach of the duty of best execution, fraud, negligent misrepresentation, violation s of Section 10(b) and 20 of the Exchange Act and SEC Rule 10b-5, violation of Nebraska's Consumer Protection Act, violation of Nebraska's Uniform Deceptive Trade Practices Act, violation of the Missouri Merchandising Practices Act, aiding and abetting, unjust enrichment and declaratory judgment. The complaints seek various kinds of relief including damages, restitution, disgorgement, injunctive relief, equitable relief and other relief. The Company, including Scottrade, Inc., moved to dismiss the putative class action complaints. On March 23, 2016, the U.S. District Court in Nebraska entered an order dismissing all of the state law claims in the five actions against TD Ameritrade, denying the motion to dismiss the federal securities claims in the Klein case, and permitting the plaintiffs in the other four actions to amend their complaints to assert a federal securities claim. On August 29, 2016, the U.S. District Court in Missouri entered an order dismissing without prejudice all of the state law claims against Scottrade, Inc. None of the plaintiffs in the actions filed an amended complaint. The plaintiffs in the Zola, Sarbacker, Verdieck and Lewis cases filed appeals. The plaintiff in the Lerner case did not file an appeal and that case is considered closed. On January 9, 2018, the Court of Appeals, 8 th Circuit, affirmed the District Court's dismissal of the Lewis case. The Court of Appeals has not yet ruled on any of the cases against TD Ameritrade. The Klein case is proceeding. The Company intends to vigorously defend against these lawsuits and is unable to predict the outcome or the timing of the ultimate resolution of these lawsuits, or the potential losses, if any, that may result. Certain regulatory authorities are conducting examinations and investigations regarding the routing of client orders. TD Ameritrade, Inc., TDAC and Scottrade, Inc. have received requests for documents and information from the regulatory authorities. TD Ameritrade, Inc., TDAC and Scottrade, Inc. are cooperating with the requests. Lawsuit regarding Scottrade Acquisition — On April 6, 2017, an alleged stockholder of the Company filed a purported stockholder derivative complaint regarding the acquisition of Scottrade by the Company and the acquisition of Scottrade Bank by TD. The suit filed in the Delaware Chancery Court is captioned Vero Beach Police Officers' Retirement Fund, derivatively on behalf of nominal defendant TD Ameritrade Holding Corp. v. Larry Bettino et al ., C.A. No. 2017-0264-JRS. On December 18, 2017, the plaintiff filed an amended complaint. The suit names as defendants TD and the members of the Company's board of directors. It also names the Company as a nominal defendant. The complaint alleges that the Scottrade acquisition and TD's acquisition of Scottrade Bank were unfair from the perspective of the Company because TD Bank, N.A. acquired Scottrade Bank for an allegedly low price, which in turn caused the Company to pay an allegedly high price to acquire Scottrade. The complaint claims that the Company's directors and TD, as the Company's alleged controlling stockholder, breached their fiduciary duties to the Company and its stockholders, and that TD aided and abetted the Company directors' breach of fiduciary duty and was unjustly enriched. The complaint seeks a declaration that demand on the Company's board is excused as futile and seeks corporate governance reforms, damages, interest and fees. On September 18, 2017, the acquisitions of Scottrade and of Scottrade Bank were completed. The Company intends to vigorously defend against this lawsuit and is unable to predict the outcome or the timing of the ultimate resolution of this lawsuit, or the potential losses, if any, that may result. Aequitas Securities Litigation — An amended putative class action complaint was filed in the U.S. District Court for the District of Oregon in Lawrence Ciuffitelli et al. v. Deloitte & Touche LLP, EisnerAmper LLP, Sidley Austin LLP, Tonkon Torp LLP, TD Ameritrade, Inc., and Integrity Bank & Trust, Case No. 3:16CV580, on May 19, 2016. A second amended putative class action complaint was filed on September 8, 2017, in which Duff & Phelps was added as a defendant. The putative class includes all persons who purchased securities of Aequitas Commercial Finance, LLC and its affiliates on or after June 9, 2010. Other groups of plaintiffs have filed four non-class action lawsuits in Oregon Circuit Court, Multnomah County, against these and other defendants: Walter Wurster, et al. v. Deloitte & Touche et al. , Case No. 16CV25920 (filed Aug. 11, 2016), Kenneth Pommier, et al. v. Deloitte & Touche et al., Case No. 16CV36439 (filed Nov. 3, 2016), Charles Ramsdell, et al. v. Deloitte & Touche et al., Case No. 16CV40659 (filed Dec. 2, 2016) and Charles Layton, et al. v. Deloitte & Touche et al., Case No. 17CV42915 (filed October 2, 2017). FINRA arbitrations have also been filed against TD Ameritrade, Inc. The claims in these actions include allegations that the sales of Aequitas securities were unlawful, the defendants participated and materially aided in such sales in violation of the Oregon securities laws, and material misstatements and omissions were made. While the factual allegations differ in various respects among the cases, plaintiffs' allegations include assertions that: TD Ameritrade customers purchased more than $140 million of Aequitas securities; TD Ameritrade served as custodian for Aequitas securities; recommended and referred investors to financial advisors as part of its advisor referral program for the purpose of purchasing Aequitas securities; participated in marketing the securities; recommended the securities; provided assurances to investors about the safety of the securities; and developed a market for the securities. In the Ciuffitelli putative class action, plaintiffs allege that more than 1,500 investors were owed more than $600 million on the Aequitas securities they purchased. In that case and the other cases, collectively over 200 named plaintiffs allege a total of over $125 million in losses plus other damages. Of that amount, over 100 plaintiffs who were TD Ameritrade customers, allege approximately $35 million in losses plus other damages. In the Wurster and Pommier cases, TD Ameritrade filed a motion to compel arbitration as to the claims by those plaintiffs who were TD Ameritrade customers and the Court dismissed those claims. In those cases, plaintiffs have filed amended complaints and defendants have filed motions to dismiss. In the Ciuffitelli case, defendants have also moved to dismiss the pending complaint. Discovery has commenced. The Ramsdell case is stayed and the Layton case may similarly be stayed. These stays are expected to remain in place until the resolution of the motions to dismiss the Wurster and Pommier cases. The Company intends to vigorously defend against this litigation. The Company is unable to predict the outcome or the timing of the ultimate resolution of this litigation, or the potential losses, if any, that may result. Other Legal and Regulatory Matters — The Company is subject to a number of other lawsuits, arbitrations, claims and other legal proceedings in connection with its business. Some of these legal actions include claims for substantial or unspecified compensatory and/or punitive damages. In addition, in the normal course of business, the Company discusses matters with its regulators raised during regulatory examinations or otherwise subject to their inquiry. These matters could result in censures, fines, penalties or other sanctions. ASC 450, Loss Contingencies, governs the recognition and disclosure of loss contingencies, including potential losses from legal and regulatory matters. ASC 450 categorizes loss contingencies using three terms based on the likelihood of occurrence of events that result in a loss: "probable" means that "the future event or events are likely to occur;" "remote" means that "the chance of the future event or events occurring is slight;" and "reasonably possible" means that "the chance of the future event or events occurring is more than remote but less than likely." Under ASC 450, the Company accrues for losses that are considered both probable and reasonably estimable. The Company may incur losses in addition to the amounts accrued where the losses are greater than estimated by management, or for matters for which an unfavorable outcome is considered reasonably possible, but not probable. The Company estimates that the aggregate range of reasonably possible losses in excess of amounts accrued is from $0 to $65 million as of December 31, 2017 . This estimated aggregate range of reasonably possible losses is based upon currently available information for those legal and regulatory matters in which the Company is involved, taking into account the Company's best estimate of reasonably possible losses for those matters as to which an estimate can be made. For certain matters, the Company does not believe an estimate can currently be made, as some matters are in preliminary stages and some matters have no specific amounts claimed. The Company's estimate involves significant judgment, given the varying stages of the proceedings and the inherent uncertainty of predicting outcomes. The estimated range will change from time to time as the underlying matters, stages of proceedings and available information change. Actual losses may vary significantly from the current estimated range. The Company believes, based on its current knowledge and after consultation with counsel, that the ultimate disposition of these legal and regulatory matters, individually or in the aggregate, is not likely to have a material adverse effect on the financial condition or cash flows of the Company. However, in light of the uncertainties involved in such matters, the Company is unable to predict the outcome or the timing of the ultimate resolution of these matters, or the potential losses, fines, penalties or equitable relief, if any, that may result, and it is possible that the ultimate resolution of one or more of these matters may be material to the Company's results of operations for a particular reporting period. Income Taxes The Company's federal and state income tax returns are subject to examination by taxing authorities. Because the application of tax laws and regulations to many types of transactions is subject to varying interpretations, amounts reported in the condensed consolidated financial statements could be significantly changed at a later date upon final determinations by taxing authorities. General Contingencies In the ordinary course of business, there are various contingencies that are not reflected in the condensed consolidated financial statements. These include the Company's broker-dealer and FCM/FDM subsidiaries' client activities involving the execution, settlement and financing of various client securities, options, futures and foreign exchange transactions. These activities may expose the Company to credit risk in the event the clients are unable to fulfill their contractual obligations. The Company extends margin credit and leverage to its clients. In margin transactions, the Company extends credit to the client, subject to various regulatory and internal margin requirements, collateralized by cash and securities in the client's account. In connection with these activities, the Company also routes client orders for execution and clears client transactions involving the sale of securities not yet purchased ("short sales"). Such margin-related transactions may expose the Company to credit risk in the event a client's assets are not sufficient to fully cover losses that the client may incur. Leverage involves securing a large potential future obligation with a lesser amount of collateral. The risks associated with margin credit and leverage increase during periods of rapid market movements, or in cases where leverage or collateral is concentrated and market movements occur. In the event the client fails to satisfy its obligations, the Company has the authority to liquidate certain positions in the client's account at prevailing market prices in order to fulfill the client's obligations. However, during periods of rapid market movements, clients who utilize margin credit or leverage and who have collateralized their obligations with securities may find that the securities have a rapidly depreciating value and may not be sufficient to cover their obligations in the event of liquidation. The Company seeks to mitigate the risks associated with its client margin and leverage activities by requiring clients to maintain margin collateral in compliance with various regulatory and internal guidelines. The Company monitors required margin levels throughout each trading day and, pursuant to such guidelines, requires clients to deposit additional collateral, or to reduce positions, when necessary. The Company contracts with unaffiliated FCM, FDM and broker-dealer entities to clear and execute futures and foreign exchange transactions for its clients. This can result in concentrations of credit risk with one or more of these counterparties. This risk is partially mitigated by the counterparties' obligation to comply with rules and regulations governing FCMs, FDMs and broker-dealers in the United States. These rules generally require maintenance of net capital and segregation of client funds and securities. In addition, the Company manages this risk by requiring credit approvals for counterparties and by utilizing account funding and sweep arrangement agreements that generally specify that all client cash in excess of futures funding requirements be transferred back to the clients' securities brokerage account at the Company on a daily basis. The Company loans securities temporarily to other broker-dealers in connection with its broker-dealer business. The Company receives cash as collateral for the securities loaned. Increases in securities prices may cause the market value of the securities loaned to exceed the amount of cash received as collateral. In the event the counterparty to these transactions does not return the loaned securities, the Company may be exposed to the risk of acquiring the securities at prevailing market prices in order to satisfy its client obligations. The Company mitigates this risk by requiring credit approvals for counterparties, by monitoring the market value of securities loaned on a daily basis and requiring additional cash as collateral when necessary, and by participating in a risk-sharing program offered through the Options Clearing Corporation ("OCC"). The Company borrows securities temporarily from other broker-dealers in connection with its broker-dealer business. The Company deposits cash as collateral for the securities borrowed. Decreases in securities prices may cause the market value of the securities borrowed to fall below the amount of cash deposited as collateral. In the event the counterparty to these transactions does not return the cash deposited, the Company may be exposed to the risk of selling the securities at prevailing market prices. The Company mitigates this risk by requiring credit approvals for counterparties, by monitoring the collateral values on a daily basis and requiring collateral to be returned by the counterparties when necessary, and by participating in a risk-sharing program offered through the OCC. The Company transacts in reverse repurchase agreements (securities purchased under agreements to resell) in connection with its broker-dealer business. The Company's policy is to take possession or control of securities with a market value in excess of the principal amount loaned, plus accrued interest, in order to collateralize resale agreements. The Company monitors the market value of the underlying securities that collateralize the related receivable on resale agreements on a daily basis and may require additional collateral when deemed appropriate. The Company has accepted collateral in connection with client margin loans and securities borrowed. Under applicable agreements, the Company is generally permitted to repledge securities held as collateral and use them to enter into securities lending arrangements. The following table summarizes the fair values of client margin securities and stock borrowings that were available to the Company to utilize as collateral on various borrowings or for other purposes, and the amount of that collateral loaned or repledged by the Company (dollars in billions): December 31, September 30, Client margin securities $ 25.6 $ 23.8 Stock borrowings 1.0 1.2 Total collateral available $ 26.6 $ 25.0 Collateral loaned $ 3.0 $ 2.4 Collateral repledged 7.8 4.1 Total collateral loaned or repledged $ 10.8 $ 6.5 The Company is subject to cash deposit and collateral requirements with clearinghouses based on its clients' trading activity. The following table summarizes cash deposited with and securities pledged to clearinghouses by the Company (dollars in millions): Assets Balance Sheet Classification December 31, September 30, Cash Receivable from brokers, dealers and clearing organizations $ 246 $ 151 U.S. government debt securities Securities owned, at fair value 469 398 Total $ 715 $ 549 The Company utilizes securities sold under agreements to repurchase (repurchase agreements) to finance its short-term liquidity and capital needs. Under these agreements, the Company receives cash from the counterparties and provides U.S. Treasury securities as collateral, allowing the counterparties the right to sell or repledge the collateral. These agreements expose the Company to credit losses in the event the counterparties cannot meet their obligations. The Company mitigates this risk by requiring credit approvals for counterparties, by monitoring the market value of pledged securities owned on a daily basis and requiring the counterparties to return cash or excess collateral pledged when necessary. Guarantees The Company is a member of and provides guarantees to securities clearinghouses and exchanges in connection with client trading activities. Under related agreements, the Company is generally required to guarantee the performance of other members. Under these agreements, if a member becomes unable to satisfy its obligations to the clearinghouse, other members would be required to meet shortfalls. The Company's liability under these arrangements is not quantifiable and could exceed the cash and securities it has posted to the clearinghouse as collateral. However, the potential for the Company to be required to make payments under these agreements is considered remote. Accordingly, no contingent liability is carried on the Condensed Consolidated Balance Sheets for these guarantees. The Company clears its clients' futures transactions on an omnibus account basis through unaffiliated clearing firms. The Company also contracts with an external provider to facilitate foreign exchange trading for its clients. The Company has agreed to indemnify these unaffiliated clearing firms and the external provider for any loss that they may incur for the client transactions introduced to them by the Company. See " Insured Deposit Account Agreement " in Note 15 for a description of the guarantees included in that agreement.

Fair Value Disclosures

Fair Value Disclosures	3 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Disclosures	Fair Value Disclosures Fair Value Measurement — Definition and Hierarchy ASC 820-10, Fair Value Measurement , defines fair value as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. ASC 820-10 establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs reflect the assumptions market participants would use in pricing the asset or liability, developed based on market data obtained from sources independent of the Company. Unobservable inputs reflect the Company's own assumptions about the assumptions market participants would use in pricing the asset or liability, developed based on the best information available in the circumstances. The fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three broad levels, as follows: • Level 1 — Quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access. This category includes active exchange-traded funds, money market mutual funds, mutual funds and equity securities. • Level 2 — Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Such inputs include quoted prices in markets that are not active, quoted prices for similar assets and liabilities in active and inactive markets, inputs other than quoted prices that are observable for the asset or liability and inputs that are derived principally from or corroborated by observable market data by correlation or other means. This category includes most debt securities, U.S. government agency mortgage-backed securities, which consist of Ginnie Mae Home Equity Conversion Mortgages, and other interest-sensitive financial instruments. • Level 3 — Unobservable inputs for the asset or liability, where there is little, if any, observable market activity or data for the asset or liability. The following tables present the Company's fair value hierarchy for assets and liabilities measured at fair value on a recurring basis as of December 31, 2017 and September 30, 2017 (dollars in millions): As of December 31, 2017 Level 1 Level 2 Level 3 Fair Value Assets: Cash equivalents: Money market mutual funds $ 1,445 $ — $ — $ 1,445 Investments segregated for regulatory purposes: U.S. government debt securities — 3,594 — 3,594 U.S. government agency mortgage-backed securities — 1,433 — 1,433 Subtotal - Investments segregated for regulatory purposes — 5,027 — 5,027 Securities owned: U.S. government debt securities — 569 — 569 Equity securities 18 1 19 Other — 5 — 5 Subtotal - Securities owned 18 575 — 593 Investments available-for-sale: U.S. government debt securities — 99 — 99 Other assets: Pay-variable interest rate swaps (1) — 16 — 16 U.S. government debt securities — 1 — 1 Auction rate securities — — 1 1 Subtotal - Other assets — 17 1 18 Total assets at fair value $ 1,463 $ 5,718 $ 1 $ 7,182 Liabilities: Accounts payable and other liabilities: Pay-variable interest rate swaps (1) $ — $ 17 $ — $ 17 Securities sold, not yet purchased: Equity securities 5 — — 5 Total liabilities at fair value $ 5 $ 17 $ — $ 22 (1) See " Fair Value Hedging " in Note 8 for details. As of September 30, 2017 Level 1 Level 2 Level 3 Fair Value Assets: Cash equivalents: Money market mutual funds $ 1,081 $ — $ — $ 1,081 Investments segregated for regulatory purposes: U.S. government debt securities — 4,094 — 4,094 U.S. government agency mortgage-backed securities — 1,486 — 1,486 Subtotal - Investments segregated for regulatory purposes — 5,580 — 5,580 Securities owned: U.S. government debt securities — 498 — 498 Other 1 4 — 5 Subtotal - Securities owned 1 502 — 503 Investments available-for-sale: U.S. government debt securities — 746 — 746 Other assets: Pay-variable interest rate swaps (1) — 26 — 26 U.S. government debt securities — 1 — 1 Auction rate securities — — 1 1 Subtotal - Other assets — 27 1 28 Total assets at fair value $ 1,082 $ 6,855 $ 1 $ 7,938 Liabilities: Accounts payable and other liabilities: Pay-variable interest rate swaps (1) $ — $ 3 $ — $ 3 (1) See " Fair Value Hedging " in Note 8 for details. There were no transfers between any levels of the fair value hierarchy during the periods covered by this report. Valuation Techniques In general, and where applicable, the Company uses quoted prices in active markets for identical assets or liabilities to determine fair value. This pricing methodology applies to the Company's Level 1 assets and liabilities. If quoted prices in active markets for identical assets and liabilities are not available to determine fair value, then the Company uses quoted prices for similar assets and liabilities or inputs other than the quoted prices that are observable, either directly or indirectly. This pricing methodology applies to the Company's Level 2 assets and liabilities. Level 2 Measurements: Debt securities — Fair values for debt securities are based on prices obtained from an independent pricing vendor. The primary inputs to the valuation include quoted prices for similar assets in active markets, quoted prices for identical or similar assets in markets that are not active, contractual cash flows, benchmark yields and credit spreads. The Company validates the vendor pricing by periodically comparing it to pricing from another independent pricing service. The Company has not adjusted prices obtained from the independent pricing vendor for any periods presented in the condensed consolidated financial statements because no significant pricing differences have been observed. U.S. government agency mortgage-backed securities — Fair values for mortgage-backed securities are based on prices obtained from an independent pricing vendor. The primary inputs to the valuation include quoted prices for similar assets in active markets and in markets that are not active, a market derived prepayment curve, weighted average yields on the underlying collateral and spreads to benchmark indices. The Company validates the vendor pricing by periodically comparing it to pricing from two other independent sources. The Company has not adjusted prices obtained from the independent pricing vendor for any periods presented in the condensed consolidated financial statements because no significant pricing differences have been observed. Interest rate swaps — These derivatives are valued by the Company using a valuation model provided by a third-party service that incorporates interest rate yield curves, which are observable for substantially the full term of the contract. The valuation model is widely accepted in the financial services industry and does not involve significant judgment because most of the inputs are observable in the marketplace. Credit risk is not an input to the valuation because in each case the Company or counterparty has possession of collateral, in the form of cash or U.S. Treasury securities, in amounts equal to or exceeding the fair value of the interest rate swaps. The Company validates the third-party service valuations by comparing them to valuation models provided by the swap counterparties. Level 3 Measurements: The Company has no material assets or liabilities classified as Level 3 of the fair value hierarchy. Fair Value of Financial Instruments Not Recorded at Fair Value Receivable from/payable to brokers, dealers and clearing organizations, receivable from/payable to clients, receivable from/payable to affiliates, other receivables, accounts payable and other liabilities and notes payable are short-term in nature and accordingly are carried at amounts that approximate fair value. These financial instruments are recorded at or near their respective transaction prices and historically have been settled or converted to cash at approximately that value (categorized as Level 2 of the fair value hierarchy). Cash and investments segregated and on deposit for regulatory purposes and other assets include reverse repurchase agreements (securities purchased under agreements to resell). Reverse repurchase agreements are treated as collateralized financing transactions and are carried at amounts at which the securities will subsequently be resold, plus accrued interest. The Company's reverse repurchase agreements generally have a maturity of seven days and are collateralized by securities in amounts exceeding the carrying value of the resale agreements. Accordingly, the carrying value of reverse repurchase agreements approximates fair value (categorized as Level 2 of the fair value hierarchy). Cash and investments segregated and on deposit for regulatory purposes also includes cash held in demand deposit accounts and on deposit with futures commission merchants, for which the carrying values approximate the fair value (categorized as Level 1 of the fair value hierarchy). See Note 4 for a summary of cash and investments segregated and on deposit for regulatory purposes. Other assets included reverse repurchase agreements of $65 million as of September 30, 2017. Securities sold under agreements to repurchase (repurchase agreements) — Under repurchase agreements the Company receives cash from the counterparties and provides U.S. Treasury securities as collateral. The obligations to repurchase securities sold are reflected as a liability on the Condensed Consolidated Balance Sheets. Repurchase agreements are treated as collateralized financing transactions and are carried at amounts at which the securities will subsequently be repurchased, plus accrued interest. The Company's repurchase agreements are short-term in nature and accordingly the carrying value is a reasonable estimate of fair value (categorized as Level 2 of the fair value hierarchy). Long-term debt — As of December 31, 2017 , the Company's Senior Notes had an aggregate estimated fair value, based on quoted market prices (categorized as Level 1 of the fair value hierarchy), of approximately $2.62 billion , compared to the aggregate carrying value of the Senior Notes on the Condensed Consolidated Balance Sheet of $2.53 billion . As of September 30, 2017 , the Company's Senior Notes had an aggregate estimated fair value, based on quoted market prices, of approximately $2.63 billion , compared to the aggregate carrying value of the Senior Notes on the Condensed Consolidated Balance Sheet of $2.56 billion .

Offsetting Assets and Liabiliti

Offsetting Assets and Liabilities	3 Months Ended
	Dec. 31, 2017
Offsetting [Abstract]
Offsetting Assets and Liabilities	Offsetting Assets and Liabilities Substantially all of the Company's securities sold under agreements to repurchase (repurchase agreements), reverse repurchase agreements, securities borrowing and securities lending activity and derivative financial instruments are transacted under master agreements that may allow for net settlement in the ordinary course of business, as well as offsetting of all contracts with a given counterparty in the event of default by one of the parties. However, for financial statement purposes, the Company does not net balances related to these financial instruments. The following tables present information about the potential effect of rights of setoff associated with the Company's recognized assets and liabilities as of December 31, 2017 and September 30, 2017 (dollars in millions): December 31, 2017 Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet Gross Amounts of Recognized Assets and Liabilities Gross Amounts Offset in the Condensed Consolidated Balance Sheet Net Amounts Presented in the Condensed Consolidated Balance Sheet Financial Instruments (5) Collateral Received or Pledged (Including Cash) (6) Net Amount (7) Assets: Investments segregated for regulatory purposes: Reverse repurchase agreements $ 750 $ — $ 750 $ — $ (750 ) $ — Receivable from brokers, dealers and clearing organizations: Deposits paid for securities borrowed (1) 1,007 — 1,007 (135 ) (846 ) 26 Other assets: Pay-variable interest rate swaps 16 — 16 — (16 ) — Total $ 1,773 $ — $ 1,773 $ (135 ) $ (1,612 ) $ 26 Liabilities: Payable to brokers, dealers and clearing organizations: Deposits received for securities loaned (2)(3) $ 2,958 $ — $ 2,958 $ (137 ) $ (2,544 ) $ 277 Securities sold under agreements to repurchase ( 4 ) 97 — 97 2 (99 ) — Accounts payable and other liabilities: Pay-variable interest rate swaps 17 — 17 — (16 ) 1 Total $ 3,072 $ — $ 3,072 $ (135 ) $ (2,659 ) $ 278 September 30, 2017 Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet Gross Amounts of Recognized Assets and Liabilities Gross Amounts Offset in the Condensed Consolidated Balance Sheet Net Amounts Presented in the Condensed Consolidated Balance Sheet Financial Instruments (5) Collateral Received or Pledged (Including Cash) (6) Net Amount (7) Assets: Investments segregated for regulatory purposes: Reverse repurchase agreements $ 1,004 $ — $ 1,004 $ — $ (1,004 ) $ — Receivable from brokers, dealers Deposits paid for securities borrowed (1) 1,154 — 1,154 (110 ) (1,023 ) 21 Other assets: Pay-variable interest rate swaps 26 — 26 — (26 ) — Reverse repurchase agreements 65 — 65 — (65 ) — Total other assets 91 — 91 — (91 ) — Total $ 2,249 $ — $ 2,249 $ (110 ) $ (2,118 ) $ 21 Liabilities: Payable to brokers, dealers and clearing organizations: Deposits received for securities loaned (2)(3) $ 2,449 $ — $ 2,449 $ (112 ) $ (2,113 ) $ 224 Securities sold under agreements to repurchase ( 4 ) 97 — 97 2 (99 ) — Accounts payable and other liabilities: Pay-variable interest rate swaps 3 — 3 — (1 ) 2 Total $ 2,549 $ — $ 2,549 $ (110 ) $ (2,213 ) $ 226 (1) Included in the gross amounts of deposits paid for securities borrowed is $577 million and $675 million as of December 31, 2017 and September 30, 2017 , respectively, transacted through a risk-sharing program with the OCC, which guarantees the return of cash to the Company. See "General Contingencies" in Note 10 for a discussion of the potential risks associated with securities borrowing transactions and how the Company mitigates those risks. (2) Included in the gross amounts of deposits received for securities loaned is $2.16 billion and $1.65 billion as of December 31, 2017 and September 30, 2017 , respectively, transacted through a risk-sharing program with the OCC, which guarantees the return of securities to the Company. See "General Contingencies" in Note 10 for a discussion of the potential risks associated with securities lending transactions and how the Company mitigates those risks. (3) Substantially all of the Company's securities lending transactions have a continuous contractual term and, upon notice by either party, may be terminated within two business days. The following table summarizes the Company's gross liability for securities lending transactions by the class of securities loaned (dollars in millions): December 31, September 30, Deposits received for securities loaned: Equity securities $ 2,513 $ 2,109 Exchange-traded funds 331 230 Closed-end funds 70 66 Other 44 44 Total $ 2,958 $ 2,449 (4) The collateral pledged includes available-for-sale U.S. government debt securities at fair value. All of the Company's repurchase agreements have a remaining contractual maturity of less than one year and, upon default by either party, may be terminated at the option of the non-defaulting party. See "General Contingencies" in Note 10 for a discussion of the potential risks associated with repurchase agreements and how the Company mitigates those risks. (5) Amounts represent recognized assets and liabilities that are subject to enforceable master agreements with rights of setoff. (6) Represents the fair value of collateral the Company had received or pledged under enforceable master agreements, limited for table presentation purposes to the net amount of the recognized assets due from or liabilities due to each counterparty. At December 31, 2017 and September 30, 2017 , the Company had received total collateral with a fair value of $1.76 billion and $2.26 billion , respectively, and pledged total collateral with a fair value of $2.79 billion and $2.32 billion , respectively. (7) Represents the amount for which, in the case of net recognized assets, the Company had not received collateral, and in the case of net recognized liabilities, the Company had not pledged collateral.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	3 Months Ended
	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The following table presents the net change in fair value recorded for each component of other comprehensive income (loss) before and after income tax for the periods indicated (dollars in millions): Three Months Ended December 31, 2017 2016 Before Tax Tax Effect Net of Tax Before Tax Tax Effect Net of Tax Investments available-for-sale: Unrealized loss $ (4 ) $ 1 $ (3 ) $ (10 ) $ 4 $ (6 ) Reclassification adjustment for realized losses included in net income (1) 11 (4 ) 7 — — — Net change in investments available-for-sale: 7 (3 ) 4 (10 ) 4 (6 ) Cash flow hedging instruments: Reclassification adjustment for portion of realized loss amortized to net income (2) 1 — 1 1 — 1 Net change in cash flow hedging instruments 1 — 1 1 — 1 Other comprehensive income (loss) $ 8 $ (3 ) $ 5 $ (9 ) $ 4 $ (5 ) (1) The before tax reclassification amount and related tax effect are included in loss on sale of investments and provision for income taxes, respectively, on the Condensed Consolidated Statement of Income. (2) The before tax reclassification amounts and the related tax effects are included in interest on borrowings and provision for income taxes, respectively, on the Condensed Consolidated Statements of Income. The following table presents after-tax changes in each component of accumulated other comprehensive loss for the periods indicated (dollars in millions): Three Months Ended December 31, 2017 2016 Investments available-for-sale: Beginning balance $ (5 ) $ — Other comprehensive loss before reclassifications (3 ) (6 ) Amounts reclassified from accumulated other comprehensive loss 7 — Current period change 4 (6 ) Ending balance $ (1 ) $ (6 ) Cash flow hedging instruments: Beginning balance $ (20 ) $ (22 ) Amount reclassified from accumulated other comprehensive loss 1 1 Ending balance $ (19 ) $ (21 ) Total accumulated other comprehensive loss: Beginning balance $ (25 ) $ (22 ) Current period change 5 (5 ) Ending balance $ (20 ) $ (27 )

Earnings Per Share

Earnings Per Share	3 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The difference between the numerator and denominator used in the computation of basic and diluted earnings per share consists of common stock equivalent shares related to stock-based compensation for all periods presented. There were no material antidilutive awards for the three months ended December 31, 2017 and 2016.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Transactions with TD and its Affiliates As a result of the Company's acquisition of TD Waterhouse Group, Inc. during fiscal 2006, TD became an affiliate of the Company. TD owned approximately 41% of the Company's common stock as of December 31, 2017 . Pursuant to the stockholders agreement between TD and the Company, TD has the right to designate five of twelve members of the Company's board of directors. The Company transacts business and has extensive relationships with TD and certain of its affiliates. Transactions with TD and its affiliates are discussed and summarized below. Insured Deposit Account Agreement The Company is party to an insured deposit account ("IDA") agreement with TD Bank USA, N.A. ("TD Bank USA"), TD Bank, N.A. and TD. Under the IDA agreement, TD Bank USA and TD Bank, N.A. (together, the "TD Depository Institutions") make available to clients of the Company FDIC-insured money market deposit accounts as either designated sweep vehicles or as non-sweep deposit accounts. The Company provides marketing, recordkeeping and support services for the TD Depository Institutions with respect to the money market deposit accounts. In exchange for providing these services, the TD Depository Institutions pay the Company an aggregate marketing fee based on the weighted average yield earned on the client IDA assets, less the actual interest paid to clients, a servicing fee to the TD Depository Institutions and the cost of FDIC insurance premiums. The current IDA agreement became effective as of January 1, 2013 and has an initial term expiring July 1, 2018 . It is automatically renewable for successive five -year terms, provided that it may be terminated by either the Company or the TD Depository Institutions by providing written notice of non-renewal at least two years prior to the initial expiration date or the expiration date of any subsequent renewal period. As of July 1, 2016, notice of non-renewal was not provided by either party, therefore the IDA agreement will automatically renew on July 1, 2018. The fee earned on the IDA agreement is calculated based on two primary components: (a) the yield on fixed-rate "notional" investments, based on prevailing fixed rates for identical balances and maturities in the interest rate swap market (generally LIBOR-based) at the time such investments were added to the IDA portfolio (including any adjustments required to adjust the variable rate leg of such swaps to a one -month reset frequency and the overall swap payment frequency to monthly) and (b) the yield on floating-rate investments. As of December 31, 2017 , the IDA portfolio was comprised of approximately 74% fixed-rate notional investments and 26% floating-rate investments. The IDA agreement provides that the Company may designate amounts and maturity dates for the fixed-rate notional investments in the IDA portfolio, subject to certain limitations. For example, if the Company designates that $100 million of deposits be invested in 5 -year fixed-rate investments, and on the day such investment is confirmed by the TD Depository Institutions the prevailing fixed yield for the applicable 5 -year U.S. dollar LIBOR-based swaps is 1.45% , then the Company will earn a gross fixed yield of 1.45% on that portion of the portfolio (before any deductions for interest paid to clients, the servicing fee to the TD Depository Institutions and the cost of FDIC insurance premiums). In the event that (1) the federal funds effective rate is established at 0.75% or greater and (2) the rate on 5 -year U.S. dollar interest rate swaps is equal to or greater than 1.50% for 20 consecutive business days, then the rate earned by the Company on new fixed-rate notional investments will be reduced by 20% of the excess of the 5 -year U.S. dollar swap rate over 1.50% , up to a maximum of 0.10% . The yield on floating-rate investments is calculated daily based on the greater of the following rates published by the Federal Reserve: (1) the interest rate paid by Federal Reserve Banks on balances held in excess of required reserve balances and contractual clearing balances under Regulation D and (2) the daily effective federal funds rate. The interest rates paid to clients are set by the TD Depository Institutions and are not linked to any index. The servicing fee to the TD Depository Institutions under the IDA agreement is equal to 25 basis points on the aggregate average daily balance in the IDA accounts, subject to adjustment as it relates to deposits of less than or equal to $20 billion kept in floating-rate investments or in fixed-rate notional investments with a maturity of up to 24 months ("short-term fixed-rate investments"). For such floating-rate and short-term fixed-rate investments, the servicing fee is equal to the difference of the interest rate earned on the investments less the FDIC premiums paid (in basis points), divided by two. The servicing fee has a floor of 3 basis points (subject to adjustment from time to time to reflect material changes to the TD Depository Institutions' leverage costs) and a maximum of 25 basis points. In the event the marketing fee computation results in a negative amount, the Company must pay the TD Depository Institutions the negative amount. This effectively results in the Company guaranteeing the TD Depository Institutions revenue equal to the servicing fee on the IDA agreement, plus the reimbursement of FDIC insurance premiums. The marketing fee computation under the IDA agreement is affected by many variables, including the type, duration, principal balance and yield of the fixed-rate and floating-rate investments, the prevailing interest rate environment, the amount of client deposits and the yield paid on client deposits. Because a negative marketing fee computation would arise only if there were extraordinary movements in many of these variables, the maximum potential amount of future payments the Company could be required to make under this arrangement cannot be reasonably estimated. Management believes the likelihood that the marketing fee calculation would result in a negative amount is remote. Accordingly, no contingent liability is carried on the Condensed Consolidated Balance Sheets for the IDA agreement. In the event the Company withdraws a notional investment prior to its maturity, the Company is required to reimburse the TD Depository Institutions an amount equal to the economic replacement value of the investment, as defined in the IDA agreement. In addition, the Company has various other services agreements and transactions with TD and its affiliates. The following tables summarize revenues and expenses resulting from transactions with TD and its affiliates for the periods indicated (dollars in millions): Revenues from TD and its Affiliates Statement of Income Classification Three months ended Description 2017 2016 Insured Deposit Account Agreement Bank deposit account fees $ 344 $ 245 Referral and Strategic Alliance Agreement Various 4 3 Mutual Fund Agreements Investment product fees 4 4 Other Various 4 2 Total revenues $ 356 $ 254 Expenses to TD and its Affiliates Statement of Income Classification Three months ended Description 2017 2016 Canadian Call Center Services Agreement (1) Professional services $ — $ 4 (1) The Company notified TD of its intent to not extend or renew the Canadian Call Center Services Agreement and services under this agreement ended by September 30, 2017 . The following table summarizes the classification and amount of receivables from and payables to TD and its affiliates on the Condensed Consolidated Balance Sheets resulting from related party transactions (dollars in millions): December 31, September 30, Assets: Receivable from affiliates $ 180 $ 110 Liabilities: Payable to brokers, dealers and clearing organizations $ 253 $ 37 Payable to affiliates 11 38 Payables to brokers, dealers and clearing organizations primarily relate to securities lending activity and are settled in accordance with customary contractual terms. Receivables from and payables to TD affiliates resulting from client cash sweep activity are generally settled in cash the next business day. Other receivables from and payables to affiliates of TD are generally settled in cash on a monthly basis. As of December 31, 2017, receivables from and payables to affiliates on the Condensed Consolidated Balance Sheets included $39 million and $44 million , respectively, in connection with the acquisition of Scottrade and are expected to be settled during fiscal 2018. As of September 30, 2017, receivables from and payables to affiliates included $27 million of assets acquired and $71 million of liabilities assumed, respectively, in connection with the acquisition of Scottrade.

Basis of Presentation (Policies

Basis of Presentation (Policies)	3 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The condensed consolidated financial statements include the accounts of TD Ameritrade Holding Corporation (the "Parent") and its wholly-owned subsidiaries (collectively, the "Company"). Intercompany balances and transactions have been eliminated.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements ASU 2016-09 — In March 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-09, Improvements to Employee Share-Based Payment Accounting . The guidance in ASU 2016-09 simplified several aspects of the accounting for share-based payment transactions, including: (1) recognize all excess tax benefits and tax deficiencies as income tax expense or benefit in the statement of income; (2) treat tax effects of exercised or vested awards as discrete items in the period in which they occur; (3) recognize excess tax benefits regardless of whether the benefit reduces taxes payable in the current period; (4) classify excess tax benefits with other income tax cash flows as an operating activity; (5) an entity can make an accounting policy election to either estimate the number of awards that are expected to vest or account for forfeitures when they occur; (6) the threshold to qualify for equity classification will permit withholding up to the maximum statutory rates in the applicable jurisdictions; and (7) classify cash paid by an employer when directly withholding shares for tax withholding purposes as a financing activity in the statement of cash flows. The Company adopted the amended accounting guidance as of October 1, 2017, and as a result, the Company's provision for income taxes was reduced by $3 million on its Condensed Consolidated Statement of Income for the three months ended December 31, 2017, due to the inclusion of excess tax benefits applied on a prospective basis. The future effects of excess tax benefits and tax deficiencies recognized in the Company's earnings will depend on the volume of equity compensation during a particular period and on the market price of the Company's common stock at the date the equity awards either vest or are exercised. In addition, the Company elected to retrospectively adopt the amendment to present excess tax benefits on share-based compensation as an operating activity on the statement of cash flows. This resulted in an increase in cash flows from operating activities and a decrease in cash flows from financing activities of $9 million on the Company's Condensed Consolidated Statement of Cash Flows for the three months ended December 31, 2016. For the purpose of recognizing compensation cost associated with share-based awards, the Company has elected to continue to follow its current practice of estimating forfeitures. None of the other provisions in this amended guidance had a significant impact on the Company's condensed consolidated financial statements.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements ASU 2016-13 — In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments . The main objective of ASU 2016-13 is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by an entity at each reporting date. To achieve this objective, the amendments in this update replace the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to develop credit loss estimates. ASU 2016-13 is effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years, with early adoption permitted. Therefore, ASU 2016-13 will be effective for the Company's fiscal year beginning on October 1, 2020, using a modified retrospective approach. The Company is currently assessing the impact this ASU will have on its condensed consolidated financial statements. ASU 2016-02 — In February 2016, the FASB issued ASU 2016-02, Leases . This ASU will supersede the guidance in Accounting Standards Codification ("ASC") Topic 840, Leases . Under ASU 2016-02, for lease arrangements exceeding a 12-month term, a lessee will be required to recognize in the balance sheet a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term. ASU 2016-02 will retain a distinction between finance and operating leases; however, the principal difference from the previous guidance is that lease assets and liabilities arising from operating leases will be recognized in the balance sheet. The recognition, measurement and presentation of expenses and cash flows arising from a lease by a lessee will not significantly change from current GAAP. The accounting applied by a lessor will be largely unchanged from that applied under current GAAP. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, and will require an entity to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. Therefore, ASU 2016-02 will be effective for the Company's fiscal year beginning October 1, 2019. Early adoption is permitted. The Company is currently assessing the impact of this ASU, but does not expect the standard to have a material impact on its net income. Upon adoption of ASU 2016-02, the Company expects to recognize right-of-use assets and lease liabilities for its operating leases, with initial measurement as defined by the ASU, in its Condensed Consolidated Balance Sheets. ASU 2014-09 — In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers , to clarify the principles of recognizing revenue from contracts with customers and to improve financial reporting by creating common revenue recognition guidance for U.S. GAAP and International Financial Reporting Standards. This ASU will supersede the revenue recognition requirements in ASC Topic 605, Revenue Recognition, and most industry-specific guidance. Entities are required to apply the following steps when recognizing revenue under ASU 2014-09: (1) identify the contract(s) with a customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when (or as) the entity satisfies a performance obligation. This ASU also requires additional disclosures related to the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. An entity may apply the amendments by using one of the following two methods: (1) retrospective application to each prior reporting period presented or (2) a modified retrospective approach, requiring the standard be applied only to the most current period presented, with the cumulative effect of initially applying the standard recognized at the date of initial application. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period, with early adoption permitted. Subsequent to issuing ASU 2014-09, the FASB has issued additional standards for the purpose of clarifying certain aspects of ASU 2014-09. The subsequently issued ASUs have the same effective date and transition requirements as ASU 2014-09. The Company plans to adopt the revenue recognition standard as of October 1, 2018. The guidance does not apply to revenue associated with financial instruments, such as interest revenue, which is accounted for under other GAAP. Accordingly, the Company does not expect the adoption of this standard to impact net interest revenue. While the Company has not yet identified any material changes in the timing of revenue recognition, its review is ongoing. The Company has not selected a transition method and continues to evaluate the potential impacts that these revenue recognition standards may have on its condensed consolidated financial statements, including the incremental costs of obtaining contracts, gross versus net reporting, and additional disclosure requirements.
Loss Contingencies (ASC) 450	ASC 450, Loss Contingencies, governs the recognition and disclosure of loss contingencies, including potential losses from legal and regulatory matters. ASC 450 categorizes loss contingencies using three terms based on the likelihood of occurrence of events that result in a loss: "probable" means that "the future event or events are likely to occur;" "remote" means that "the chance of the future event or events occurring is slight;" and "reasonably possible" means that "the chance of the future event or events occurring is more than remote but less than likely." Under ASC 450, the Company accrues for losses that are considered both probable and reasonably estimable.
Fair Value Measurement (ASC) 820-10	ASC 820-10, Fair Value Measurement , defines fair value as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. ASC 820-10 establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs reflect the assumptions market participants would use in pricing the asset or liability, developed based on market data obtained from sources independent of the Company. Unobservable inputs reflect the Company's own assumptions about the assumptions market participants would use in pricing the asset or liability, developed based on the best information available in the circumstances.

Business Acquisition (Tables)

Business Acquisition (Tables)	3 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Schedule of Total Purchase Price	The purchase price for Scottrade was comprised of the following (dollars in millions): TD Ameritrade Holding Corporation common stock issued to the Riney Stockholder and the Escrow Account (1) $ 1,261 Cash paid at closing (2) 3,073 Total purchase price $ 4,334 (1) Represents the value of 27,685,493 shares of the Company's common stock at a price of $45.55 per share. The per share value is based on the opening market price of the Company's common stock as of September 18, 2017, the Acquisition date. As discussed above, the shares held in the Escrow Account were sold and replaced with cash. (2) Includes $1.37 billion of Bank Merger Consideration paid by TD Bank, N.A. to Scottrade, which was used to fund a portion of the Acquisition.
Schedule of Provisional Purchase Price Allocation	The provisional purchase price allocation for Scottrade as of December 31, 2017 is summarized as follows (dollars in millions): Cash and cash equivalents (1) $ 1,785 Cash and investments segregated and on deposit for regulatory purposes 3,535 Receivable from brokers, dealers and clearing organizations 167 Receivable from clients, net 3,136 Receivable from affiliates 38 Other receivables 54 Securities owned 37 Property and equipment 133 Goodwill 1,730 Acquired intangible assets 974 Deferred tax assets 76 Other assets 34 Total assets acquired 11,699 Payable to brokers, dealers and clearing organizations (354 ) Payable to clients (6,248 ) Accounts payable and other liabilities (239 ) Payable to affiliates (88 ) Long-term debt (2) (436 ) Total liabilities assumed (7,365 ) Total provisional purchase price allocated $ 4,334 (1) Includes $1.37 billion of Bank Merger Consideration paid by TD Bank, N.A. to Scottrade, which was used to fund a portion of the Acquisition. (2) On the date of Acquisition, amounts owed by Scottrade under its 6.125% senior notes, including a prepayment premium, and the amount owed under its 6.18% secured loan were repaid by the Company.
Schedule of Pro Forma Financial Information (Unaudited)	The following table summarizes the unaudited pro forma financial information for the three months ended December 31, 2016, (dollars in millions): Three Months Ended December 31, 2016 (unaudited) Pro forma net revenues $ 1,072 Pro forma net income $ 219 Pro forma basic earnings per share $ 0.39 Pro forma diluted earnings per share $ 0.38

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	3 Months Ended
	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Summary of Cash and Cash Equivalents	The Company's cash and cash equivalents is summarized in the following table (dollars in millions): December 31, September 30, Corporate $ 771 $ 279 Broker-dealer subsidiaries 668 997 Futures commission merchant and forex dealer member subsidiary 102 98 Trust company subsidiary 74 79 Investment advisory subsidiaries 29 19 Total $ 1,644 $ 1,472

Cash and Investments Segregat26

Cash and Investments Segregated and on Deposit for Regulatory Purposes (Tables)	3 Months Ended
	Dec. 31, 2017
Restricted Cash and Investments [Abstract]
Cash and Investments Segregated and on Deposit for Regulatory Purposes	Cash and investments segregated and on deposit for regulatory purposes consists of the following (dollars in millions): December 31, September 30, Cash in demand deposit accounts $ 4,131 $ 3,653 U.S. government debt securities 3,544 4,019 U.S. government agency mortgage-backed securities 1,433 1,486 Reverse repurchase agreements (collateralized by U.S. government debt securities) 750 1,004 Cash on deposit with futures commission merchants 228 209 U.S. government debt securities on deposit with futures commission merchant 50 75 Total $ 10,136 $ 10,446

Goodwill (Tables)

Goodwill (Tables)	3 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes in the Carrying Amount of Goodwill	The following table summarizes changes in the carrying amount of goodwill for the three months ended December 31, 2017 (dollars in millions): Balance as of September 30, 2017 $ 4,213 Purchase accounting adjustments (1) (16 ) Balance as of December 31, 2017 $ 4,197 (1) The purchase accounting adjustments are primarily attributable to post-closing adjustments related to the Bank Merger Consideration and liabilities assumed in the acquisition of Scottrade. The purchase price allocation for the Scottrade acquisition is provisional as of December 31, 2017. The provisional amounts consist primarily of estimates related to property acquired and liabilities assumed. The Company expects to finalize the valuation of assets and liabilities as soon as practicable, but not later than one year from the date of acquisition.

Exit Liabilities (Tables)

Exit Liabilities (Tables)	3 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Summary of the Activity in Exit Liabilities During the Period	The following table summarizes activity in the Company's exit liabilities for the three-month period ended December 31, 2017, which are included in accounts payable and other liabilities on the Condensed Consolidated Balance Sheets (dollars in millions): Severance Pay and Other Termination Benefits Contract Termination and Other Costs Total Balance, September 30, 2017 $ 138 $ — $ 138 Exit liabilities assumed - post closing adjustments — 9 9 Costs incurred and charged to expense 82 (1) 98 (2) 180 Costs paid or otherwise settled (20 ) (95 ) (115 ) Balance, December 31, 2017 $ 200 $ 12 $ 212 (1) Costs incurred for severance pay and other termination benefits are included in employee compensation and benefits on the Condensed Consolidated Statements of Income. (2) Costs incurred for contract termination and other costs are primarily included in other operating expense on the Condensed Consolidated Statements of Income.
Summary of the Cumulative Amount of Acquisition-Related Exit Costs	The following table summarizes the cumulative amount of acquisition-related exit costs incurred by the Company related to the Scottrade acquisition as of December 31, 2017 (dollars in millions): Severance Pay and Other Termination Benefits Contract Termination and Other Costs Total Exit liabilities assumed in business acquisition $ 100 $ 9 $ 109 Employee compensation and benefits 116 — 116 Communications — 1 1 Occupancy and equipment costs — 2 2 Professional services — 8 8 Other operating expense — 85 85 Other non-operating expense — 2 2 Total $ 216 $ 107 $ 323

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Deferred Tax Assets (Liabilities)	Deferred tax assets (liabilities) are comprised of the following for the periods indicated (dollars in millions): December 31, 2017 September 30, 2017 Deferred tax assets: Accrued and other liabilities $ 67 $ 131 Stock-based compensation 16 28 Unrecognized loss on cash flow hedging instruments 8 15 Allowance for doubtful accounts 3 6 Intangible assets, state tax benefit 5 5 Operating loss carryforwards 1 1 Gross deferred tax assets 100 186 Less: Valuation allowance (1 ) (1 ) Net deferred tax assets 99 185 Deferred tax liabilities: Acquired intangible assets (219 ) (331 ) Property and equipment (38 ) (35 ) Prepaid expenses (23 ) (11 ) Other deferred tax liabilities (1 ) (1 ) Total deferred tax liabilities (281 ) (378 ) Net deferred tax liabilities $ (182 ) $ (193 )

Long-term Debt and Other Borr30

Long-term Debt and Other Borrowings (Tables)	3 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Long-term Debt and Other Borrowings	Long-term debt and other borrowings consist of the following (dollars in millions): December 31, 2017 Face Value Unamortized Discounts and Debt Issuance Costs Fair Value Adjustment (1) Net Carrying Value Other borrowings: Notes payable $ 50 $ — $ — $ 50 Securities sold under agreements to repurchase 97 — — 97 Subtotal - Other borrowings 147 — — 147 Long-term debt: Senior Notes: 5.600% Notes due 2019 500 (1 ) 11 510 2.950% Notes due 2022 750 (5 ) (7 ) 738 3.625% Notes due 2025 500 (3 ) 5 502 3.300% Notes due 2027 800 (9 ) (10 ) 781 Subtotal - Long-term debt 2,550 (18 ) (1 ) 2,531 Total long-term debt and other borrowings $ 2,697 $ (18 ) $ (1 ) $ 2,678 September 30, 2017 Face Value Unamortized Discounts and Debt Issuance Costs Fair Value Adjustment (1) Net Carrying Value Other borrowings: Securities sold under agreements to repurchase $ 97 $ — $ — $ 97 Long-term debt: Senior Notes: 5.600% Notes due 2019 500 (1 ) 15 514 2.950% Notes due 2022 750 (5 ) — 745 3.625% Notes due 2025 500 (3 ) 11 508 3.300% Notes due 2027 800 (9 ) (3 ) 788 Subtotal - Long-term debt 2,550 (18 ) 23 2,555 Total long-term debt and other borrowings $ 2,647 $ (18 ) $ 23 $ 2,652 (1) Fair value adjustments relate to changes in the fair value of the debt while in a fair value hedging relationship. See " Fair Value Hedging " below.
Schedule of Gains and Losses Resulting from Changes in Fair Value of Interest Rate Swaps and Hedged Fixed Rate Debt	The following table summarizes gains and losses resulting from changes in the fair value of interest rate swaps designated as fair value hedges and the hedged fixed-rate debt for the periods indicated (dollars in millions): Three Months Ended December 31, 2017 2016 Gain (loss) on fair value of interest rate swaps $ (24 ) $ (49 ) Gain (loss) on fair value of hedged fixed-rate debt 24 49 Net gain (loss) recorded in interest on borrowings $ — $ —
Schedule of Fair Value of Outstanding Derivatives Designated as Hedging Instruments in the Condensed Consolidated Balance Sheets	The following table summarizes the fair value of outstanding derivatives designated as hedging instruments on the Condensed Consolidated Balance Sheets (dollars in millions): December 31, September 30, Pay-variable interest rate swaps designated as fair value hedges: Other assets $ 16 $ 26 Accounts payable and other liabilities $ (17 ) $ (3 )

Capital Requirements (Tables)

Capital Requirements (Tables)	3 Months Ended
	Dec. 31, 2017
Regulatory Capital Requirements [Abstract]
Net Capital and Net Capital Requirements for Company's Broker-dealer Subsidiaries	Net capital and net capital requirements for the Company's broker-dealer subsidiaries are summarized in the following tables (dollars in millions): TD Ameritrade Clearing, Inc. Date Net Capital Required Net Capital (2% of Aggregate Debit Balances) Net Capital in Excess of Required Net Capital Ratio of Net Capital to Aggregate Debit Balances December 31, 2017 $ 1,704 $ 362 $ 1,342 9.42 % September 30, 2017 $ 1,595 $ 340 $ 1,255 9.39 % TD Ameritrade, Inc. Date Net Capital Required Net Capital (Minimum Dollar Requirement) Net Capital in Excess of Required Net Capital December 31, 2017 $ 186 $ 0.25 $ 186 September 30, 2017 $ 155 $ 0.25 $ 155 Scottrade, Inc. Date Net Capital Required Net Capital (2% of Aggregate Debit Balances) Net Capital in Excess of Required Net Capital Ratio of Net Capital to Aggregate Debit Balances December 31, 2017 $ 367 $ 73 $ 294 10.04 % September 30, 2017 $ 348 $ 70 $ 278 9.99 %
Adjusted Net Capital and Adjusted Net Capital Requirements for Company's FCM and FDM Subsidiary	Adjusted net capital and adjusted net capital requirements for the Company's FCM and FDM subsidiary are summarized in the following table (dollars in millions): TD Ameritrade Futures & Forex LLC Date Adjusted Net Capital Required Adjusted Net Capital ($20 Million Plus 5% of All Foreign Exchange Liabilities Owed to Forex Clients in Excess of $10 Million) Adjusted Net Capital in Excess of Required Adjusted Net Capital December 31, 2017 $ 84 $ 23 $ 61 September 30, 2017 $ 77 $ 22 $ 55

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Summary of Collateral Available, Loaned or Repledged	The following table summarizes the fair values of client margin securities and stock borrowings that were available to the Company to utilize as collateral on various borrowings or for other purposes, and the amount of that collateral loaned or repledged by the Company (dollars in billions): December 31, September 30, Client margin securities $ 25.6 $ 23.8 Stock borrowings 1.0 1.2 Total collateral available $ 26.6 $ 25.0 Collateral loaned $ 3.0 $ 2.4 Collateral repledged 7.8 4.1 Total collateral loaned or repledged $ 10.8 $ 6.5
Summary of Cash Deposited with and Securities Pledged to Clearinghouses	The following table summarizes cash deposited with and securities pledged to clearinghouses by the Company (dollars in millions): Assets Balance Sheet Classification December 31, September 30, Cash Receivable from brokers, dealers and clearing organizations $ 246 $ 151 U.S. government debt securities Securities owned, at fair value 469 398 Total $ 715 $ 549

Fair Value Disclosures (Tables)

Fair Value Disclosures (Tables)	3 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Hierarchy for Assets and Liabilities Measured on Recurring Basis	The following tables present the Company's fair value hierarchy for assets and liabilities measured at fair value on a recurring basis as of December 31, 2017 and September 30, 2017 (dollars in millions): As of December 31, 2017 Level 1 Level 2 Level 3 Fair Value Assets: Cash equivalents: Money market mutual funds $ 1,445 $ — $ — $ 1,445 Investments segregated for regulatory purposes: U.S. government debt securities — 3,594 — 3,594 U.S. government agency mortgage-backed securities — 1,433 — 1,433 Subtotal - Investments segregated for regulatory purposes — 5,027 — 5,027 Securities owned: U.S. government debt securities — 569 — 569 Equity securities 18 1 19 Other — 5 — 5 Subtotal - Securities owned 18 575 — 593 Investments available-for-sale: U.S. government debt securities — 99 — 99 Other assets: Pay-variable interest rate swaps (1) — 16 — 16 U.S. government debt securities — 1 — 1 Auction rate securities — — 1 1 Subtotal - Other assets — 17 1 18 Total assets at fair value $ 1,463 $ 5,718 $ 1 $ 7,182 Liabilities: Accounts payable and other liabilities: Pay-variable interest rate swaps (1) $ — $ 17 $ — $ 17 Securities sold, not yet purchased: Equity securities 5 — — 5 Total liabilities at fair value $ 5 $ 17 $ — $ 22 (1) See " Fair Value Hedging " in Note 8 for details. As of September 30, 2017 Level 1 Level 2 Level 3 Fair Value Assets: Cash equivalents: Money market mutual funds $ 1,081 $ — $ — $ 1,081 Investments segregated for regulatory purposes: U.S. government debt securities — 4,094 — 4,094 U.S. government agency mortgage-backed securities — 1,486 — 1,486 Subtotal - Investments segregated for regulatory purposes — 5,580 — 5,580 Securities owned: U.S. government debt securities — 498 — 498 Other 1 4 — 5 Subtotal - Securities owned 1 502 — 503 Investments available-for-sale: U.S. government debt securities — 746 — 746 Other assets: Pay-variable interest rate swaps (1) — 26 — 26 U.S. government debt securities — 1 — 1 Auction rate securities — — 1 1 Subtotal - Other assets — 27 1 28 Total assets at fair value $ 1,082 $ 6,855 $ 1 $ 7,938 Liabilities: Accounts payable and other liabilities: Pay-variable interest rate swaps (1) $ — $ 3 $ — $ 3 (1) See " Fair Value Hedging " in Note 8 for details.

Offsetting Assets and Liabili34

Offsetting Assets and Liabilities (Tables)	3 Months Ended
	Dec. 31, 2017
Offsetting [Abstract]
Effect of Rights of Setoff Associated with Company's Recognized Assets and Liabilities	The following tables present information about the potential effect of rights of setoff associated with the Company's recognized assets and liabilities as of December 31, 2017 and September 30, 2017 (dollars in millions): December 31, 2017 Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet Gross Amounts of Recognized Assets and Liabilities Gross Amounts Offset in the Condensed Consolidated Balance Sheet Net Amounts Presented in the Condensed Consolidated Balance Sheet Financial Instruments (5) Collateral Received or Pledged (Including Cash) (6) Net Amount (7) Assets: Investments segregated for regulatory purposes: Reverse repurchase agreements $ 750 $ — $ 750 $ — $ (750 ) $ — Receivable from brokers, dealers and clearing organizations: Deposits paid for securities borrowed (1) 1,007 — 1,007 (135 ) (846 ) 26 Other assets: Pay-variable interest rate swaps 16 — 16 — (16 ) — Total $ 1,773 $ — $ 1,773 $ (135 ) $ (1,612 ) $ 26 Liabilities: Payable to brokers, dealers and clearing organizations: Deposits received for securities loaned (2)(3) $ 2,958 $ — $ 2,958 $ (137 ) $ (2,544 ) $ 277 Securities sold under agreements to repurchase ( 4 ) 97 — 97 2 (99 ) — Accounts payable and other liabilities: Pay-variable interest rate swaps 17 — 17 — (16 ) 1 Total $ 3,072 $ — $ 3,072 $ (135 ) $ (2,659 ) $ 278 September 30, 2017 Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet Gross Amounts of Recognized Assets and Liabilities Gross Amounts Offset in the Condensed Consolidated Balance Sheet Net Amounts Presented in the Condensed Consolidated Balance Sheet Financial Instruments (5) Collateral Received or Pledged (Including Cash) (6) Net Amount (7) Assets: Investments segregated for regulatory purposes: Reverse repurchase agreements $ 1,004 $ — $ 1,004 $ — $ (1,004 ) $ — Receivable from brokers, dealers Deposits paid for securities borrowed (1) 1,154 — 1,154 (110 ) (1,023 ) 21 Other assets: Pay-variable interest rate swaps 26 — 26 — (26 ) — Reverse repurchase agreements 65 — 65 — (65 ) — Total other assets 91 — 91 — (91 ) — Total $ 2,249 $ — $ 2,249 $ (110 ) $ (2,118 ) $ 21 Liabilities: Payable to brokers, dealers and clearing organizations: Deposits received for securities loaned (2)(3) $ 2,449 $ — $ 2,449 $ (112 ) $ (2,113 ) $ 224 Securities sold under agreements to repurchase ( 4 ) 97 — 97 2 (99 ) — Accounts payable and other liabilities: Pay-variable interest rate swaps 3 — 3 — (1 ) 2 Total $ 2,549 $ — $ 2,549 $ (110 ) $ (2,213 ) $ 226 (1) Included in the gross amounts of deposits paid for securities borrowed is $577 million and $675 million as of December 31, 2017 and September 30, 2017 , respectively, transacted through a risk-sharing program with the OCC, which guarantees the return of cash to the Company. See "General Contingencies" in Note 10 for a discussion of the potential risks associated with securities borrowing transactions and how the Company mitigates those risks. (2) Included in the gross amounts of deposits received for securities loaned is $2.16 billion and $1.65 billion as of December 31, 2017 and September 30, 2017 , respectively, transacted through a risk-sharing program with the OCC, which guarantees the return of securities to the Company. See "General Contingencies" in Note 10 for a discussion of the potential risks associated with securities lending transactions and how the Company mitigates those risks. (3) Substantially all of the Company's securities lending transactions have a continuous contractual term and, upon notice by either party, may be terminated within two business days. The following table summarizes the Company's gross liability for securities lending transactions by the class of securities loaned (dollars in millions): December 31, September 30, Deposits received for securities loaned: Equity securities $ 2,513 $ 2,109 Exchange-traded funds 331 230 Closed-end funds 70 66 Other 44 44 Total $ 2,958 $ 2,449 (4) The collateral pledged includes available-for-sale U.S. government debt securities at fair value. All of the Company's repurchase agreements have a remaining contractual maturity of less than one year and, upon default by either party, may be terminated at the option of the non-defaulting party. See "General Contingencies" in Note 10 for a discussion of the potential risks associated with repurchase agreements and how the Company mitigates those risks. (5) Amounts represent recognized assets and liabilities that are subject to enforceable master agreements with rights of setoff. (6) Represents the fair value of collateral the Company had received or pledged under enforceable master agreements, limited for table presentation purposes to the net amount of the recognized assets due from or liabilities due to each counterparty. At December 31, 2017 and September 30, 2017 , the Company had received total collateral with a fair value of $1.76 billion and $2.26 billion , respectively, and pledged total collateral with a fair value of $2.79 billion and $2.32 billion , respectively. (7) Represents the amount for which, in the case of net recognized assets, the Company had not received collateral, and in the case of net recognized liabilities, the Company had not pledged collateral.
Disaggregation of Gross Secured Lending Transactions	The following table summarizes the Company's gross liability for securities lending transactions by the class of securities loaned (dollars in millions): December 31, September 30, Deposits received for securities loaned: Equity securities $ 2,513 $ 2,109 Exchange-traded funds 331 230 Closed-end funds 70 66 Other 44 44 Total $ 2,958 $ 2,449

Accumulated Other Comprehensi35

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Other Comprehensive Income (Loss)	The following table presents the net change in fair value recorded for each component of other comprehensive income (loss) before and after income tax for the periods indicated (dollars in millions): Three Months Ended December 31, 2017 2016 Before Tax Tax Effect Net of Tax Before Tax Tax Effect Net of Tax Investments available-for-sale: Unrealized loss $ (4 ) $ 1 $ (3 ) $ (10 ) $ 4 $ (6 ) Reclassification adjustment for realized losses included in net income (1) 11 (4 ) 7 — — — Net change in investments available-for-sale: 7 (3 ) 4 (10 ) 4 (6 ) Cash flow hedging instruments: Reclassification adjustment for portion of realized loss amortized to net income (2) 1 — 1 1 — 1 Net change in cash flow hedging instruments 1 — 1 1 — 1 Other comprehensive income (loss) $ 8 $ (3 ) $ 5 $ (9 ) $ 4 $ (5 ) (1) The before tax reclassification amount and related tax effect are included in loss on sale of investments and provision for income taxes, respectively, on the Condensed Consolidated Statement of Income. (2) The before tax reclassification amounts and the related tax effects are included in interest on borrowings and provision for income taxes, respectively, on the Condensed Consolidated Statements of Income.
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table presents after-tax changes in each component of accumulated other comprehensive loss for the periods indicated (dollars in millions): Three Months Ended December 31, 2017 2016 Investments available-for-sale: Beginning balance $ (5 ) $ — Other comprehensive loss before reclassifications (3 ) (6 ) Amounts reclassified from accumulated other comprehensive loss 7 — Current period change 4 (6 ) Ending balance $ (1 ) $ (6 ) Cash flow hedging instruments: Beginning balance $ (20 ) $ (22 ) Amount reclassified from accumulated other comprehensive loss 1 1 Ending balance $ (19 ) $ (21 ) Total accumulated other comprehensive loss: Beginning balance $ (25 ) $ (22 ) Current period change 5 (5 ) Ending balance $ (20 ) $ (27 )

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	The following tables summarize revenues and expenses resulting from transactions with TD and its affiliates for the periods indicated (dollars in millions): Revenues from TD and its Affiliates Statement of Income Classification Three months ended Description 2017 2016 Insured Deposit Account Agreement Bank deposit account fees $ 344 $ 245 Referral and Strategic Alliance Agreement Various 4 3 Mutual Fund Agreements Investment product fees 4 4 Other Various 4 2 Total revenues $ 356 $ 254 Expenses to TD and its Affiliates Statement of Income Classification Three months ended Description 2017 2016 Canadian Call Center Services Agreement (1) Professional services $ — $ 4 (1) The Company notified TD of its intent to not extend or renew the Canadian Call Center Services Agreement and services under this agreement ended by September 30, 2017 . The following table summarizes the classification and amount of receivables from and payables to TD and its affiliates on the Condensed Consolidated Balance Sheets resulting from related party transactions (dollars in millions): December 31, September 30, Assets: Receivable from affiliates $ 180 $ 110 Liabilities: Payable to brokers, dealers and clearing organizations $ 253 $ 37 Payable to affiliates 11 38

Basis of Presentation - Additio

Basis of Presentation - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Provision for income tax expense (benefit)	$ 6	$ 123
ASU 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Provision for income tax expense (benefit)	$ (3)
Prior period reclassification adjustment - from cash flows from financing activities to cash flows from operating activities		$ 9

Business Acquisition - Provisio

Business Acquisition - Provisional Purchase Price for Acquisition (Detail) - Scottrade [Member] $ / shares in Units, $ in Millions	Sep. 18, 2017USD ($)$ / sharesshares
Business Acquisition [Line Items]
TD Ameritrade Holding Corporation common stock issued to the Riney Stockholder and the Escrow Account	$ 1,261
Cash paid at closing	3,073
Total purchase price	4,334
Bank merger consideration amount paid by TD Bank, N.A. to Scottrade after post-closing adjustments	$ 1,370
Riney Stockholder [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Equity interests issued in connection with the acquisition, number of shares, total | shares	27,685,493
Equity interests issued in connection with the acquisition, share price | $ / shares	$ 45.55

Business Acquisition - Provis39

Business Acquisition - Provisional Fair Values of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017	Sep. 18, 2017
Business Acquisition [Line Items]
Goodwill	$ 4,197	$ 4,213
Scottrade [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	1,785
Cash and investments segregated and on deposit for regulatory purposes	3,535
Receivable from brokers and dealers and clearing organizations	167
Receivable from clients, net	3,136
Receivable from affiliates	38
Other receivables	54
Securities owned	37
Property and equipment	133
Goodwill	1,730
Acquired intangible assets	974
Deferred tax assets	76
Other assets	34
Total assets acquired	11,699
Payable to brokers and dealers and clearing organizations	(354)
Payable to clients	(6,248)
Accounts payable and other liabilities	(239)
Payable to affiliates	(88)
Long-term debt	(436)
Total liabilities assumed	(7,365)
Total provisional purchase price allocated	$ 4,334
Bank merger consideration amount paid by TD Bank, N.A. to Scottrade, included in Cash and cash equivalents after post-closing adjustments			$ 1,370
Scottrade [Member] | Senior Notes [Member] | 6.125% Senior Notes [Member]
Business Acquisition [Line Items]
Interest rate, stated percentage			6.125%
Scottrade [Member] | Secured Debt [Member] | 6.18% Secured Loan [Member]
Business Acquisition [Line Items]
Interest rate, stated percentage			6.18%

Business Acquisition - Pro Form

Business Acquisition - Pro Forma Financial Information (Unaudited) (Detail) - Scottrade [Member] $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 31, 2016USD ($)$ / shares
Pro Forma Financial Information (Unaudited):
Pro forma net revenues | $	$ 1,072
Pro forma net income | $	$ 219
Pro forma basic earnings per share | $ / shares	$ 0.39
Pro forma diluted earnings per share | $ / shares	$ 0.38

Business Acquisition - Addition

Business Acquisition - Additional Information (Detail) $ / shares in Units, $ in Millions	Dec. 14, 2017	Sep. 18, 2017USD ($)branch$ / sharesshares	Dec. 31, 2017USD ($)	Sep. 30, 2017
Business Acquisition [Line Items]
Purchase accounting adjustments, reduction to goodwill			$ (16)
Senior Notes [Member] | 3.300% Notes due 2027 [Member]
Business Acquisition [Line Items]
Interest rate, stated percentage			3.30%	3.30%
Debt instrument, issuance date			Apr. 27, 2017
Scottrade [Member]
Business Acquisition [Line Items]
Effective date of acquisition		Sep. 18, 2017
Date of Agreement and Plan of Merger agreement		Oct. 24, 2016
Approximate number of branch locations acquired | branch		500
Bank merger consideration amount paid by TD Bank, N.A. to Scottrade after post-closing adjustments		$ 1,370
Cash paid at acquisition closing, subject to closing adjustments		$ 3,073
Purchase accounting adjustments, reduction to goodwill			$ (16)
Goodwill associated with the Acquisition, expected to be deductible for income tax purposes			$ 1,600
Scottrade [Member] | TD [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Stock issued, number of shares | shares		11,074,197
Stock issued, price per share | $ / shares		$ 36.12
Stock issued, value of shares		$ 400
Scottrade [Member] | Riney Stockholder [Member]
Business Acquisition [Line Items]
Stockholders agreement, expiration date	Dec. 14, 2017
Scottrade [Member] | Riney Stockholder [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Equity interests issued in connection with the acquisition, number of shares, total | shares		27,685,493
Equity interests issued in connection with the acquisition, number of shares, shares deposited in escrow | shares		1,736,815

Cash and Cash Equivalents - Sum

Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 1,644	$ 1,472	$ 1,662	$ 1,855
Corporate [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	771	279
Broker-dealer subsidiaries [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	668	997
Futures commission merchant and forex dealer member subsidiary [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	102	98
Trust company subsidiary [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	74	79
Investment advisory subsidiaries [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 29	$ 19

Cash and Investments Segregat43

Cash and Investments Segregated and on Deposit for Regulatory Purposes (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and investments segregated and on deposit for regulatory purposes	$ 10,136	$ 10,446
Cash in demand deposit accounts [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and investments segregated and on deposit for regulatory purposes	4,131	3,653
U.S. government debt securities [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and investments segregated and on deposit for regulatory purposes	3,544	4,019
U.S. government agency mortgage-backed securities [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and investments segregated and on deposit for regulatory purposes	1,433	1,486
Reverse repurchase agreements (collateralized by U.S. government debt securities) [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and investments segregated and on deposit for regulatory purposes	750	1,004
Cash on deposit with futures commission merchants [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and investments segregated and on deposit for regulatory purposes	228	209
U.S. government debt securities on deposit with futures commission merchant [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and investments segregated and on deposit for regulatory purposes	$ 50	$ 75

Goodwill - Schedule of Changes

Goodwill - Schedule of Changes in the Carrying Amount of Goodwill (Details) $ in Millions	3 Months Ended
	Dec. 31, 2017USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, beginning balance	$ 4,213
Purchase accounting adjustments	(16)
Goodwill, ending balance	$ 4,197

Exit Liabilities - Summary of t

Exit Liabilities - Summary of the Activity in Exit Liabilities During the Period (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2017USD ($)
Restructuring Reserve [Roll Forward]
Beginning balance	$ 138
Exit liabilities assumed - post closing adjustments	9
Costs incurred and charged to expense	180
Costs paid or otherwise settled	(115)
Ending balance	212
Severance Pay and Other Termination Benefits [Member]
Restructuring Reserve [Roll Forward]
Beginning balance	138
Exit liabilities assumed - post closing adjustments	0
Costs incurred and charged to expense	82
Costs paid or otherwise settled	(20)
Ending balance	200
Contract Termination and Other Costs [Member]
Restructuring Reserve [Roll Forward]
Beginning balance	0
Exit liabilities assumed - post closing adjustments	9
Costs incurred and charged to expense	98
Costs paid or otherwise settled	(95)
Ending balance	$ 12

Exit Liabilities - Summary of46

Exit Liabilities - Summary of the Cumulative Acquisition-Related Exit Costs (Detail) - Scottrade [Member] $ in Millions	3 Months Ended
	Dec. 31, 2017USD ($)
Restructuring Cost and Reserve [Line Items]
Exit liabilities assumed in business acquisition	$ 109
Total cumulative exit liabilities assumed and acquisition-related exit costs incurred	323
Employee Compensation and Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	116
Communications [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	1
Occupancy and Equipment Costs [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	2
Professional Services [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	8
Other Operating Expense [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	85
Other Non-operating Expense [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	2
Severance Pay and Other Termination Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Exit liabilities assumed in business acquisition	100
Total cumulative exit liabilities assumed and acquisition-related exit costs incurred	216
Severance Pay and Other Termination Benefits [Member] | Employee Compensation and Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	116
Severance Pay and Other Termination Benefits [Member] | Communications [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	0
Severance Pay and Other Termination Benefits [Member] | Occupancy and Equipment Costs [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	0
Severance Pay and Other Termination Benefits [Member] | Professional Services [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	0
Severance Pay and Other Termination Benefits [Member] | Other Operating Expense [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	0
Severance Pay and Other Termination Benefits [Member] | Other Non-operating Expense [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	0
Contract Termination and Other Costs [Member]
Restructuring Cost and Reserve [Line Items]
Exit liabilities assumed in business acquisition	9
Total cumulative exit liabilities assumed and acquisition-related exit costs incurred	107
Contract Termination and Other Costs [Member] | Employee Compensation and Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	0
Contract Termination and Other Costs [Member] | Communications [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	1
Contract Termination and Other Costs [Member] | Occupancy and Equipment Costs [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	2
Contract Termination and Other Costs [Member] | Professional Services [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	8
Contract Termination and Other Costs [Member] | Other Operating Expense [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	85
Contract Termination and Other Costs [Member] | Other Non-operating Expense [Member]
Restructuring Cost and Reserve [Line Items]
Cumulative acquisition-related exit costs incurred since the date of acquisition	$ 2

Exit Liabilities - Additional I

Exit Liabilities - Additional Information (Detail) - Scottrade [Member] $ in Millions	Dec. 31, 2017USD ($)
Minimum [Member]
Restructuring Cost and Reserve [Line Items]
Expected acquisition-related exit costs	$ 455
Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Expected acquisition-related exit costs	545
Severance Pay and Other Termination Benefits [Member] | Minimum [Member]
Restructuring Cost and Reserve [Line Items]
Expected acquisition-related exit costs	300
Severance Pay and Other Termination Benefits [Member] | Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Expected acquisition-related exit costs	320
Contract Termination and Other Costs [Member] | Minimum [Member]
Restructuring Cost and Reserve [Line Items]
Expected acquisition-related exit costs	155
Contract Termination and Other Costs [Member] | Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Expected acquisition-related exit costs	$ 225

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Deferred tax assets:
Accrued and other liabilities	$ 67	$ 131
Stock-based compensation	16	28
Unrecognized loss on cash flow hedging instruments	8	15
Allowance for doubtful accounts	3	6
Intangible assets, state tax benefit	5	5
Operating loss carryforwards	1	1
Gross deferred tax assets	100	186
Less: Valuation allowance	(1)	(1)
Net deferred tax assets	99	185
Deferred tax liabilities:
Acquired intangible assets	(219)	(331)
Property and equipment	(38)	(35)
Prepaid expenses	(23)	(11)
Other deferred tax liabilities	(1)	(1)
Total deferred tax liabilities	(281)	(378)
Net deferred tax liabilities	$ (182)	$ (193)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Income tax rate applied during period of change in U.S. federal corporate tax rate	27.00%
Effective income tax rate	2.00%	36.30%
Estimated net favorable deferred income tax adjustment related to Tax Cuts and Jobs Act	$ 68
Provision for income tax expense (benefit)	6	$ 123
Net favorable resolutions of state income tax matters	10	$ 7
Favorable benefit primarily related to acquisition-related exit costs	6
Unfavorable remeasurement of uncertain tax positions related to federal incentives	$ 9
Net favorable per share impact on earnings	$ 0.14	$ 0.01
Effective income tax rate, fiscal year estimate as a result of the Tax Cuts and Jobs Act	22.00%
Effective income tax rate, remainder of fiscal year estimate as a result of the Tax Cuts and Jobs Act	27.00%
Pre-Tax Cuts and Jobs Act [Member]
Income Taxes [Line Items]
U.S. federal corporate income tax rate	35.00%
Post-Tax Cuts and Jobs Act [Member]
Income Taxes [Line Items]
U.S. federal corporate income tax rate	21.00%
ASU 2016-09 [Member]
Income Taxes [Line Items]
Provision for income tax expense (benefit)	$ (3)
Minimum [Member]
Income Taxes [Line Items]
Income tax rates at which deferred tax balance are expected to reverse in the future	24.00%
Maximum [Member]
Income Taxes [Line Items]
Income tax rates at which deferred tax balance are expected to reverse in the future	25.00%

Long-term Debt and Other Borr50

Long-term Debt and Other Borrowings - Schedule of Long-Term Debt and Other Borrowings (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Debt Instrument [Line Items]
Face Value	$ 2,697	$ 2,647
Unamortized Discounts and Debt Issuance Costs	(18)	(18)
Fair Value Adjustment	(1)	23
Net Carrying Value	2,678	2,652
Senior Notes [Member]
Debt Instrument [Line Items]
Face Value	2,550	2,550
Unamortized Discounts and Debt Issuance Costs	(18)	(18)
Fair Value Adjustment	(1)	23
Net Carrying Value	2,531	2,555
Senior Notes [Member] | 5.600% Notes due 2019 [Member]
Debt Instrument [Line Items]
Face Value	500	500
Unamortized Discounts and Debt Issuance Costs	(1)	(1)
Fair Value Adjustment	11	15
Net Carrying Value	$ 510	$ 514
Interest rate, stated percentage	5.60%	5.60%
Senior Notes [Member] | 2.950% Notes due 2022 [Member]
Debt Instrument [Line Items]
Face Value	$ 750	$ 750
Unamortized Discounts and Debt Issuance Costs	(5)	(5)
Fair Value Adjustment	(7)	0
Net Carrying Value	$ 738	$ 745
Interest rate, stated percentage	2.95%	2.95%
Senior Notes [Member] | 3.625% Notes due 2025 [Member]
Debt Instrument [Line Items]
Face Value	$ 500	$ 500
Unamortized Discounts and Debt Issuance Costs	(3)	(3)
Fair Value Adjustment	5	11
Net Carrying Value	$ 502	$ 508
Interest rate, stated percentage	3.625%	3.625%
Senior Notes [Member] | 3.300% Notes due 2027 [Member]
Debt Instrument [Line Items]
Face Value	$ 800	$ 800
Unamortized Discounts and Debt Issuance Costs	(9)	(9)
Fair Value Adjustment	(10)	(3)
Net Carrying Value	$ 781	$ 788
Interest rate, stated percentage	3.30%	3.30%
Other Borrowings [Member]
Debt Instrument [Line Items]
Face Value	$ 147
Unamortized Discounts and Debt Issuance Costs	0
Fair Value Adjustment	0
Net Carrying Value	147
Notes Payable [Member]
Debt Instrument [Line Items]
Face Value	50
Unamortized Discounts and Debt Issuance Costs	0
Fair Value Adjustment	0
Net Carrying Value	50
Securities Sold Under Agreements to Repurchase [Member]
Debt Instrument [Line Items]
Face Value	97	$ 97
Unamortized Discounts and Debt Issuance Costs	0	0
Fair Value Adjustment	0	0
Net Carrying Value	$ 97	$ 97

Long-term Debt and Other Borr51

Long-term Debt and Other Borrowings - Notes Payable and Securities Sold Under Agreements to Repurchase - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Sep. 30, 2017
Debt Instrument [Line Items]
Debt instrument, face value	$ 2,697	$ 2,647
Notes Payable [Member]
Debt Instrument [Line Items]
Debt instrument, face value	50
Notes Payable [Member] | TD Ameritrade Clearing, Inc. [Member]
Debt Instrument [Line Items]
Debt instrument, face value	50
Securities Sold Under Agreements to Repurchase [Member]
Debt Instrument [Line Items]
Debt instrument, face value	$ 97	$ 97
Debt instrument, offering date	Dec. 15, 2017
Debt instrument, maturity date	Mar. 15, 2018
Debt instrument, effective interest rate	1.58%
Debt instrument, date to be repurchased	Mar. 15, 2018
Debt instrument, face value of collateral to be repurchased on March 15, 2018	$ 97
Securities Sold Under Agreements to Repurchase [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Debt instrument, description of basis spread on variable rate	one-month LIBOR, plus an interest rate margin of ten basis points
Debt instrument, basis spread on variable rate	0.10%

Long-term Debt and Other Borr52

Long-term Debt and Other Borrowings - Fair Value Hedging - Additional Information (Detail) - Senior Notes [Member]	3 Months Ended
	Dec. 31, 2017
Debt Instrument [Line Items]
Weighted-average effective interest rate	2.65%
LIBOR [Member] | Pay Variable Interest Rate Swap [Member]
Debt Instrument [Line Items]
Description of basis spread on variable rate	three-month LIBOR
2019 Notes [Member] | LIBOR [Member] | Pay Variable Interest Rate Swap [Member]
Debt Instrument [Line Items]
Basis spread on variable rate, percentage	2.3745%
2022 Notes [Member] | LIBOR [Member] | Pay Variable Interest Rate Swap [Member]
Debt Instrument [Line Items]
Basis spread on variable rate, percentage	0.9486%
2025 Notes [Member] | LIBOR [Member] | Pay Variable Interest Rate Swap [Member]
Debt Instrument [Line Items]
Basis spread on variable rate, percentage	1.1022%
2027 Notes [Member] | LIBOR [Member] | Pay Variable Interest Rate Swap [Member]
Debt Instrument [Line Items]
Basis spread on variable rate, percentage	1.034%

Long-term Debt and Other Borr53

Long-term Debt and Other Borrowings - Gains and Losses Resulting from Changes in Fair Value of Interest Rate Swaps and Hedged Fixed Rate Debt (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Gain (loss) on fair value of interest rate swaps	$ (24)	$ (49)
Gain (loss) on fair value of hedged fixed-rate debt	24	49
Net gain (loss) recorded in interest on borrowings	$ 0	$ 0

Long-term Debt and Other Borr54

Long-term Debt and Other Borrowings - Fair Value of Outstanding Derivatives Designated as Hedging Instruments (Detail) - Pay Variable Interest Rate Swap [Member] - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Other assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of outstanding derivative assets designated as hedging instruments in the Consolidated Balance Sheets	$ 16	$ 26
Accounts payable and other liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of outstanding derivative liabilities designated as hedging instruments in the Consolidated Balance Sheets	$ (17)	$ (3)

Long-term Debt and Other Borr55

Long-term Debt and Other Borrowings - Balance Sheet Impact of Hedging Instruments - Additional Information (Detail) - Pay Variable Interest Rate Swap [Member] - Cash [Member] - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Derivative [Line Items]
Pledged collateral from interest rate swap counterparty, aggregate fair value	$ 18	$ 40
Pledged collateral to interest rate swap counterparty, aggregate fair value	$ 16	$ 1

Capital Requirements - Net Capi

Capital Requirements - Net Capital and Net Capital Requirements for Company's Subsidiaries (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017
TD Ameritrade Clearing, Inc. [Member]
Net Capital and Net Capital Requirements For Company's Subsidiaries [Line Items]
Net Capital	$ 1,704,000	$ 1,595,000
Required Net Capital (2% of Aggregate Debit Balances)	362,000	340,000
Net Capital in Excess of Required Net Capital	$ 1,342,000	$ 1,255,000
Ratio of Net Capital to Aggregate Debit Balances	9.42%	9.39%
TD Ameritrade, Inc. [Member]
Net Capital and Net Capital Requirements For Company's Subsidiaries [Line Items]
Net Capital	$ 186,000	$ 155,000
Required Net Capital (Minimum Dollar Requirement)	250	250
Net Capital in Excess of Required Net Capital	186,000	155,000
Scottrade, Inc. [Member]
Net Capital and Net Capital Requirements For Company's Subsidiaries [Line Items]
Net Capital	367,000	348,000
Required Net Capital (2% of Aggregate Debit Balances)	73,000	70,000
Net Capital in Excess of Required Net Capital	$ 294,000	$ 278,000
Ratio of Net Capital to Aggregate Debit Balances	10.04%	9.99%
TD Ameritrade Futures & Forex LLC [Member]
Net Capital and Net Capital Requirements For Company's Subsidiaries [Line Items]
Adjusted Net Capital under Commodity Exchange Act	$ 84,000	$ 77,000
Required Adjusted Net Capital under Commodity Exchange Act	23,000	22,000
Adjusted Net Capital in Excess of Required Adjusted Net Capital	$ 61,000	$ 55,000

Capital Requirements - Addition

Capital Requirements - Additional Information (Detail) - USD ($)	Dec. 31, 2017	Sep. 30, 2017
Net Capital and Net Capital Requirements For Company's Subsidiaries [Line Items]
Alternative net capital requirement, percentage of net capital to aggregate debit balances required for a broker-dealer to repay subordinated borrowings, pay cash dividends, or make any unsecured advances or loans to its parent company or employees	5.00%
Alternative net capital requirement, percentage of net capital to the minimum dollar requirement required for a broker-dealer to repay subordinated borrowings, pay cash dividends, or make any unsecured advances or loans to its parent company or employees	120.00%
TD Ameritrade Clearing, Inc. [Member]
Net Capital and Net Capital Requirements For Company's Subsidiaries [Line Items]
Alternative net capital requirement, dollar amount threshold	$ 1,500,000
Alternative net capital requirement, percentage of aggregate debit balances	2.00%
TD Ameritrade, Inc. [Member]
Net Capital and Net Capital Requirements For Company's Subsidiaries [Line Items]
Alternative net capital requirement, dollar amount threshold	$ 250,000
Alternative net capital requirement, percentage of aggregate debit balances	2.00%
Scottrade, Inc. [Member]
Net Capital and Net Capital Requirements For Company's Subsidiaries [Line Items]
Alternative net capital requirement, dollar amount threshold	$ 250,000
Alternative net capital requirement, percentage of aggregate debit balances	2.00%
TD Ameritrade Futures & Forex LLC [Member]
Net Capital and Net Capital Requirements For Company's Subsidiaries [Line Items]
FCM required net capital under the Commodity Exchange Act, dollar amount threshold	$ 1,000,000
FCM required net capital under the Commodity Exchange Act, percentage of total risk margin requirements for all positions carried in client accounts	8.00%
FCM required net capital under the Commodity Exchange Act, percentage of total risk margin requirements for all positions carried in non-client accounts	8.00%
FDM required net capital under the Commodity Exchange Act, dollar amount threshold	$ 20,000,000
FDM required net capital under the Commodity Exchange Act, percentage of forex liabilities in excess of $10 million added to the dollar amount threshold	5.00%
FDM required net capital under the Commodity Exchange Act, minimum forex client liability dollar amount threshold	$ 10,000,000
FCM and FDM required net capital under the Commodity Exchange Act, required notice to CFTC, minimum percentage of adjusted net capital to the risk-based capital requirement	110.00%
FCM and FDM required net capital under the Commodity Exchange Act, required notice to CFTC, minimum percentage of adjusted net capital to the FCM's $1 million threshold	150.00%
FCM and FDM required net capital under the Commodity Exchange Act, required notice to CFTC, minimum percentage of adjusted net capital to the FDM's $20 million plus 5% of foreign exchange liabilities owed to forex clients in excess of $10 million threshold	110.00%
TD Ameritrade Trust Company [Member]
Net Capital and Net Capital Requirements For Company's Subsidiaries [Line Items]
Tier 1 capital, balance at period end	$ 34,000,000	$ 32,000,000
Amount in excess of required Tier 1 capital	$ 14,000,000	$ 13,000,000

Commitments and Contingencies -

Commitments and Contingencies - Collateral Available, Loaned or Repledged (Detail) - USD ($) $ in Billions	Dec. 31, 2017	Sep. 30, 2017
Customer Securities for which Entity has Right to Sell or Repledge (Including Securities Sold or Repledged) [Line Items]
Total collateral available	$ 26.6	$ 25
Total collateral loaned or repledged, collateral loaned	3	2.4
Total collateral loaned or repledged, collateral repledged	7.8	4.1
Total collateral loaned or repledged	10.8	6.5
Client Margin Securities [Member]
Customer Securities for which Entity has Right to Sell or Repledge (Including Securities Sold or Repledged) [Line Items]
Total collateral available	25.6	23.8
Stock Borrowings [Member]
Customer Securities for which Entity has Right to Sell or Repledge (Including Securities Sold or Repledged) [Line Items]
Total collateral available	$ 1	$ 1.2

Commitments and Contingencies59

Commitments and Contingencies - Summary of Cash Deposited with and Securities Pledged to Clearinghouses (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Cash Deposited with and Securities Pledged to Clearinghouses [Line Items]
Cash deposited and securities pledged	$ 715	$ 549
Cash [Member] | Receivable from brokers, dealers and clearing organizations [Member]
Cash Deposited with and Securities Pledged to Clearinghouses [Line Items]
Cash deposited and securities pledged	246	151
U.S. government debt securities [Member] | Securities owned, at fair value [Member]
Cash Deposited with and Securities Pledged to Clearinghouses [Line Items]
Cash deposited and securities pledged	$ 469	$ 398

Commitments and Contingencies60

Commitments and Contingencies - Additional Information (Detail)	3 Months Ended
	Dec. 31, 2017USD ($)plaintiffinvestorlitigation_cases	Sep. 30, 2017USD ($)
Contingencies and Commitments [Line Items]
Contingent liability for guarantees to securities clearinghouses and exchanges	$ 0	$ 0
Aequitas Securities Litigation [Member]
Contingencies and Commitments [Line Items]
Number of claims previously filed | plaintiff	4
Alleged amount of securities purchased (more than $140 million)	$ 140,000,000
Alleged number of investors involved in the claim (more than 1,500) | investor	1,500
Alleged amount of securities owed to investors (more than $600 million)	$ 600,000,000
Number of plaintiffs | plaintiff	200
Alleged approximate losses plus other damages	$ 125,000,000
Order Routing Matters [Member]
Contingencies and Commitments [Line Items]
Number of plaintiffs who filed amended claims | plaintiff	0
Minimum [Member]
Contingencies and Commitments [Line Items]
Aggregate range of reasonably possible losses in excess of amounts accrued	$ 0
Maximum [Member]
Contingencies and Commitments [Line Items]
Aggregate range of reasonably possible losses in excess of amounts accrued	$ 65,000,000
TD Ameritrade, Inc. [Member] | Aequitas Securities Litigation [Member]
Contingencies and Commitments [Line Items]
Number of plaintiffs | plaintiff	100
Alleged approximate losses plus other damages	$ 35,000,000
TD Ameritrade, Inc. [Member] | Order Routing Matters [Member]
Contingencies and Commitments [Line Items]
Number of claims previously filed | litigation_cases	5
Number of claims dismissed, state law claims | litigation_cases	5
Number of claims allowed to be amended | litigation_cases	4
Scottrade, Inc. [Member] | Order Routing Matters [Member]
Contingencies and Commitments [Line Items]
Number of claims previously filed | litigation_cases	1

Fair Value Disclosures - Fair V

Fair Value Disclosures - Fair Value Hierarchy for Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Assets:
Securities owned	$ 593	$ 503
Investments available-for-sale	99	746
Recurring [Member]
Assets:
Investments segregated for regulatory purposes	5,027	5,580
Securities owned	593	503
Other assets	18	28
Total assets at fair value	7,182	7,938
Liabilities:
Total liabilities at fair value	22
Recurring [Member] | Pay Variable Interest Rate Swap [Member]
Assets:
Other assets	16	26
Liabilities:
Accounts payable and other liabilities	17	3
Recurring [Member] | U.S. Government Debt Securities [Member]
Assets:
Investments segregated for regulatory purposes	3,594	4,094
Securities owned	569	498
Investments available-for-sale	99	746
Other assets	1	1
Recurring [Member] | U.S. Government Agency Mortgage-Backed Securities [Member]
Assets:
Investments segregated for regulatory purposes	1,433	1,486
Recurring [Member] | Other Securities [Member]
Assets:
Securities owned	5	5
Recurring [Member] | Auction Rate Securities [Member]
Assets:
Other assets	1	1
Recurring [Member] | Equity Securities [Member]
Assets:
Securities owned	19
Liabilities:
Accounts payable and other liabilities	5
Recurring [Member] | Money Market Mutual Funds [Member]
Assets:
Cash equivalents	1,445	1,081
Recurring [Member] | Level 1 [Member]
Assets:
Securities owned	18	1
Total assets at fair value	1,463	1,082
Liabilities:
Total liabilities at fair value	5
Recurring [Member] | Level 1 [Member] | Other Securities [Member]
Assets:
Securities owned		1
Recurring [Member] | Level 1 [Member] | Equity Securities [Member]
Assets:
Securities owned	18
Liabilities:
Accounts payable and other liabilities	5
Recurring [Member] | Level 1 [Member] | Money Market Mutual Funds [Member]
Assets:
Cash equivalents	1,445	1,081
Recurring [Member] | Level 2 [Member]
Assets:
Investments segregated for regulatory purposes	5,027	5,580
Securities owned	575	502
Other assets	17	27
Total assets at fair value	5,718	6,855
Liabilities:
Total liabilities at fair value	17
Recurring [Member] | Level 2 [Member] | Pay Variable Interest Rate Swap [Member]
Assets:
Other assets	16	26
Liabilities:
Accounts payable and other liabilities	17	3
Recurring [Member] | Level 2 [Member] | U.S. Government Debt Securities [Member]
Assets:
Investments segregated for regulatory purposes	3,594	4,094
Securities owned	569	498
Investments available-for-sale	99	746
Other assets	1	1
Recurring [Member] | Level 2 [Member] | U.S. Government Agency Mortgage-Backed Securities [Member]
Assets:
Investments segregated for regulatory purposes	1,433	1,486
Recurring [Member] | Level 2 [Member] | Other Securities [Member]
Assets:
Securities owned	5	4
Recurring [Member] | Level 2 [Member] | Equity Securities [Member]
Assets:
Securities owned	1
Recurring [Member] | Level 3 [Member]
Assets:
Other assets	1	1
Total assets at fair value	1	1
Recurring [Member] | Level 3 [Member] | Auction Rate Securities [Member]
Assets:
Other assets	$ 1	$ 1

Fair Value Disclosures - Additi

Fair Value Disclosures - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Reverse repurchase agreements, general maturity	7 days
Reverse repurchase agreements, included in other assets		$ 65
Debt Instrument [Line Items]
Long-term debt, aggregate carrying value	$ 2,531	2,555
Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt, aggregate estimated fair value	2,620	2,630
Long-term debt, aggregate carrying value	$ 2,530	$ 2,560

Offsetting Assets and Liabili63

Offsetting Assets and Liabilities - Effect of Rights of Setoff Associated with Company's Recognized Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Offsetting Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed [Abstract]
Total recognized assets, gross	$ 1,773	$ 2,249
Total recognized assets, gross amounts offset in the balance sheet	0	0
Total recognized assets, net amounts presented in the balance sheet	1,773	2,249
Total recognized assets, gross amounts of financial instruments not offset in the balance sheet	(135)	(110)
Total recognized assets, gross amounts of collateral received (including cash) not offset in the balance sheet	(1,612)	(2,118)
Total recognized assets, net amount	26	21
Offsetting Securities Loaned [Abstract]
Deposits received for securities loaned, gross	2,958	2,449
Securities Sold under Agreements to Repurchase [Abstract]
Securities sold under agreements to repurchase, net amounts presented in the balance sheet	97	97
Securities sold under agreements to repurchase, gross amounts of collateral pledged (including cash) not offset in the balance sheet	(99)	(99)
Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract]
Total recognized liabilities, gross	3,072	2,549
Total recognized liabilities, gross amounts offset in the balance sheet	0	0
Total recognized liabilities, net amounts presented in the balance sheet	3,072	2,549
Total recognized liabilities, gross amounts of financial instruments not offset in the balance sheet	(135)	(110)
Total recognized liabilities, gross amounts of collateral pledged (including cash) not offset in the balance sheet	(2,659)	(2,213)
Total recognized liabilities, net amount	278	226
Investments segregated for regulatory purposes [Member]
Offsetting Securities Purchased under Agreements to Resell [Abstract]
Reverse repurchase agreements, gross	750	1,004
Reverse repurchase agreements, gross amounts offset in the balance sheet	0	0
Reverse repurchase agreements, net amounts presented in the balance sheet	750	1,004
Reverse repurchase agreements, gross amounts of financial instruments not offset in the balance sheet	0	0
Reverse repurchase agreements, gross amounts of collateral received (including cash) not offset in the balance sheet	(750)	(1,004)
Reverse repurchase agreements, net amount	0	0
Receivable from brokers, dealers and clearing organizations [Member]
Offsetting Securities Borrowed [Abstract]
Deposits paid for securities borrowed, gross	1,007	1,154
Deposits paid for securities borrowed, gross amounts offset in the balance sheet	0	0
Deposits paid for securities borrowed, net amounts presented in the balance sheet	1,007	1,154
Deposits paid for securities borrowed, gross amounts of financial instruments not offset in the balance sheet	(135)	(110)
Deposits paid for securities borrowed, gross amounts of collateral received (including cash) not offset in the balance sheet	(846)	(1,023)
Deposits paid for securities borrowed, net amount	26	21
Other assets [Member]
Offsetting Securities Purchased under Agreements to Resell [Abstract]
Reverse repurchase agreements, gross		65
Reverse repurchase agreements, gross amounts offset in the balance sheet		0
Reverse repurchase agreements, net amounts presented in the balance sheet		65
Reverse repurchase agreements, gross amounts of financial instruments not offset in the balance sheet		0
Reverse repurchase agreements, gross amounts of collateral received (including cash) not offset in the balance sheet		(65)
Reverse repurchase agreements, net amount		0
Offsetting Derivative Assets [Abstract]
Pay-variable interest rate swaps, gross	16	26
Pay-variable interest rate swaps, gross amounts offset in the balance sheet	0	0
Pay-variable interest rate swaps, net amounts presented in the balance sheet	16	26
Pay-variable interest rate swaps, gross amounts of financial instruments not offset in the balance sheet	0	0
Pay-variable interest rate swaps, gross amounts of collateral received (including cash) not offset in the balance sheet	(16)	(26)
Pay-variable interest rate swaps, net amount	0	0
Offsetting Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed [Abstract]
Total recognized assets, gross		91
Total recognized assets, gross amounts offset in the balance sheet		0
Total recognized assets, net amounts presented in the balance sheet		91
Total recognized assets, gross amounts of financial instruments not offset in the balance sheet		0
Total recognized assets, gross amounts of collateral received (including cash) not offset in the balance sheet		(91)
Total recognized assets, net amount		0
Payable to brokers, dealers and clearing organizations [Member]
Offsetting Securities Loaned [Abstract]
Deposits received for securities loaned, gross	2,958	2,449
Deposits received for securities loaned, gross amounts offset in the balance sheet	0	0
Deposits received for securities loaned, net amounts presented in the balance sheet	2,958	2,449
Deposits received for securities loaned, gross amounts of financial instruments not offset in the balance sheet	(137)	(112)
Deposits received for securities loaned, gross amounts of collateral pledged (including cash) not offset in the balance sheet	(2,544)	(2,113)
Deposits received for securities loaned, net amount	277	224
Securities sold under agreements to repurchase [Member]
Securities Sold under Agreements to Repurchase [Abstract]
Securities sold under agreements to repurchase, gross	97	97
Securities sold under agreements to repurchase, gross amounts offset in the balance sheet	0	0
Securities sold under agreements to repurchase, net amounts presented in the balance sheet	97	97
Securities sold under agreements to repurchase, gross amounts of financial instruments not offset in the balance sheet	2	2
Securities sold under agreements to repurchase, gross amounts of collateral pledged (including cash) not offset in the balance sheet	(99)	(99)
Securities sold under agreements to repurchase, net amount	0	0
Accounts payable and other liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Pay-variable rate interest rate swaps, gross	17	3
Pay-variable rate interest rate swaps, gross amounts offset in the balance sheet	0	0
Pay-variable rate interest rate swaps, net amounts presented in the balance sheet	17	3
Pay-variable rate interest rate swaps, gross amounts of financial instruments not offset in the balance sheet	0	0
Pay-variable rate interest rate swaps, gross amounts of collateral pledged (including cash) not offset in the balance sheet	(16)	(1)
Pay-variable rate interest rate swaps, net amount	$ 1	$ 2

Offsetting Assets and Liabili64

Offsetting Assets and Liabilities - Disaggregation of Secured Lending Transactions (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Disaggregation of Gross Securities Lending Transactions [Line Items]
Deposits received for securities loaned, gross	$ 2,958	$ 2,449
Equity Securities [Member]
Disaggregation of Gross Securities Lending Transactions [Line Items]
Deposits received for securities loaned, gross	2,513	2,109
Exchange-traded Funds [Member]
Disaggregation of Gross Securities Lending Transactions [Line Items]
Deposits received for securities loaned, gross	331	230
Closed-end Funds [Member]
Disaggregation of Gross Securities Lending Transactions [Line Items]
Deposits received for securities loaned, gross	70	66
Other Securities [Member]
Disaggregation of Gross Securities Lending Transactions [Line Items]
Deposits received for securities loaned, gross	$ 44	$ 44

Offsetting Assets and Liabili65

Offsetting Assets and Liabilities - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Offsetting Assets And Liabilities [Line Items]
Fair value of collateral the Company has received under enforceable master agreements	$ 1,760	$ 2,260
Fair value of collateral the Company has pledged under enforceable master agreements	2,790	2,320
Transacted Through the Option Clearing Corporation [Member]
Offsetting Assets And Liabilities [Line Items]
Gross amounts of deposits paid for securities borrowed	577	675
Gross amounts of deposits received for securities loaned	$ 2,160	$ 1,650

Accumulated Other Comprehensi66

Accumulated Other Comprehensive Loss - Net Change (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Investments available-for-sale:
Unrealized gain (loss), before tax	$ (4)	$ (10)
Unrealized gain (loss), tax effect	1	4
Unrealized gain (loss), net of tax	(3)	(6)
Reclassification adjustment for realized losses included in net income, before tax	11	0
Reclassification adjustment for realized losses included in net income, tax effect	(4)	0
Reclassification adjustment for realized losses included in net income, net of tax	7	0
Net change in investments available-for-sale	7	(10)
Net change in investments available-for-sale, tax effect	(3)	4
Net change in investments available-for-sale, net of tax	4	(6)
Cash flow hedging instruments:
Reclassification adjustment for portion of realized loss amortized to net income, before tax	1	1
Reclassification adjustment for portion of realized loss amortized to net income, tax effect	0	0
Reclassification adjustment for portion of realized loss amortized to net income, net of tax	1	1
Net change in cash flow hedging instruments, before tax	1	1
Net change in cash flow hedging instruments, tax effect	0	0
Net change in cash flow hedging instruments, net of tax	1	1
Total other comprehensive income (loss), before tax	8	(9)
Income tax effect	(3)	4
Total other comprehensive income (loss), net of tax	$ 5	$ (5)

Accumulated Other Comprehensi67

Accumulated Other Comprehensive Loss - Balance Rollforward (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 7,247
Current period change in other comprehensive income (loss)	5	$ (5)
Ending balance	7,433
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(25)	(22)
Current period change in other comprehensive income (loss)	5	(5)
Ending balance	(20)	(27)
Investments Available-for-sale [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(5)	0
Other comprehensive income (loss) before reclassification	(3)	(6)
Amount reclassified from accumulated other comprehensive loss	7	0
Current period change in other comprehensive income (loss)	4	(6)
Ending balance	(1)	(6)
Cash Flow Hedging Instruments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(20)	(22)
Amount reclassified from accumulated other comprehensive loss	1	1
Ending balance	$ (19)	$ (21)

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Antidilutive awards excluded from the calculation of diluted earnings per share (in shares)	0	0

Related Party Transactions - Su

Related Party Transactions - Summary of Revenues Resulting from Transactions with Related Parties (Detail) - TD and its affiliates [Member] - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Revenues from related parties	$ 356	$ 254
Insured Deposit Account Agreement [Member] | Bank Deposit Account Fees [Member]
Related Party Transaction [Line Items]
Revenues from related parties	344	245
Referral and Strategic Alliance Agreement [Member] | Various [Member]
Related Party Transaction [Line Items]
Revenues from related parties	4	3
Mutual Fund Agreements [Member] | Investment Product Fees [Member]
Related Party Transaction [Line Items]
Revenues from related parties	4	4
Other [Member] | Various [Member]
Related Party Transaction [Line Items]
Revenues from related parties	$ 4	$ 2

Related Party Transactions - 70

Related Party Transactions - Summary of Expenses Resulting from Transactions with Related Parties (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
TD and its affiliates [Member] | Canadian Call Center Services Agreement [Member] | Professional Services [Member]
Related Party Transaction [Line Items]
Expenses to related parties	$ 0	$ 4

Related Party Transactions - 71

Related Party Transactions - Summary of Classification and Amount of Receivables from and Payables to Affiliates of Company (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Assets:
Receivable from brokers, dealers and clearing organizations	$ 1,291	$ 1,334
Receivable from affiliates	219	137
Liabilities:
Payable to brokers, dealers and clearing organizations	3,064	2,504
Payable to affiliates	55	109
TD and its affiliates [Member]
Assets:
Receivable from affiliates	180	110
Liabilities:
Payable to brokers, dealers and clearing organizations	253	37
Payable to affiliates	$ 11	$ 38

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail)	3 Months Ended
	Dec. 31, 2017USD ($)board_of_directors_membercomponent	Sep. 30, 2017USD ($)
Related Party Transaction [Line Items]
Number of Board of Directors members, total | board_of_directors_member	12
Receivable from affiliates	$ 219,000,000	$ 137,000,000
Payable to affiliates	$ 55,000,000	109,000,000
Canadian Call Center Services Agreement [Member]
Related Party Transaction [Line Items]
Related party transaction, agreement expiration date	Sep. 30, 2017
TD and its affiliates [Member]
Related Party Transaction [Line Items]
Percentage ownership in the Company	41.00%
Number of Board of Directors members, designated by related party | board_of_directors_member	5
Receivable from affiliates	$ 180,000,000	110,000,000
Payable to affiliates	$ 11,000,000	38,000,000
TD and its affiliates [Member] | Insured Deposit Account Agreement [Member]
Related Party Transaction [Line Items]
Related party transaction, agreement effective date	Jan. 1, 2013
Related party transaction, agreement expiration date	Jul. 1, 2018
Related party transaction, agreement successive renewal term	5 years
Related party transaction, non-renewal terms, prior written notice period for termination of related party agreement by any party	2 years
Number of primary components related to the fee earned on IDA agreement | component	2
Reset frequency of adjustments required to adjust variable rate leg of interest rate swaps under current IDA Agreement	1 month
Percentage of fixed rate notional investments	74.00%
Percentage of floating rate investments	26.00%
Deposit amount threshold for floating-rate or fixed-rate notional investments with a maturity of up to 24 months subject to servicing fee adjustment	$ 20,000,000,000
Contingent liability carried on the condensed consolidated balance sheets for the Insured Deposit Account Agreement	$ 0	0
TD and its affiliates [Member] | Insured Deposit Account Agreement [Member] | Minimum [Member]
Related Party Transaction [Line Items]
Servicing fee percentage	0.03%
TD and its affiliates [Member] | Insured Deposit Account Agreement [Member] | Maximum [Member]
Related Party Transaction [Line Items]
Servicing fee percentage	0.25%
Maturity of short-term fixed-rate notional investments	24 months
TD and its affiliates [Member] | Insured Deposit Account Agreement [Member] | New Fixed Rate Notional Investments [Member]
Related Party Transaction [Line Items]
Event one, federal funds effective rate, minimum	0.75%
Term of U.S. dollar interest rate swaps	5 years
Event two, minimum rate on five-year U.S. dollar interest rate swaps for 20 consecutive business days	1.50%
Event two, number of consecutive business days required above the minimum rate on U.S. dollar interest rate swaps for reduction in rate earned by Company	20 days
Percentage used in the calculation to reduce the rate earned by the Company on new fixed-rate notional investments in the case event 1 and event 2 are both fulfilled	20.00%
Maximum reduction to rate on new fixed-rate notional investments earned by Company in the case event 1 and event 2 are both fulfilled	0.10%
TD and its affiliates [Member] | Insured Deposit Account Agreement Fee Example [Member]
Related Party Transaction [Line Items]
Designated deposit amount	$ 100,000,000
Term of deposits invested in fixed rate investments	5 years
Term of applicable swaps	5 years
Fixed yield for applicable LIBOR-based swaps	1.45%
Gross fixed yield earned on deposits	1.45%
Management [Member] | Scottrade [Member]
Related Party Transaction [Line Items]
Receivable from affiliates	$ 39,000,000	27,000,000
Payable to affiliates	$ 44,000,000	$ 71,000,000