Stock Issued During Period New Issues Per Share

No definition available.

Name:	ato_StockIssuedDuringPeriodNewIssuesPerShare
Namespace Prefix:	ato_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The per share price of the Company's stock at which the contract holder of the freestanding contract has the right to purchase or sell the Company's stock at a future date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 50
-Paragraph 5
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6445032&loc=d3e90205-114008

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(1)
-URI http://asc.fasb.org/extlink&oid=109262807&loc=d3e22047-110879

+ Details

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Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Number of shares as a settlement alternative for each freestanding forward contract.

+ References

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Settlement date of the forward contract indexed to issuer's equity, in CCYY-MM-DD format.

+ References

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The maximum number of shares that could be issued to net share settle a contract, if applicable. If a contract does not have a fixed or determinable maximum number of shares that may be required to be issued, disclose the fact that a potentially infinite number of shares could be issued to settle the contract.

+ References

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Number of new stock issued during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	na
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- Details

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Shareholders' Equity Shareholders' Equity - Schedule of Forward Sales Executed (Details) - $ / shares	3 Months Ended				12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Forward Contract Indexed to Issuer's Equity [Line Items]
Forward sales equity agreement, shares	1,423,599	1,050,563	1,670,509	2,668,464
Forward sales equity agreement, forward rate per share	$ 108.70	$ 101.41	$ 95.46	$ 91.77		$ 0
Forward sales equity agreement, settlement in shares	4,629,860				4,629,860	0
Stock Issued During Period, Shares, New Issues	(1,093,575)	(1,089,700)
Stock Issued During Period New Issues Per Share	$ 91.78	$ 91.44
Forward Sales Equity, Maturity September 2020
Forward Contract Indexed to Issuer's Equity [Line Items]
Forward sales equity agreement, shares	1,423,599	1,050,563	0	0
Forward sales equity agreement, forward rate per share	$ 108.70	$ 101.41	$ 0	$ 0		$ 0
Forward sales equity agreement, settlement date					Sep. 30, 2020
Forward sales equity agreement, settlement in shares	2,474,162				2,474,162	0
Stock Issued During Period, Shares, New Issues	0	0
Stock Issued During Period New Issues Per Share	$ 0	$ 0
Forward Sales Equity, Maturity March 2020
Forward Contract Indexed to Issuer's Equity [Line Items]
Forward sales equity agreement, shares	0	0	1,670,509	2,668,464
Forward sales equity agreement, forward rate per share	$ 0	$ 0	$ 95.46	$ 91.77		$ 0
Forward sales equity agreement, settlement date					Mar. 31, 2020
Forward sales equity agreement, settlement in shares	2,155,698				2,155,698	0
Stock Issued During Period, Shares, New Issues	(1,093,575)	(1,089,700)
Stock Issued During Period New Issues Per Share	$ 91.78	$ 91.44