Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Average Price Per Share

No definition available.

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- Definition

Stock Issuable, Value, Maximum

+ References

No definition available.

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- 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.

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- Definition

The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

+ References

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-Name Accounting Standards Codification
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- Definition

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

+ References

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- 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.

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- Definition

The number of issuer's shares to which the forward contract is indexed.

+ References

+ Details

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- Definition

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

+ References

+ Details

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- 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

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- Definition

The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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- Definition

The cash inflow from the additional capital contribution to the entity.

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- Definition

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

+ Details

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- Definition

The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

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- Definition

Total cost of shares repurchased divided by the total number of shares repurchased.

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- Definition

Number of shares that have been repurchased during the period and are being held in treasury.

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Stockholders' Equity - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 31, 2018	Jan. 31, 2017
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	153,000,000	153,000,000
Proceeds from issuance of common stock	$ 9,700,000	$ 41,900,000	$ 465,800,000
Common stock, shares outstanding (in shares)	58,500,000	58,500,000
Forward Equity Agreement
Class of Stock [Line Items]
Proceeds from issuance of common stock	$ 0
Stock program, maximum amount authorized			$ 500,000,000
Voting Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	150,000,000.0
Common Class B
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	3,000,000.0
Common Stock
Class of Stock [Line Items]
Shares repurchased (in shares)	3,300,000	2,400,000	200,000
Average price of stock repurchased (in dollars per share)	$ 150.31	$ 173.19	$ 161.16
Common Stock \| Forward Equity Agreement
Class of Stock [Line Items]
Maximum number of shares available for sale under agreement (in shares)			2,900,000
Average share price on forward basis (in dollars per share)			$ 167.25
Number of shares issued to settle portion of forward equity sale (in shares)			2,700,000
Proceeds from issuance of common stock			$ 440,300,000
Number of shares issued to settle portion of forward equity sale in cash (in shares)			200,000
Average share price of shares settled in cash (in dollars per share)			$ 144.59
Common stock, shares outstanding (in shares)			0
Common Stock \| January 2018 Program
Class of Stock [Line Items]
Stock repurchase program, number of shares authorized (in shares)				3,400,000.0
Stock repurchase plan, number of remaining shares to be repurchased (in shares)	1,700,000
Common Stock \| January 2017 Program
Class of Stock [Line Items]
Stock repurchase program, number of shares authorized (in shares)					1,900,000.0
Stock repurchase plan, number of remaining shares to be repurchased (in shares)	0
Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	5,000,000.0