Common Stock, Dividends, Percent Increase Over Prior Quarter

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Common Stock Holder Voting Rights

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- Definition

Share Repurchase Program, Additional Amount Authorized

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- Definition

Stockholders Equity [Line Items]

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Stockholders' Equity, Number Of Votes

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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

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

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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

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Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

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Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.

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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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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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Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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Amount of stock repurchase plan authorized.

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Amount remaining of a stock repurchase plan authorized.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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

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Nasdaq Stockholders' Equity (Narrative) (Details)				1 Months Ended		3 Months Ended		9 Months Ended
Nasdaq Stockholders' Equity (Narrative) (Details)	Jul. 24, 2018 USD ($) $ / shares	Mar. 26, 2018 USD ($) $ / shares	Jan. 30, 2018 USD ($) $ / shares	Oct. 31, 2018 USD ($) $ / shares	Mar. 31, 2018 $ / shares	Sep. 30, 2018 USD ($) vote $ / shares shares	Sep. 30, 2017 $ / shares	Sep. 30, 2018 USD ($) vote $ / shares shares	Sep. 30, 2017 $ / shares shares	Jan. 31, 2018 USD ($)	Dec. 31, 2017 shares
Stockholders Equity [Line Items]
Common stock, shares authorized (in shares)						300,000,000		300,000,000			300,000,000
Common stock, shares issued (in shares)						169,423,805		169,423,805			172,373,432
Common stock, shares outstanding (in shares)						163,949,047		163,949,047			167,441,030
Common stock (in votes per share) \| vote						1		1
Common stock holder voting rights, maximum percentage of the then-outstanding shares of Nasdaq common stock						5.00%		5.00%
Common stock in treasury (in shares)						5,474,758		5,474,758			4,932,402
Share repurchase program additional amount authorized \| $										$ 500,000,000
Share repurchase program, authorized amount \| $						$ 726,000,000		$ 726,000,000
Remaining authorized share repurchase amounts under repurchase program \| $						$ 332,000,000		$ 332,000,000
Number of shares of common stock repurchased (in shares)								4,508,426	2,455,171
Preferred stock, shares authorized (in shares)						30,000,000		30,000,000
Preferred stock par value (in dollars per share) \| $ / shares						$ 0.01		$ 0.01
Payments of dividends \| $								$ 208,000,000
Cash dividends declared per common share (in dollars per share) \| $ / shares	$ 0.44	$ 0.44	$ 0.38		$ 0.44	$ 0.44	$ 0.38	$ 1.26	$ 1.08
Dividends declared \| $	$ 72,000,000	$ 73,000,000	$ 63,000,000					$ 208,000,000
Percent increase over prior quarter dividend								16.00%
Other Repurchases of Common Stock
Stockholders Equity [Line Items]
Number of shares of common stock repurchased (in shares)								542,356
Series A Preferred Stock
Stockholders Equity [Line Items]
Preferred stock, series A convertible preferred stock, shares issued (in shares)						0		0			0
Preferred stock, series A convertible preferred stock, shares outstanding (in shares)						0		0			0
Subsequent Event
Stockholders Equity [Line Items]
Cash dividends declared per common share (in dollars per share) \| $ / shares				$ 0.44
Dividends declared \| $				$ 72,000,000