Nasdaq Stockholders' Equity (Narrative) (Details) $ / shares in Units, $ in Millions	1 Months Ended				3 Months Ended			6 Months Ended
	Jul. 31, 2026 USD ($) $ / shares	Jun. 30, 2026 USD ($) vote $ / shares shares	Feb. 28, 2026 USD ($) shares	Jan. 31, 2026 USD ($)	Jun. 30, 2026 USD ($) vote $ / shares shares	Mar. 31, 2026 USD ($) $ / shares	Jun. 30, 2025 $ / shares shares	Jun. 30, 2026 USD ($) vote $ / shares shares	Jun. 30, 2025 USD ($) $ / shares shares	Dec. 31, 2025 shares
Stockholders Equity [Line Items]
Common stock, shares authorized (in shares)		900,000,000			900,000,000			900,000,000		900,000,000
Common stock, shares issued (in shares)		587,518,685			587,518,685			587,518,685		594,620,320
Common stock, shares outstanding (in shares)		561,990,385			561,990,385		574,000,000	561,990,385	574,000,000	569,894,024
Common stock (in votes per share) | vote		1			1			1
Common stock holder voting rights, maximum percentage of the then-outstanding shares of Nasdaq common stock		5.00%			5.00%			5.00%
Common stock in treasury (in shares)		25,528,300			25,528,300			25,528,300		24,726,296
Remaining authorized amount under share repurchase program | $		$ 2,500	$ 3,000		$ 2,500			$ 2,500
Repurchases of common stock | $								$ 903	$ 215
Preferred stock, shares authorized (in shares)		30,000,000			30,000,000			30,000,000
Preferred stock par value (in dollars per share) | $ / shares		$ 0.01			$ 0.01			$ 0.01
Preferred stock, shares issued (in shares)		0			0			0		0
Preferred stock, shares outstanding (in shares)		0			0			0		0
Dividends declared | $					$ 174	$ 153		$ 327
Cash dividends declared per common share (in dollars per share) | $ / shares					$ 0.31	$ 0.27	$ 0.27	$ 0.58	$ 0.51
Subsequent event
Stockholders Equity [Line Items]
Dividends declared | $	$ 174
Cash dividends declared per common share (in dollars per share) | $ / shares	$ 0.31
January Accelerated Share Repurchase Agreement Program
Stockholders Equity [Line Items]
Repurchases of common stock | $				$ 300
February Accelerated Share Repurchase Agreement Program
Stockholders Equity [Line Items]
Share-based payment arrangement, shares withheld for tax withholding obligation (in shares)			3,142,730
Repurchases of common stock | $			$ 15
June 2026 Accelerated Share Repurchase Agreement Program
Stockholders Equity [Line Items]
Repurchases of common stock | $		$ 250
Other repurchases of common stock
Stockholders Equity [Line Items]
Share-based payment arrangement, shares withheld for tax withholding obligation (in shares)								802,004