Nasdaq Stockholders' Equity (Schedule of Dividends Declared) (Details) - USD ($) $ / shares in Units, $ in Millions			1 Months Ended		3 Months Ended
	Mar. 26, 2018	Jan. 30, 2018	Mar. 31, 2018	Jan. 31, 2018	Mar. 31, 2018	Mar. 31, 2017
Dividends Payable [Line Items]
Dividend per common share (in dollars per share)					$ 0.82	$ 0.32
Total Amount					$ 136
January 30, 2018
Dividends Payable [Line Items]
Dividend per common share (in dollars per share)		$ 0.38		$ 0.38
Total Amount					63
March 26, 2018
Dividends Payable [Line Items]
Dividend per common share (in dollars per share)	$ 0.44		$ 0.44
Total Amount					$ 73