Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2024	Dec. 31, 2023
Fiserv, Inc. Shareholders’ Equity:
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,800,000,000	1,800,000,000
Common stock, shares issued (in shares)	784,000,000	784,000,000
Treasury stock (in shares)	207,000,000	190,000,000