CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Millions	Total	Common Stock and Additional Paid-In Capital	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Income
Beginning balance at Dec. 31, 2020	$ 607	$ 747	$ (144)	$ 4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for employee stock purchase plan		5
Stock based compensation expense		24
Net income	192		192
Repurchase of common stock			(74)
Awards effectively repurchased for required employee withholding taxes			(9)
Other comprehensive loss	(1)			(1)
Ending balance at Jun. 30, 2021	744	776	(35)	3
Beginning balance at Mar. 31, 2021	653	758	(108)	3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for employee stock purchase plan		5
Stock based compensation expense		13
Net income	91		91
Repurchase of common stock			(14)
Awards effectively repurchased for required employee withholding taxes			(4)
Other comprehensive loss	0			0
Ending balance at Jun. 30, 2021	744	776	(35)	3
Beginning balance at Dec. 31, 2021	881	808	74	(1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from exercise of stock options		1
Issuance of common stock for employee stock purchase plan		5
Issuance of common stock for the acquisition of Zenefits		17
Stock based compensation expense		30
Net income	230		230
Repurchase of common stock	(380)		(382)
Awards effectively repurchased for required employee withholding taxes			(8)
Other comprehensive loss	(11)
Ending balance at Jun. 30, 2022	763	861	(86)	(12)
Beginning balance at Mar. 31, 2022	695	837	(133)	(9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from exercise of stock options		1
Issuance of common stock for employee stock purchase plan		5
Stock based compensation expense		18
Net income	85		85
Repurchase of common stock			(33)
Awards effectively repurchased for required employee withholding taxes			(5)
Other comprehensive loss	(3)
Ending balance at Jun. 30, 2022	$ 763	$ 861	$ (86)	$ (12)