Note 3 - Acquisitions and Divestitures - Unaudited Pro Forma Results (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Revenue (less agency commissions)	$ 3,153	$ 3,353
Net income	199	488
Net income attributable to common stockholders	$ 147	$ 436
Basic net income attributable to common stockholders, per share (in dollars per share)	$ 2.09	$ 4.54
Diluted net income attributable to common stockholders, per share (in dollars per share)	$ 2.09	$ 4.49