Stock Plans - Restricted shares and performance shares (Details) - RSAs, RSUs, PSAs and PSUs - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Number of Shares
Outstanding at the beginning of the period (in shares)	2,496	2,083	2,040
Granted (in shares)	1,282	1,253	1,031
Performance award adjustments (in shares)	183	85	159
Vested (in shares)	(1,364)	(844)	(1,014)
Forfeited (in shares)	(133)	(81)	(133)
Outstanding at the end of the period (in shares)	2,464	2,496	2,083
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 23.83	$ 17.33	$ 12.73
Granted (in dollars per share)	23.83	29.12	24.26
Performance award adjustments (in dollars per share)	10.59	14.03	18.38
Vested (in dollars per share)	17.47	15.00	15.50
Forfeited (in dollars per share)	29.29	20.18	15.08
Outstanding at the end of the period (in dollars per share)	$ 26.19	$ 23.83	$ 17.33
Total fair value of shares vested	$ 30.3	$ 22.1	$ 22.8
Minimum
Weighted Average Grant Date Fair Value
Vesting period	1 year
Maximum
Weighted Average Grant Date Fair Value
Vesting period	4 years