v3.20.1
Stock-based compensation - Narrative (Details) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Mar. 31, 2017
Jan. 31, 2020
Jan. 31, 2019
Jan. 31, 2018
Aug. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Weighted-average fair value at date of grant (usd per share)       $ 25.97 $ 26.40 $ 17.16  
Expected dividend yield       0.00% 0.00% 0.00%  
Share based compensation       $ 45,424 $ 21,057 $ 14,310  
WageWorks, Inc.              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share based compensation       $ 8,100      
WageWorks, Inc. | Restricted stock units              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Number of service-based common stock (in shares)       523,318      
Fair value of equity awards exchanged for cash attributable to pre-Acquisition service       $ 29,700      
WageWorks, Inc. | Pre Acquisition Restricted Stock Units              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Fair value of equity awards exchanged for cash attributable to pre-Acquisition service       3,800      
WageWorks, Inc. | Post Acquisition Restricted Stock Units              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Fair value of equity awards exchanged for cash attributable to pre-Acquisition service       25,900      
WageWorks, Inc. | Pre-acquisition Equity Awards              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Fair value of equity awards exchanged for cash attributable to pre-Acquisition service       18,100      
WageWorks, Inc. | Equity Awards              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Fair value of equity awards exchanged for cash attributable to pre-Acquisition service       23,600      
WageWorks, Inc. | Post-acquisition Equity Awards              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Fair value of equity awards exchanged for cash attributable to pre-Acquisition service       $ 5,600      
Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Number of share authorized (in shares)       2,600,000      
Additional shares available for grants as percentage of capital stock outstanding       3.00%      
Shares available for grant (shares)       4,800,000      
WageWorks Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Number of common stock issuable (in shares)             5,255,027
Stock options              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Expiration period after termination       10 years      
Expiration period from termination of employment       90 days      
Recognition period for stock-based compensation       1 year 4 months 24 days      
Unrecognized stock compensation expense to be recognized in future       $ 7,200      
Share based compensation       6,612 7,581 7,826  
Restricted stock units              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Aggregate intrinsic value       $ 22,500 $ 65,500 $ 44,800  
Recognition period for stock-based compensation       2 years 7 months 6 days      
Award vesting period       4 years      
Weighted-average grant date fair value (usd per share)       $ 65.20 $ 67.69 $ 44.61  
Share based compensation       $ 25,781 $ 7,657 $ 3,224  
Granted (in shares)       1,306,000      
Compensation not yet recognized, other than options       $ 65,900      
Aggregate intrinsic value       25,000 6,400 700  
Performance restricted stock units              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share based compensation       4,862 2,419 1,882  
Granted (in shares) 129,963   146,964        
Performance restricted stock units | Minimum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Percentage of options vested     0.00%        
Performance restricted stock units | Maximum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Percentage of options vested     150.00%        
Performance stock options              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share based compensation       $ 0 681 1,378  
Restricted stock awards              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Recognition period for stock-based compensation       1 year 3 months 18 days      
Award vesting period       4 years      
Weighted-average grant date fair value (usd per share)       $ 0      
Share based compensation       $ 655 570 0  
Granted (in shares)       0      
Compensation not yet recognized, other than options       $ 3,600      
Performance restricted stock awards              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share based compensation       $ 1,934 $ 2,149 $ 0  
Granted (in shares)   227,760          
Performance restricted stock awards | Minimum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Percentage of options vested 0.00% 0.00%          
Performance restricted stock awards | Maximum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Percentage of options vested 200.00% 200.00%