v3.26.1
Corporate Investments and Funds Held for Clients - Schedule of Corporate Investments and Funds Held for Clients (Details) - USD ($)
Mar. 31, 2026
Jun. 30, 2025
Mar. 31, 2025
Debt Securities, Available-for-sale [Line Items]      
Money market securities, cash and other cash equivalents - Amortized Cost $ 3,228,400,000 $ 3,347,800,000 $ 2,680,600,000
Available-for-sale, Amortized Cost 37,405,000,000 34,203,400,000  
Available-for-sale, Gross Unrealized Gains 175,800,000 256,600,000  
Available-for-sale, Gross Unrealized Losses (537,200,000) (682,300,000)  
Available-for-sale, Fair Market Value 37,043,600,000 33,777,700,000  
Total corporate investments and funds held for clients - Amortized Cost 50,002,900,000 39,258,000,000  
Total corporate investments and funds held for clients - Gross Unrealized Gains 175,800,000 256,600,000  
Total corporate investments and funds held for clients - Gross Unrealized Losses (537,200,000) (682,300,000)  
Total corporate investments and funds held for clients -  Fair Market Value 49,641,500,000 38,832,300,000  
Corporate bonds      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale, Amortized Cost 18,465,400,000 17,515,200,000  
Available-for-sale, Gross Unrealized Gains 73,700,000 108,700,000  
Available-for-sale, Gross Unrealized Losses (330,500,000) (420,200,000)  
Available-for-sale, Fair Market Value 18,208,600,000 17,203,700,000  
U.S. Treasury securities      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale, Amortized Cost 10,658,100,000 8,416,800,000  
Available-for-sale, Gross Unrealized Gains 53,500,000 85,600,000  
Available-for-sale, Gross Unrealized Losses (27,000,000.0) (43,700,000)  
Available-for-sale, Fair Market Value 10,684,600,000 8,458,700,000  
Asset-backed securities      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale, Amortized Cost 2,258,100,000 1,837,800,000  
Available-for-sale, Gross Unrealized Gains 17,300,000 22,600,000  
Available-for-sale, Gross Unrealized Losses (12,600,000) (15,500,000)  
Available-for-sale, Fair Market Value 2,262,800,000 1,844,900,000  
Canadian government obligations and Canadian government agency obligations      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale, Amortized Cost 1,891,300,000 1,972,000,000  
Available-for-sale, Gross Unrealized Gains 10,300,000 16,400,000  
Available-for-sale, Gross Unrealized Losses (24,800,000) (32,400,000)  
Available-for-sale, Fair Market Value 1,876,800,000 1,956,000,000  
Canadian provincial bonds      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale, Amortized Cost 1,162,600,000 1,155,800,000  
Available-for-sale, Gross Unrealized Gains 11,900,000 13,800,000  
Available-for-sale, Gross Unrealized Losses (20,900,000) (27,700,000)  
Available-for-sale, Fair Market Value 1,153,600,000 1,141,900,000  
U.S. government agency securities      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale, Amortized Cost 930,300,000 1,328,500,000  
Available-for-sale, Gross Unrealized Gains 2,800,000 2,300,000  
Available-for-sale, Gross Unrealized Losses (67,300,000) (80,000,000.0)  
Available-for-sale, Fair Market Value 865,800,000 1,250,800,000  
Other securities      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale, Amortized Cost 2,039,200,000 1,977,300,000  
Available-for-sale, Gross Unrealized Gains 6,300,000 7,200,000  
Available-for-sale, Gross Unrealized Losses (54,100,000) (62,800,000)  
Available-for-sale, Fair Market Value 1,991,400,000 1,921,700,000  
Funds Held For Clients      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale, Fair Market Value 37,043,600,000 29,278,900,000  
Corporate Investments      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale, Fair Market Value 0 4,498,800,000  
Money market securities, cash and other cash equivalents      
Debt Securities, Available-for-sale [Line Items]      
Money market securities, cash and other cash equivalents - Amortized Cost 12,597,900,000 5,054,600,000  
Money market securities and other cash equivalents -  Fair Market Value $ 12,597,900,000 $ 5,054,600,000