Condensed Consolidating Financial Statements (Cash Flows) (Details) - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Apr. 30, 2016	Apr. 30, 2015
Condensed Financial Statements, Captions [Line Items]
Net cash used in operating activities:	$ (725,797)	$ (602,713)
Sales, maturities of and payments received on AFS securities	144	434,261
Principal payments on mortgage loans, net	16,706	17,006
Capital expenditures	(44,918)	(38,779)
Payments made for business acquisitions, net of cash acquired	(36,151)	(61,846)
Loans made to franchisees	(10,171)	(10,281)
Repayments from franchisees	(14,263)	(17,473)
Other, net	4,336	7,246
Net cash provided by (used in) investing activities	(55,791)	365,080
Repayments of Long-term Lines of Credit	50,000	0
Proceeds from Long-term Lines of Credit	525,000	0
Proceeds from Issuance of Long-term Debt	0	996,831
Customer banking deposits, net	0	(326,705)
Transfer of bank deposits	0	(419,028)
Dividends paid	(95,971)	(110,338)
Repurchase of common stock, including shares surrendered	(215,511)	(1,517,786)
Proceeds from exercise of stock options	1,630	16,875
Other, net	(43,734)	(37,820)
Net cash used in financing activities	121,414	(1,397,971)
Effects of exchange rates on cash	(4,117)	(10,905)
Net decrease in cash and cash equivalents	(664,291)	(1,646,509)
Cash & cash equivalents	232,510	360,681	$ 896,801	$ 2,007,190
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends paid	(95,971)	(110,338)
Repurchase of common stock, including shares surrendered	(215,511)	(1,517,786)
Proceeds from exercise of stock options	1,630	16,875
Intercompany borrowings (payments)	309,852	1,611,564
Other, net		(315)
Block Financial Issuer [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash used in operating activities:	(77,916)	36,078
Sales, maturities of and payments received on AFS securities	144	430,460
Principal payments on mortgage loans, net	16,706	17,006
Capital expenditures	(5)	(20)
Loans made to franchisees	(10,064)	(10,206)
Repayments from franchisees	(14,052)	(17,301)
Intercompany borrowings (payments)	(426,824)	(1,200,465)
Other, net	1,847	4,854
Net cash provided by (used in) investing activities	(404,144)	(741,070)
Repayments of Long-term Lines of Credit	50,000
Proceeds from Long-term Lines of Credit	525,000
Proceeds from Issuance of Long-term Debt		996,831
Customer banking deposits, net		(327,145)
Transfer of bank deposits		(419,028)
Other, net		(16,879)
Net cash used in financing activities	475,000	233,779
Net decrease in cash and cash equivalents	(7,060)	(471,213)
Cash & cash equivalents	1,965	6,864	9,025	478,077
Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash used in operating activities:	(647,881)	(638,791)
Sales, maturities of and payments received on AFS securities		3,801
Capital expenditures	(44,913)	(38,759)
Payments made for business acquisitions, net of cash acquired	(36,151)	(61,846)
Loans made to franchisees	(107)	(75)
Repayments from franchisees	(211)	(172)
Intercompany borrowings (payments)	(309,852)	(1,611,564)
Other, net	2,489	2,392
Net cash provided by (used in) investing activities	(388,323)	(1,705,879)
Intercompany borrowings (payments)	426,824	1,200,465
Other, net	(43,734)	(20,626)
Net cash used in financing activities	383,090	1,179,839
Effects of exchange rates on cash	(4,117)	(10,905)
Net decrease in cash and cash equivalents	(657,231)	(1,175,736)
Cash & cash equivalents	230,545	353,817	$ 887,776	1,529,553
Intersegment Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Intercompany borrowings (payments)	736,676	2,812,029
Net cash provided by (used in) investing activities	736,676	2,812,029
Customer banking deposits, net		440
Intercompany borrowings (payments)	(736,676)	(2,812,029)
Net cash used in financing activities	$ (736,676)	(2,811,589)
Net decrease in cash and cash equivalents		$ 440
Cash & cash equivalents				$ (440)