Condensed Consolidating Financial Statements (Cash Flows) (Details) - USD ($) $ in Thousands	9 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Apr. 30, 2015	Apr. 30, 2014
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities:	$ (1,426,949)	$ (1,247,200)
Sales, maturities of and payments received on AFS securities	436,380	68,013
Principal payments on mortgage loans held for investment, net	24,664	18,098
Capital expenditures	(66,418)	(98,876)
Payments made for business acquisitions, net of cash acquired	(85,329)	(112,163)
Loans made to franchisees	(21,377)	(48,013)
Repayments from franchisees	22,234	34,164
Other, net	3,887	6,079
Net cash provided by (used in) investing activities	314,041	(132,698)
Repayments of Commercial Paper	0	457,576
Proceeds from Issuance of Commercial Paper	0	1,049,062
Repayments of long-term debt	(225,000)	(400,000)
Proceeds from issuance of long-term debt	2,346,831	0
Customer banking deposits, net	(326,705)	515,015
Transfer of bank deposits	(419,028)	0
Dividends paid	(157,530)	(164,905)
Repurchase of common stock, including shares surrendered	(1,888,595)	(10,355)
Proceeds from exercise of stock options	25,803	16,026
Other, net	(43,972)	(15,993)
Net cash used in financing activities	(688,196)	531,274
Effects of exchange rates on cash	(16,575)	(15,549)
Net decrease in cash and cash equivalents	(1,817,679)	(864,173)
Cash & cash equivalents	189,511	1,321,134	$ 2,007,190	$ 2,185,307
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends paid	(157,530)	(164,905)
Repurchase of common stock, including shares surrendered	(1,888,595)	(10,355)
Proceeds from exercise of stock options	25,803	16,026
Intercompany borrowings	2,024,025	159,234
Other, net	(3,703)
Block Financial Issuer [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities:	(403,132)	(290,104)
Sales, maturities of and payments received on AFS securities	430,460	68,013
Principal payments on mortgage loans held for investment, net	24,664	18,098
Capital expenditures	(24)	(119)
Loans made to franchisees	(20,940)	(47,835)
Repayments from franchisees	22,006	33,927
Intercompany payments/investments in subsidiaries	(1,871,617)	(128,713)
Other, net	(5,455)	(1,925)
Net cash provided by (used in) investing activities	(1,420,906)	(58,554)
Repayments of Commercial Paper		457,576
Proceeds from Issuance of Commercial Paper		1,049,062
Repayments of long-term debt	(225,000)	(400,000)
Proceeds from issuance of long-term debt	2,346,831
Customer banking deposits, net	(327,145)	514,183
Transfer of bank deposits	(419,028)
Other, net	(19,282)
Net cash used in financing activities	1,356,376	705,669
Net decrease in cash and cash equivalents	(467,662)	357,011
Cash & cash equivalents	10,415	969,387	478,077	612,376
Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities:	(1,023,817)	(957,096)
Sales, maturities of and payments received on AFS securities	5,920
Capital expenditures	(66,394)	(98,757)
Payments made for business acquisitions, net of cash acquired	(85,329)	(112,163)
Loans made to franchisees	(437)	(178)
Repayments from franchisees	228	237
Intercompany payments/investments in subsidiaries	(2,024,025)	(159,234)
Other, net	9,342	8,004
Net cash provided by (used in) investing activities	(2,160,695)	(362,091)
Intercompany borrowings	1,871,617	128,713
Other, net	(20,987)	(15,993)
Net cash used in financing activities	1,850,630	112,720
Effects of exchange rates on cash	(16,575)	(15,549)
Net decrease in cash and cash equivalents	(1,350,457)	(1,222,016)
Cash & cash equivalents	179,096	352,015	1,529,553	1,574,031
Intersegment Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Intercompany payments/investments in subsidiaries	3,895,642	287,947
Net cash provided by (used in) investing activities	3,895,642	287,947
Customer banking deposits, net	440	832
Intercompany borrowings	(3,895,642)	(287,947)
Net cash used in financing activities	(3,895,202)	(287,115)
Net decrease in cash and cash equivalents	$ 440	832
Cash & cash equivalents		$ (268)	$ (440)	$ (1,100)