Summary of Significant Accounting Policies (Details) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended				12 Months Ended															12 Months Ended			12 Months Ended					0 Months Ended				0 Months Ended				0 Months Ended				12 Months Ended			12 Months Ended
	May 31, 2012 reporting_units	May 31, 2011	May 31, 2010	May 31, 2009	May 31, 2012 Check guarantee loss reserve [Member]	May 31, 2011 Check guarantee loss reserve [Member]	May 31, 2010 Check guarantee loss reserve [Member]	May 31, 2012 Hardware and Software [Member]	May 31, 2012 Customer-related	May 31, 2012 Stock Options [Member]	May 31, 2011 Stock Options [Member]	May 31, 2010 Stock Options [Member]	May 31, 2012 Notes Payable UCS	May 31, 2012 UNITED KINGDOM	May 31, 2011 UNITED KINGDOM	May 31, 2010 Paid-in Capital [Member]	May 31, 2012 Paid-in Capital [Member]	May 31, 2011 Paid-in Capital [Member]	May 31, 2009 Paid-in Capital [Member]	May 31, 2012 Paid-in Capital [Member] Adjustment for correction error [Member]	May 31, 2011 Paid-in Capital [Member] Adjustment for correction error [Member]	May 31, 2010 Paid-in Capital [Member] Adjustment for correction error [Member]	May 31, 2011 Treasury Stock [Member] Adjustment for correction error [Member]	May 31, 2010 Retained Earnings [Member]	May 31, 2012 Retained Earnings [Member]	May 31, 2011 Retained Earnings [Member]	May 31, 2009 Retained Earnings [Member]	May 31, 2009 Previously Reported [Member]	May 31, 2011 Previously Reported [Member]	May 31, 2010 Previously Reported [Member]	May 29, 2009 Previously Reported [Member]	May 31, 2009 Previously Reported [Member] Paid-in Capital [Member]	May 31, 2011 Previously Reported [Member] Paid-in Capital [Member]	May 31, 2010 Previously Reported [Member] Paid-in Capital [Member]	May 29, 2009 Previously Reported [Member] Paid-in Capital [Member]	May 31, 2009 Previously Reported [Member] Retained Earnings [Member]	May 31, 2011 Previously Reported [Member] Retained Earnings [Member]	May 31, 2010 Previously Reported [Member] Retained Earnings [Member]	May 29, 2009 Previously Reported [Member] Retained Earnings [Member]	May 31, 2012 Supplemental Employee Retirement Plans, Defined Benefit [Member] participant	May 31, 2012 Merchant Reserves [Member]	May 31, 2011 Merchant Reserves [Member]	May 31, 2012 Fair value of guarantees of customer chargebacks [Member]	May 31, 2011 Fair value of guarantees of customer chargebacks [Member]	May 31, 2010 Fair value of guarantees of customer chargebacks [Member]
Accounting Policies [Line Items]
Decrease to treasury stock and increase to paid-in capital due to error correction																				$ 13,000,000			$ (12,980,000)
Equity	1,300,921,000	1,337,817,000	871,517,000	678,243,000												390,325,000	358,728,000	419,591,000	420,688,000					515,194,000	843,456,000	685,624,000	257,643,000		1,337,817,000	871,517,000	678,243,000		419,591,000	390,325,000	405,241,000		685,624,000	515,194,000	273,090,000
Retrospective adjustment for the correction of an error																					113,000,000	100,000,000
Retrospective adjustment for the change in accounting method for the retirement of repurchased shares			0													14,131,000								(14,131,000)				0				15,447,000				(15,447,000)
Number of merchant services segments	2
Cash and cash equivalents	781,275,000	1,354,285,000	769,946,000	426,935,000																																					328,200,000	271,400,000
Cost of service	784,756,000	665,017,000	584,609,000																																								8,800,000	6,000,000	9,600,000
Recoverability of guaranteed checks	have not historically recovered 100% of the guaranteed checks
Claims receivable, allowance for losses	3,435,000	3,870,000			3,400,000	3,900,000
Provision for doubtful accounts	22,417,000	20,577,000	25,025,000		13,400,000	14,200,000	14,900,000
Property and equipment	467,759,000	403,971,000						86,500,000
Property, plant and equipment placed into service during period								31,600,000
Number of reporting units	6
Intangible assets, useful life, maximum (in years)									30
Net deferred tax asset	145,202,000	126,171,000												92,800,000
Effective tax rate	27.60%	29.30%	28.20%
Effective income tax rate reconciliation, change in enacted tax rate														2.00%	1.00%
Interest rate, minimum													8.00%
Interest rate, range, maximum													8.50%
Financing receivable	$ 13,500,000	$ 18,900,000
Number of plan participants																																								1
Employee compensation, number of highest consecutive years of earnings used to compute benefits																																								3 years
Employee compensation, number of most recent years of service used to compute benefits																																								10 years
Antidilutive securities excluded from computation of diluted share base (in shares)										0.2	0.7	0.5