Goodwill (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2014	May 31, 2013
Bank Reporting Unit [Member]
Goodwill [Line Items]
Goodwill allocated to bank reporting unit	$ 1,165,200	$ 1,165,200
Fair value of the bank reporting unit exceeding carrying value	25.40%	44.60%
Wealth Management Reporting Unit [Member]
Goodwill [Line Items]
Goodwill allocated to wealth management reporting unit	82,746	82,746
Future economic benefit period, in years	10 years
Fair value of the wealth management reporting unit exceeding carrying value	51.50%	45.90%
Property And Casualty Insurance Reporting Unit [Member]
Goodwill [Line Items]
Goodwill allocated to property and casualty insurance reporting unit	$ 17,177	$ 17,177
Number of key ratios used in measuring the fair value of the property and casualty insurance reporting unit	2
Fair value of the property and casualty insurance reporting unit exceeding carrying value	25.60%	21.70%