Banking Regulatory Ratios (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Tier 1 capital	$ 7,449.2	$ 6,788.8
Total risk-based capital	$ 7,482.6	$ 6,799.6
Tier 1 leverage ratio	58.00%	59.00%
Tier 1 risk-based capital ratio	58.00%	54.00%
Total risk-based capital ratio	58.00%	54.00%
Capital Adequacy Minimum [Member]
Tier 1 leverage ratio	4.00%
Tier 1 risk-based capital ratio	4.00%
Total risk-based capital ratio	8.00%