Condensed Financial Information (Parent Company) (Details Textuals 1) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended				9 Months Ended	12 Months Ended
	Dec. 31, 2012 Series B Non-Cumulative Perpetual Preferred Shares [Member]	Dec. 31, 2012 Parent Company [Member]	Dec. 31, 2011 Parent Company [Member]	Dec. 31, 2012 Parent Company [Member] Investments in Majority-owned Subsidiaries [Member]	Sep. 30, 2012 Parent Company [Member] Investments in Majority-owned Subsidiaries [Member] Series A Non-Cumulative Perpetual Preferred Shares [Member]	Dec. 31, 2012 Parent Company [Member] Investments in Majority-owned Subsidiaries [Member] Series B Non-Cumulative Perpetual Preferred Shares [Member]
Condensed Financial Statements, Captions [Line Items]
Investment in subsidiaries		$ 81,769	$ 74,281	$ 2,000
Investments in subsidiaries, shares					75,000	125,000
Investments in subsidiaries, annual rate	6.50%				7.69%	7.75%