Advances From Federal Home Loan Bank (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Sep. 30, 2011	Dec. 30, 2011	Dec. 31, 2012 Advances From FHLB [Member]	Dec. 31, 2011 Advances From FHLB [Member]	Sep. 30, 2011 Advances From FHLB [Member]
Payments for Federal Home Loan Bank Advances	$ 125.0	$ 175.0
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Interest Rate	3.15%
Liabilities Subject to Compromise, Early Contract Termination Fees	8.5
Federal Home Loan Bank, Advances Yield Rate		3.93%
Loans Pledged as Collateral				590.9	730.8	692.7
Trading Securities Pledged as Collateral				28.2	104.6	126.8
Line of Credit Facility, Remaining Borrowing Capacity	70.0	35.0	40.0	348.2	267.2	254.5
Maximum borrowings permitted, as a percentage of total eligible assets				40.00%
Line of Credit Facility, Maximum Borrowing Capacity				$ 619.1	$ 834.9	$ 819.5