Long-Term Debt - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Sep. 30, 2012 Capital Trust Five [Member]	Sep. 30, 2012 Capital Trust Six [Member]	Mar. 31, 2012 Senior Debt Obligations Fixed Rate 3.5 Percent Notes Due 2022	Mar. 31, 2012 Structured Repurchase Agreements	Sep. 30, 2012 Structured Repurchase Agreements Capital Trust Five [Member]	Sep. 30, 2012 Structured Repurchase Agreements Capital Trust Six [Member]
Debt Instrument [Line Items]
Issue of senior notes to third party investors			$ 500
Interest rate			3.50%
Maturity date			March 15, 2022
Gains (Losses) on Extinguishment of Debt				(9)	(17)	(9)
Issuance date			March 7, 2012
Extinguishment of Debt, Amount				375
Trust Preferred Securities Redemption Amount	$ 575.0	$ 862.5
Redemption date	Aug. 15, 2012	Aug. 08, 2012
Distribution rate	7.25%	7.25%
Redemption price, per share	$ 25	$ 25
Unpaid or accrued distribution factor through the actual redemption date	$ 0.453125	$ 0.422917
Maturity date	Aug. 15, 2067	Nov. 15, 2067