Loan Securitization (Narrative) (Detail) (USD $)	3 Months Ended							0 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Sep. 30, 2009	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Restricted Assets And Liabilities [Member]	Dec. 31, 2012 Restricted Assets And Liabilities [Member]	Aug. 15, 2012 Class A [Member]	Aug. 15, 2012 Class B and C [Member]	Sep. 30, 2009 Capital Unit, Class A [Member]
Debt Instrument [Line Items]
Instruments issued by the securitization entity										$ 600,000,000
Debt Instrument, Description of Variable Rate Basis			One-month LIBOR
Incremental interest rate over base rate										1.45%
Company repurchased notes	67,200,000	172,000,000						360,800,000	49,600,000
Secured borrowings-owed to securitization investors	360,800,000	428,000,000		0	0	0	0
Proceeds from Secured Debt Intercompany								239,200,000
Cash Collateral for Borrowed Securities						$ 36,000	$ 36,000