Carrying amount and classification of assets related to the Corporation's variable interests in non-consolidated VIEs and maximum exposure to loss (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Prlp2011 Holdings Llc Joint Venture [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	$ 89,224	$ 102,272
Liabilities	(4,781)	(48)
Net assets	84,443	102,224
Variable Interest Entity Entity Maximum Loss Exposure Amount	84,443	102,224
Fnma Gnma Fhlmc Vie [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	130,436	104,538
Variable Interest Entity Entity Maximum Loss Exposure Amount	130,436	104,538
Loan | Prlp2011 Holdings Llc Joint Venture [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	50,877	64,711
Acquisition Loan [Member] | Prlp2011 Holdings Llc Joint Venture [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	45,504	64,711
Advances Working Capital Line [Member] | Prlp2011 Holdings Llc Joint Venture [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	538	0
Advances Advance Facility [Member] | Prlp2011 Holdings Llc Joint Venture [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	4,835	0
Accrued Income Receivable [Member] | Prlp2011 Holdings Llc Joint Venture [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	138	0
Other Assets Member | Prlp2011 Holdings Llc Joint Venture [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	38,209	37,561
Other Assets Member | Fnma Gnma Fhlmc Vie [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	1,799	3,027
Other Advances [Member] | Fnma Gnma Fhlmc Vie [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	1,799	3,027
Equity Method Investments [Member] | Prlp2011 Holdings Llc Joint Venture [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	38,209	37,561
Servicing Asset At Fair Value Amount [Member] | Fnma Gnma Fhlmc Vie [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	128,637	101,511
Mortgage Servicing Rights [Member] | Fnma Gnma Fhlmc Vie [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Assets	128,637	101,511
Deposits Member | Prlp2011 Holdings Llc Joint Venture [Member]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Liabilities	$ (4,781)	$ (48)