Derivative Financial Instruments - Schedule of Net Gains (Losses) Related to Derivatives Not Designated as Hedging Instruments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Net fair value gains (losses) on derivatives	$ (11,927)	$ 184,503
Interest Rate Lock Commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net fair value gains (losses) on derivatives	53,791	95,195
Forward Sales Commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net fair value gains (losses) on derivatives	(116,131)	63,557
MBS purchase commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net fair value gains (losses) on derivatives	$ 50,413	$ 25,751