Liabilities and Assets Subject to Netting Arrangements (Detail) - USD ($) $ in Thousands		Dec. 31, 2019		Dec. 31, 2018
Derivative Assets Derivative Liabilities And Repurchase Agreements Subject To Netting Agreements [Line Items]
Gross Amounts of Recognized Assets		$ 5,833		$ 46,207
Net Amounts of Assets Presented in the Balance Sheets		5,833		46,207
Gross Assets Not Offset Financial instruments		(5,833)	[1]	(46,207)
Gross Assets Not Offset Cash Collateral Received	[1]	367
Gross Assets Not Offset Net Amounts	[1]	(5,466)
Gross Amounts of Recognized Liabilities		3,843,881		3,827,528
Net Amounts of Liabilities Presented in the Balance Sheets		3,843,881		3,827,528
Gross Liabilities Not Offset Financial instruments		(3,843,881)	[1]	(3,827,528)
Derivative Financial Instruments, Assets
Derivative Assets Derivative Liabilities And Repurchase Agreements Subject To Netting Agreements [Line Items]
Gross Amounts of Recognized Assets		5,833		46,207
Net Amounts of Assets Presented in the Balance Sheets		5,833		46,207
Gross Assets Not Offset Financial instruments		(5,833)	[1]	(46,207)
Gross Assets Not Offset Cash Collateral Received	[1]	367
Gross Assets Not Offset Net Amounts	[1]	(5,466)
Repurchase Agreements
Derivative Assets Derivative Liabilities And Repurchase Agreements Subject To Netting Agreements [Line Items]
Gross Amounts of Recognized Liabilities		3,657,873		3,811,627
Net Amounts of Liabilities Presented in the Balance Sheets		3,657,873		3,811,627
Gross Liabilities Not Offset Financial instruments		(3,657,873)	[1]	(3,811,627)
Warehouse Line of Credit
Derivative Assets Derivative Liabilities And Repurchase Agreements Subject To Netting Agreements [Line Items]
Gross Amounts of Recognized Liabilities		133,811
Net Amounts of Liabilities Presented in the Balance Sheets		133,811
Gross Liabilities Not Offset Financial instruments	[1]	(133,811)
Derivative Financial Instruments, Liabilities
Derivative Assets Derivative Liabilities And Repurchase Agreements Subject To Netting Agreements [Line Items]
Gross Amounts of Recognized Liabilities		52,197		15,901
Net Amounts of Liabilities Presented in the Balance Sheets		52,197		15,901
Gross Liabilities Not Offset Financial instruments		$ (52,197)	[1]	$ (15,901)

[1] Amounts presented are limited to collateral pledged sufficient to reduce the related net amount to zero in accordance with ASU No. 201111, as amended by ASU No. 201301.