Short-Term Debt - Liabilities and Assets Subject to Netting Arrangements (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Derivative Assets Derivative Liabilities And Repurchase Agreements Subject To Netting Agreements [Line Items]
Gross Amounts of Recognized Assets	$ 2,205	$ 5,833
Net Amounts of Assets Presented in the Balance Sheets	2,205	5,833
Gross Assets Not Offset Financial instruments	(2,205)	(5,833)
Gross Assets Not Offset Cash Collateral Received	2,056	367
Gross Assets Not Offset Net Amounts	(149)	(5,466)
Gross Amounts of Recognized Liabilities	1,895,118	3,843,881
Net Amounts of Liabilities Presented in the Balance Sheets	1,895,118	3,843,881
Gross Liabilities Not Offset Financial instruments	(1,895,118)	(3,843,881)
Derivative Financial Instruments, Assets
Derivative Assets Derivative Liabilities And Repurchase Agreements Subject To Netting Agreements [Line Items]
Gross Amounts of Recognized Assets	2,205	5,833
Net Amounts of Assets Presented in the Balance Sheets	2,205	5,833
Gross Assets Not Offset Financial instruments	(2,205)	(5,833)
Gross Assets Not Offset Cash Collateral Received	2,056	367
Gross Assets Not Offset Net Amounts	(149)	(5,466)
Repurchase Agreements.
Derivative Assets Derivative Liabilities And Repurchase Agreements Subject To Netting Agreements [Line Items]
Gross Amounts of Recognized Liabilities	1,697,181	3,657,873
Net Amounts of Liabilities Presented in the Balance Sheets	1,697,181	3,657,873
Gross Liabilities Not Offset Financial instruments	(1,697,181)	(3,657,873)
Warehouse Line of Credit
Derivative Assets Derivative Liabilities And Repurchase Agreements Subject To Netting Agreements [Line Items]
Gross Amounts of Recognized Assets		133,811
Net Amounts of Assets Presented in the Balance Sheets		133,811
Gross Assets Not Offset Financial instruments		(133,811)
Gross Amounts of Recognized Liabilities	104,620
Net Amounts of Liabilities Presented in the Balance Sheets	104,620
Gross Liabilities Not Offset Financial instruments	(104,620)
Derivative Financial Instruments, Liabilities
Derivative Assets Derivative Liabilities And Repurchase Agreements Subject To Netting Agreements [Line Items]
Gross Amounts of Recognized Liabilities	93,317	52,197
Net Amounts of Liabilities Presented in the Balance Sheets	93,317	52,197
Gross Liabilities Not Offset Financial instruments	$ (93,317)	$ (52,197)