Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity) - Changes in Carrying Amount of Mortgage Loans Held-for-sale (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Loans Receivable Held-for-sale, Net, Reconciliation to Cash Flow [Roll Forward]
Balance at beginning of period	$ 107,734	$ 134,916	$ 157,041
Originations and purchases	1,967,532	1,469,847	1,844,358
Sales, net of gains	(1,869,148)	(1,498,386)	(1,859,565)
Mortgage loans transferred from (transferred to) held for investment	7,239	1,058	(6,918)
Other	0	(299)	0
Balance at end of period	213,357	107,734	134,916
Mortgage loans held for sale
Loans Receivable Held-for-sale, Net, Reconciliation to Cash Flow [Roll Forward]
Balance at beginning of period	107,734	134,916
Balance at end of period	$ 213,357	$ 107,734	$ 134,916