Loans Receivable and Allowance for Credit Losses on Loans (Schedule of Allowance for Loan Losses by Portfolio Segment) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 55,525	$ 55,562
Retained earnings (due to initial CECL adoption)	7,920
Provision charged (credited) to operations	14,700	200
Recoveries of loans previously charged-off	529	412
Loans charged-off	(3,531)	(821)
Balance at end of period	75,143	55,353
Mortgage Portfolio Segment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	25,511	27,678
Retained earnings (due to initial CECL adoption)	14,188
Provision charged (credited) to operations	7,710	(982)
Recoveries of loans previously charged-off	93	230
Loans charged-off	(2)	0
Balance at end of period	47,500	26,926
Commercial Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	28,263	25,693
Retained earnings (due to initial CECL adoption)	(9,974)
Provision charged (credited) to operations	7,619	1,282
Recoveries of loans previously charged-off	313	52
Loans charged-off	(3,380)	(676)
Balance at end of period	22,841	26,351
Consumer Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	1,751	2,191
Retained earnings (due to initial CECL adoption)	3,706
Provision charged (credited) to operations	(629)	(100)
Recoveries of loans previously charged-off	123	130
Loans charged-off	(149)	(145)
Balance at end of period	$ 4,802	$ 2,076