Deposits (Summary of Deposits) (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Balance:
Non-interest bearing	$ 6,520,724	$ 6,792,497	$ 6,294,052
NOW and interest bearing demand deposits	2,452,474	2,315,055	2,459,238
Wealth management deposits	2,523,572	2,323,699	2,464,162
Money market	5,205,678	4,515,353	4,449,385
Savings	2,763,062	2,829,373	2,419,463
Time certificates of deposit	4,899,969	4,407,370	4,519,392
Total deposits	$ 24,365,479	$ 23,183,347	$ 22,605,692
Mix:
Non-interest bearing	27.00%	29.00%	28.00%
NOW and interest bearing demand deposits	10.00%	10.00%	11.00%
Wealth management deposits	11.00%	10.00%	11.00%
Money market	21.00%	20.00%	19.00%
Savings	11.00%	12.00%	11.00%
Time certificates of deposit	20.00%	19.00%	20.00%
Total deposits	100.00%	100.00%	100.00%