Deposits (Summary of Deposits) (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Balance:
Non-interest bearing	$ 6,294,052	$ 5,927,377	$ 5,367,672
NOW and interest bearing demand deposits	2,459,238	2,624,442	2,450,710
Wealth management deposits	2,464,162	2,209,617	1,904,121
Money market	4,449,385	4,441,811	4,384,134
Savings	2,419,463	2,180,482	1,851,863
Time certificates of deposit	4,519,392	4,274,903	4,083,250
Total deposits	$ 22,605,692	$ 21,658,632	$ 20,041,750
Mix:
Non-interest bearing	28.00%	27.00%	27.00%
NOW and interest bearing demand deposits	11.00%	12.00%	12.00%
Wealth management deposits	11.00%	10.00%	10.00%
Money market	19.00%	21.00%	22.00%
Savings	11.00%	10.00%	9.00%
Time certificates of deposit	20.00%	20.00%	20.00%
Total deposits	100.00%	100.00%	100.00%