Deposits (Summary of Deposits) (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Balance:
Non-interest bearing	$ 6,353,456	$ 6,569,880	$ 6,612,319
NOW and interest bearing demand deposits	2,948,576	2,897,133	2,315,122
Wealth management deposits	3,328,781	2,996,764	2,495,134
Money market	6,093,596	5,704,866	4,617,122
Savings	2,729,626	2,665,194	2,901,504
Time certificates of deposit	5,350,707	5,260,841	4,338,126
Total deposits	$ 26,804,742	$ 26,094,678	$ 23,279,327
Mix:
Non-interest bearing	24.00%	25.00%	28.00%
NOW and interest bearing demand deposits	11.00%	11.00%	10.00%
Wealth management deposits	12.00%	12.00%	11.00%
Money market	23.00%	22.00%	20.00%
Savings	10.00%	10.00%	12.00%
Time certificates of deposit	20.00%	20.00%	19.00%
Total deposits	100.00%	100.00%	100.00%