Deposits (Summary of Deposits) (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Balance:
Non-interest bearing	$ 5,711,042	$ 4,836,420	$ 4,705,994
NOW and interest bearing demand deposits	2,552,611	2,390,217	2,231,258
Wealth management deposits	2,283,233	1,643,653	1,469,920
Money market	4,421,631	4,041,300	4,001,518
Savings	1,977,661	1,723,367	1,684,007
Time certificates of deposit	4,201,477	4,004,677	4,135,772
Total deposits	$ 21,147,655	$ 18,639,634	$ 18,228,469
Mix:
Non-interest bearing	27.00%	26.00%	26.00%
NOW and interest bearing demand deposits	12.00%	13.00%	12.00%
Wealth management deposits	11.00%	9.00%	8.00%
Money market	21.00%	22.00%	22.00%
Savings	9.00%	9.00%	9.00%
Time certificates of deposit	20.00%	21.00%	23.00%
Total deposits	100.00%	100.00%	100.00%