Deposits (Summary of Deposits) (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Balance:
Non-interest bearing	$ 5,367,672	$ 4,836,420	$ 3,910,310
NOW and interest bearing demand deposits	2,450,710	2,390,217	2,240,832
Wealth management deposits	1,904,121	1,643,653	1,591,251
Money market	4,384,134	4,041,300	3,898,495
Savings	1,851,863	1,723,367	1,504,654
Time certificates of deposit	4,083,250	4,004,677	3,936,876
Total deposits	$ 20,041,750	$ 18,639,634	$ 17,082,418
Mix:
Non-interest bearing	27.00%	26.00%	23.00%
NOW and interest bearing demand deposits	12.00%	13.00%	13.00%
Wealth management deposits	10.00%	9.00%	9.00%
Money market	22.00%	22.00%	23.00%
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%