Deposits (Summary of Deposits) (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Balance:
Non-interest bearing	$ 5,205,410	$ 4,836,420	$ 3,779,609
NOW and interest bearing demand deposits	2,369,474	2,390,217	2,262,928
Wealth management deposits	1,761,710	1,643,653	1,528,963
Money market	4,157,083	4,041,300	3,791,762
Savings	1,766,552	1,723,367	1,563,752
Time certificates of deposit	3,956,842	4,004,677	4,011,755
Total deposits	$ 19,217,071	$ 18,639,634	$ 16,938,769
Mix:
Non-interest bearing	27.00%	26.00%	22.00%
NOW and interest bearing demand deposits	12.00%	13.00%	13.00%
Wealth management deposits	9.00%	9.00%	9.00%
Money market	22.00%	22.00%	23.00%
Savings	9.00%	9.00%	9.00%
Time certificates of deposit	21.00%	21.00%	24.00%
Total deposits	100.00%	100.00%	100.00%