Deposits Deposits (Summary of Deposits) (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Balance:
Non-interest bearing	$ 3,910,310	$ 3,518,685	$ 3,072,430
NOW and interest bearing demand deposits	2,240,832	2,236,089	2,002,868
Wealth management deposits	1,591,251	1,226,916	1,220,102
Money market	3,898,495	3,651,467	3,591,540
Savings	1,504,654	1,508,877	1,427,222
Time certificates of deposit	3,936,876	4,139,810	4,242,214
Total deposits	$ 17,082,418	$ 16,281,844	$ 15,556,376
Mix:
Non-interest bearing	23.00%	22.00%	20.00%
NOW and interest bearing demand deposits	13.00%	14.00%	13.00%
Wealth management deposits	9.00%	8.00%	8.00%
Money market	23.00%	22.00%	23.00%
Savings	9.00%	9.00%	9.00%
Time certificates of deposit	23.00%	25.00%	27.00%
Total deposits	100.00%	100.00%	100.00%