Deposits (Summary of Deposits) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deposits [Abstract]
Non-interest bearing	$ 7,216,758	$ 6,569,880
NOW and interest bearing demand deposits	3,093,159	2,897,133
Wealth management deposits	3,123,063	2,996,764
Money market	7,854,189	5,704,866
Savings	3,196,698	2,665,194
Time certificates of deposit	5,623,271	5,260,841
Total deposits	$ 30,107,138	$ 26,094,678
Non-interest bearing (as a percent)	24.00%	25.00%
NOW and interest bearing demand deposits (as a percent)	10.00%	11.00%
Wealth management deposits (as a percent)	10.00%	12.00%
Money market (as a percent)	26.00%	22.00%
Savings (as a percent)	11.00%	10.00%
Time certificates of deposit (as a percent)	19.00%	20.00%
Total deposits (as a percent)	100.00%	100.00%