Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deposits [Line Items]
Noninterest-bearing demand	$ 4,310,105	$ 4,437,294
Interest-bearing demand	4,240,974	4,018,107
Savings and money market accounts	4,926,937	4,586,746
Total demand and savings	13,478,016	13,042,147
Time deposits	2,721,904	2,664,912
Total Deposits	16,376,159	15,797,532
Time Deposits, $250,000 or More	425,100	373,900
Maturities of Time Deposits [Abstract]
2019	1,561,694
2020	667,265
2021	253,314
2022	153,447
2023	31,230
Thereafter	54,954
Total	2,721,904	2,664,912
Interest-bearing Domestic Deposit, Brokered	176,239	90,473
Certificates of Deposit
Deposits [Line Items]
Time Deposits, $100,000 or More	$ 1,200,000	$ 1,200,000