Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Interest-bearing Deposit Liabilities [Abstract]
Interest-bearing demand deposits	$ 4,756,239	$ 5,157,175
Money market accounts, excluding brokered deposits	8,143,975	7,435,941
Savings accounts	817,385	798,935
Time deposits, excluding brokered deposits	3,803,726	3,108,385
Brokered deposits	1,548,030	1,961,125
Total interest-bearing deposits	19,069,355	18,461,561
Aggregate amount of time deposits of $250,000 or more	1,100,000	$ 921,800
Time Deposits, by Maturity [Abstract]
Maturing within one year	3,323,071
Between 1 - 2 years	973,732
2 - 3 years	426,823
3 - 4 years	57,347
4 - 5 years	217,622
Thereafter	4,801
Time deposits	$ 5,003,396