Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Interest-bearing Deposit Liabilities [Abstract]
Interest bearing demand deposits	$ 5,157,175	$ 4,768,313
Money market accounts, excluding brokered deposits	7,435,941	7,251,093
Savings accounts	798,935	929,402
Time deposits, excluding brokered deposits	3,108,385	3,234,465
Brokered deposits	1,961,125	1,378,983
Total interest bearing deposits	18,461,561	17,562,256
Aggregate amount of time deposits of $250,000 or more	921,800	$ 829,500
Time Deposits, by Maturity [Abstract]
Maturing within one year	2,544,033
Between 1 — 2 years	851,665
2 — 3 years	567,279
3 — 4 years	248,473
4 — 5 years	65,521
Thereafter	242,909
Time deposits	$ 4,519,880