Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deposits [Line Items]
Noninterest-bearing demand	$ 4,437,294	$ 4,376,137
Interest-bearing demand	4,018,107	3,703,712
Savings and money market accounts	4,586,746	4,179,773
Total demand and savings	13,042,147	12,259,622
Time deposits	2,664,912	2,753,242
Total Deposits	15,797,532	15,012,864
Time Deposits, $250,000 or More	373,900	374,400
Maturities of Time Deposits [Abstract]
2018	1,085,369
2019	866,233
2020	436,690
2021	122,516
2022	76,962
Thereafter	77,142
Total	2,664,912	2,753,242
Interest-bearing Domestic Deposit, Brokered	90,473	0
Certificates of Deposit
Deposits [Line Items]
Time Deposits, $100,000 or More	$ 1,200,000	$ 1,200,000