Deposits - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Banking and Thrift [Abstract]
Deposits	$ 21,178,134		$ 21,178,134		$ 18,943,158
Brokered deposits	11,800,000		11,800,000		10,300,000
Retail and other deposits	9,400,000		9,400,000		8,600,000
Stable interest-bearing deposits, total	6,200,000		6,200,000		5,900,000
Brokered deposit placement fee	4,000	$ 3,000	8,000	$ 6,000
Third party broker fees paid	14,000	$ 12,000	15,000	$ 19,000
Deposits exceeding FDIC insurance limits	693,000		693,000		523,000
Accrued interest on deposits	$ 60,000		$ 60,000		$ 53,000