Deposits - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Banking and Thrift [Abstract]
Deposits	$ 19,663,986		$ 18,943,158
Brokered deposits	10,600,000		10,300,000
Retail and other deposits	9,100,000		8,600,000
Stable interest-bearing deposits, total	6,200,000		5,900,000
Brokered deposit placement fee	4,000	$ 3,000
Third party broker fees paid	1,000	$ 7,000
Deposits exceeding FDIC insurance limits	638,000		523,000
Accrued interest on deposits	$ 57,000		$ 53,000