Deposits - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Banking and Thrift [Abstract]
Deposits	$ 22,628,677		$ 22,628,677		$ 18,943,158
Brokered deposits	12,500,000		12,500,000		10,300,000
Retail and other deposits	10,100,000		10,100,000		8,600,000
Stable interest-bearing deposits, total	6,800,000		6,800,000		5,900,000
Brokered deposit placement fee	4,000	$ 4,000	12,000	$ 9,000
Third party broker fees paid	5,000	$ 6,000	20,000	$ 25,000
Deposits exceeding FDIC insurance limits	557,000		557,000		523,000
Accrued interest on deposits	$ 72,000		$ 72,000		$ 53,000