Mortgage Banking - Schedule of Mortgage Loans Sold and Serviced for Others (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	$ 6,992,530	$ 6,834,874
Federal National Mortgage Association [Member]
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	4,295,468	4,204,336
Government National Mortgage Association [Member]
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	2,602,577	2,537,238
Federal Home Loan Mortgage Corporation [Member]
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	74,572	71,343
Other [Member]
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	$ 19,913	$ 21,957