Borrowings - Summary of Short-Term Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Short Term Debt [Line Items]
Total short-term borrowings	$ 79,006	$ 971,049
Federal Home Loan Bank Advances [Member]
Short Term Debt [Line Items]
Total short-term borrowings		900,013
Serviced GNMA Loans Eligible for Repurchase [Member]
Short Term Debt [Line Items]
Total short-term borrowings	61,564	48,211
Other [Member]
Short Term Debt [Line Items]
Total short-term borrowings	$ 17,442	$ 22,825