Fair Value Measurements - Quantitative Inputs and Assumptions Used to Determine Fair Value for Private Label CMOs and Asset-backed Securities Available-for-sale (Details) - Level 3 - Fair Value, Measurements, Recurring	3 Months Ended
	Mar. 31, 2021
Measurement Input, Prepayment Rate | Minimum | Private label collateralized mortgage obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private Label Collateralized Mortgage Obligations, Measurement Input	0.046
Measurement Input, Prepayment Rate | Minimum | Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-Backed Securities, Measurement Input	0.100
Measurement Input, Prepayment Rate | Maximum | Private label collateralized mortgage obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private Label Collateralized Mortgage Obligations, Measurement Input	0.199
Measurement Input, Prepayment Rate | Maximum | Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-Backed Securities, Measurement Input	0.150
Measurement Input, Prepayment Rate | Weighted Average | Covered Private Label Collateralized Mortgage Obligations Member [Domain]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private Label Collateralized Mortgage Obligations, Measurement Input	0.115	[1]
Measurement Input, Prepayment Rate | Weighted Average | Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-Backed Securities, Measurement Input	0.121	[2]
Measurement Input, Default Rate | Minimum | Private label collateralized mortgage obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private Label Collateralized Mortgage Obligations, Measurement Input	0.003	[3]
Measurement Input, Default Rate | Minimum | Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-Backed Securities, Measurement Input	0.020
Measurement Input, Default Rate | Maximum | Private label collateralized mortgage obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private Label Collateralized Mortgage Obligations, Measurement Input	0.182	[3]
Measurement Input, Default Rate | Maximum | Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-Backed Securities, Measurement Input	0.020
Measurement Input, Default Rate | Weighted Average | Covered Private Label Collateralized Mortgage Obligations Member [Domain]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private Label Collateralized Mortgage Obligations, Measurement Input	0.024	[1],[3]
Measurement Input, Default Rate | Weighted Average | Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-Backed Securities, Measurement Input	0.020	[2],[3]
Measurement Input, Loss Severity | Minimum | Private label collateralized mortgage obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private Label Collateralized Mortgage Obligations, Measurement Input	0.169	[3]
Measurement Input, Loss Severity | Minimum | Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-Backed Securities, Measurement Input	0.600
Measurement Input, Loss Severity | Maximum | Private label collateralized mortgage obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private Label Collateralized Mortgage Obligations, Measurement Input	0.804	[3]
Measurement Input, Loss Severity | Maximum | Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-Backed Securities, Measurement Input	0.600
Measurement Input, Loss Severity | Weighted Average | Covered Private Label Collateralized Mortgage Obligations Member [Domain]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private Label Collateralized Mortgage Obligations, Measurement Input	0.558	[1],[3]
Measurement Input, Loss Severity | Weighted Average | Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-Backed Securities, Measurement Input	0.600	[2],[3]
Measurement Input, Discount Rate | Minimum | Private label collateralized mortgage obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private Label Collateralized Mortgage Obligations, Measurement Input	0.016
Measurement Input, Discount Rate | Minimum | Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-Backed Securities, Measurement Input	0.027
Measurement Input, Discount Rate | Maximum | Private label collateralized mortgage obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private Label Collateralized Mortgage Obligations, Measurement Input	0.099
Measurement Input, Discount Rate | Maximum | Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-Backed Securities, Measurement Input	0.036
Measurement Input, Discount Rate | Weighted Average | Covered Private Label Collateralized Mortgage Obligations Member [Domain]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private Label Collateralized Mortgage Obligations, Measurement Input	0.068	[1]
Measurement Input, Discount Rate | Weighted Average | Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-Backed Securities, Measurement Input	0.028	[2]

[1] Unobservable inputs for private label residential CMOs were weighted by the relative fair values of the instruments.

[2] Voluntary annual prepayment speeds and discount rates for asset-backed securities were weighted by the relative fair values of the instruments.

[3] Annual default rates and loss severity rates were the same for all of the asset-backed securities.