Fair Value of Financial Instruments - Schedule of Quantitative Information for Level 3 Fair Value Measurements (Details) - Level 3 $ in Thousands	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 8,919,760	$ 8,691,019
Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	660	2,257
Nonrecurring | Fair value of collateral | Investor loans secured by real estate | Commercial real estate (“CRE”) non-owner-occupied
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 318	$ 569
Nonrecurring | Fair value of collateral | Investor loans secured by real estate | Commercial real estate (“CRE”) non-owner-occupied | Collateral discount and cost to sell | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financing receivable, input	0.1000	0.1000
Nonrecurring | Fair value of collateral | Investor loans secured by real estate | Commercial real estate (“CRE”) non-owner-occupied | Collateral discount and cost to sell | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financing receivable, input	0.1000	0.1000
Nonrecurring | Fair value of collateral | Investor loans secured by real estate | Commercial real estate (“CRE”) non-owner-occupied | Collateral discount and cost to sell | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financing receivable, input	0.1000	0.1000
Nonrecurring | Fair value of collateral | Investor loans secured by real estate | SBA secured by real estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		$ 408
Nonrecurring | Fair value of collateral | Investor loans secured by real estate | SBA secured by real estate | Collateral discount and cost to sell | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financing receivable, input		0.1000
Nonrecurring | Fair value of collateral | Investor loans secured by real estate | SBA secured by real estate | Collateral discount and cost to sell | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financing receivable, input		0.1000
Nonrecurring | Fair value of collateral | Investor loans secured by real estate | SBA secured by real estate | Collateral discount and cost to sell | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financing receivable, input		0.1000
Nonrecurring | Fair value of collateral | Business loans secured by real estate | SBA secured by real estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 277	$ 140
Nonrecurring | Fair value of collateral | Business loans secured by real estate | SBA secured by real estate | Collateral discount and cost to sell | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financing receivable, input	0.1000	0.0700
Nonrecurring | Fair value of collateral | Business loans secured by real estate | SBA secured by real estate | Collateral discount and cost to sell | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financing receivable, input	0.1000	0.1000
Nonrecurring | Fair value of collateral | Business loans secured by real estate | SBA secured by real estate | Collateral discount and cost to sell | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financing receivable, input	0.1000	0.0781
Nonrecurring | Fair value of collateral | Commercial loans | SBA non-real estate secured
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 65	$ 1,140
Nonrecurring | Fair value of collateral | Commercial loans | SBA non-real estate secured | Collateral discount and cost to sell | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financing receivable, input	0.0700	0.0700
Nonrecurring | Fair value of collateral | Commercial loans | SBA non-real estate secured | Collateral discount and cost to sell | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financing receivable, input	0.1000	0.6300
Nonrecurring | Fair value of collateral | Commercial loans | SBA non-real estate secured | Collateral discount and cost to sell | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financing receivable, input	0.0732	0.1533