Loans Held for Investment - Schedule of Loan Investment Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Loans And Leases Receivable Disclosure [Line Items]
Outstanding Principal, before allowance for loan losses	$ 4,732,962	$ 4,313,591
Unamortized Premium (Discount), Loan Origination Fees net, before allowance for loan losses	(20,828)	(19,804)
Carrying Amount, before allowance for loan losses	4,712,134	4,293,787
Senior Loans
Loans And Leases Receivable Disclosure [Line Items]
Outstanding Principal, before allowance for loan losses	4,732,962	4,313,591
Unamortized Premium (Discount), Loan Origination Fees net, before allowance for loan losses	(20,828)	(19,804)
Carrying Amount, before allowance for loan losses	$ 4,712,134	$ 4,293,787

Amount, before allowance and fees, of loans and leases receivable. Excludes loans and leases covered under loss sharing agreements.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

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Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6378536&loc=d3e10092-111533

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