Summary of Significant Accounting Policies - Schedule of Impact of this Adoption (Detail) - USD ($)	Jun. 30, 2020	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	$ 178,050,000	$ 112,694,000		$ 0
Current expected credit loss reserve	4,119,000	5,122,000		0
Impact of ASU 2016-13 Adoption [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve			$ 13,942,000
Current expected credit loss reserve	445,000			445,000
Impact of ASU 2016-13 Adoption [Member] | Adoption of ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	17,650,000
Current expected credit loss reserve	445,000
CECL reserve on unfunded loan commitments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	15,002,000	22,536,000		0
CECL reserve on unfunded loan commitments [Member] | Impact of ASU 2016-13 Adoption [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	3,300,000		3,263,000
CECL reserve on unfunded loan commitments [Member] | Impact of ASU 2016-13 Adoption [Member] | Adoption of ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	3,263,000
U.S. Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	61,404,000	64,861,000		0
Current expected credit loss reserve	4,119,000	5,122,000		0
U.S. Loans [Member] | Impact of ASU 2016-13 Adoption [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve			8,955,000
Current expected credit loss reserve				445,000
U.S. Loans [Member] | Impact of ASU 2016-13 Adoption [Member] | Adoption of ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	8,955,000
U.S. Loans [Member] | CECL reserve on unfunded loan commitments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	12,836,000	19,793,000		0
U.S. Loans [Member] | CECL reserve on unfunded loan commitments [Member] | Impact of ASU 2016-13 Adoption [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve			2,801,000
Non-U.S. Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	19,745,000	21,825,000		0
Current expected credit loss reserve	0	0		0
Non-U.S. Loans [Member] | Impact of ASU 2016-13 Adoption [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve			3,631,000
Current expected credit loss reserve				0
Non-U.S. Loans [Member] | Impact of ASU 2016-13 Adoption [Member] | Adoption of ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	3,631,000
Non-U.S. Loans [Member] | CECL reserve on unfunded loan commitments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	2,078,000	2,672,000		0
Non-U.S. Loans [Member] | CECL reserve on unfunded loan commitments [Member] | Impact of ASU 2016-13 Adoption [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve			453,000
Unique Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	27,240,000	26,008,000		0
Current expected credit loss reserve	0	0		0
Unique Loans [Member] | Impact of ASU 2016-13 Adoption [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve			1,356,000
Current expected credit loss reserve				0
Unique Loans [Member] | Impact of ASU 2016-13 Adoption [Member] | Adoption of ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	1,356,000
Unique Loans [Member] | CECL reserve on unfunded loan commitments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	88,000	$ 71,000		$ 0
Unique Loans [Member] | CECL reserve on unfunded loan commitments [Member] | Impact of ASU 2016-13 Adoption [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve			$ 9,000
CECL reserve on loans [Member] | Impact of ASU 2016-13 Adoption [Member] | Adoption of ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	$ 13,942,000