Summary of Significant Accounting Policies - Schedule of Impact of this Adoption (Detail) - USD ($)	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	$ 173,549,000		$ 0
Current expected credit loss reserve	1,723,000		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	10,031,000		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	42,995,000		0
Current expected credit loss reserve	1,723,000		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	6,953,000		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	27,734,000		0
Current expected credit loss reserve	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	2,994,000		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	33,159,000		0
Current expected credit loss reserve	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	84,000		$ 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