Summary of Significant Accounting Policies - Schedule of Impact of this Adoption (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	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	$ 128,945	$ 172,100	$ 173,549	$ 178,050	$ 112,694		$ 0
Current expected credit loss reserve	122	889	1,723	4,119	5,122		0
Impact of ASU 2016-13 Adoption [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve						$ 13,942
Current expected credit loss reserve						445,000	445
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
Current expected credit loss reserve	445
CECL reserve on unfunded loan commitments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	4,037	11,021	10,031	15,002	22,536		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					3,263
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
U.S. Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	17,673	44,534	42,995	61,404	64,861
Current expected credit loss reserve	122	889	1,723	4,119	5,122		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
Current expected credit loss reserve							445
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
U.S. Loans [Member] | CECL reserve on unfunded loan commitments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	2,854	7,169	6,953	12,836	19,793		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
Non-U.S. Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	8,829	24,600	27,734	19,745	21,825
Current expected credit loss reserve	0	0	0	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
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
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	1,140	3,772	2,994	2,078	2,672		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
Unique Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	32,782	33,305	33,159	27,240	26,008		0
Current expected credit loss reserve	0	0	0	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
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
Unique Loans [Member] | CECL reserve on unfunded loan commitments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserve	43	$ 80	$ 84	$ 88	$ 71		$ 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
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