Investments Variable Interest Entity (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Investments	[1]	$ 155,213	$ 224,932
Due from brokers	[1]	1,743	14,240
Other assets	[1]	7,433	9,208
Total assets		402,419	481,039
Due to brokers	[1]	366	5,121
Other liabilities and accrued expenses	[1]	13,972	13,935
Total liabilities		135,304	144,201
SICAV RAP
Variable Interest Entity [Line Items]
Investments		29,976	8,929
Due from brokers		613	167
Other assets		268	297
Total assets		30,857	9,393
Due to brokers		229	24
Other liabilities and accrued expenses		213	149
Total liabilities		442	173
GLI SICAV, GRP-CIP, SICAV GRE and SICAV RAP [Member]
Variable Interest Entity [Line Items]
Investments		82,829
Due from brokers		1,743
Other assets		1,041
Total assets		85,613
Due to brokers		366
Other liabilities and accrued expenses		784
Total liabilities		1,150
GLI SICAV
Variable Interest Entity [Line Items]
Investments		7,048	5,704
Due from brokers		264	49
Other assets		92	171
Total assets		7,404	5,924
Due to brokers		45	0
Other liabilities and accrued expenses		100	74
Total liabilities		145	74
GRP-CIP
Variable Interest Entity [Line Items]
Investments		337	550
Due from brokers		203	103
Other assets		0	0
Total assets		540	653
Due to brokers		0	0
Other liabilities and accrued expenses		5	5
Total liabilities		5	5
SICAV Preferred
Variable Interest Entity [Line Items]
Investments			120,930
Due from brokers			10,868
Other assets			2,136
Total assets			133,934
Due to brokers			4,398
Other liabilities and accrued expenses			212
Total liabilities			4,610
SICAV GRE
Variable Interest Entity [Line Items]
Investments		45,468
Due from brokers		663
Other assets		681
Total assets		46,812
Due to brokers		92
Other liabilities and accrued expenses		466
Total liabilities		$ 558
GLI SICAV, GRP-CIP, SICAV Preferred and SICAV RAP [Member]
Variable Interest Entity [Line Items]
Investments			136,113
Due from brokers			11,187
Other assets			2,604
Total assets			149,904
Due to brokers			4,422
Other liabilities and accrued expenses			440
Total liabilities			$ 4,862

[1] Asset and liability amounts in parentheses represent the aggregated balances at December 31, 2019 and 2018 attributable to variable interest entities consolidated by the Company. Refer to Note 4 for further discussion.