Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Operating Revenues:
Total revenues		$ 268,403		$ 274,116	$ 228,295
Operating Expenses:
Compensation and benefits		80,761		74,515	81,493
Fund management and administration		61,502		56,686	42,144
Marketing and advertising		12,163		13,884	14,402
Sales and business development		18,276		17,153	13,811
Contractual gold payments (Note 12)		13,226		8,512
Professional and consulting fees		5,641		7,984	5,254
Occupancy, communications and equipment		6,302		6,203	5,415
Depreciation and amortization		1,045		1,301	1,395
Third-party distribution fees		6,968		6,611	3,393
Acquisition and disposition-related costs (Note 3)		902		11,454	4,832
Other		8,083		8,534	7,068
Total expenses		214,869		212,837	179,207
Operating income		53,534		61,279	49,088
Other Income/(Expenses):
Interest expense		(11,240)		(7,962)
(Loss)/gain on revaluation of deferred consideration – gold payments (Note 12)	[1]	(11,293)		12,220
Interest income		3,332		3,093	2,861
Impairments (Note 26)		(30,710)		(17,386)
Settlement gain (Note 10)					6,909
Other losses, net		(3,502)		(205)	(666)
Income before income taxes		121		51,039	58,192
Income tax expense		10,546		14,406	30,993
Net (loss)/income		$ (10,425)		$ 36,633	$ 27,199
(Loss)/earnings per share—basic (Note 22)		$ (0.08)		$ 0.23	$ 0.20
(Loss)/earnings per share—diluted (Note 22)		$ (0.08)		$ 0.23	$ 0.20
Weighted-average common shares—basic (Note 22)		151,823		146,645	134,614
Weighted-average common shares—diluted (Note 22)		151,823	[2]	158,415	136,003
Cash dividends declared per common share		$ 0.12		$ 0.12	$ 0.32
Advisory Fees [Member]
Operating Revenues:
Total revenues		$ 265,652		$ 271,104	$ 226,692
Other Income [Member]
Operating Revenues:
Total revenues		$ 2,751		$ 3,012	$ 1,603

[1] (Losses)/gains arise due to increases/(decreases) in the forward-looking price of gold and the magnitude of any gain or loss is highly correlated to the magnitude of the change in the forward-looking price of gold. See Note 5 for a reconciliation of changes in the deferred consideration balances

[2] Excludes participating securities and potentially dilutive common stock equivalents as the Company reported a net loss for the period.