Deferred Consideration (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Contractual Gold Payments		$ 3,760	$ 3,098
Contractual Gold Payments – gold ounces paid		2,375	2,375
(Loss)/gain on revaluation of deferred consideration – gold payments	[1]	$ (2,208)	$ 4,404

[1] Gains/(losses) arise due to (decreases)/increases 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 4 for significant unobservable assumption and a reconciliation of changes in the deferred consideration balances.