Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current Assets:
Cash and cash equivalents	$ 463,395	$ 277,077
Short-term investments	6,840	21,849
Accounts receivable, net	59,078	58,706
Inventories, net	67,091	65,004
Prepaid expenses and other current assets	10,375	9,921
Income tax deposits	939	6,583
Total current assets	607,718	439,140
Property, plant and mine development, net	553,005	561,196
Goodwill	68,647	68,647
Trade names	14,474	14,474
Customer relationships, net	6,329	6,453
Other assets	18,127	18,709
Total assets	1,268,300	1,108,619
Current Liabilities:
Accounts payable	45,394	49,631
Dividends payable	3,339	3,453
Accrued liabilities	11,547	11,708
Accrued interest	57	58
Current portion of long-term debt	3,333	3,330
Current portion of deferred revenue	7,216	15,738
Total current liabilities	70,886	83,918
Long-term debt	487,540	488,375
Deferred revenue	66,948	59,676
Deferred revenue	60,600	55,893
Deferred income taxes, net	9,770	19,513
Other long-term obligations	17,563	17,077
Total liabilities	713,307	724,452
Stockholders’ Equity:
Preferred Stock, Value, Outstanding	0	0
Common stock	639	539
Additional paid-in capital	379,336	194,670
Retained earnings	207,040	220,974
Treasury stock, at cost	(13,323)	(15,845)
Accumulated other comprehensive loss	(18,699)	(16,171)
Total stockholders’ equity	554,993	384,167
Total liabilities and stockholders’ equity	$ 1,268,300	$ 1,108,619