Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
OIL AND NATURAL GAS SALES (NOTE 9)	$ 570,983	$ 613,431	$ 421,734
EXPENSES
Operating	142,086	111,272	87,855
Workover	41,118	34,437	22,014
Transportation	20,400	28,993	25,107
Depletion, depreciation and accretion (Note 5)	225,033	197,867	131,335
Asset impairment (Note 5)	0	0	1,514
General and administrative	34,730	39,483	39,014
Severance	1,771	2,361	1,287
Equity tax	0	0	1,224
Foreign exchange loss	627	9,957	2,067
Financial instruments (gain) loss (Note 13)	(46,215)	12,296	15,929
Interest expense (Note 6)	43,268	27,364	13,882
TOTAL EXPENSES	462,818	464,030	341,228
OTHER LOSS (Notes 5, 6 and 10)	(12,886)	0	(44,385)
INTEREST INCOME	696	2,086	1,209
INCOME BEFORE INCOME TAXES	95,975	151,487	37,330
INCOME TAX EXPENSE
Current (Note 10)	17,058	43,903	24,322
Deferred (Note 10)	40,227	4,968	44,716
INCOME TAX EXPENSE (RECOVERY)	57,285	48,871	69,038
NET AND COMPREHENSIVE INCOME (LOSS)	$ 38,690	$ 102,616	$ (31,708)
NET INCOME (LOSS) PER SHARE - BASIC (in USD per share)	$ 0.10	$ 0.26	$ (0.08)
NET INCOME (LOSS) PER SHARE - DILUTED (in USD per share)	$ 0.10	$ 0.26	$ (0.08)
WEIGHTED AVERAGE SHARES OUTSTANDING - BASIC (Note 7) (in shares)	376,495,306	390,930,453	396,683,593
WEIGHTED AVERAGE SHARES OUTSTANDING - DILUTED (Note 7) (in shares)	376,507,812	427,119,872	396,683,593