Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	ORTP Class B Membership [Member] Common Stock [Member]	ORTP Class B Membership [Member] Additional Paid-in Capital [Member]	ORTP Class B Membership [Member] Retained Earnings [Member]	ORTP Class B Membership [Member] AOCI Attributable to Parent [Member]	ORTP Class B Membership [Member] Parent [Member]	ORTP Class B Membership [Member] Noncontrolling Interest [Member]	ORTP Class B Membership [Member]	OPC Class B Membership [Member] Common Stock [Member]	OPC Class B Membership [Member] Additional Paid-in Capital [Member]	OPC Class B Membership [Member] Retained Earnings [Member]	OPC Class B Membership [Member] AOCI Attributable to Parent [Member]	OPC Class B Membership [Member] Parent [Member]	OPC Class B Membership [Member] Noncontrolling Interest [Member]	OPC Class B Membership [Member]	Guadeloupe 1 [Member] Common Stock [Member]	Guadeloupe 1 [Member] Additional Paid-in Capital [Member]	Guadeloupe 1 [Member] Retained Earnings [Member]	Guadeloupe 1 [Member] AOCI Attributable to Parent [Member]	Guadeloupe 1 [Member] Parent [Member]	Guadeloupe 1 [Member] Noncontrolling Interest [Member]	Guadeloupe 1 [Member]	Tungsten [Member] Common Stock [Member]	Tungsten [Member] Additional Paid-in Capital [Member]	Tungsten [Member] Retained Earnings [Member]	Tungsten [Member] AOCI Attributable to Parent [Member]	Tungsten [Member] Parent [Member]	Tungsten [Member] Noncontrolling Interest [Member]	Tungsten [Member]	McGinness Hills Phase III [Member] Common Stock [Member]	McGinness Hills Phase III [Member] Additional Paid-in Capital [Member]	McGinness Hills Phase III [Member] Retained Earnings [Member]	McGinness Hills Phase III [Member] AOCI Attributable to Parent [Member]	McGinness Hills Phase III [Member] Parent [Member]	McGinness Hills Phase III [Member] Noncontrolling Interest [Member]	McGinness Hills Phase III [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Parent [Member]	Noncontrolling Interest [Member]	Total
Balance (in shares) at Dec. 31, 2016																																				49,667
Balance at Dec. 31, 2016																																				$ 50	$ 869,463	$ 215,352	$ (8,175)	$ 1,076,690	$ 91,582	$ 1,168,272
Stock-based compensation																																				$ 0	8,760	0	0	8,760	0	8,760
Exercise of options by employees and directors (in shares)																																				942
Exercise of options by employees and directors																																				$ 1	16,111	0	0	16,112	0	16,112
Cash paid to noncontrolling interest																																				0	0	0	0	0	(21,313)	(21,313)
Cash dividend declared																																				0	0	(20,511)	0	(20,511)	0	(20,511)
Buyout of Class B membership	$ 0	$ 2,913	$ 0	$ 0	$ 2,913	$ (6,964)	$ (4,051)	$ 0	$ (8,469)	$ 0	$ 0	$ (8,469)	$ 6,537	$ (1,932)
Net income																																				0	0	132,414	0	132,414	13,643	146,057
Change in foreign currency translation adjustments																																				0	0	0	2,603	2,603	837	3,440
Change in respect of derivative instruments designated for cash flow hedge																																				0	0	0	135	135	0	135
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment																																				0	0	0	804	804	0	804
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																																				$ 0	0	0	(73)	(73)	0	(73)
Balance (in shares) at Dec. 31, 2017																																				50,609
Balance at Dec. 31, 2017																																				$ 51	888,778	327,255	(4,706)	1,211,378	84,322	1,295,700
Stock-based compensation																																				$ 0	10,218	0	0	10,218	0	10,218
Exercise of options by employees and directors (in shares)																																				91
Exercise of options by employees and directors																																				$ 0	0	0	0	0	0	0
Cash paid to noncontrolling interest																																				0	0	0	0	0	(10,972)	(10,972)
Cash dividend declared																																				0	0	(26,834)	0	(26,834)	0	(26,834)
Net income																																				0	0	97,966	0	97,966	11,155	109,121
Change in foreign currency translation adjustments																																				0	0	0	(1,352)	(1,352)	(479)	(1,831)
Change in respect of derivative instruments designated for cash flow hedge																																				0	0	0	81	81	0	81
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment																																				0	0	0	2,235	2,235	0	2,235
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																																				0	0	0	(57)	(57)	0	(57)
Cumulative effect of changes in accounting principles at Dec. 31, 2017																																				0	0	23,835	0	23,835	0	23,835
Adjusted balance as of the beginning of the year at Dec. 31, 2017																																				51	888,778	351,090	(4,706)	1,235,213	84,322	1,319,535
Increase in noncontrolling interest															$ 0	$ 0	$ 0	$ 0	$ 0	$ 5,339	$ 5,339	$ 0	$ 0	$ 0	$ 0	$ 0	$ 996	$ 996
Tax effect of partnership interest buyout																																				0	2,367	0	0	2,367	0	2,367
Purchase of U.S. Geothermal																																				$ 0	0	0	0	0	34,898	34,898
Balance (in shares) at Dec. 31, 2018																																				50,700
Balance at Dec. 31, 2018																																				$ 51	901,363	422,222	(3,799)	1,319,837	125,259	1,445,096
Stock-based compensation																																				$ 0	9,358	0	0	9,358	0	9,358
Exercise of options by employees and directors (in shares)																																				332
Exercise of options by employees and directors																																				$ 0	2,429	0	0	2,429	0	2,429
Cash paid to noncontrolling interest																																				0	0	0	0	0	(8,329)	(8,329)
Cash dividend declared																																				0	0	(22,386)	0	(22,386)	0	(22,386)
Net income																																				0	0	88,095	0	88,095	4,316	92,411
Change in foreign currency translation adjustments																																				0	0	0	(1,482)	(1,482)	(328)	(1,810)
Change in respect of derivative instruments designated for cash flow hedge																																				0	0	0	75	75	0	75
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment																																				0	0	0	(3,417)	(3,417)	0	(3,417)
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																																				0	0	0	(31)	(31)	0	(31)
Cumulative effect of changes in accounting principles at Dec. 31, 2018																																				0	0	(58)	0	(58)	0	(58)
Adjusted balance as of the beginning of the year at Dec. 31, 2018																																				$ 51	901,363	422,164	(3,799)	1,319,779	125,259	1,445,038
Increase in noncontrolling interest																													$ 0	$ 0	$ 0	$ 0	$ 0	$ 2,072	$ 2,072
Balance (in shares) at Dec. 31, 2019																																				51,032
Balance at Dec. 31, 2019																																				$ 51	$ 913,150	$ 487,873	$ (8,654)	$ 1,392,420	$ 122,990	$ 1,515,410