CHANGE IN ACCOUNTING POLICIES AND ATS ACQUISITION - Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents	$ 486,208	$ 329,848
Other current assets		573,751
Property, plant and equipment, net	5,760,479	6,023,826
Goodwill	8,012,416	8,019,861
Other assets, long-term		19,864,796
Total assets	33,956,567	34,812,082
Current liabilities	2,476,677	2,520,362
Deferred tax liability	4,809,745	4,769,286
Liabilities, long-term		21,786,391
Total liabilities	30,105,795	29,076,039
Redeemable equity	179,799	231,290
Paid-in capital	3,618,709	4,665,229
Retained earnings	38,744	840,636
Total stockholders' equity	3,670,973	5,504,753
Total liabilities and stockholders' equity	$ 33,956,567	34,812,082
As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents		273,329
Other current assets		580,231
Property, plant and equipment, net		6,063,829
Goodwill		7,996,760
Other assets, long-term		19,861,076
Total assets		34,775,225
Current liabilities		2,492,983
Deferred tax liability		4,775,115
Liabilities, long-term		21,779,997
Total liabilities		29,048,095
Redeemable equity		231,290
Paid-in capital		4,642,128
Retained earnings		854,824
Total stockholders' equity		5,495,840
Total liabilities and stockholders' equity		34,775,225
Impact of ASC 606 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents		0
Other current assets		14,068
Property, plant and equipment, net		0
Goodwill		0
Other assets, long-term		10,261
Total assets		24,329
Current liabilities		6,978
Deferred tax liability		4,685
Liabilities, long-term		0
Total liabilities		11,663
Redeemable equity		0
Paid-in capital		0
Retained earnings		12,666
Total stockholders' equity		12,666
Total liabilities and stockholders' equity		24,329
ATS Acquisition | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents		56,519
Other current assets		(20,548)
Property, plant and equipment, net		(40,003)
Goodwill		23,101
Other assets, long-term		(6,541)
Total assets		12,528
Current liabilities		20,401
Deferred tax liability		(10,514)
Liabilities, long-term		6,394
Total liabilities		16,281
Redeemable equity		0
Paid-in capital		23,101
Retained earnings		(26,854)
Total stockholders' equity		(3,753)
Total liabilities and stockholders' equity		$ 12,528