STOCKHOLDERS' EQUITY - Capital Stock (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	1 Months Ended	3 Months Ended	9 Months Ended
	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2019
Equity offering [Line Items]
Issuance of common stock		$ 76,280	$ 942,436
At-The-Market Equity Offering Program
Equity offering [Line Items]
Common stock authorized under equity offering program		1,000,000	$ 1,000,000
Stock issued during period, shares, new issues, equity offering program			2.7
Stock issued during period, gross proceeds per share, equity offering program			$ 66.75
Equity offering program, remaining authorized offering amount		$ 822,100	$ 822,100
June 2019 Registered Public Offering
Equity offering [Line Items]
Stock issued during period, shares, new issues, equity offering program	12.7
Stock issued during period, gross proceeds per share, equity offering program	$ 62.75