EARNINGS PER SHARE - Reconciliation of weighted average shares outstanding (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net income available for stockholders:	$ 59,943	$ 43,840	$ 112,073	$ 47,474
Less: Adjustments for earnings attributable to participating securities	(673)	(592)	(1,266)	(652)
Net income used in calculating earnings per share	$ 59,270	$ 43,248	$ 110,807	$ 46,822
Weighted average shares outstanding (including participating securities)	215,194	217,530	215,641	217,622
Adjustment for participating securities	(2,473)	(2,936)	(2,528)	(2,989)
Shares used in calculating basic and diluted earnings per share	212,721	214,594	213,113	214,633

Represents weighted number of shares including participating securities.

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The total amount of dividends declared in the period for each class of stock and the contractual amount of dividends (or interest on participating income bonds) that must be paid for the period (for example, unpaid cumulative dividends). Dividends declared in the current period do not include dividends declared in respect of prior-period unpaid cumulative dividends. Preferred dividends that are cumulative only if earned are deducted only to the extent that they are earned.

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This element represents nonvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid). Basic and dilutive earnings per share are generally disclosed for such shares using the two-class method.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).

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