FAIR VALUE MEASUREMENT - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Fair Value Measured on a Recurring Basis - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Level I
Assets:
Investment securities	$ 1,816,147	$ 1,462,626
Level III
Liabilities:
Contingent consideration related to 2017 and 2018 acquisitions	5,139	6,195
Prepaid forward contracts \| Level II
Assets:
Derivative asset	0	109,344
Liabilities:
Derivative liability	117,309	0
Interest rate swap contracts \| Level II
Assets:
Derivative asset	0	1,975
Liabilities:
Derivative liability	172,325	132,978
Money market funds \| Level I
Assets:
Money market funds	$ 26,280	$ 91,852

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Amount of liability recognized arising from contingent consideration in a business combination.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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