Fair Value Measurement - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Available-for-sale securities:
Available-for-sale securities	$ 1,064,018	$ 601,035
Time deposits
Available-for-sale securities:
Available-for-sale securities	590,000	235,000
Money market funds
Available-for-sale securities:
Available-for-sale securities	192,971	140,800
Recurring \| Total Estimated Fair Value
Available-for-sale securities:
Totals	791,056	393,433
Liabilities:
Totals	1,258	5,409
Recurring \| Total Estimated Fair Value \| Interest rate contracts
Available-for-sale securities:
Derivative asset	7,824	2,138
Liabilities:
Derivative liabilities	0	392
Recurring \| Total Estimated Fair Value \| Foreign exchange forward contracts
Available-for-sale securities:
Derivative asset	261	15,495
Liabilities:
Derivative liabilities	1,258	5,017
Recurring \| Total Estimated Fair Value \| Time deposits
Available-for-sale securities:
Available-for-sale securities	590,000	235,000
Recurring \| Total Estimated Fair Value \| Money market funds
Available-for-sale securities:
Available-for-sale securities	192,971	140,800
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale securities:
Totals	192,971	140,800
Liabilities:
Totals	0	0
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Interest rate contracts
Available-for-sale securities:
Derivative asset	0	0
Liabilities:
Derivative liabilities	0	0
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Foreign exchange forward contracts
Available-for-sale securities:
Derivative asset	0	0
Liabilities:
Derivative liabilities	0	0
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Time deposits
Available-for-sale securities:
Available-for-sale securities	0	0
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Money market funds
Available-for-sale securities:
Available-for-sale securities	192,971	140,800
Recurring \| Significant Other Observable Inputs (Level 2)
Available-for-sale securities:
Totals	598,085	252,633
Liabilities:
Totals	1,258	5,409
Recurring \| Significant Other Observable Inputs (Level 2) \| Interest rate contracts
Available-for-sale securities:
Derivative asset	7,824	2,138
Liabilities:
Derivative liabilities	0	392
Recurring \| Significant Other Observable Inputs (Level 2) \| Foreign exchange forward contracts
Available-for-sale securities:
Derivative asset	261	15,495
Liabilities:
Derivative liabilities	1,258	5,017
Recurring \| Significant Other Observable Inputs (Level 2) \| Time deposits
Available-for-sale securities:
Available-for-sale securities	590,000	235,000
Recurring \| Significant Other Observable Inputs (Level 2) \| Money market funds
Available-for-sale securities:
Available-for-sale securities	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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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 of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

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