Cash and Available-for-Sale Securities - Summary of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 882,739	$ 824,622
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	882,739	824,622
Cash and Cash Equivalents	637,739	309,622
Investments	245,000	515,000
Cash
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	261,194	215,606
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	261,194	215,606
Cash and Cash Equivalents	261,194	215,606
Investments	0	0
Time deposits
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	370,000	515,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	370,000	515,000
Cash and Cash Equivalents	125,000	0
Investments	245,000	515,000
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	251,545	94,016
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	251,545	94,016
Cash and Cash Equivalents	251,545	94,016
Investments	$ 0	$ 0

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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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Amortized cost 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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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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Amount 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. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Sum of the carrying amounts as of the balance sheet date of all investments.

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