v3.19.3

INVESTMENTS - Short-Term and Long-Term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,122,269
Fair Value	1,122,164
Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	557,380	$ 541,684
Gross Unrealized Gains	773	329
Gross Unrealized Losses	(497)	(1,022)
Fair Value	557,656	540,991
Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	564,889	464,545
Gross Unrealized Gains	790	1,361
Gross Unrealized Losses	(1,171)	(1,226)
Fair Value	564,508	464,680
U.S. agency securities | Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	132,217	80,160
Gross Unrealized Gains	257	32
Gross Unrealized Losses	(126)	(70)
Fair Value	132,348	80,122
U.S. agency securities | Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	87,848	114,444
Gross Unrealized Gains	219	194
Gross Unrealized Losses	(164)	(78)
Fair Value	87,903	114,560
Corporate bonds | Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	55,399	109,807
Gross Unrealized Gains	194	80
Gross Unrealized Losses	(92)	(368)
Fair Value	55,501	109,519
Corporate bonds | Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	185,675	159,783
Gross Unrealized Gains	286	419
Gross Unrealized Losses	(398)	(950)
Fair Value	185,563	159,252
Commercial paper | Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,245
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	2,245
Municipal securities | Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,713	27,839
Gross Unrealized Gains	5	52
Gross Unrealized Losses	(49)	(59)
Fair Value	2,669	27,832
Municipal securities | Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	12,668	28,453
Gross Unrealized Gains	12	167
Gross Unrealized Losses	(98)	(26)
Fair Value	12,582	28,594
U.S. government securities | Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	351,592	292,615
Gross Unrealized Gains	317	161
Gross Unrealized Losses	(192)	(509)
Fair Value	351,717	292,267
U.S. government securities | Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	250,434	153,743
Gross Unrealized Gains	267	553
Gross Unrealized Losses	(436)	(172)
Fair Value	250,265	154,124
Foreign securities | Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	13,214	31,263
Gross Unrealized Gains	0	4
Gross Unrealized Losses	(38)	(16)
Fair Value	13,176	31,251
Foreign securities | Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	28,264	8,122
Gross Unrealized Gains	6	28
Gross Unrealized Losses	(75)	0
Fair Value	$ 28,195	$ 8,150

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- Definition

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