Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Deferred tax assets:    
Net operating loss $ 512,256 $ 882,014
Tax credit carryforwards 549,543 487,635
Intangible assets 275,290 241,775
Deferred revenues 18,833 19,311
Stock-based compensation 85,199 93,915
Accrued expenses 44,367 17,795
Finance lease liabilities 119,160 130,849
Operating lease assets 13,114  
Other 8,596 6,831
Gross deferred tax assets 1,626,358 1,880,125
Valuation allowance (205,192) (168,491)
Total deferred tax assets 1,421,166 1,711,634
Deferred tax liabilities:    
Property and equipment (101,235) (128,407)
Acquired intangibles (87,160) 0
Deferred revenue 0 (73,357)
Unrealized gain (28,838) (10,198)
Operating lease liabilities (13,118)  
Unrealized gain $ 1,190,815 $ 1,499,672