Summary of Significant Accounting Policies - Impact of Adoption of ASU2016-02 (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets	$ 725,605
Total assets	31,686,377	$ 30,587,012
Other accrued expenses	1,039,856	802,388
Operating lease liabilities	491,842
Long-term deferred revenue and other long-term liabilities	452,337	470,932
Total liabilities	22,253,718	21,532,755
Total stockholders' equity (deficit)	8,951,217	8,594,189	$ 7,325,263	$ 6,937,906
Total liabilities and stockholders' equity (deficit)	31,686,377	$ 30,587,012
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets	725,605
Total assets	31,686,377
Other accrued expenses	1,039,856
Operating lease liabilities	491,842
Long-term deferred revenue and other long-term liabilities	452,337
Total liabilities	22,253,718
Total stockholders' equity (deficit)	8,951,217
Total liabilities and stockholders' equity (deficit)	31,686,377
Accounting Standards Update 2016-02 [Member] | As would have been reported under previous standards
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total assets	30,960,772
Other accrued expenses	802,323
Long-term deferred revenue and other long-term liabilities	456,107
Total liabilities	21,528,113
Total stockholders' equity (deficit)	8,951,217
Total liabilities and stockholders' equity (deficit)	30,960,772
Accounting Standards Update 2016-02 [Member] | Impact of adopting ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets	725,605
Total assets	725,605
Other accrued expenses	237,533
Operating lease liabilities	491,842
Long-term deferred revenue and other long-term liabilities	(3,770)
Total liabilities	725,605
Total liabilities and stockholders' equity (deficit)	$ 725,605