Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Summary of Significant Accounting Policies
Decrease of depreciation expenses	$ 8,592	$ 6,596
Decrease in accrued expenses	8,553		$ 10,595
Recognition of finance obligation	51,948
Decrease in prepaid expenses and other assets	16,050		16,774
Decrease in leased property, net of accumulated depreciation	130,015		87,065
Increase in accumulated deficit	(1,243,430)		$ (1,178,636)
ASU 2016-02 | Early adoption | Restatement adjustment
Summary of Significant Accounting Policies
Decrease of depreciation expenses	300
Recognition of right of use asset	34,416
Decrease in accrued expenses	385
Recognition of finance obligation	(34,161)
Decrease in prepaid expenses and other assets	(3,229)
Decrease in leased property, net of accumulated depreciation	(563)
Increase in accumulated deficit	$ 3,487