Summary of Significant Accounting Policies - Accounting Standards Recently Adopted (Details) - USD ($) $ in Thousands		9 Months Ended
	Jan. 01, 2019	Sep. 30, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Package - Practical expedients		true
Hindsight - Practical expedients		false
Operating lease ROU assets	$ 214,000	$ 206,096
Lease liabilities		214,739
Current portion of operating lease liabilities	20,883	28,059
Accounts payable and accrued expenses	525,496	707,069	$ 525,863
Operating lease liabilities	199,857	186,680
Other non-current liabilities	208	131	6,581
Total liabilities	746,444	$ 2,234,119	1,775,578
Adjustments due to ASC 842
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease ROU assets	214,000
Adjustment to retained earnings	0
Current portion of operating lease liabilities	20,883
Accounts payable and accrued expenses	(367)		525,863
Operating lease liabilities	199,857
Other non-current liabilities	(6,373)		6,581
Total liabilities	214,000		$ 532,444
Adjustments due to ASC 842 | Measurement Period Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease liabilities	220,700
Liabilities for deferred rent and various lease incentives	$ 6,700