Summary of Significant Accounting Policies New Accounting Pronouncements (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets, net	$ 77,888	$ 0
Other current liabilities	(14,451)
Operating lease liabilities	(66,865)	0
Other current assets	129,975	118,085
Other Liabilities, Noncurrent	$ (140,637)	(127,739)
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets, net		74,600
Other current liabilities		(14,500)
Operating lease liabilities		(61,500)
Other current assets		(1,500)
Other Liabilities, Noncurrent		$ 2,900