Summary of Significant Accounting Policies Summary of Significant Accounting Policies Leases (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset	$ 85,907	$ 0	$ 0
Total assets	905,855	806,371	806,371
Current portion of operating lease liability	5,385	0	0
Other current liabilities	13,521	12,992	12,992
Total current liabilities	159,553	159,735	159,735
Operating lease liability	83,818	0	0
Other non-current liabilities	7,968	9,577	9,577
Total liabilities and stockholders’ equity	$ 905,855	806,371	$ 806,371
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset		87,086
Total assets		893,457
Current portion of operating lease liability		5,290
Other current liabilities		12,544
Total current liabilities		164,577
Operating lease liability		84,866
Other non-current liabilities		6,955
Total liabilities and stockholders’ equity		893,457
Accounting Standards Update 2016-02 | Effect of Change in Accounting Principle
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset		87,086
Total assets		87,086
Current portion of operating lease liability		5,290
Other current liabilities		(448)
Total current liabilities		4,842
Operating lease liability		84,866
Other non-current liabilities		(2,622)
Total liabilities and stockholders’ equity		$ 87,086