Summary of Significant Accounting Policies - Newly Adopted Accounting Pronouncements (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Jun. 30, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets	$ 180,600	$ 173,854
Present value of lease liabilities		$ 175,072
Straight-line rent liability	5,100
Prepaid rent	4,900
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets	175,700
Present value of lease liabilities	$ 181,600