Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Thousands		6 Months Ended
	Jan. 01, 2019	Jun. 30, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in Accounting Principle, Accounting Standards Update, Transition Option Elected [Fixed List]		Prospective
Lease, Practical Expedient, Use of Hindsight [true false]	false
Operating Lease, Right-of-Use Asset	$ 55,600	$ 53,363	$ 0
Operating Lease, Liability	65,800	$ 63,407
Deferred rent	9,300
Sublease loss	2,400
Intangible assets	$ 1,500
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease, Practical Expedients, Package [true false]		true
New Accounting Pronouncement or Change in Accounting Principle, Prior Period Not Restated [true false]		true