Summary of Significant Accounting Policies (Recent accounting change) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets	$ 193,311
Lease liabilities	$ 230,338
Deferred rent liability			$ 30,000
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets		$ 185,000
Lease liabilities		$ 215,000