Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Rent expense	$ 85,000	$ 82,500	$ 83,600
Assumption of capital lease obligations upon acquisition	75,030	$ 0	$ 118,923
Commitments related to construction contracts, amount reimbursable	13,400
Commitments related to construction contracts	401,400
Ascenty Acquisition
Business Acquisition [Line Items]
Assumption of capital lease obligations upon acquisition	$ 50,000