Commitments and Contingencies - Facility Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Leases, Operating [Abstract]
Cash basis payment - operating leases	$ 324,870	$ 365,077	$ 384,104
Straight-line lease (income) expense	(17,218)	(20,990)	(6,097)
Amortization of deferred gain	(4,358)	(4,366)	(4,372)
Facility lease expense	$ 303,294	$ 339,721	$ 373,635