Commitments and Contingencies - Facility Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Leases, Operating [Abstract]
Cash basis payment - operating leases	$ 365,077	$ 384,104	$ 372,148
Straight-line lease (income) expense	(14,313)	767	6,956
Amortization of (above) below market lease, net	(6,677)	(6,864)	(7,158)
Amortization of deferred gain	(4,366)	(4,372)	(4,372)
Facility lease expense	$ 339,721	$ 373,635	$ 367,574