Leasing (Net Rent Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Leases, Rent Expense, Net [Abstract]
Minimum operating lease expense	$ 289,245	$ 273,559	$ 263,479
Contingent rents	1,049	892	947
Other lease related occupancy costs	12,478	13,241	12,852
Total rent expense	302,772	287,692	277,278
Less: sublease income	4,158	4,439	4,019
Net rent expense	$ 298,614	$ 283,253	$ 273,259