Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Other Intangibles
Increase in Goodwill	$ 3,659	$ 28,257
Goodwill impairment	0	0
Increase in non-compete agreements	200	1,100
Indefinite-lived intangible assets, other than goodwill	0	0
Amortization expense of amortizable intangible assets	$ 1,600	2,100	$ 2,700
Favorable Leases [Member]
Goodwill and Other Intangibles
Weighted-average remaining useful life of favorable leases	8 years 9 months 26 days
Unfavorable Leases [Member]
Goodwill and Other Intangibles
Weighted-average remaining useful life of unfavorable leases	3 years 4 months 2 days
Amortization benefit of unfavorable operating leases	$ 1,500	$ 2,100	$ 2,800