Accrued Expenses (Schedule of Accrued Expenses) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accrued Expenses [Abstract]
Accrued earnouts on business combinations	$ 2,194	$ 2,470
Salaries and benefits	9,415	13,506
Real estate and property taxes	8,913	7,125
Non-cash capital expenditures	10,926	12,408
Other	29,189	34,353
Total accrued expenses	$ 60,637	$ 69,862