Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Unrealized gain on derivative instruments	$ 930	$ 2,296
Liabilities
Contingent consideration	12,545	9,241
Level 1
Assets
Unrealized gain on derivative instruments	0	0
Liabilities
Contingent consideration	0	0
Level 2
Assets
Unrealized gain on derivative instruments	930	2,296
Liabilities
Contingent consideration	0	0
Level 3
Assets
Unrealized gain on derivative instruments	0	0
Liabilities
Contingent consideration	$ 12,545	$ 9,241