Unconsolidated Subsidiaries (Schedule) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Variable Interest Entity [Line Items]
Revenues	$ 33,681	$ 28,100	$ 64,881	$ 56,400
Gross profit	4,846	4,597	10,270	9,155
Variable interest entity, not primary beneficiary
Variable Interest Entity [Line Items]
Revenues	182,018	174,554	365,064	368,728
Gross profit	20,405	19,857	41,468	41,854
Income before income taxes	$ 15,456	$ 13,616	$ 31,578	$ 29,326

Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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