Goodwill and Other Intangible Assets (Schedule of intangible assets and goodwill) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Amortized intangible assets:
Gross carrying value	$ 66,724	$ 66,724
Accumulated amortization	(20,635)	(17,518)
Net carrying amount	46,089	49,206
Goodwill
Gross carrying value	164,083	164,382
Accumulated amortization
Net carrying amount	164,083	164,382
AEC Trade Names [Member]
Amortized intangible assets:
Gross carrying value	140	140
Accumulated amortization	(131)	(129)
Net carrying amount	$ 9	$ 11
Goodwill
Amortization life in years	15 years	15 years
AEC Technology [Member]
Amortized intangible assets:
Gross carrying value	$ 370	$ 370
Accumulated amortization	(327)	(314)
Net carrying amount	$ 43	$ 56
Goodwill
Amortization life in years	15 years	15 years
Customer Relationships [Member]
Amortized intangible assets:
Gross carrying value	$ 48,421	$ 48,421
Accumulated amortization	(10,497)	(8,883)
Net carrying amount	$ 37,924	$ 39,538
Goodwill
Amortization life in years	15 years	15 years
Customer Contracts [Member]
Amortized intangible assets:
Gross carrying value	$ 17,471	$ 17,471
Accumulated amortization	(9,471)	(8,015)
Net carrying amount	$ 8,000	$ 9,456
Goodwill
Amortization life in years	6 years	6 years
Other Intangible [Member]
Amortized intangible assets:
Gross carrying value	$ 322	$ 322
Accumulated amortization	(209)	(177)
Net carrying amount	$ 113	$ 145
Goodwill
Amortization life in years	5 years	5 years
MC Goodwill [Member]
Goodwill
Gross carrying value	$ 68,353	$ 68,652
Accumulated amortization
Net carrying amount	68,353	68,652
AEC Goodwill [Member]
Goodwill
Gross carrying value	95,730	95,730
Accumulated amortization
Net carrying amount	$ 95,730	$ 95,730