Intangible Assets and Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill information
Terminal growth rate for key assumptions used in applying income approach	3.00%	3.00%
Goodwill information for each reporting unit
Balance at the beginning of the period	$ 204,794	$ 116,899
Addition to goodwill	803	93,641
Goodwill impairment charge	0	0
Balance at the end of the period	209,661	204,794
Goodwill, Foreign Currency Translation Gain (Loss)	$ 4,064	$ (5,746)
MID
Goodwill information
Percentage of fair value in excess of carrying amount	270.00%	299.00%
Discount rates for key assumptions used in applying income approach	12.00%	12.00%
Goodwill information for each reporting unit
Balance at the beginning of the period	$ 66,643	$ 19,905
Addition to goodwill	0	46,738
Goodwill impairment charge	0	0
Balance at the end of the period	66,643	$ 66,643
Goodwill, Foreign Currency Translation Gain (Loss)	$ 0
RSD
Goodwill information
Percentage of fair value in excess of carrying amount	155.00%	89.00%
Discount rates for key assumptions used in applying income approach	17.00%	17.00%
Goodwill information for each reporting unit
Balance at the beginning of the period	$ 138,151	$ 96,994
Addition to goodwill	803	46,903
Goodwill impairment charge	0	0
Balance at the end of the period	143,018	138,151
Goodwill, Foreign Currency Translation Gain (Loss)	4,064	(5,746)
Other
Goodwill information for each reporting unit
Balance at the beginning of the period	0
Balance at the end of the period	$ 0	$ 0