Goodwill and Other Intangible Assets (Estimated Annual Amortization Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization charge of intangible assets	$ 4,500	$ 2,000	$ 8,100	$ 3,800
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Remainder of 2018	9,415		9,415
2019	17,855		17,855
2020	15,896		15,896
2021	15,195		15,195
2022	13,070		13,070
2023 and thereafter	43,346		43,346
Net Carrying Amount	$ 114,777		$ 114,777		$ 70,043