Revenue (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Increase in total assets	$ 1,785,153		$ 1,651,983
Increase to retained earnings	105,642		72,741
Contract balances, deferred revenue	3,900		$ 3,400
Contract costs	8,800	$ 9,300
Amortization expense, deferred costs	2,900
Adjustments | ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Increase in total assets	(8,776)	9,300
Increase to retained earnings	$ 6,578	6,900
Increase in deferred tax liabilities		$ 2,400