Revenue Recognition (Costs to Obtain a Contract) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Deferred commission costs included within other assets	$ 9,470	$ 11,800	$ 0
Commissions expense recognized	3,600
Deferred commission costs	$ 13,900
Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Amortization period	3 years
Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Amortization period	7 years