Revenue Recognition (Deferred Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue Recognition [Abstract]
Balance at beginning of period	$ 85,600	$ 63,500	$ 81,600	$ 59,900
New contracts sold	13,600	11,500	26,800	21,400
Less: reductions for revenue recognized	(9,400)	(7,300)	(18,600)	(13,600)
Balance at end of period	$ 89,800	$ 67,700	$ 89,800	$ 67,700

Amount of deferred revenue recognized for transactions arising during the current reporting period. Deferred revenue is a liability as of the balance sheet date related to a revenue producing activity for which revenue has not yet been recognized. Generally, an Entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

No definition available.

Name:	us-gaap_DeferredRevenueAdditions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration