Revenue Recognition (Deferred Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue Recognition [Abstract]
Balance at beginning of period	$ 89,800	$ 67,700	$ 81,600	$ 59,900
New contracts sold	15,800	11,100	42,600	32,500
Less: reductions for revenue recognized	(7,300)	(6,400)	(25,900)	(20,000)
Balance at end of period	$ 98,300	$ 72,400	$ 98,300	$ 72,400

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