Revenue from Contracts with Customers (Contract Liability) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Jan. 01, 2018
Revenue from Contract with Customer [Abstract]
Deferred Revenue	$ 299,068	$ 311,214
Deferred Revenue, Period Decrease Percentage	(4.00%)

Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets 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_DeferredRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant