Summary of Significant Accounting Policies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of Significant Accounting Policies [Line Items]
Property and equipment per unit value, minimum	$ 1,000
Property, plant and equipment, estimated useful life, minimum (in years)	1 year
Minimum percentage of tax benefit to be recognized (in percentage)	50.00%
Net Cash Provided by Operating Activities	$ 800,983,000	$ 871,812,000	$ 793,452,000
Net Cash Used in Financing Activities	(365,005,000)	(359,779,000)	(297,029,000)
Revenue Recognition [Member]
Summary of Significant Accounting Policies [Line Items]
Cumulative effect adjustment on assets	58,600,000
Intra-Entity Asset Transfers [Member] | Other Current Assets [Member]
Summary of Significant Accounting Policies [Line Items]
Cumulative effect adjustment on assets	11,600,000
Intra-Entity Asset Transfers [Member] | Other Assets [Member]
Summary of Significant Accounting Policies [Line Items]
Cumulative effect adjustment on assets	$ 27,000,000
Scenario, Previously Reported [Member] | Accounting Standards Update 2016-09 [Member]
Summary of Significant Accounting Policies [Line Items]
Net Cash Provided by Operating Activities		866,298,000	764,151,000
Net Cash Used in Financing Activities		$ (354,265,000)	$ (267,728,000)