Represents the percentage of revenues impacted by the new accounting pronouncement.

No definition available.

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- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

+ References

No definition available.

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

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Summary of Significant Accounting Policies - New Accounting Pronouncements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Jan. 01, 2018
New Accounting Pronouncements
Cumulative effect adjustment			$ 7,264
Retained Earnings (Accumulated Deficit)	$ (4,782,173)		(4,896,754)
Accounting Standards Update 2014-09 \| Maximum
New Accounting Pronouncements
Percentage of revenues impacted by ASU (as a percent)	6.00%	7.00%
Accounting Standards Update 2014-09 \| Difference between Revenue Guidance in Effect before and after Topic 606
New Accounting Pronouncements
Retained Earnings (Accumulated Deficit)				$ 0
Accounting Standards Update 2016-01 \| Adjustment
New Accounting Pronouncements
Cumulative effect adjustment				7,300
Accounting Standards Update 2016-02 \| Scenario Forecast Adjustment
New Accounting Pronouncements
Future minimum gross lease payments			$ 782,800
Accounting Standards Update 2017-05 \| Adjustment
New Accounting Pronouncements
Cumulative effect adjustment				$ 0