Revenue Recognition (Up-Front Customer Loyalty Programs) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 576,056	$ 537,656
Up front customer loyalty programs
Disaggregation of Revenue [Line Items]
Capitalized customer acquisition costs	125,200		$ 124,400
Recognized as a reduction of revenue	$ 8,900

Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer.

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Amount, before accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
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