Accounting Policies Narrative (Details) agreement in Thousands, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($) agreement
Accounting Changes and Error Corrections [Abstract]
Excess tax deficiency from stock-based compensation, increase in income tax provision \| $	$ 0.1	$ 1.8
Number of franchise agreements \| agreement		4

Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount

No definition available.

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Balance Type:	credit
Period Type:	duration