Commitments and Contingent Liabilities - Narrative (Details)	12 Months Ended
Dec. 31, 2018 USD ($) Jurisdiction	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2014 USD ($)
Commitments And Contingent Liabilities [Line Items]
Total minimum rent expense	$ 8,000,000.0	$ 7,500,000	$ 7,000,000.0
Contingent rent expense	0	$ 0	$ 0
Letter of credit, outstanding	$ 299,600,000
Number of jurisdiction \| Jurisdiction	30
Letter of Credit [Member]
Commitments And Contingent Liabilities [Line Items]
Letter of credit, outstanding	$ 450,000,000.0			$ 507,000,000.0

- Definition

The increases or decreases in lease payments that result from changes occurring after the inception of the lease in the factors (other than the passage of time) on which lease payments are based, except that any escalation of minimum lease payments relating to increases in construction or acquisition cost of the leased property or for increases in some measure of cost or value during the construction or preconstruction period, are excluded from contingent rentals. Contingent rentals also may include amounts for which the triggering events have not yet occurred or the specified targets for which have not yet been achieved (such as sales based percentage rent), but which events are considered probable of occurring or which specified targets are considered probable of being achieved.

+ References + Details