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Retirement Plan | 12 Months Ended
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Dec. 31, 2017
Retirement Benefits [Abstract] |
Retirement Plan | Retirement Plan We maintain a defined contribution plan covering shoreside employees. Effective January 1, 2016, we commenced annual, non-elective contributions to the plan on behalf of all eligible participants equal to 3% of participants' eligible earnings. Remaining annual contributions to the plan are discretionary and are based on fixed percentages of participants' salaries and years of service, not to exceed certain maximums. Contribution expenses were $17.4 million, $16.7 million and $16.8 million for the years ended December 31, 2017, 2016 and 2015, respectively.

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- Definition The entire disclosure for pension and other postretirement benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -URI http://asc.fasb.org/topic&trid=2235017 + Details
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