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Commitments and Contingencies (Tables) | 12 Months Ended
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Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract] |
Schedule of Roll Forward Activity in Insurance Reserves [Table Text Block] | The insurance and claims accruals are based on known facts, actuarial estimates and historical trends. While recorded accruals are based on the ultimate liability, which includes amounts in excess of the deductible, a corresponding receivable for amounts in excess of the deductible is included in total assets in the consolidated balance sheets at December 31:
(in thousands) |  | 2017 |  | 2016 |  | 2015
Balance at beginning of period |  | $ | 42,584 |  |  | $ | 36,967 |  |  | $ | 39,480 |
Net increases in reserves |  |  | 22,938 |  |  |  | 25,139 |  |  |  | 15,686 |
Net payments made |  |  | (20,159 | ) |  |  | (19,522 | ) |  |  | (18,199 | )
Balance at end of period |  | $ | 45,363 |  |  | $ | 42,584 |  |  | $ | 36,967 |

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