Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

At December 31, 2017, we were obligated under various operating lease agreements. Rental expense in 2017, 2016 and 2015 was $13.3 million, $11.7 million and $10.5 million, respectively.

At December 31, 2017, future minimum rental payments under non-cancelable operating leases were:



Year	($ in millions)
2018	$	13.2
2019	11.4
2020	8.5
2021	6.7
2022	6.2
Thereafter	33.1
Total	$	79.1

At December 31, 2017, outstanding unconditional contractual commitments for the purchase of raw materials and finished goods amounted to $75.6 million, of which $5.3 million is due to be paid in 2018.

We have letters of credit totaling $2.9 million supporting the reimbursement of workers' compensation and other claims paid on our behalf by insurance carriers. Our accrual for insurance obligations was $3.8 million at December 31, 2017, of which $0.9 million is in excess of our deductible and, therefore, is reimbursable by the insurance company.

Our SmartDose contingent consideration is payable to the selling shareholders based upon a percentage of product sales over the life of the underlying product patent, with no cap on total payments. Given the length of the earnout period and the uncertainty in forecasted product sales, we do not believe it is meaningful to estimate the upper end of the range over the entire period. However, our estimated probable range which could become payable over the next five years is between zero and $5.5 million.