Commitments and Contingencies - Future Minimum Annual Commitments (Details) $ in Thousands	Jun. 30, 2018 USD ($)
Operating Lease Minimum Rental Payments
2018	$ 39,115
2019	73,080
2020	57,683
2021	38,639
2022	31,652
Thereafter	61,790
Total future lease commitments	301,959
Minimum Purchase Commitments
2018	12,413
2019	21,037
2020	15,663
2021	8,008
2022	5,640
Thereafter	4,141
Total future purchase commitments	$ 66,902