Leases - Leases Assets and Liabilities (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Assets:
Operating lease assets	$ 952,890
Finance lease assets	21,541
Total leased assets	974,431
Current
Operating	97,517
Finance	4,705
Non-current
Operating	871,588
Finance	20,763
Total lease liabilities	$ 994,573