Leases - Maturities Of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Remainder of 2019	$ 36,140
2020	66,937
2021	60,369
2022	57,209
2023	39,070
Thereafter	12,767
Total lease payments	272,492
Less: imputed interest	(39,312)
Total operating lease liabilities	233,180
Current operating lease liabilities	54,449	$ 0
Non-current operating lease liabilities	178,731	$ 0
Vessels
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Remainder of 2019	32,625
2020	60,451
2021	54,638
2022	52,106
2023	34,580
Thereafter	2,470
Total lease payments	236,870
Less: imputed interest	(31,997)
Total operating lease liabilities	204,873
Current operating lease liabilities	49,371
Non-current operating lease liabilities	155,502
Facilities and Equipment
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Remainder of 2019	3,515
2020	6,486
2021	5,731
2022	5,103
2023	4,490
Thereafter	10,297
Total lease payments	35,622
Less: imputed interest	(7,315)
Total operating lease liabilities	28,307
Current operating lease liabilities	5,078
Non-current operating lease liabilities	$ 23,229