Leases - Maturities Of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Less than one year	$ 57,990	$ 60,649
One to two years	54,945	57,541
Two to three years	18,279	39,229
Three to four years	4,145	6,844
Four to five years	1,041	2,340
Over five years	4,835	4,054
Total lease payments	141,235	170,657
Less: imputed interest	(13,532)	(18,049)
Total operating lease liabilities	127,703	152,608
Current operating lease liabilities	50,769	51,599
Non-current operating lease liabilities	76,934	101,009
Vessels
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Less than one year	52,106	54,621
One to two years	49,760	52,106
Two to three years	13,557	34,580
Three to four years		2,470
Total lease payments	115,423	143,777
Less: imputed interest	(9,021)	(13,352)
Total operating lease liabilities	106,402	130,425
Current operating lease liabilities	45,940	46,748
Non-current operating lease liabilities	60,462	83,677
Facilities and Equipment
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Less than one year	5,884	6,028
One to two years	5,185	5,435
Two to three years	4,722	4,649
Three to four years	4,145	4,374
Four to five years	1,041	2,340
Over five years	4,835	4,054
Total lease payments	25,812	26,880
Less: imputed interest	(4,511)	(4,697)
Total operating lease liabilities	21,301	22,183
Current operating lease liabilities	4,829	4,851
Non-current operating lease liabilities	$ 16,472	$ 17,332