Leases - Maturities of Operating and Finance Lease Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Operating Leases
2019	$ 196,381
2020	230,500
2021	192,525
2022	151,581
2023	111,167
Thereafter	501,279
Total undiscounted cash flows	1,383,433
Less: Imputed interest	358,281
Total operating lease liabilities	1,025,152
Finance Leases
2019	431
2020	526
2021	537
2022	548
2023	558
Thereafter	5,075
Total undiscounted cash flows	7,675
Less: Imputed interest	3,294
Total finance lease liabilities	4,381
Total
2019	196,812
2020	231,026
2021	193,062
2022	152,129
2023	111,725
Thereafter	506,354
Total undiscounted cash flows	1,391,108
Less: Imputed interest	361,575
Total operating lease liabilities	$ 1,029,533
Operating Leases
2019		$ 267,846
2020		231,711
2021		193,155
2022		150,155
2023		107,759
Thereafter		484,038
Total		$ 1,434,664