Commitments and Contingencies (Maturity of Operating Lease Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Remainder of 2019	$ 44,266
2020	59,080
2021	57,605
2022	55,098
2023	50,564
Thereafter	259,664
Total operating lease payments	526,277
Less: imputed interest	(103,381)
Present value of operating lease liabilities	$ 422,896
2019		$ 55,435
2020		60,996
2021		63,348
2022		67,707
2023		72,491
Thereafter		578,874
Total		$ 898,851

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Amount of lessee's undiscounted obligation for lease payments for operating lease.

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