Leases - Future minimum payments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Operating lease liabilities under Topic 842
Operating leases - 2020	$ 22,908	$ 29,872
Operating leases - 2021	28,201	27,445
Operating leases - 2022	24,113	23,540
Operating leases - 2023	21,829	21,257
Operating leases - 2024	20,729	20,176
Operating leases - later years	70,978	70,842
Operating leases - Total	188,758	193,132
Less: Imputed interest	(26,797)	(27,993)
Operating lease liabilities	161,961	165,139
Finance lease liabilities under Topic 842
Finance leases - 2020	2,411	3,068
Finance leases - 2021	3,299	3,159
Finance leases - 2022	3,392	3,252
Finance leases - 2023	3,489	3,349
Finance leases - 2024	3,594	3,448
Finance leases - later years	8,938	8,220
Finance leases - Total	25,123	24,496
Less: imputed interest	(4,594)	(4,686)
Finance lease liabilities	$ 20,529	$ 19,810