Business Segments and Geographic Information (Asset Reconciliation) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Asset Reconciliation of Segments
Cash	$ 32,463	$ 31,255	$ 81,377
Deferred income tax assets	110,068	87,763
Total segment assets	4,317,534	4,258,118
Operating Segments
Asset Reconciliation of Segments
Total segment assets	4,185,452	4,122,830	$ 4,046,323
Segment Reconciling Items
Asset Reconciliation of Segments
Cash	32,463	31,255
Deferred income tax assets	36,278	29,924
Restricted cash and investments, current and non-current	$ 63,341	$ 74,109