New Accounting Standards (Adoption of New Standard) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
New Accounting Standards [Abstract]
Operating lease right-of-use assets	$ 168,974	$ 183,220
Total assets	13,849,447	13,737,695
Current portion of operating lease liabilities	30,196	29,929
Total current liabilities	1,135,466	1,007,228
Long-term portion of operating lease liabilities	145,642	160,033
Deferred income taxes	725,343	818,622
Total liabilities	7,183,258	6,799,341
Retained earnings	2,582,298	2,654,207
Total liabilities and equity	$ 13,849,447	$ 13,737,695