Stock Incentive Plan (Schedule of Share-based Compensation, Unearned Compensation Related to RSU's) (Details) - Restricted Stock Units (RSUs) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Changes In Unearned Compensation [Roll Forward]
Unearned compensation at beginning of year	$ 129,669	$ 122,910	$ 115,965
RSUs granted, net of cancellations	53,583	52,204	52,897
RSUs expensed	47,329	(34,408)	(38,796)
RSUs forfeitures	7,533	(11,037)	(7,156)
Unearned compensation at end of year	$ 128,390	$ 129,669	$ 122,910