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, 2016	Dec. 31, 2015	Dec. 31, 2014
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	$ 103,538	$ 88,015	$ 73,205
RSUs granted, net of cancellations	52,697	50,442	51,575
RSUs expensed	35,585	(30,691)	(27,966)
RSUs forfeitures	4,685	(4,228)	(8,799)
Unearned compensation at end of year		$ 103,538	$ 88,015
Year-End Adjustment [Member]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Changes In Unearned Compensation [Roll Forward]
Unearned compensation at end of year	$ 115,965