Stock Incentive Plan (Schedule of Share-based Compensation, Unearned Compensation Related to RSU's) (Details) (Restricted Stock Units (RSUs), USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Stock Units (RSUs)
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	$ 73,205	$ 93,653	$ 57,315
RSUs granted, net of cancellations	51,575	4,406	73,255
RSUs expensed	27,966	(22,881)	(25,728)
RSUs forfeitures	8,799	(1,973)	(11,189)
Unearned compensation at end of year	$ 88,015	$ 73,205	$ 93,653