Stock-Based Compensation (Schedule of Restricted Stock Unit Activity) (Details) - Restricted Stock Units [Member] - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Number of Shares
Granted and Unvested, Beginning of Period, Number of Shares	1,056,597
Vested, Number of Shares	(365,940)
Granted, Number of Shares	321,500
Forfeited, Number of Shares	(1,560)
Total Granted and Unvested, Number of Shares	1,010,597
Approved for grant, Number of Shares	709,500
Total Awarded and Unvested, End of Period, Number of Shares	1,720,097
Weighted Average Grant Date Fair Value
Granted and Unvested, Beginning of Period, Weighted Average Grant Date Fair Value	$ 26.54
Vested, Weighted Average Grant Date Fair Value	27.18
Granted, Weighted Average Grant Date Fair Value	23.07	$ 27.33
Forfeited, Weighted Average Grant Date Fair Value	28.59
Total Granted and Unvested, End of Period, Weighted Average Grant Date Fair Value	$ 26.70
Aggregate Intrinsic Value
Granted and Unvested, Beginning of Period, Aggregate Intrinsic Value	$ 25,432
Vested, Aggregate Intrinsic Value	7,896
Granted, Aggregate Intrinsic Value	6,938
Total Granted and Unvested, Aggregate Intrinsic Value	21,809
Approved for grant, Aggregate Intrinsic Value	15,311
Total Awarded and Unvested, End of Period, Aggregate Intrinsic Value	$ 37,120