Stock-Based Compensation (Details) (Restricted Stock [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2013	Jun. 30, 2012
Grants of Restricted Stock [Line Items]
Restricted Shares Granted (in shares)	156	1,036
Total value of restricted shares granted	$ 4,216	$ 27,858
Minimum [Member]
Grants of Restricted Stock [Line Items]
Percentage of estimated forfeitures			0.00%	0.00%
Value Per Share (in dollars per share)	$ 26.85	$ 25.32
Maximum [Member]
Grants of Restricted Stock [Line Items]
Percentage of estimated forfeitures			10.00%	10.00%
Value Per Share (in dollars per share)	$ 27.50	$ 27.36