Equity-Based Compensation (Summary Of Outstanding Performance Share Awards / Restricted Stock Units) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Performance shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested shares outstanding at January 1, Shares	160,214
Granted (in shares)	83,111	85,028
Forfeited (in shares)	(10,786)
Unvested shares outstanding at June 30, Shares	232,539
Unvested shares outstanding at January 1, Weighted Avg. Grant Date Fair Value (in dollars per share)	$ 44.50
Granted, Weighted Av.g Exercise Price (in dollars per share)	$ 62.78	$ 34.24
Forfeited, Weighted Avg. Grant Date Fair Value (in dollars per share)	$ 45.83
Unvested shares outstanding at June 30, Weighted Avg. Grant Date Fair Value (in dollars per share)	$ 50.97
Aggregate Intrinsic Value	$ 9,097
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested shares outstanding at January 1, Shares	40,219
Granted (in shares)	18,949
Vested (in shares)	(3,100)
Forfeited (in shares)	(5,410)
Unvested shares outstanding at June 30, Shares	50,658
Unvested shares outstanding at January 1, Weighted Avg. Grant Date Fair Value (in dollars per share)	$ 34.82
Granted, Weighted Av.g Exercise Price (in dollars per share)	$ 45.43
Vested, Weighted Avg. Grant Date Fair Value (in dollars per share)	$ 36.60
Forfeited, Weighted Avg. Grant Date Fair Value (in dollars per share)	$ 35.83
Unvested shares outstanding at June 30, Weighted Avg. Grant Date Fair Value (in dollars per share)	$ 38.57
Aggregate Intrinsic Value	$ 2,049