Earnings per Share (Reconciliation Of Number Of Common Shares Used In Calculating Basic And Diluted EPS) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings per Share [Line Items]
Net income	$ 20,136		$ 33,154		$ 16,270		$ 20,350		$ 13,721		$ 22,191		$ 19,182		$ 15,487		$ 89,910	$ 70,581	$ 42,594
Basic weighted-average shares outstanding (in shares)																	40,748,924	40,502,878	40,333,333
Diluted weighted-average shares outstanding (in shares)																	40,894,382	40,709,287	40,553,149
Basic net income per share (in dollars per share)	$ 0.49	[1]	$ 0.81	[1]	$ 0.40	[1]	$ 0.50	[1]	$ 0.34	[1]	$ 0.55	[1]	$ 0.47	[1]	$ 0.38	[1]	$ 2.21	$ 1.74	$ 1.06
Diluted net income per share (in dollars per share)	$ 0.49	[1]	$ 0.81	[1]	$ 0.40	[1]	$ 0.50	[1]	$ 0.34	[1]	$ 0.54	[1]	$ 0.47	[1]	$ 0.38	[1]	$ 2.20	$ 1.73	$ 1.05
Anti-dilutive shares excluded from the calculation (in shares)																	1,216	3,441	315
Performance Shares [Member]
Earnings per Share [Line Items]
Incremental shares (in shares)																	117,830	133,766	134,079
Anti-dilutive shares excluded from the calculation (in shares)																	0	3,441	0
Restricted Stock Units (RSUs) [Member]
Earnings per Share [Line Items]
Incremental shares (in shares)																	27,628	69,076	70,217
Anti-dilutive shares excluded from the calculation (in shares)																	1,216	0	315
Stock Options [Member]
Earnings per Share [Line Items]
Incremental shares (in shares)																	0	3,567	15,520

[1] 1 Per-share amounts are computed independently for each of the quarters presented. Therefore, the sum of the quarterly per-share amounts may not equal the total computed for the year.