Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Numerator [Abstract]
Net income	$ 10,938us-gaap_NetIncomeLoss	$ 10,140us-gaap_NetIncomeLoss
Basic earnings per share [Abstract]
Weighted average shares (in shares)	17,400,000	17,308,000
Diluted earnings per share [Abstract]
Effect of dilutive stock options and restricted stock grants (in shares)	51,000	95,000
Adjusted weighted average shares (in shares)	17,451,000	17,403,000
Earnings per share [Abstract]
Basic earnings per share (in dollars per share)	$ 0.63us-gaap_EarningsPerShareBasic	$ 0.59us-gaap_EarningsPerShareBasic
Diluted earnings per share (in dollars per share)	$ 0.63us-gaap_EarningsPerShareDiluted	$ 0.58us-gaap_EarningsPerShareDiluted
Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options excluded from diluted calculations (in shares)	68,063	0
Weighted average price for anti dilutive securities (in dollars per share)	$ 35.409	$ 0

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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