Earnings Per Share (Calculation of Basic and Diluted EPS) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]
Net income	$ 6,024	$ 11,333	$ 11,787	$ 6,950	$ 4,199	$ 8,575	$ 9,344	$ 6,785	$ 36,094	$ 28,903	$ 32,687
Average common shares:
Basic (weighted-average outstanding shares)									12,050,000	11,899,000	11,848,000
Dilutive potential common shares from stock options, shares									162,000	159,000	118,000
Diluted (weighted-average outstanding shares)	12,262	12,229	12,200	12,158	12,090	12,056	12,058	12,027	12,212,000	12,058,000	11,966,000
Basic earnings per share (in dollars per share)									$ 3.00	$ 2.43	$ 2.76
Diluted earnings per share (in dollars per share)	$ 0.49	$ 0.93	$ 0.97	$ 0.57	$ 0.35	$ 0.71	$ 0.77	$ 0.56	$ 2.96	$ 2.40	$ 2.73
Stock options excluded from diluted earnings per share calculation (shares)									3,831	38,954	78,337