Income Per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income per share:
Shares used to calculate basic income per share	31,272	31,287	31,386	31,231
Dilutive effect of outstanding stock options, performance stock units and restricted stock units	255	368	316	410
Shares used to calculate diluted income per share	31,527	31,655	31,702	31,641
Stock options
Income per share:
Anti-dilutive securities excluded from computation of diluted income per share	7	212	10	247
Performance stock units
Income per share:
Anti-dilutive securities excluded from computation of diluted income per share	0	198	0	20