Compensation Plans- Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Stock options [Member]	Dec. 31, 2013 Stock appreciation rights (SARs) [Member]	Dec. 31, 2013 Restricted stock units (RSUs) [Member]	Dec. 31, 2012 Restricted stock units (RSUs) [Member]	Dec. 31, 2011 Restricted stock units (RSUs) [Member]	Dec. 31, 2013 Restricted stock [Member]	Dec. 31, 2012 Restricted stock [Member]	Dec. 31, 2011 Restricted stock [Member]	Dec. 31, 2013 Performance shares [Member]	Dec. 31, 2012 Performance shares [Member]	Dec. 31, 2011 Performance shares [Member]	Dec. 31, 2013 Minimum [Member] Stock options [Member]	Dec. 31, 2013 Minimum [Member] Restricted stock [Member]	Dec. 31, 2013 Maximum [Member] Stock options [Member]	Dec. 31, 2013 Maximum [Member] Restricted stock [Member]	Dec. 31, 2013 Stock Plan for Non-Management Directors [Member]	Dec. 31, 2012 Stock Plan for Non-Management Directors [Member]	Dec. 31, 2011 Stock Plan for Non-Management Directors [Member]	Dec. 31, 2006 Stock Plan for Non-Management Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term					10 years
Award vesting period		3 years				5 years	5 years						3 years			3 years	2 years	5 years	5 years
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures	146,700
Exercisable, Weighted Average Remaining Contractual Term						10 years
Total unrecognized compensation cost for nonvested stock units						$ 153,000	$ 2,168,000	$ 1,256,000	$ 273,000
Expected years to recognize unearned compensation						1 year 7 months 2 days	3 years 7 months	4 years	10 months 24 days
Number of shares authorized																					200,000		100,000
Number of shares available for grant		978,660																		83,764
Stock Issued During Period, Shares, Issued for Services										37,943	71,899	6,724								16,990	18,410	19,830
Weighted average grant date fair value of options and SSARs																				$ 15.40	$ 14.00	$ 12.90
Share-based compensation expense		5,000,000	2,500,000	1,800,000			1,142,000	658,000	555,000	590,000	179,000	30,000	3,200,000	1,300,000	0					262,000
Tax benefit (expense) from compensation expense		222,000	66,000	(53,000)
Employee minimum age to participate in plan		21 years
401 k plan, cost recognized		$ 1,200,000	$ 1,200,000	$ 1,100,000