Stock Compensation Plans (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee stock options
Options
Outstanding at the beginning of year (in shares)	753,063
Granted (in shares)	343,080
Exercised (in shares)	(356,375)
Forfeited (in shares)	(19,751)
Expired (in shares)	(17,280)
Outstanding at the end of year (in shares)	702,737	753,063
Exercisable at the end of the period (in shares)	258,662
Expected to vest at the end of the period (in shares)	702,737
Weighted-Average Exercise Price
Outstanding at the beginning of year (in dollars per share)	$ 12.78
Granted (in dollars per share)	$ 17.17
Exercised (in dollars per share)	$ 11.23
Forfeited (in dollars per share)	$ 15.98
Expired (in dollars per share)	$ 9.08
Outstanding at the end of year (in dollars per share)	$ 15.70	$ 12.78
Exercisable at the end of the period (in dollars per share)	$ 14.27
Expected to vest at the end of the period (in dollars per share)	$ 15.70
Weighted-Average Remaining Contractual Term
Outstanding at the end of the period	5 years 7 months 17 days
Exercisable at the end of the period	4 years 11 months 19 days
Expected to vest at the end of the period	5 years 7 months 17 days
Aggregate Intrinsic Value
Outstanding at the end of the period	$ 3,508,000
Exercisable at the end of the period	1,661,000
Expected to vest at the end of the period (in dollars)	3,508,000
Weighted-average grant date fair value per share of options granted (in dollars per share)	$ 4.51	$ 5.28	$ 5.47
Total grant date fair value of options granted	1,500,000	1,500,000	1,000,000
Weighted-average grant date fair value options vested (in dollars per share)	$ 5.32	$ 5.86	$ 6.79
Total grant date fair value of options vested	1,000,000	700,000	500,000
Non-employee director stock options
Options
Outstanding at the beginning of year (in shares)	74,222
Exercised (in shares)	(12,300)
Outstanding at the end of year (in shares)	61,922
Exercisable at the end of the period (in shares)	61,922
Weighted-Average Exercise Price
Outstanding at the beginning of year (in dollars per share)	$ 6.45
Exercised (in dollars per share)	$ 5.08
Outstanding at the end of year (in dollars per share)	$ 6.73
Exercisable at the end of the period (in dollars per share)	$ 6.73
Weighted-Average Remaining Contractual Term
Outstanding at the end of the period	2 years 3 months 14 days
Exercisable at the end of the period	2 years 3 months 14 days
Aggregate Intrinsic Value
Outstanding at the end of the period	803,000
Exercisable at the end of the period	803,000
Employee and non-employee director stock options
Aggregate Intrinsic Value
Total intrinsic value of stock options exercised	2,500,000	1,900,000	2,700,000
Cash received from the exercise of options	$ 4,100,000	$ 1,600,000	$ 2,100,000