Stock based Compensation (Details 1) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward
Outstanding, beginning of year	1,293
Stock Issued During Period Shares Stock Options Exercised	(461)	(381)	(2,079)
Forfeited and expired	(40)
Outstanding, end of year	802	1,293
ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstrac
Outstanding, weighted average exercise price	$ 31.61	$ 29.5
Granted, weighted-average exercise price	$ 52.51
Exercised, weighted-average exercise price	$ 25.66
Forfeited and expired, weighted-average exercise price	$ 37.28
Outstanding, end of year, weighted-average contractual life, Options	4 years 2 months 12 days
Outstanding, end of year, aggregate intrinsic value, options	$ 17,575
Vested or expected to vest, end of year, number of shares	771
Vested or expected to vest, end of year, weighted-average exercise price	$ 31.49
Vested or expected to vest, end of year, weighted-average contractual life	4 years 2 months 12 days
Vested or expected to vest, end of year, aggregate intrinsic value	16,983
Exercisable, end of year, number of shares	311
Exercisable, end of year, weighted-average exercise price	$ 29.26
Exercisable, end of year, weighted-average contractual life	3 years 8 months 12 days
Exercisable, end of year, aggregate intrinsic value	$ 7,554