Share-Based Compensation - Information pertaining to options oustanding - (Details 2) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation
Range of exercise prices, low end of range (in dollars per share)	$ 61.42	$ 61.49	$ 41.45
Range of exercise prices, high end of range (in dollars per share)	$ 66.32	$ 66.32	$ 41.45
Options Outstanding
Number outstanding (in shares)	285,405
Weighted Average Remaining Contractual Life	4 years 4 months 24 days
Weighted Average Exercise Price (in dollars per share)	$ 38.85
Options Exercisable
Number outstanding (in shares)	227,130
Weighted Average Exercise Price (in dollars per share)	$ 34.48
Weighted Average Remaining Contractual Life	3 years 4 months 24 days
Restricted Stock
Vesting schedule of shares
2016	70,568
2017	54,892
2018	36,720
2019	32,067
2020	5,832
Thereafter	18,203
Total	218,282	228,907
$26.01 - $ 30.00
Share Based Compensation
Range of exercise prices, low end of range (in dollars per share)	$ 26.01
Range of exercise prices, high end of range (in dollars per share)	$ 30.00
Options Outstanding
Number outstanding (in shares)	33,313
Weighted Average Remaining Contractual Life	3 years 3 months 18 days
Weighted Average Exercise Price (in dollars per share)	$ 27.49
Options Exercisable
Number outstanding (in shares)	33,313
Weighted Average Exercise Price (in dollars per share)	$ 27.49
$30.01 - $35.00
Share Based Compensation
Range of exercise prices, low end of range (in dollars per share)	30.01
Range of exercise prices, high end of range (in dollars per share)	$ 35.00
Options Outstanding
Number outstanding (in shares)	121,000
Weighted Average Remaining Contractual Life	3 years 7 months 6 days
Weighted Average Exercise Price (in dollars per share)	$ 31.78
Options Exercisable
Number outstanding (in shares)	114,855
Weighted Average Exercise Price (in dollars per share)	$ 31.78
$35.01 - $40.00
Share Based Compensation
Range of exercise prices, low end of range (in dollars per share)	35.01
Range of exercise prices, high end of range (in dollars per share)	$ 40.00
Options Outstanding
Number outstanding (in shares)	57,659
Weighted Average Remaining Contractual Life	2 years 1 month 6 days
Weighted Average Exercise Price (in dollars per share)	$ 38.20
Options Exercisable
Number outstanding (in shares)	57,655
Weighted Average Exercise Price (in dollars per share)	$ 38.20
$40.01 - $45.00
Share Based Compensation
Range of exercise prices, low end of range (in dollars per share)	40.01
Range of exercise prices, high end of range (in dollars per share)	$ 45.00
Options Outstanding
Number outstanding (in shares)	24,507
Weighted Average Remaining Contractual Life	6 years 10 months 24 days
Weighted Average Exercise Price (in dollars per share)	$ 41.42
Options Exercisable
Number outstanding (in shares)	13,824
Weighted Average Exercise Price (in dollars per share)	$ 41.40
$45.01 - $69.48
Share Based Compensation
Range of exercise prices, low end of range (in dollars per share)	45.01
Range of exercise prices, high end of range (in dollars per share)	$ 69.48
Options Outstanding
Number outstanding (in shares)	48,926
Weighted Average Remaining Contractual Life	8 years 7 months 6 days
Weighted Average Exercise Price (in dollars per share)	$ 63.51
Options Exercisable
Number outstanding (in shares)	7,483
Weighted Average Exercise Price (in dollars per share)	$ 65.52