Shareholders' Equity - Share-based payments and shareholders' rights plan (Details)	12 Months Ended
	Dec. 31, 2012 item $ / shares shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 shares
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Common stock, shares authorized		4,000,000	4,000,000
Unrecognized compensation | $		$ 0
2012 Long Term Incentive Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Common stock, shares authorized		300,000
Rights Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of rights for each outstanding share	1
Percentage of beneficial ownership	25%
Number of business days	10 days
Exercise price | $ / shares	$ 32.00
Rights Plan | Event Any Person Becomes Acquiring Person [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of times the exercise price | item	3
Rights Plan | Common | Event Any Person Becomes Acquiring Person [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of rights for each outstanding share	2
Rights Plan | Series A Preferred Stock
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares for each right	0.01
Rights Plan | Series A Preferred Stock | Event Any Person Becomes Acquiring Person [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares for each right	0.02