Shareholders' equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended			1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Apr. 30, 2013 Banker's Dashboard, LLC	Apr. 30, 2011 Banker's Dashboard, LLC
Acquisitions [Line Items]
Number of shares of common stock issued for acquisition				193,000
Number of years after closing that shares will be issued minimum					2 years
Common shares repurchased
Common shares authorized for repurchase	10,000,000
Common shares that remain available for repurchase	3,095,000
Common shares repurchased	1,162,000	999,000	940,000
Payments for common shares repurchased	$ 48,798	$ 27,155	$ 23,620
Common stock purchase rights
Number of common shares each right entitles holder to purchase	1
Exercise price of common stock purchase rights (per share)	100
Beneficial ownership that could trigger the exercise of stock purchase rights	20.00%
Percentage of market price of one common share used to determine number of shares purchasable	50.00%
Expiration date of rights	December 31, 2016
Redemption price of stock purchase rights	0.01