Equity and redeemable securities (Schedule of equity) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended		9 Months Ended										9 Months Ended			9 Months Ended
	Aug. 14, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Convertible Class C Preferred Stock [Member]	Sep. 30, 2013 Class B Preferred [Member]	Sep. 30, 2013 Class A Common Stock [Member]	Dec. 31, 2012 Class A Common Stock [Member]	Sep. 30, 2013 Class B Common Stock [Member]	Dec. 31, 2012 Class B Common Stock [Member]	Sep. 30, 2013 Class A Common Stock [Member]	Dec. 31, 2012 Class A Common Stock [Member]	Sep. 30, 2013 Class A Common Stock [Member]	Sep. 30, 2013 Class B Common Stock [Member]	Dec. 31, 2012 Class B Common Stock [Member]	Sep. 30, 2013 Class B Common Stock [Member]	Sep. 30, 2013 Common Stock [Member]	Sep. 30, 2013 Common Stock [Member] Class A Common Stock [Member]	Sep. 30, 2013 Common Stock [Member] Class B Common Stock [Member]	Sep. 30, 2013 Additional Paid-in Capital [Member]	Sep. 30, 2013 Retained Earnings [Member]
Class of Stock [Line Items]
Common stock, shares, outstanding				0				0	11,590,005	0	2,870,712	0	11,590,005		0	2,870,712		0
Total stockholders' equity				$ 34,164								$ 0	$ 116		$ 0	$ 29		$ 0			$ 46,534	$ (12,515)
Dividends				(1,836)																	(1,836)
Stock issued, shares	7,000,000																	4,411,765
Stock issued, value				55,225														44			55,181
Conversion of stock, shares														(11,590,005)			(2,870,712)		11,590,005	2,870,712
Conversion of stock, value														(116)			(29)		116	29
Conversion of preferred stock to common stock in connection with the IPO (Note 2), shares						(5,000)	(37,467)											7,191,891
Conversion of preferred stock to common stock in connection with the IPO (Note 2), value				43,313		(5,000)	(38,313)											72			43,241
Issuance of nonvested stock awards, net of forfeitures, shares																		42,858
Stockholder loans related to tax withholding on stock issuance				401																	401
Stock compensation expense				573																	573
Net loss		(5,513)	40	(7,592)	(10,763)																	(7,592)
Common stock, shares, outstanding	26,107,231	26,107,231		26,107,231				0	11,590,005	0	2,870,712	0	11,590,005		0	2,870,712		26,107,231
Total stockholders' equity		$ 124,248		$ 124,248								$ 0	$ 116		$ 0	$ 29		$ 261			$ 144,094	$ (20,107)