Common stock (Details)	3 Months Ended			3 Months Ended		0 Months Ended	3 Months Ended		0 Months Ended				3 Months Ended						3 Months Ended		0 Months Ended
	Mar. 31, 2014	Mar. 31, 2014 Common Stock	Dec. 31, 2013 Common Stock	Mar. 31, 2014 Common Class A		Jan. 13, 2014 Common Class A Healthcare of Ontario Pension Plan Trust Fund	Mar. 31, 2014 Common Class B		Jan. 13, 2014 Common Class B Healthcare of Ontario Pension Plan Trust Fund		Mar. 31, 2014 Common Class C	Dec. 31, 2013 Common Class C	Mar. 31, 2014 Common Class D		Mar. 31, 2014 Common Class E	Dec. 31, 2013 Common Class E	Mar. 31, 2014 Common Class F	Dec. 31, 2013 Common Class F	Mar. 31, 2014 Common Class G		Jan. 13, 2014 C H K Energy Holdings Inc. Common Class A Healthcare of Ontario Pension Plan Trust Fund
Common stock rollforward
Shares outstanding at January 1, 2014		1,425,705	1,422,160	70,117			357,882				209,882	209,882	279,999		504,276	504,276	1	1	3
Stock transfers				293,023	[1]		(13,023)	[1]	(13,023)	[1]			(279,999)	[1]					(1)	[1]
Restricted stock issuances	4,613			4,613
Restricted stock repurchased	(1,068)			(1,068)
Shares outstanding at March 31, 2014		1,425,705	1,422,160	366,685			344,859				209,882	209,882	0		504,276	504,276	1	1	2
Company shares bought and sold by Company stockholders						15,078															280,000

[1] In this transaction, Healthcare of Ontario Pension Plan Trust Fund (“HOOPP”) purchased 280,000 shares of Class A common stock converted from Class D and Class G common stock held by CHK Energy Holdings, Inc. (“CHK Energy Holdings”) effective January 13, 2014. An additional 15,078 shares of Class A common stock was purchased by HOOPP from various other stockholders of which 13,023 shares were converted from Class B common stock.