Convertible Senior debt (Details 2) - Subsequent Event [Member] - USD ($) $ in Thousands			1 Months Ended
	Jul. 16, 2015	Jul. 15, 2015	Jul. 31, 2015
Senior Notes due 2016 [Member]
Subsequent Event [Line Items]
Aggregate Principal, Subsequent Event		$ 8,151
Cash Payments to Noteholders, Subsequent Event		1,305
Losses on Extinguishment, Subsequent Event		489
Senior Notes due 2018 [Member]
Subsequent Event [Line Items]
Aggregate Principal, Subsequent Event	$ 75,387
Cash Payments to Noteholders, Subsequent Event	13,052
Losses on Extinguishment, Subsequent Event	$ 11,664
Senior Notes due 2020 [Member]
Subsequent Event [Line Items]
Aggregate Principal, Subsequent Event		55,407
Cash Payments to Noteholders, Subsequent Event		11,371
Losses on Extinguishment, Subsequent Event		$ 10,500
Senior Notes due 2016, 2018 and 2020 [Member]
Subsequent Event [Line Items]
Aggregate Principal, Subsequent Event			$ 138,945
Cash Payments to Noteholders, Subsequent Event			25,728
Losses on Extinguishment, Subsequent Event			$ 22,653
Common Class A [Member] | Senior Notes due 2016 [Member]
Subsequent Event [Line Items]
Class A Commons Shares Issued, Subsequent Event		555,016
Common Class A [Member] | Senior Notes due 2018 [Member]
Subsequent Event [Line Items]
Class A Commons Shares Issued, Subsequent Event	3,478,511
Common Class A [Member] | Senior Notes due 2020 [Member]
Subsequent Event [Line Items]
Class A Commons Shares Issued, Subsequent Event		2,289,013
Common Class A [Member] | Senior Notes due 2016, 2018 and 2020 [Member]
Subsequent Event [Line Items]
Class A Commons Shares Issued, Subsequent Event			6,322,540