Convertible Senior Debt (Details Textuals)			3 Months Ended			9 Months Ended
	Jul. 16, 2015 d	Mar. 03, 2015 USD ($) shares	Sep. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) d	Sep. 30, 2014 USD ($)
Debt Instrument [Line Items]
Number of trading days to determine additional interest payable | d	5					20
Loss on extinguishment of debt			$ (23,609,000)		$ (49,000)	$ (61,953,000)	$ (927,000)
Proceeds from termination and settlement of convertible note hedge		$ 17,818,000				17,818,000	$ 0
Common stock Class A
Debt Instrument [Line Items]
Shares received for termination and settlement of convertible note hedge | shares		258,350
2016, 2018 and 2020 Senior Notes [Member]
Debt Instrument [Line Items]
Loss on extinguishment of debt			$ 22,653,000	$ 35,142,000		$ 57,795,000