Convertible Notes (Summary of Convertible Notes) (Detail) (USD $)	3 Months Ended				1 Months Ended	3 Months Ended	9 Months Ended				3 Months Ended	9 Months Ended		1 Months Ended		0 Months Ended	9 Months Ended			9 Months Ended
	Sep. 30, 2014		Dec. 31, 2013		Jan. 31, 2012 Series 2012 Notes [Member]	Sep. 30, 2014 Series 2012 Notes [Member]	Sep. 30, 2014 Series 2012 Notes [Member]	Feb. 06, 2014 Series 2012 Notes [Member]	Dec. 31, 2013 Series 2012 Notes [Member]	Aug. 01, 2013 Series 2012 Notes [Member]	Sep. 30, 2014 May 2015 Notes [Member]	Sep. 30, 2014 May 2015 Notes [Member]	Dec. 31, 2013 May 2015 Notes [Member]	Jan. 31, 2012 February 2015 Notes [Member]	Sep. 30, 2014 February 2015 Notes [Member]	Feb. 11, 2014 February 2018 Notes [Member]	Sep. 30, 2014 February 2018 Notes [Member]	Feb. 12, 2014 February 2018 Notes [Member]	Dec. 31, 2013 February 2018 Notes [Member]	Sep. 30, 2014 Term Loan. [Member]	Dec. 31, 2013 Term Loan. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					2.875%						3.75%	3.75%						4.00%
Debt Instrument, Convertible, Conversion Ratio						191.671					167.9812					109.1048
Convertible notes, conversion price (in Dollars per Share)						$ 5.22	$ 5.22				$ 5.95	$ 5.95						$ 9.17
Principal amount a $5 incentive cash payment per each to convert debt	$ 1,000				$ 1,000	$ 1,000								$ 1,000
Convertible Notes, Maturity Date (Date)							Feb. 15, 2015					May 01, 2015					Feb. 01, 2018			Oct. 28, 2014
Convertible Notes, Principal Balance Outstanding						48,311,000	48,311,000	48,300,000	180,000,000	180,000,000	155,250,000	155,250,000	155,250,000		0		300,000,000	300,000,000		18,750,000
Term loan payable	18,720,000	[1]	74,397,000	[1]
Convertible Notes Payable, Carrying Value	$ 492,901,000		$ 395,280,000			$ 47,564,000	$ 47,564,000		$ 172,630,000		$ 152,105,000	$ 152,105,000	$ 148,253,000				$ 274,512,000		$ 0	$ 18,720,000	$ 74,397,000

[1] unaudited