Description of the business and recent developments: (Details 2) (USD $)	3 Months Ended			12 Months Ended			3 Months Ended		3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Convertible senior notes	Dec. 31, 2012 Convertible senior notes	Mar. 31, 2012 Convertible senior notes	Jun. 30, 2007 Convertible senior notes	Mar. 31, 2013 Restricted stock	Mar. 31, 2012 Restricted stock	Mar. 31, 2013 Options	Mar. 31, 2012 Options
Basic and diluted net (loss) income per common share
Unvested restricted common stock not included in computation of basic (loss) income per share as shares were not vested (in shares)							1,600,000	700,000
Interest rate (as a percent)			1.00%		1.00%	1.00%
Initial conversion price of notes (in dollars per share)			$ 49.18	$ 49.18
Number of shares yield after conversion			1,900,000	1,900,000
Shares not included in the computation of basic or diluted income (loss) income per share as the effect would be anti-dilutive										200,000
Weighted-average exercise price of options excluded from computation of diluted loss per share (in dollars per share)										$ 13.52
Options exercised during the period (in shares)									14,270	11,687
Diluted weighted average shares
Weighted average common shares - basic	45,537,607	45,241,418
Dilutive effect of awards (in shares)							816,600		81,470
Weighted average common shares - diluted	46,435,677	45,241,418