Description of the business and summary of significant accounting policies: (Details 3)	3 Months Ended								12 Months Ended			3 Months Ended	12 Months Ended			12 Months Ended			12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Convertible senior notes	Dec. 31, 2013 Convertible senior notes	Dec. 31, 2012 Convertible senior notes	Jun. 30, 2007 Convertible senior notes	Dec. 31, 2013 Restricted stock	Dec. 31, 2011 Restricted stock	Dec. 31, 2012 Restricted stock	Dec. 31, 2013 Options	Dec. 31, 2012 Options	Dec. 31, 2011 Options
Basic and diluted net (loss) income per common share
Restricted common stock not included in computation of basic (loss) income per share as shares were not vested (in shares)																1,000,000	800,000	1,700,000
Interest rate (as a percent)												1.00%	1.00%	1.00%	1.00%
Number of shares yield after conversion												1,900,000	1,900,000
Shares not included in the computation of diluted loss per share as the effect would be anti-dilutive																				200,000	100,000
Diluted weighted average shares
Weighted average common shares -basic	46,302,926	46,171,194	46,040,692	45,537,607	45,492,847	45,377,732	45,313,804	45,241,418	46,286,735	45,514,844	45,180,485
Dilutive effect of awards (in shares)																633,285	440,375		76,884		83,192
Weighted average common shares -diluted	48,800,560	46,823,167	46,769,184	46,435,677	45,492,847	45,377,732	45,313,804	45,241,418	46,996,904	45,514,844	45,704,052