Description of the business and recent developments: Basic and diluted net (loss) income per common share (Details) - shares	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Diluted weighted average shares
Weighted-average common shares - basic (in shares)	44,323,131	44,474,724	44,774,831	45,158,250	45,229,125,000	45,629,079,000	45,897,449,000	46,409,735,000	44,888,723	45,960,720	46,286,735
Weighted average common shares-diluted	44,558,089	44,702,127	45,054,507	45,158,250	45,229,125	45,629,079	46,294,966	46,907,360	45,159,489	46,349,670	46,996,904
Unvested shares of restricted common stock	870,751				1,282,646				870,751	1,282,646	1,039,323
Restricted stock
Diluted weighted average shares
Dilutive effect of awards (in shares)									230,570	329,754	633,285
Stock options
Diluted weighted average shares
Dilutive effect of awards (in shares)									40,196	59,196	76,884
Common stock
Diluted weighted average shares
Anti-dilutive shares									119,872	84,690	28,628
Restricted common stock
Diluted weighted average shares
Anti-dilutive shares									362,241	379,639