SEGMENT AND GEOGRAPHIC INFORMATION: (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
SEGMENT AND GEOGRAPHIC INFORMATION
Net product sales:	$ 139,881	$ 183,806	$ 107,528	$ 105,477	$ 137,929	$ 191,093	$ 104,061	$ 106,812	$ 536,692	$ 539,895	$ 539,627
Long-lived assets:	184,586				190,081				184,586	190,081	196,916
United States
SEGMENT AND GEOGRAPHIC INFORMATION
Net product sales:									492,450	488,795	495,082
Long-lived assets:	149,144				153,444				149,144	153,444	160,099
Canada and Other
SEGMENT AND GEOGRAPHIC INFORMATION
Net product sales:									44,242	51,100	44,545
Long-lived assets:	$ 35,442				$ 36,637				$ 35,442	$ 36,637	$ 36,817