Subsequent Events	3 Months Ended
	Mar. 31, 2022
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS On April 11, 2022, we entered into a second amendment (the "Amendment") to the 2017 KKC Agreement. Under the terms of the Amendment, the parties have agreed to a reduction in the royalty rate payable to us by KKC upon net sales of tenapanor in Japan. The royalty rate will be reduced from the high teens to low double digits for a two-year period of time following the first commercial sale in Japan, and then to mid-single digits for the remainder of the royalty term. As consideration for the reduction in the royalty rate, KKC has agreed to pay us up to an additional U.S. $40.0 million payable in two tranches, with the first payment due following KKC's filing with the Japanese Ministry Health, Labour and Welfare (MHLW) of its application for marketing approval for tenapanor and the second payment due following KKC's receipt of regulatory approval to market tenapanor for hyperphosphatemia in Japan.