CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2021	Nov. 30, 2021	Apr. 30, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2016	Nov. 30, 2014
0 Percent Convertible Senior Notes [Member]
Consolidated Statements of Cash Flows [Abstract]
Interest rate on convertible senior notes	0.00%		0.00%		0.00%
0.125 Percent Convertible Senior Notes [Member]
Consolidated Statements of Cash Flows [Abstract]
Interest rate on convertible senior notes	0.125%			0.125%	0.125%
1 Percent Convertible Senior Notes [Member]
Consolidated Statements of Cash Flows [Abstract]
Interest rate on convertible senior notes	1.00%	1.00%	1.00%	1.00%	1.00%	1.00%	1.00%
Principal amount repurchased	$ 247.9		$ 247.9		$ 375.6