Consolidated Statements Of Stockholders' Equity (Parenthetical) - Convertible Notes [Member]	Dec. 31, 2019	Jun. 21, 2019	Dec. 31, 2018	Dec. 31, 2017
3.25% Convertible Notes Due 2018 [Member]
Interest rate, stated percentage			3.25%	3.25%
3.25% Convertible Notes Due 2019 [Member]
Interest rate, stated percentage	3.25%		3.25%
4.00% Convertible Notes Due 2024 [Member]
Interest rate, stated percentage	4.00%
Corporate Activities [Member] | 3.25% Convertible Notes Due 2018 [Member]
Interest rate, stated percentage				3.25%
Corporate Activities [Member] | 3.25% Convertible Notes Due 2019 [Member]
Interest rate, stated percentage	3.25%		3.25%
Corporate Activities [Member] | 4.00% Convertible Notes Due 2024 [Member]
Interest rate, stated percentage	4.00%	4.00%