Consolidated Statements Of Cash Flows (Parenthetical) - Convertible Notes [Member]	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
3.25% Convertible Notes Due 2019 [Member]
Debt Instrument [Line Items]
Interest rate, stated percentage	3.25%	3.25%
3.25% Convertible Notes Due 2019 [Member] | Corporate Activities [Member]
Debt Instrument [Line Items]
Interest rate, stated percentage	3.25%	3.25%
3.25% Convertible Notes Due 2018 [Member]
Debt Instrument [Line Items]
Interest rate, stated percentage		3.25%	3.25%
3.25% Convertible Notes Due 2018 [Member] | Corporate Activities [Member]
Debt Instrument [Line Items]
Interest rate, stated percentage			3.25%