Nature of Ops and Sign. Acctg Policies (Reconciliation of Weighted Average Shares Table) (Details 3) - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator
Net income - basic		$ 216,959	$ 322,698	$ 163,152
Interest expensed on convertible senior notes including amortization of discount, net of tax		14,134	539	49
Net income - diluted		$ 231,093	$ 323,237	$ 163,201
Denominator
Weighted average common shares outstanding – basic		459,524	432,483	390,928
Restricted stock and performance-based equity awards		2,396	6,500	2,242
Convertible senior notes	[1]	48,421	17,186	2,751
Weighted average common shares outstanding – diluted		510,341	456,169	395,921
Convertible debt instrument, number of equity instruments		90,900

[1] For the year ended December 31, 2019, shares shown under “convertible senior notes” represent the prorated portion of the approximately 90.9 million shares of the Company’s common stock issuable upon full conversion of our convertible senior notes which were issued on June 19, 2019 (see Note 6, Long-Term Debt – 2019 Debt Reduction Transactions).