Condensed Statements of Comprehensive Income (Parenthetical) (unaudited) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Tax effect of the unrealized gain (loss) on short-term investment securities and cash and cash equivalents	$ 54	$ 39
Loss reclassified from AOCI into earnings, tax	$ 24	$ 27

Other Comprehensive Income (Loss), Securities, Available-for-Sale, Cash And Cash Equivalents Unrealized Holding Gain (Loss) Arising During Period, Tax

No definition available.

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Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration