Supplemental Quarterly Information (Unaudited) - (Details Textual) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net benefit of the BTC	$ 260,850	$ 238,564
2017 BTC retroactive reinstatement			$ 206,521