Amtrak Agreement - Schedule of Remaining Track Mileage Credit (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Agreement With Related Party [Abstract]
Mileage credit available	$ 288,000		$ 418,000
Utilized	$ 288,000		$ 418,000
Mileage credit remaining		$ 0