Income Taxes - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Apr. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes Disclosure [Line Items]
Foreign investments benefit (losses)		$ 323,000	$ (847,000)	$ (2,980,000)
Foreign tax assets valuation allowance		0	1,230,000	4,300,000
Net operating losses		51,722,000	39,360,000
Income tax refund received	$ 37,397,000
Income tax refund claimed		$ 1,199,000	0
Net operating losses carry forwards, expiration year		2036
Claim of bonus tax depreciation		$ 0	29,221,000	$ 61,781,000
Uncertain tax positions		0	$ 153,000
Uncertain tax positions reduced		0
Tax Years 2012 Through 2014
Income Taxes Disclosure [Line Items]
Income tax refund claimed		$ 1,732,000