Investment in Variable Interest Entity and Other Investments and Affiliates - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Variable Interest Entity [Line Items]
Loan to affiliate for operating purposes			$ 274	$ 0
PHI Century Limited [Member]
Variable Interest Entity [Line Items]
Investment in the common stock			49.00%	49.00%
PHIC's date of incorporation			May 26, 2011
Earnings (loss) in equity of unconsolidated affiliate	$ (100)	$ (1,000)	$ 100	$ (2,000)
Trade receivables	5,500		5,500		$ 4,000
Loan to affiliate for operating purposes			300
Other assets	400		400		$ 300
Accounts Receivable - Other [Member] | PHI Century Limited [Member]
Variable Interest Entity [Line Items]
Loan to affiliate	$ 300		$ 300