Debt (Detail) - Revolving Credit Facility [Member] - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Term for credit facility	5 years
Maximum borrowing capacity	$ 75,000,000
Limit for the issuance of standby letters of credit	7,500,000.0
Credit facility amount increase in borrowing capacity on condition	50,000,000
Outstanding under the Credit Facility	0	$ 0
Remaining borrowing capacity	$ 75,000,000
Minimum interest coverage ratio	4.00
Maximum leverage ratio	2.75
Minimum [Member]
Line of Credit Facility [Line Items]
Commitment fee	0.35%
Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Percentage of margin on principal amount	0.75%
Maximum [Member]
Line of Credit Facility [Line Items]
Commitment fee	0.50%
Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Percentage of margin on principal amount	2.50%