Debt (Detail)	Feb. 06, 2017 USD ($)	Feb. 01, 2017 USD ($)	Dec. 16, 2016 USD ($)	Sep. 30, 2016 USD ($)	Feb. 07, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Subsequent event [Member]
Line of Credit Facility [Line Items]
Net proceeds from stock issuance		$ 207,100,000
Revolving credit facility [Member] | Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt term				5 years
Maximum borrowing capacity				$ 150,000,000.0
Potential maximum borrowing capacity				$ 200,000,000.0
Amount outstanding						$ 30,000,000	$ 0
Leverage ratio				3.00
Minimum interest coverage ratio for four consecutive fiscal quarters				4.00
Revolving credit facility [Member] | Credit Facility [Member] | Subsequent event [Member]
Line of Credit Facility [Line Items]
Repayment of debt	$ 30,000,000
Revolving credit facility [Member] | Credit Facility [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Commitment fee on undrawn amounts				0.30%
Revolving credit facility [Member] | Credit Facility [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Commitment fee on undrawn amounts				0.45%
Revolving credit facility [Member] | Credit Facility [Member] | LIBOR or alternate base rate [Member]
Line of Credit Facility [Line Items]
Interest rate at end of period						2.5625%
Revolving credit facility [Member] | Credit Facility [Member] | LIBOR or alternate base rate [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate				0.75%
Revolving credit facility [Member] | Credit Facility [Member] | LIBOR or alternate base rate [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate				2.25%
Revolving credit facility [Member] | Loan Facility [Member]
Line of Credit Facility [Line Items]
Debt term			5 years
Maximum borrowing capacity			$ 100,000,000.0
Standby letters of credit [Member] | Credit Facility [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity				$ 7,500,000.0
Term loan [Member] | Loan Facility [Member]
Line of Credit Facility [Line Items]
Debt term			7 years
Maximum borrowing capacity			$ 475,000,000.0
Term loan [Member] | Loan Facility [Member] | Subsequent event [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity					$ 260,000,000.0