Financing Arrangements - Additional Information (Detail) - USD ($)		12 Months Ended
	Nov. 06, 2015	Dec. 31, 2015	Dec. 31, 2014	Aug. 31, 2013	Jan. 09, 2013
Line of Credit Facility [Line Items]
Revolving line of credit, maturity date		Jan. 09, 2018
Unused commitment and administrative fees paid		$ 300,000
Initial applicable rate		0.25%
Maximum expense excluded from covenant calculation	$ 130,000,000
Maximum borrowing capacity	$ 25,000,000
Minimum percentage required by lenders to increase borrowing capacity	66.67%
Letter of credit outstanding		$ 0
Letter of credit				$ 1,200,000
Base Rate
Line of Credit Facility [Line Items]
Initial applicable rate		0.50%
Eurodollar Rate Loans
Line of Credit Facility [Line Items]
Initial applicable rate		1.50%
Letter of Credit
Line of Credit Facility [Line Items]
Initial applicable rate		1.50%
Letters of credit released			$ 300,000
Letter Of Credit Sub Facility
Line of Credit Facility [Line Items]
Revolving line of credit					$ 10,000,000
Swing Line Loan Subfacility
Line of Credit Facility [Line Items]
Revolving line of credit					5,000,000
Federal Funds Rate
Line of Credit Facility [Line Items]
Interest rate above LIBOR		0.50%
Eurodollar | Base Rate
Line of Credit Facility [Line Items]
Interest rate above LIBOR		1.00%
Letter of Credit
Line of Credit Facility [Line Items]
Minimum percentage of State Attorney Generals with proceedings pending or initiated	50.00%
Maximum borrowing capacity	$ 2,000,000
Letter of credit outstanding		$ 300,000
Minimum
Line of Credit Facility [Line Items]
Revolving line of credit					85,000,000
Commitment fee rate		0.25%
Minimum | Eurodollar | Base Rate
Line of Credit Facility [Line Items]
Applicable interest rate		0.50%
Minimum | Eurodollar | Eurodollar Rate Loans
Line of Credit Facility [Line Items]
Applicable interest rate		1.50%
Maximum
Line of Credit Facility [Line Items]
Revolving line of credit					$ 110,000,000
Commitment fee rate		0.50%
Maximum | Eurodollar | Base Rate
Line of Credit Facility [Line Items]
Applicable interest rate		1.25%
Maximum | Eurodollar | Eurodollar Rate Loans
Line of Credit Facility [Line Items]
Applicable interest rate		2.25%