Subsequent Event - Additional Information (Detail) - USD ($) $ in Millions		6 Months Ended
	Jul. 09, 2015	Jun. 30, 2015	Dec. 31, 2014
Subsequent Event [Line Items]
Debt instrument, covenant compliance		The Company was in compliance with each of these covenants at June 30, 2015.
Letters of credit, maximum effective in force period		1 year
Unsecured Credit Agreement | Revolving Credit Facility
Subsequent Event [Line Items]
Credit facility, outstanding letters of credit		$ 1.2	$ 1.4
Credit facility, available capacity to issue additional letters of credit		3.8
Credit facility, available borrowing capacity		8.8
Credit facility,increase available capacity under the credit agreement		$ 50.0
Subsequent Event | Unsecured Credit Agreement | Covenant Requirement
Subsequent Event [Line Items]
Consolidated leverage ratio	150.00%
Consolidated tangible net worth required	$ 36.0
Subsequent Event | Unsecured Credit Agreement | Revolving Credit Facility
Subsequent Event [Line Items]
Credit facility, amended expiration date	May 01, 2017
Subsequent Event | Unsecured Credit Agreement | Revolving Credit Facility | Letter of Credit | If the Company's consolidated leverage ratio is less than or equal to 1.25:1
Subsequent Event [Line Items]
Fees on outstanding letters of credit	1.15%
Consolidated leverage ratio	150.00%
Subsequent Event | Unsecured Credit Agreement | Revolving Credit Facility | Letter of Credit | If the Company's consolidated leverage ratio is greater than 1.25:1
Subsequent Event [Line Items]
Fees on outstanding letters of credit	1.25%
Consolidated leverage ratio	150.00%