Required and Actual Financial Ratios Under Senior Secured Credit Facility (Detail) (Senior Secured Credit Facility)	Dec. 31, 2012
Required Ratio | Maximum [Member]
Debt Disclosure [Line Items]
Maximum consolidated leverage ratio	3.50
Required Ratio | Minimum
Debt Disclosure [Line Items]
Minimum consolidated interest coverage ratio	3.00
Scenario, Actual [Member] | Maximum [Member]
Debt Disclosure [Line Items]
Maximum consolidated leverage ratio	1.96
Scenario, Actual [Member] | Minimum
Debt Disclosure [Line Items]
Minimum consolidated interest coverage ratio	10.97