Income Taxes - Reconciles Statutory Federal Income Tax Rate to Company' s Effective Tax Rate (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
Increases (decreases) resulting from:
Disallowed meals & entertainment	0.40%	0.20%	0.30%	0.20%
Fines and penalties	1.50%		0.90%
Disallowed compensation	2.00%	1.00%	1.50%	0.70%
State income tax, net of federal tax benefit	3.60%	3.60%	3.60%	3.60%
Other, net	0.10%	0.30%	0.10%	0.10%
Effective tax rate	42.60%	40.10%	41.40%	39.60%