Stock-Based Compensation - Weighted Average Assumptions Used to Determine Fair Value of Option Grants (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	1.25%	0.75%	0.75%
Expected life	6 years	6 years	6 years
6 month	0.14%	0.18%	0.19%
1 year	0.18%	0.25%	0.32%
3 year	0.41%	1.18%	1.36%
5 year	0.84%	2.13%	2.30%
10 year	1.94%	3.42%	3.61%
Near term [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility	37.00%	36.00%	37.00%
Long term [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility	46.00%	44.00%	45.00%