Stock-Settled Performance Units (Detail)	12 Months Ended
	Dec. 31, 2013
Performance Unit Awards 2013
Schedule of Share based Compensation Arrangements by Share based Payment Award, Performance Options [Line Items]
Target number of shares	236,500
Performance Unit Awards 2012
Schedule of Share based Compensation Arrangements by Share based Payment Award, Performance Options [Line Items]
Target number of shares	192,000
Performance Unit Awards 2011
Schedule of Share based Compensation Arrangements by Share based Payment Award, Performance Options [Line Items]
Target number of shares	144,375
Performance Unit Awards 2010
Schedule of Share based Compensation Arrangements by Share based Payment Award, Performance Options [Line Items]
Target number of shares	178,750