Stock-Settled Performance Units (Detail)	9 Months Ended
	Sep. 30, 2014
Performance Unit Awards 2014
Schedule Of Share Based Compensation Arrangements By Share Based Payment Award Performance Options [Line Items]
Target number of shares	154,000
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