Employee Benefit Plans (Target Asset Allocation Based on Funded Status) (Detail)	12 Months Ended
	Dec. 31, 2014
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Settlement funded status	85.00%
Funded Ratio 100%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Settlement funded status	100.00%
Funded Ratio 97.5%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Settlement funded status	97.50%
Funded Ratio 95%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Settlement funded status	95.00%
Funded Ratio 92.5%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Settlement funded status	92.50%
Funded Ratio 90%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Settlement funded status	90.00%
Funded Ratio 87.5%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Settlement funded status	87.50%
Funded Ratio 85%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Settlement funded status	85.00%
Return Seeking Assets
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	85.00%
Return Seeking Assets | Funded Ratio 100%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	0.00%
Return Seeking Assets | Funded Ratio 97.5%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	15.00%
Return Seeking Assets | Funded Ratio 95%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	30.00%
Return Seeking Assets | Funded Ratio 92.5%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	40.00%
Return Seeking Assets | Funded Ratio 90%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	50.00%
Return Seeking Assets | Funded Ratio 87.5%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	60.00%
Return Seeking Assets | Funded Ratio 85%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	70.00%
Liability Tracking Assets
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	15.00%
Liability Tracking Assets | Funded Ratio 100%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	100.00%
Liability Tracking Assets | Funded Ratio 97.5%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	85.00%
Liability Tracking Assets | Funded Ratio 95%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	70.00%
Liability Tracking Assets | Funded Ratio 92.5%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	60.00%
Liability Tracking Assets | Funded Ratio 90%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	50.00%
Liability Tracking Assets | Funded Ratio 87.5%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	40.00%
Liability Tracking Assets | Funded Ratio 85%
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Asset allocation target	30.00%