Benefit Plans - Actuarial Present Value of Benefit Obligations (Detail)	Dec. 31, 2014		Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.89%	[1]			4.87%	[1]
Future compensation increase rate			2.75%		2.75%
Other Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.02%		4.89%	4.87%	4.26%
Future compensation increase rate	0.00%		2.75%

[1] The discount rate for 2013 increased from 4.26 percent to 4.87 percent due to the plans’ freeze and remeasurement at June 30, 2013.