Restructuring Activities - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012 Person	Dec. 31, 2014	Dec. 31, 2013
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, noncurrent		$ 12,042,000	$ 13,245,000
Canonsburg, PA Regional Office
Restructuring Cost and Reserve [Line Items]
Organization restructuring, termination of employees	30
Restructuring and related costs in 2015, undiscounted		2,700,000
Restructuring and related costs in 2016, undiscounted		2,700,000
Restructuring and related costs in 2017, undiscounted		2,700,000
Restructuring and related costs in 2018, undiscounted		2,700,000
Restructuring and related costs in 2019, undiscounted		2,700,000
Restructuring and related costs due 2020 - 2022, undiscounted		7,600,000
Accounts Payable and Accrued Liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, current		2,900,000
Other Noncurrent Liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, noncurrent		$ 12,000,000