Commitments and Contingencies (Narrative) (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended			1 Months Ended
	Dec. 31, 2014 Officers	Dec. 31, 2013	Dec. 31, 2012	Feb. 28, 2013	Oct. 31, 2012	Jun. 07, 2013
Employee Separation Expenses [Line Items]
Unaccrued contractual and other commitments	$ 11.0
Number of officers	4
Aggregate base compensation	1.7
Termination expenses	2.7
Separation expenses for employees		2.7
Environmental insurance coverage claims per occurrence	25.0
Environmental insurance coverage claims aggregate	25.0
Restricted Stock [Member]
Employee Separation Expenses [Line Items]
RSUs granted	253,922	253,920	459,526
Grant date fair value (in dollars per share)	$ 19.20	$ 18.54	$ 14.46
Officer [Member]
Employee Separation Expenses [Line Items]
Renewal of agreements term	1 year
Officer [Member] | Minimum [Member]
Employee Separation Expenses [Line Items]
Initial year of employment agreement of employee	1 year
Officer [Member] | Maximum [Member]
Employee Separation Expenses [Line Items]
Initial year of employment agreement of employee	3 years
Mr. Rubin [Member]
Employee Separation Expenses [Line Items]
Total to be recorded for the year December 31, 2013	4.5
Total to be recorded for the year December 31, 2012	2.6
Total cash to be recorded for the year December 31, 2012	1.9
Founder's retirement payment						3.5
Mr. Rubin [Member] | Restricted Stock [Member]
Employee Separation Expenses [Line Items]
RSUs granted				16,000
Fair Value				0.3
Grant date fair value (in dollars per share)				$ 18.28
Mr. Glickman [Member]
Employee Separation Expenses [Line Items]
Total cash to be recorded for the year December 31, 2012					2.7
Employee separation expense	4.1
Separation payment					$ 2.8