Carrying Value of Senior Notes (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Total	$ 946,287	$ 755,383
Less current portion of term credit facility	83,381	47,313
Total long-term debt	862,906	708,070
Term credit facility
Debt Instrument [Line Items]
Total	567,787	455,383
Revolving Credit Facility
Debt Instrument [Line Items]
Total	78,500
6.375% Senior Notes, due August 2020
Debt Instrument [Line Items]
Total	$ 300,000	$ 300,000