Components of Debt Obligations (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Notes payable to former shareholders of acquired businesses	$ 11,000	$ 11,000
Total debt	711,000	711,000
Less current portion	11,000	11,000
Long-term debt, net of current portion	700,000	700,000
Total debt	711,000	711,000
6 3/4 % Senior Notes Due 2020
Debt Instrument [Line Items]
Senior notes	400,000	400,000
6.0% Senior Notes Due 2022
Debt Instrument [Line Items]
Senior notes	$ 300,000	$ 300,000