Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value (Parenthetical) (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments	$ 8,384	$ 628
Current maturities on long-term debt	16,850	14,050
Long-term debt	1,584,365	1,569,400
Other Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments	$ 8,384	$ 628