Fair Value Measurements - Carrying Amounts and Fair Values of Company's Amended and Restated Senior Credit Facilities, Derivative Instruments and Contingent Consideration Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	$ 40,459
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	40,459
Contingent consideration liabilities	667	$ 667
Fair Value [Member] | Amended and Restated Senior Credit Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amended and Restated Senior Credit Facility	2,164,959	1,135,861
Fair Value [Member] | 6.125% Senior Notes Due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	151,375	149,288
Fair Value [Member] | 5.125% Senior Notes Due 2022 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	286,237	275,590
Fair Value [Member] | 5.625% Senior Notes Due 2023 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	627,190	604,262
Fair Value [Member] | 6.500% Senior Notes Due 2024 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	386,891
Fair Value [Member] | 9.0% and 9.5% Revenue Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
9.0% and 9.5% Revenue Bonds	23,407	23,621
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	40,459
Contingent consideration liabilities	667	667
Carrying Amount [Member] | Amended and Restated Senior Credit Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amended and Restated Senior Credit Facility	2,164,959	1,135,861
Carrying Amount [Member] | 6.125% Senior Notes Due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	147,324	147,082
Carrying Amount [Member] | 5.125% Senior Notes Due 2022 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	295,090	294,749
Carrying Amount [Member] | 5.625% Senior Notes Due 2023 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	639,990	639,431
Carrying Amount [Member] | 6.500% Senior Notes Due 2024 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	381,173
Carrying Amount [Member] | 9.0% and 9.5% Revenue Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
9.0% and 9.5% Revenue Bonds	$ 23,407	$ 23,621