Summary of Long-Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Revolving credit facility	$ 162,000us-gaap_LineOfCredit	$ 35,000us-gaap_LineOfCredit
Long-term Debt, gross	1,237,000us-gaap_LongTermDebt	1,110,000us-gaap_LongTermDebt
Unamortized Debt Issuance Expense	25,090us-gaap_UnamortizedDebtIssuanceExpense	26,194us-gaap_UnamortizedDebtIssuanceExpense
Long-term Debt, net	1,211,910us-gaap_LongTermDebtNoncurrent	1,083,806us-gaap_LongTermDebtNoncurrent
Revolving Credit Facility
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense	1,476	1,623
7.25% Senior Notes due 2019
Debt Instrument [Line Items]
Senior notes	300,000	300,000
Unamortized Debt Issuance Expense	3,928	4,131
8.50% Senior Notes due 2020
Debt Instrument [Line Items]
Senior notes	775,000	775,000
Unamortized Debt Issuance Expense	$ 19,686	$ 20,440

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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