Summary of Carrying Amounts and Estimated Fair Values of Other Financial Instruments (Detail) (USD $) In Thousands	Jun. 30, 2011
Liabilities:
Derivative liabilities	$ 9,200
7 1/4% Senior Notes | Carrying Amount
Liabilities:
Long term debt fair value	244,817
Carrying Amount
Assets:
Cash and cash equivalents	127,546
Carrying Amount | Bank debt
Liabilities:
Long term debt fair value	1,247,612
Carrying Amount | Interest rate swap agreements
Liabilities:
Derivative liabilities	9,185
Carrying Amount | Natural gas swap agreements
Liabilities:
Derivative liabilities	46
7 1/4% Senior Notes | Fair Value
Liabilities:
Long term debt fair value	267,500
Fair Value
Assets:
Cash and cash equivalents	127,546
Fair Value | Bank debt
Liabilities:
Long term debt fair value	1,247,612
Fair Value | Interest rate swap agreements
Liabilities:
Derivative liabilities	9,185
Fair Value | Natural gas swap agreements
Liabilities:
Derivative liabilities	$ 46