Reclassifications Out of AOCI (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012		Sep. 30, 2013	Sep. 30, 2012
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
General and administrative expenses	$ 4,540	$ 4,603	[1]	$ 13,025	$ 14,537	[1]
Amount Reclassified from AOCI
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
General and administrative expenses				55
Amortization of prior service costs | Amount Reclassified from AOCI
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
General and administrative expenses				17
Amortization of transition obligation | Amount Reclassified from AOCI
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
General and administrative expenses				$ 38

[1] Certain amounts shown in the table above have changed as compared to amounts reported in prior periods as noted in Item 1, Financial Statements, Note 1 of Notes to Condensed Consolidated Financial Statements, Reclassifications and Restatements.