Reclassifications Out of AOCI (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012		Jun. 30, 2013	Jun. 30, 2012
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
General and administrative expenses	$ 3,881	$ 4,410	[1]	$ 8,485	$ 9,934	[1]
Amount Reclassified from AOCI
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
General and administrative expenses				37
Amortization of prior service costs | Amount Reclassified from AOCI
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
General and administrative expenses				11
Amortization of transition obligation | Amount Reclassified from AOCI
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
General and administrative expenses				$ 26

[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, for more details.