Components of Selected Balance Sheet Accounts (Parenthetical) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Compensation	$ 6,853,000	[1],[2]	$ 5,186,000	[1],[2]
Unfunded Defined Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension and postretirement health care plans	5,100,000		5,400,000
Pension and postretirement benefit expense	300,000		400,000		600,000
Defined Contribution Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Compensation	200,000		300,000
Recognized expense	$ 900,000		$ 1,200,000		$ 1,700,000

[1] Includes employer matching obligations under our defined contribution retirement plan of $0.2 million and $0.3 million as of December 31, 2012 and 2011, respectively. The expense recognized with respect to this plan was $0.9 million, $1.2 million and $1.7 million for the years ended December 31, 2012, 2011 and 2010, respectively.

[2] Includes the combined unfunded benefit obligations under our defined benefit pension and postretirement health care plans of $5.1 million and $5.4 million as of December 31, 2012 and 2011. The expense recognized with respect to these plans was $0.3 million, $0.4 million and $0.6 million for the years ended December 31, 2012, 2011 and 2010, respectively.