Future Commitments Pursuant to Current and Former Senior Executive Employment Agreements (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Commitments and Contingencies Disclosure [Line Items]
Contractual Obligation, Due in Next Twelve Months	$ 3,934
Contractual Obligation, Due in Second Year	3,203
Contractual Obligation, Due in Third Year	1,061
Contractual Obligation, Due in Fourth Year	788
Contractual Obligation, Due in Fifth Year	515
Contractual Obligation, Due after Fifth Year	515
Other Postretirement Defined Benefit Plan, Liabilities	11,600	12,400
Other Postretirement Benefits Payable	1,200	1,400
Contractual Obligation	10,016
Maximum Cash Bonus
Commitments and Contingencies Disclosure [Line Items]
Contractual Obligation, Due in Next Twelve Months	1,452
Contractual Obligation, Due in Second Year	950
Contractual Obligation, Due in Third Year	0
Contractual Obligation, Due in Fourth Year	0
Contractual Obligation, Due in Fifth Year	0
Contractual Obligation, Due after Fifth Year	0
Contractual Obligation	2,402
Base Salary
Commitments and Contingencies Disclosure [Line Items]
Contractual Obligation, Due in Next Twelve Months	2,482
Contractual Obligation, Due in Second Year	2,253
Contractual Obligation, Due in Third Year	1,061
Contractual Obligation, Due in Fourth Year	788
Contractual Obligation, Due in Fifth Year	515
Contractual Obligation, Due after Fifth Year	515
Contractual Obligation	$ 7,614