Fair Value Measurements - Additional Information (Detail) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Available-for-sale securities	$ 10,467,000	$ 0
Equity securities held in Rabbi Trusts	772,000
Certificates of deposit-long term	1,500,000
Other Noncurrent Assets [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Equity securities held in Rabbi Trusts	800,000
Certificates of deposit-long term	500,000
Certificates of Deposit [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Certificates of deposit	2,000,000
Level 1 [Member] | US Treasury and Government [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Available-for-sale securities	10,500,000
Level 1 [Member] | Money Market Funds [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Cash equivalents as investments in money market funds	$ 1,300,000