Auction Rate Securities (Narrative) (Detail) (USD $)	9 Months Ended							9 Months Ended			3 Months Ended			3 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Auction Rate Securities [Member]	Dec. 31, 2012 Auction Rate Securities [Member]	Sep. 30, 2013 Auction Rate Securities [Member] Fair Value [Member]	Dec. 31, 2012 Auction Rate Securities [Member] Fair Value [Member]	Sep. 30, 2013 Auction Rate Securities [Member] Asset-backed Securities [Member]	Sep. 30, 2013 Auction Rate Securities [Member] Asset-backed Securities [Member] Minimum [Member]	Sep. 30, 2013 Auction Rate Securities [Member] Asset-backed Securities [Member] Maximum [Member]	Sep. 30, 2013 Auction Rate Securities [Member] Asset-backed Securities [Member] Fair Value [Member]	Jun. 30, 2013 Auction Rate Securities [Member] Securities Redeemed or Sold [Member] Asset-backed Securities [Member]	May 31, 2013 Auction Rate Securities [Member] Securities Redeemed or Sold [Member] Asset-backed Securities [Member]	May 31, 2013 Auction Rate Securities [Member] Securities Redeemed or Sold [Member] Asset-backed Securities [Member] Fair Value [Member]	Jun. 30, 2013 Auction Rate Securities [Member] Securities Redeemed or Sold [Member] Collateralized Debt Obligations [Member]	May 31, 2013 Auction Rate Securities [Member] Securities Redeemed or Sold [Member] Collateralized Debt Obligations [Member]	May 31, 2013 Auction Rate Securities [Member] Securities Redeemed or Sold [Member] Collateralized Debt Obligations [Member] Fair Value [Member]
Auction Rate Securities [Line Items]
Auction rate securities, par value												$ 2,600,000			$ 5,000,000
Auction rate securities, redeemed at par, proceeds											2,600,000
Aucition rate securities, proceeds from sale	5,025,000	0												2,400,000
Auction rate securities, fair value					9,200,000	14,400,000				9,200,000			2,600,000			2,400,000
Adjusted cost basis															1,700,000
Auction rate securities, realized gain														700,000
Auction rate securities, gross unrealized net losses				$ 200,000			$ 1,100,000
Fair value measurements, valuation techniques			Fair values of the Company's auction rate securities are estimated by an independent valuation firm, Houlihan Capital Advisors, LLC, using a probability weighted discounted cash flow model.
Contractual maturities of securities								Mar. 27, 2028	Oct. 28, 2047