Schedule Of Valuation Of Assets And Liabilities Measured At Fair Value On Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total assets measured at fair value	$ 20,000		$ 20,006
Total liabilities measured at fair value	16,935		21,595
Short-Term [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Acquisition-related contingent consideration	8,085	[1]	10,483	[1]
Long-Term [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Acquisition-related contingent consideration	8,850	[2]	11,112	[2]
Money Market Funds [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total assets measured at fair value	392	[3]	67	[3]
Variable Rate Demand Obligation [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total assets measured at fair value	19,608	[4]	19,939	[4]
Level 1 [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total assets measured at fair value	392		67
Total liabilities measured at fair value	0		0
Level 1 [Member] | Short-Term [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Acquisition-related contingent consideration	0	[1]	0	[1]
Level 1 [Member] | Long-Term [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Acquisition-related contingent consideration	0	[2]	0	[2]
Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total assets measured at fair value	392	[3]	67	[3]
Level 1 [Member] | Variable Rate Demand Obligation [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total assets measured at fair value	0	[4]	0	[4]
Level 2 [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total assets measured at fair value	19,608		19,939
Total liabilities measured at fair value	0		0
Level 2 [Member] | Short-Term [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Acquisition-related contingent consideration	0	[1]	0	[1]
Level 2 [Member] | Long-Term [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Acquisition-related contingent consideration	0	[2]	0	[2]
Level 2 [Member] | Money Market Funds [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total assets measured at fair value	0	[3]	0	[3]
Level 2 [Member] | Variable Rate Demand Obligation [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total assets measured at fair value	19,608	[4]	19,939	[4]
Level 3 [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total assets measured at fair value	0		0
Total liabilities measured at fair value	16,935		21,595
Level 3 [Member] | Short-Term [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Acquisition-related contingent consideration	8,085	[1]	10,483	[1]
Level 3 [Member] | Long-Term [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Acquisition-related contingent consideration	8,850	[2]	11,112	[2]
Level 3 [Member] | Money Market Funds [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total assets measured at fair value	0	[3]	0	[3]
Level 3 [Member] | Variable Rate Demand Obligation [Member]
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total assets measured at fair value	$ 0	[4]	$ 0	[4]

[1] Included in current installments of long-term obligations in the accompanying condensed consolidated balance sheets.

[2] Included in long-term obligations, excluding current installments in the accompanying condensed consolidated balance sheets.

[3] Included in cash and cash equivalents in the accompanying condensed consolidated balance sheets.

[4] Included in short-term investments in the accompanying condensed consolidated balance sheets. The interest rates on the variable rate demand notes ("VRDNs") reset every seven days to adjust to current market conditions. The Company can redeem these investments at cost at any time with seven days' notice. Therefore, the investments are held at cost, which approximates fair value, and are classified as available-for-sale short-term investments on the accompanying consolidated balance sheets. VRDNs are generally valued using published interest rates for instruments with similar terms and maturities, and, accordingly, are classified as Level 2 instruments of the fair value hierarchy. The Company believes the recorded values of its VRDNs approximate their fair values because of their nature and relatively short maturity dates or durations. The payment of principal and interest on the VRDNs held by the Company is guaranteed by letters of credit from the issuing financial institution.