Fair Value Of Financial Instruments (Reconciliation Of Assets And Liabilities Measured At Fair Value On Recurring Basis, Level 3) (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reversal of unrealized losses on redeemed or sold securities	$ 0	$ 0	$ 0	$ (458,000)
Earn-out Arrangements [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	80,500,000	80,500,000	80,500,000	45,000,000
Additions from new business combinations	0		0	47,700,000
Changes in fair value recorded in earnings		0
Payments of contingent consideration	(1,500,000)	0	(1,500,000)	(12,200,000)
Ending balance	79,000,000	80,500,000	79,000,000	80,500,000
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	13,500,000	14,400,000	13,600,000	19,000,000
Redemption or sale of securities, cost basis				(4,600,000)
Reversal of unrealized losses on redeemed or sold securities				400,000
Changes in fair value recorded in earnings	0	(500,000)	0	(500,000)
Changes in unrealized (losses)/gains included in other comprehensive income	600,000	(300,000)	500,000	(700,000)
Ending balance	14,100,000	13,600,000	14,100,000	13,600,000
Auction Rate Securities [Member] | Asset-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	11,700,000	12,100,000	11,900,000	16,400,000
Redemption or sale of securities, cost basis				(4,600,000)
Reversal of unrealized losses on redeemed or sold securities				400,000
Changes in fair value recorded in earnings	0	0	0	0
Changes in unrealized (losses)/gains included in other comprehensive income	0	(300,000)	(200,000)	(400,000)
Ending balance	11,700,000	11,800,000	11,700,000	11,800,000
Auction Rate Securities [Member] | Collateralized Debt Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	1,800,000	2,300,000	1,700,000	2,600,000
Redemption or sale of securities, cost basis				0
Reversal of unrealized losses on redeemed or sold securities				0
Changes in fair value recorded in earnings	0	(500,000)	0	(500,000)
Changes in unrealized (losses)/gains included in other comprehensive income	600,000	0	700,000	(300,000)
Ending balance	$ 2,400,000	$ 1,800,000	$ 2,400,000	$ 1,800,000