Fair Value Measurements (Summary of Quantitative Information About Level 3 Fair Value Measurements) (Details)	12 Months Ended
	Dec. 31, 2012
Auction Rate Securities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Estimated Market Recovery Period, Years	5 years
Minimum [Member] | Auction Rate Securities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Estimated Market Rate, Percent	2.30%
Minimum [Member] | Private Equity Funds [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Earnings Before Interest, Tax, Depreciation And Amortization Multiple	4.0
Maximum [Member] | Auction Rate Securities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Estimated Market Rate, Percent	4.00%
Maximum [Member] | Private Equity Funds [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Earnings Before Interest, Tax, Depreciation And Amortization Multiple	5.4