Fair Value Measurements (Financial Instruments Measured At Fair Value On A Recurring Basis) (Details) $ in Millions | Mar. 31, 2018USD ($) |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | $ 547.9 |
Fair Value, Measurements, Recurring [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Derivative Asset | 30 |
Marketable Securities | 90.4 |
Total Assets at Fair Value | 668.3 |
Fair Value, Measurements, Recurring [Member] | U.S. Government Agency Security Performance Bond [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 547.9 |
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 19.2 |
Fair Value, Measurements, Recurring [Member] | Exchange Traded Funds [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Trading Securities at Fair Value | 70.8 |
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 0.1 |
Fair Value, Measurements, Recurring [Member] | Asset Backed Securities [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 0.3 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Derivative Asset | 0 |
Marketable Securities | 90.1 |
Total Assets at Fair Value | 638 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Government Agency Security Performance Bond [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 547.9 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 19.2 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange Traded Funds [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Trading Securities at Fair Value | 70.8 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 0.1 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Asset Backed Securities [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Derivative Asset | 30 |
Marketable Securities | 0.3 |
Total Assets at Fair Value | 30.3 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Government Agency Security Performance Bond [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Exchange Traded Funds [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Trading Securities at Fair Value | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Asset Backed Securities [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 0.3 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Derivative Asset | 0 |
Marketable Securities | 0 |
Total Assets at Fair Value | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Government Agency Security Performance Bond [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Exchange Traded Funds [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Trading Securities at Fair Value | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Asset Backed Securities [Member] | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | |
Available-for-sale Securities at Fair Value | $ 0 |