Interest Rate Swap Arrangements (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Notional Amount Of Derivatives	$ 6,630.0	$ 3,740.0
Senior Notes [Member] | 1.30% Senior Notes Due 2017 [Member] | Interest Rate Swaps [Member]
Debt Instrument [Line Items]
Notional Amount Of Derivatives	$ 900.0
Interest Rate Swap, Spread above One-month LIBOR	0.6616%
Interest Rate Swap, Variable Rate at Period End	0.9054%
Interest Rate Swap, Fixed Rate	1.30%
Senior Notes [Member] | 4.70% Senior Notes Due 2020 [Member] | Interest Rate Swaps [Member]
Debt Instrument [Line Items]
Notional Amount Of Derivatives	$ 300.0
Interest Rate Swap, Spread above One-month LIBOR	3.156%
Interest Rate Swap, Variable Rate at Period End	3.3998%
Interest Rate Swap, Fixed Rate	4.70%
Senior Notes [Member] | 4.50% Senior Notes Due 2021 [Member] | Interest Rate Swaps [Member]
Debt Instrument [Line Items]
Notional Amount Of Derivatives	$ 1,000.0
Interest Rate Swap, Spread above One-month LIBOR	2.868%
Interest Rate Swap, Variable Rate at Period End	3.1118%
Interest Rate Swap, Fixed Rate	4.50%
Senior Notes [Member] | 3.60% Senior Notes Due 2021 [Member] | Interest Rate Swaps [Member]
Debt Instrument [Line Items]
Notional Amount Of Derivatives	$ 1,100.0
Interest Rate Swap, Spread above One-month LIBOR	1.937%
Interest Rate Swap, Variable Rate at Period End	2.2675%
Interest Rate Swap, Fixed Rate	3.60%