Indebtedness (Senior Notes Narrative) (Details) (Senior notes, net [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2014
Debt Instrument [Line Items]
Call feature description	The 2014, 2015, 2016, 2018, 2020, 2022 and 2024 Notes (collectively, the “Senior Notes”) contain covenants that restrict the incurrence of liens and limit sale and leaseback transactions. The Company has the option to redeem the Senior Notes prior to their maturity, in whole or in part, at 100% of the principal plus any accrued but unpaid interest and applicable make-whole payments.
Percentage of principal that must be repaid in addition to accrued interest and applicable make-whole payments under call feature of notes	100.00%
3.65% Senior Notes Maturing July 2024 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 300
Debt instrument, interest rate	3.65%
Debt instrument, maturity date	Jul. 15, 2024
Debt instrument, interest rate, effective percentage	3.673%
Debt instrument, frequency of periodic payments	semi-annually on January 15 and July 15 of each year
Debt instrument, date of first required payment	Jan. 15, 2015
4.5% Senior Notes Maturing September 2014 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	400
Debt instrument, interest rate	4.50%
Debt instrument, maturity date	Sep. 15, 2014
Debt instrument, interest rate, effective percentage	4.527%
Debt instrument, frequency of periodic payments	semi-annually on March 15 and September 15 of each year
3.25% Senior Notes Maturing October 2015 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	250
Debt instrument, interest rate	3.25%
Debt instrument, maturity date	Oct. 01, 2015
Debt instrument, interest rate, effective percentage	3.283%
Debt instrument, frequency of periodic payments	semi-annually on April 1 and October 1 of each year
2.95% Senior Notes Maturing June 2016 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	250
Debt instrument, interest rate	2.95%
Debt instrument, maturity date	Jun. 15, 2016
Debt instrument, interest rate, effective percentage	2.98%
Debt instrument, frequency of periodic payments	semi-annually on June 15 and December 15 of each year
1.65% Senior Notes Maturing February 2018 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	325
Debt instrument, interest rate	1.65%
Debt instrument, maturity date	Feb. 15, 2018
Debt instrument, interest rate, effective percentage	1.685%
Debt instrument, frequency of periodic payments	semi-annually on February 15 and August 15 of each year
2.375% Senior Notes Maturing February 2020 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	275
Debt instrument, interest rate	2.375%
Debt instrument, maturity date	Feb. 15, 2020
Debt instrument, interest rate, effective percentage	2.392%
Debt instrument, frequency of periodic payments	semi-annually on February 15 and August 15 of each year
2.90% Senior Notes Maturing November 2022 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 250
Debt instrument, interest rate	2.90%
Debt instrument, maturity date	Nov. 15, 2022
Debt instrument, interest rate, effective percentage	2.913%
Debt instrument, frequency of periodic payments	semi-annually on May 15 and November 15 of each year.