Borrowings (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 contract
Line of Credit Facility [Line Items]
Facility agreement initiation date	Nov. 11, 2013
Facilitiy agreement total amount	$ 2,600
Number of term loan facilities	2
Term loan facility one
Line of Credit Facility [Line Items]
Facility agreement expiration date	Nov. 10, 2014
Facility amount outstanding	350
Term loan facilitly two
Line of Credit Facility [Line Items]
Facility agreement expiration date	Nov. 11, 2015
Term loan facility	850
Facility amount outstanding	850
Original facility | Term loan facility one
Line of Credit Facility [Line Items]
Term loan facility	550
Revised facility
Line of Credit Facility [Line Items]
Facilitiy agreement total amount	1,200
Revised facility | Term loan facility one
Line of Credit Facility [Line Items]
Term loan facility	350
Revolving Credit Facility
Line of Credit Facility [Line Items]
Facility agreement initiation date	Nov. 23, 2010
Facilitiy agreement total amount	1,200
Facility agreement expiration date	Nov. 23, 2015
Swingline Facility	250.0
Facility amount outstanding	$ 320