Senior Notes (Narrative) (Details) (Senior Notes [Member], USD $)	Mar. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Face Value	$ 705,000,000	$ 405,000,000
Balance sheet leverage ratio	0.78
Maximum [Member]
Debt Instrument [Line Items]
Balance sheet leverage ratio	1.50
5.875% Senior Notes Dues April 2024 [Member]
Debt Instrument [Line Items]
Interest Rate	5.875%
Face Value	$ 300,000,000	$ 0
Public offering price percentage of principal amount	99.068%