Deferred Compensation Plan (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012	Apr. 30, 2013	Dec. 31, 2012	Oct. 18, 2013 Subordinated Debt [Member]	Aug. 01, 2013 Subordinated Debt [Member]	Mar. 08, 2013 Subordinated Debt [Member]	Mar. 10, 2010 Subordinated Debt [Member]	Sep. 30, 2013 2013 through 2014 [Member]	Sep. 30, 2013 2015 through 2017 [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Debt Instrument, Repurchased Face Amount									$ 155,000,000	$ 324,000,000	$ 50,000,000	$ 28,500,000
RDU Plan, units authorized for issuance	28,500			28,500
RDU Plan, units outstanding	28,500			28,500
Deferred Compensation Arrangement with Individual, Requisite Service Period				P3Y0M0D
Deferred Compensation Arrangement with Individual, Distributions Paid							1,700,000
Charge for payment of RDU Plan cash retention pool	7,500,000	[1]		7,500,000	[1]
Redemption premium added to debt face amount, RDU plan	1,300,000
RDU Plan, unrecognized compensation expense													11,000,000	7,000,000
RDU Plan, compensation expense	10,400,000		2,100,000	14,700,000		6,300,000
RDU Plan, liability	$ 21,000,000			$ 21,000,000				$ 15,500,000

[1] See Note 9 for additional discussion of this transaction.