Lines of Credit Lines of Credit (AMP Lender) (Details) (USD $)	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Line of Credit Facility
Line of credit with Ameriprise Financial, Inc.	$ 0	$ 150,000,000
Line of Credit Agreement, one | Ameriprise Financial [Member]
Line of Credit Facility
Line of credit with Ameriprise Financial, Inc.	0	150,000,000
Maximum borrowing capacity under the line of credit	800,000,000
Prepayment penalty	$ 0
London Interbank Offered Rate (LIBOR) [Member] | Line of Credit Agreement, one | Ameriprise Financial [Member]
Line of Credit Facility
Interest rate added to reference rate (as a percent)	0.90%