Debt (Narrative) (Details) (USD $)	1 Months Ended	9 Months Ended	12 Months Ended					1 Months Ended											3 Months Ended			1 Months Ended			1 Months Ended		3 Months Ended	1 Months Ended		1 Months Ended		9 Months Ended
	Feb. 28, 2011 interest_rate_swap	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Feb. 28, 2012	Mar. 31, 2011 interest_rate_swap	Sep. 30, 2013 Senior Debt Obligations Due 2018 [Member]	Dec. 31, 2013 Senior Debt Obligations Due 2018 [Member]	Dec. 31, 2013 Other Debt Facilities [Member]	Dec. 31, 2012 Other Debt Facilities [Member]	Dec. 31, 2013 Senior Debt Obligations Due 2021 [Member]	Dec. 31, 2013 Revolving Credit Facility [Member]	Dec. 31, 2013 Senior Debt Obligations Due 2013 [Member]	Dec. 31, 2013 Senior Debt Obligations Due 2015 [Member]	Sep. 30, 2013 Senior Debt Obligations Due 2015 [Member]	Dec. 31, 2013 Senior Debt Obligations Due 2014 [Member]	Feb. 28, 2011 Senior Debt Obligations Due 2014 [Member]	Mar. 31, 2012 Senior Debt Obligations Due 2017 [Member]	Dec. 31, 2013 Senior Debt Obligations Due 2017 [Member]	Mar. 31, 2012 Senior Debt Obligations Due 2012 [Member]	Dec. 31, 2012 Three-Year Delayed Draw Term Loan Facility [Member]	Dec. 31, 2013 Three-Year Delayed Draw Term Loan Facility [Member]	Sep. 30, 2013 Three-Year Delayed Draw Term Loan Facility [Member]	Sep. 30, 2013 Senior Debt Obligations Due 2023 [Member]	Dec. 31, 2013 Senior Debt Obligations Due 2023 [Member]	Mar. 31, 2012 Senior Debt Obligations Due 2012 [Member]	Oct. 31, 2013 Senior Debt Obligations Due 2015 [Member]	Sep. 30, 2013 Senior Debt Obligations Due 2015 [Member]	Feb. 28, 2013 Senior Debt Obligations Due 2013 [Member]	Feb. 28, 2011 London Interbank Offered Rate (LIBOR) [Member]	Sep. 30, 2013 Interest Rate Swap [Member]	Feb. 28, 2011 Interest Rate Swap [Member]
Debt Instrument [Line Items]
Debt instrument, amount								$ 250,000,000											$ 250,000,000						$ 250,000,000
Interest rate								2.55%	2.55%			4.80%		4.85%	5.75%	5.75%	5.375%	5.375%	2.30%	2.30%	6.25%				4.05%	4.05%				4.85%
Debt instrument, term								5 years											5 years			3 years			10 years
Partial redemption of notes																													250,000,000
Repayments of long-term debt			260,000,000	259,000,000	11,000,000																							275,000,000
Cost for early redemption			(24,000,000)	0	(72,000,000)																							(24,000,000)
Revised Purchase Price Allocation For Principal Amount Outstanding of Notes																											250,000,000			250,000,000
Revolving credit facility, borrowing capacity													1,000,000,000.0									50,000,000
Revolving credit facility, amount outstanding										1,000,000	0		0										50,000,000
Line of Credit Facility, Interest Rate at Period End																								1.29%
Number of interest rate swaps	2						2
Interest rate swap for hedging	125,000,000
Interest rate swap maturity, in years	3 years 6 months
5.375% senior notes due in 2014, hedged value																	250,000,000	250,000,000
Derivative, Fixed Interest Rate																																	5.375%
Floating rate three-month LIBOR plus fixed spread interest percentage																															3.726%
Derivative Instrument, Net Settlement Period		6 months
Interest rate swaps, fair value adjustment						0
Swap agreements, effectiveness recognized during the period																																0
Debt instrument, unused borrowing capacity										$ 282,000,000	$ 247,000,000