Derivative Instruments and Hedging Activities (Details) (Designated as Hedging Instrument [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2013 Instrument	Dec. 31, 2012
Interest Rate Cap [Member]
Derivative [Line Items]
Notional amount of interest rate contracts	$ 186.1
Number of derivative instruments held	11
Aggregate carrying value of the interest rate cap contracts	0	0
Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount of interest rate contracts	300.0
Total amount of unsecured loan	350
Interest rate (in hundredths)	2.29%
Aggregate carrying value of the interest rate swap contracts	$ 1.9	$ 6.6

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.

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Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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- Definition

Fair value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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