Derivative Instruments, Hedging Activities and Fair Value (Details 4) (Designated as hedging instrument, USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Cross Currency Interest Rate Swap Maturing 2018 [Member]
Derivatives Designated as Hedging Instruments
Contractual Amount	$ 250,000
Cross Currency Interest Rate Swap Maturing 2020 [Member]
Derivatives Designated as Hedging Instruments
Contractual Amount	220,000
Cross Currency Interest Rate Swap Maturing 2013 [Member]
Derivatives Designated as Hedging Instruments
Contractual Amount	$ 10,800