Derivative Instruments, Hedging Activities and Fair Value (Details 4) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012
Cross-Currency Interest Rate Swaps Maturing 2018
Derivatives Designated as Hedging Instruments
Contractual Amount	$ 250,000
Cross-Currency Interest Rate Swaps Maturing 2020
Derivatives Designated as Hedging Instruments
Contractual Amount	220,000
Cross-Currency Interest Rate Swaps Maturing 2013
Derivatives Designated as Hedging Instruments
Contractual Amount	$ 1,800