Derivative Instruments (Details) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended							3 Months Ended		9 Months Ended		3 Months Ended		4 Months Ended	9 Months Ended
	Sep. 30, 2012 USD ($) Number	Sep. 30, 2011 USD ($)	Sep. 30, 2012 USD ($) Number	Sep. 30, 2011 USD ($)	Sep. 17, 2012 CAD	Sep. 17, 2012 GBP (£)	Aug. 30, 2012 GBP (£)	Feb. 15, 2012 CAD	Dec. 31, 2011 USD ($)	Sep. 30, 2012 Interest Rate Swap [Member] USD ($)	Sep. 30, 2011 Interest Rate Swap [Member] USD ($)	Sep. 30, 2012 Interest Rate Swap [Member] USD ($)	Sep. 30, 2011 Interest Rate Swap [Member] USD ($)	Sep. 30, 2012 Foreign Exchange Contract [Member] USD ($)	Sep. 30, 2011 Foreign Exchange Contract [Member] USD ($)	May 01, 2012 Foreign Exchange Contract [Member] USD ($)	Sep. 30, 2012 Foreign Exchange Contract [Member] USD ($)	Sep. 30, 2011 Foreign Exchange Contract [Member] USD ($)
Derivative Instruments (Textual) [Abstract]
Other liabilities	$ 405,798		$ 405,798						$ 371,557
Number of interest rate swaps	5		5
Foreign exchange contract					14,000	23,000		250,000
Gain (loss) on recognized in OCI										797	658	2,342	2,499	(12,663)	0		(5,747)	0
Gain (loss) reclassified from AOCI into income										383	467	1,204	1,440
Gain (loss) recognized in income	409	0	(1,712)	0						0	0	(96)	0	(409)	0	2,772	2,363	0
Gain (loss) recognized in income (ineffective portion)														0	0		(555)	0
Additional Derivative Instruments (Textual) [Abstract]
Hedging losses included in accumulated other comprehensive income			1,974
Notional amount of interest rate swap	$ 101,040		$ 101,040				£ 125,000