Share-based Compensation (Details 2) (Stock Settled Stock Appreciation Rights (SSARS) [Member], USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Jun. 30, 2013
Stock Settled Stock Appreciation Rights (SSARS) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Rights Outstanding at April 1, 2012	683,119,000
Weighted Average Exercise Price Outstanding at April 1, 2012	$ 6.27
Number of Rights Granted,	116,405,000
Weighted Average Exercise Price Granted,	$ 12.38
Number of Rights Exercised	(216,061,000)
Weighted Average Exercise Price Exercised	$ 6.69
Number of Rights, Forfeited	0
Weighted Average Exercise Price, Forfeited	$ 0.00
Number of Rights Outstanding at December 31, 2012	583,463,000
Weighted Average Exercise Price Outstanding at December 31, 2012	$ 8.50
Remaining Contractual Term Outstanding at December 31, 2012	6 years 3 months 29 days
Aggregate Intrinsic Value Outstanding at December 31, 2012	$ 1,754
Number of Rights Exercisable at December 31, 2012	214,697,000
Weighted Average Exercise Price Exercisable at December 31, 2012	$ 7.70
Remaining Contractual Term Exercisable at December 31, 2012	5 years 2 months 23 days
Aggregate Intrinsic Value Exercisable at December 31, 2012	$ 784