Other-than-temporary Impairment Not Previously Recognized (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Dec. 31, 2012
Other than temporary impairment credit losses recognized in earnings [Roll Forward]
Balance at March 31, 2012	$ 552
Other-than-temporary impairment not previously recognized	0
Balance at December 31, 2012	$ 552