Quarter	Millions of US Dollars
1997-07-01	200
2004-07-01	-200
2006-10-01	250
2007-01-01	431
2009-01-01	-50
2010-10-01	284
2011-01-01	40
2012-01-01	-147
2012-04-01	-205
2012-10-01	550
2013-04-01	0
2013-10-01	-250
2014-01-01	0
2015-10-01	-259
2016-01-01	-40
2016-04-01	370
2016-07-01	1
2017-01-01	-233
2017-07-01	-1