Quarter	Millions of US Dollars
1977-01-01	0
1977-04-01	0
1977-07-01	0
1977-10-01	0
1978-01-01	0
1978-04-01	0
1978-07-01	0
1978-10-01	0
1979-01-01	0
1979-04-01	0
1979-07-01	0
1979-10-01	0
1980-01-01	0
1980-04-01	0
1980-07-01	0
1980-10-01	0
1981-01-01	15
1981-04-01	15
1981-07-01	15
1981-10-01	15
2012-10-01	0
2013-01-01	0
2013-04-01	0
2013-07-01	0
2013-10-01	0
2014-01-01	0
2014-04-01	0
2014-07-01	0
2014-10-01	0
2015-01-01	0
2015-04-01	0
2015-07-01	0
2015-10-01	0
2016-01-01	0
2016-04-01	0
2016-07-01	0
2016-10-01	0
2017-01-01	0
2017-04-01	0
2017-07-01	0
2017-10-01	0
2018-01-01	0
2018-04-01	0