Stockholders' Equity 1 (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Cash dividends
Declaration date	Feb. 01, 2017	Nov. 02, 2016	Aug. 03, 2016	May 04, 2016	Feb. 03, 2016	Nov. 05, 2015	Aug. 06, 2015	May 05, 2015
Dividend per share (in dollars per share)	$ 0.255	$ 0.255	$ 0.255	$ 0.255	$ 0.25	$ 0.25	$ 0.25	$ 0.25
Record date	Feb. 16, 2017	Nov. 17, 2016	Aug. 25, 2016	May 26, 2016	Feb. 18, 2016	Nov. 19, 2015	Aug. 27, 2015	May 28, 2015
Total amount	$ 107	$ 107	$ 107	$ 107	$ 104	$ 105	$ 110	$ 110	$ 428	$ 429	$ 444
Payment date	Mar. 14, 2017	Dec. 06, 2016	Sep. 13, 2016	Jun. 14, 2016	Mar. 15, 2016	Dec. 08, 2015	Sep. 15, 2015	Jun. 16, 2015