Stockholders' Equity (Details 2) - Collared Accelerated Repurchase Program - USD ($) shares in Millions, $ in Millions	Jul. 27, 2015	Mar. 31, 2015	Feb. 27, 2015	Jul. 21, 2014	Mar. 31, 2014	Feb. 27, 2014
Share Repurchase Program
Common stock repurchase authorized amount			$ 75			$ 75
Additional Shares Delivered Under Share Repurchase Program	0.0			0.2
Minimum
Share Repurchase Program
Number of shares authorized to be repurchased		1.5			1.4