Stockholders' Equity - Narrative (Details) (USD $) Share data in Millions, unless otherwise specified	1 Months Ended	3 Months Ended
	Feb. 28, 2014	Mar. 31, 2015	Mar. 31, 2014	Oct. 31, 2013
Stockholders' Equity Note [Abstract]
Stock repurchase program, authorized amount				$ 750,000,000
Shares repurchased during period (in shares)		0.9
Repurchases of common stock	62,000,000	62,680,000	116,147,000
Amortization expense from capitalized stock-based compensation		$ 3,000,000	$ 1,900,000