Stockholders' Equity - Narrative (Details) (USD $) Share data in Millions, unless otherwise specified	1 Months Ended		3 Months Ended
	Oct. 31, 2013	Jan. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Stockholders' Equity Note [Abstract]
Stock repurchase program, authorized amount	$ 750,000,000	$ 150,000,000
Shares repurchased during period (in shares)			2.0	1.1
Value of shares repurchased during period			116,100,000	40,300,000
Amortization expense from capitalized stock-based compensation			$ 1,900,000