Stock Repurchases (Details) - USD ($) shares in Millions		3 Months Ended
	Feb. 10, 2016	Mar. 31, 2016	Mar. 31, 2015
Stockholders' Equity Note [Abstract]
Stock repurchase program, authorized amount		$ 1,400,000,000
Stock repurchase program, remaining authorized amount		$ 196,200,000
Accelerated share repurchases, initial price to be paid	$ 200,000,000
Accelerated share repurchases, number of shares	1.3
Accelerated share repurchases, percentage of shares to be repurchased	75.00%
Shares repurchased from employees who surrendered shares to satisfy minimum tax withholding obligations		0.1
Shares repurchased from employees who surrendered shares to satisfy minimum tax withholding obligations, value		$ 16,800,000	$ 20,500,000