Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, shares in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Cash dividends declared (usd per share)	$ 0.36	$ 0.33	$ 0.23
Dividends declared	$ 122,240,000	$ 117,873,000	$ 86,370,000
Stock repurchases	603,206,000	$ 442,738,000	$ 253,019,000
Share repurchase plan [Member]
Class of Stock [Line Items]
Remaining value of stock repurchase programs authorization	$ 1,000,000,000
Shares repurchased under authorized repurchase programs	30.9	21.2	12.9
Stock repurchases	$ 600,000,000	$ 433,690,000	$ 245,834,000
Shares withheld to pay taxes [Member]
Class of Stock [Line Items]
Stock repurchases	$ 3,200,000	$ 9,000,000	$ 7,200,000