Share Repurchase Program (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions		1 Months Ended	12 Months Ended
	Aug. 03, 2015	May. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Feb. 09, 2015	Feb. 06, 2014	Oct. 24, 2012
Stock repurchased and retired during period, average amount per share			$ 43.99	$ 45.29	$ 31.87
Stock repurchased and retired during period, shares		0.6	4.9	2.0	0.1
Payments for Repurchase of Common Stock			$ 179,090	$ 88,815	$ 32,241
Refund of accelerated share repurchase	$ 38,200		38,179	0	0
Prepayment of Accelerated Share Repurchase			$ 75,000	$ 0	$ 0
Common stock repurchased and retired		$ 30,000
Stock repurchase program, authorized amount						$ 300,000	$ 100,000	$ 60,000
Accelerated Share Repurchase Agreement [Member]
Stock repurchased and retired during period, average amount per share	$ 46.49
Stock repurchased and retired during period, shares	0.8
Payments for Repurchase of Common Stock	$ 36,800