Retirement and Share-based Compensation Plans (Changes in the Number of Stock Options Outstanding) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding, number of shares	3,443,991	4,044,175	3,976,725	5,732,450
Outstanding, weighted-average exercise price per share	$ 15.17	$ 15.02	$ 10.86	$ 10.35
Outstanding, total exercise price	$ 52,240	$ 60,760	$ 43,171	$ 59,321
Granted, number of shares	0	1,277,650	1,210,950
Granted, weighted-average exercise price per share	$ 0.00	$ 24.79	$ 13.13
Granted, total exercise price	$ 0	$ 31,673	$ 15,899
Canceled, number of shares	(47,300)	(35,400)	(29,400)
Canceled, weighted-average exercise price per share	$ 10.54	$ 11.64	$ 9.96
Canceled, total exercise price	$ (499)	$ (412)	$ (293)
Exercised, number of shares	(552,884)	(1,174,800)	(2,937,275)
Exercised, weighted-average exercise price per share	$ 14.51	$ 11.64	$ 10.81
Exercised, total exercise price	$ (8,021)	$ (13,672)	$ (31,756)