Stock-Based Compensation (Nonvested Performance-based Award Activity) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Non-vested PVS Awards, Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding, Beginning (in usd per share)	$ 20.98	$ 19.65	$ 19.47
Granted at target level	$ 29.56	$ 21.22	$ 20.56
Adjustments above/(below) target	$ 25.30	$ 15.22	$ 20.53
Vested and converted	$ 29.56	$ 21.22	$ 20.43
Forfeited	$ 0.00	$ 0.00	$ 18.77
Outstanding, Ending (in usd per share)	$ 23.86	$ 20.98	$ 19.65
Performance-Vesting Shares [Member]
Non-vested PVS Awards [Roll Forward]
Outstanding, Beginning	652,662	657,038	695,100
Granted at target level	175,498	209,680	202,198
Adjustments above/(below) target	38,330	(120,155)	(116,355)
Vested and converted	(273,044)	(83,859)	(103,507)
Forfeited	(15,088)	(10,042)	(20,398)
Outstanding, Ending	578,358	652,662	657,038
Non-vested PVS Awards, Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding, Beginning (in usd per share)	$ 21.42	$ 19.39	$ 19.61
Granted at target level	$ 29.67	$ 21.33	$ 20.43
Adjustments above/(below) target	$ 23.83	$ 13.86	$ 20.97
Vested and converted	$ 29.56	$ 21.22	$ 20.43
Forfeited	$ 23.29	$ 20.98	$ 19.23
Outstanding, Ending (in usd per share)	$ 23.79	$ 21.42	$ 19.39
Performance-Vesting Units [Member]
Non-vested PVS Awards [Roll Forward]
Outstanding, Beginning	69,240	54,572	46,840
Granted at target level	25,538	27,100	26,884
Adjustments above/(below) target	3,000	(7,156)	(8,330)
Vested and converted	(18,322)	(5,276)	(7,386)
Forfeited	0	0	(3,436)
Outstanding, Ending	79,456	69,240	54,572