Share-Based Compensation (Nonvested Share Transactions) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Nonvested Shares Outstanding
Nonvested Shares Outstanding, Beginning Balance	339	226
Nonvested Shares Outstanding, Granted	84	272
Nonvested Shares Outstanding, Vested	(88)	(155)
Nonvested Shares Outstanding, Cancelled		(4)
Nonvested Shares Outstanding, Ending Balance	335	339
Weighted-Average Price at Grant Date (in dollars per share)
Weighted-Average Price at Grant Date, Beginning Balance	$ 47.34	$ 29.58
Weighted-Average Price at Grant Date, Granted	$ 52.49	$ 56.69
Weighted-Average Price at Grant Date, Vested	$ 32.25	$ 37.34
Weighted-Average Price at Grant Date, Cancelled		$ 50.41
Weighted-Average Price at Grant Date, Ending Balance	$ 52.60	$ 47.34
Long-Term Incentive Programs [Member]
Nonvested Shares Outstanding
Nonvested Shares Outstanding, Beginning Balance	488	434
Nonvested Shares Outstanding, Granted	132	111
Nonvested Shares Outstanding, Adjustments for actual performance		222
Nonvested Shares Outstanding, Vested	(252)	(279)
Nonvested Shares Outstanding, Cancelled	(3)
Nonvested Shares Outstanding, Ending Balance	365	488
Weighted-Average Price at Grant Date (in dollars per share)
Weighted-Average Price at Grant Date, Beginning Balance	$ 30.52	$ 25.79
Weighted-Average Price at Grant Date, Granted	$ 52.47	$ 49.60
Weighted-Average Price at Grant Date, Adjustments for actual performance (in dollars per share)		$ 22.32
Weighted-Average Price at Grant Date, Vested	$ 20.21	$ 24.21
Weighted-Average Price at Grant Date, Cancelled	$ 30.36
Weighted-Average Price at Grant Date, Ending Balance	$ 45.60	$ 30.52