Stock-Based Compensation (Summary of Restricted Share and Performance Share Activity) (Details) - 6 months ended Jun. 30, 2015 - $ / shares	Total
Time-Based [Member]
Number of Shares [Roll Forward]
Outstanding - beginning of year, number of shares	344,932
Granted, number of shares	41,000
Vested, number of shares	(139,748)
Canceled or expired, number of shares	(21,501)
Outstanding - end of year, number of shares	224,683
Weighted Average Grant Date Fair Value [Abstract]
Outstanding - beginning of year, weighted average grant date fair value (in dollars per share)	$ 33.55
Granted, weighted average grant date fair value (in dollars per share)	49.35
Vested, weighted average grant date fair value (in dollars per share)	32.78
Canceled or expired, weighted average grant date fair value (in dollars per share)	40.47
Outstanding - end of year, weighted average grant date fair value (in dollars per share)	$ 36.25
Performance-Based [Member]
Number of Shares [Roll Forward]
Outstanding - beginning of year, number of shares	28,000
Granted, number of shares	120,000
Vested, number of shares	(14,000)
Canceled or expired, number of shares	0
Outstanding - end of year, number of shares	134,000
Weighted Average Grant Date Fair Value [Abstract]
Outstanding - beginning of year, weighted average grant date fair value (in dollars per share)	$ 20.30
Granted, weighted average grant date fair value (in dollars per share)	48.72
Vested, weighted average grant date fair value (in dollars per share)	20.30
Canceled or expired, weighted average grant date fair value (in dollars per share)	0.00
Outstanding - end of year, weighted average grant date fair value (in dollars per share)	$ 45.75