Stock Compensation Plans and Other Employee Benefit Plans (Summary of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Shares
Outstanding at beginning of the period (in shares)	1,084,756	1,698,912	1,551,734
Granted (in shares)	0	0	562,166
Exercised (in shares)	(282,614)	(593,459)	(313,900)
Forfeited or canceled (in shares)	(7,128)	(20,697)	(101,088)
Outstanding at end of the period (in shares)	795,014	1,084,756	1,698,912
Exercisable (in shares)	613,932	562,810	703,892
Vested or expected to vest (in shares)	787,753
Weighted Average Strike Price
Outstanding at beginning of the period (in dollars per share)	$ 41.98	$ 41.50	$ 41.32
Granted (in dollars per share)	0.00	0.00	41.04
Exercised (in dollars per share)	41.25	40.57	37.71
Forfeited or canceled (in dollars per share)	39.84	42.83	48.00
Outstanding at end of the period (in dollars per share)	42.25	41.98	41.50
Exercisable (in dollars per share)	42.54	$ 41.82	$ 39.62
Vested or expected to vest (in dollars per share)	$ 42.26
Stock Options Additional Disclosures
Outstanding, remaining contractual term	3 years 1 month 6 days	4 years	4 years 7 months 6 days
Outstanding, intrinsic value	$ 19,268	$ 43,817	$ 52,790
Exercisable, remaining contractual term	3 years 1 month 6 days	3 years 4 months	3 years 4 months 24 days
Exercisable, intrinsic value	$ 14,705	$ 22,820	$ 23,195
Vested or expected to vest, remaining contractual term	3 years 1 month 6 days
Vested or expected to vest, intrinsic value	$ 19,085