Stock Incentive Compensation and Employee Benefit Plans (Equity Compensation Other than Options) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Settled Restricted Stock Unit (CSRSUs)
Number of shares:
Nonvested, beginning balance (in shares)	308,344	326,078	338,323
Awards granted (in shares)	98,067	135,119	160,817
Awards vested (in shares)	(122,088)	(133,278)	(144,440)
Awards forfeited (in shares)	(21,993)	(19,575)	(28,622)
Nonvested, Ending balance (in shares)	262,330	308,344	326,078
Performance Shares
Number of shares:
Nonvested, beginning balance (in shares)	211,381	230,271	248,572
Awards granted (in shares)	64,947	77,045	103,024
Awards vested (in shares)	(62,499)	(58,032)	0
Awards forfeited (in shares)	(46,156)	(37,903)	(121,325)
Nonvested, Ending balance (in shares)	167,673	211,381	230,271
Weighted average grant-dated fair value:
Nonvested, Weighted average grant-dated fair value, beginning balance (in usd per share)	$ 44.63	$ 41.40	$ 39.62
Awards granted, Weighted average grant-dated fair value (in usd per share)	65.27	48.31	44.98
Awards vested, Weighted average grant-dated fair value (in usd per share)	43.51	38.30
Nonvested, Weighted average grant-dated fair value, ending balance (in usd per share)	$ 53.11	$ 44.63	$ 41.40
Employee restricted stock
Number of shares:
Nonvested, beginning balance (in shares)	402,170	479,040	451,722
Awards granted (in shares)	116,345	179,003	195,337
Awards vested (in shares)	(185,478)	(255,873)	(168,019)
Awards forfeited (in shares)	0	0	0
Nonvested, Ending balance (in shares)	333,037	402,170	479,040
Weighted average grant-dated fair value:
Nonvested, Weighted average grant-dated fair value, beginning balance (in usd per share)	$ 103.34	$ 94.95	$ 87.29
Awards granted, Weighted average grant-dated fair value (in usd per share)	148.66	112.41	102.17
Awards vested, Weighted average grant-dated fair value (in usd per share)	100.17	93.98	82.75
Awards forfeited, Weighted average grant-dated fair value (in usd per share)	0.00	0.00	0.00
Nonvested, Weighted average grant-dated fair value, ending balance (in usd per share)	$ 120.93	$ 103.34	$ 94.95
Non-employee director restricted stock
Number of shares:
Nonvested, beginning balance (in shares)	25,545	26,886	30,055
Awards granted (in shares)	12,193	14,727	14,575
Awards vested (in shares)	(17,612)	(16,068)	(17,744)
Awards forfeited (in shares)	0	0	0
Nonvested, Ending balance (in shares)	20,126	25,545	26,886
Weighted average grant-dated fair value:
Nonvested, Weighted average grant-dated fair value, beginning balance (in usd per share)	$ 107.95	$ 97.61	$ 88.41
Awards granted, Weighted average grant-dated fair value (in usd per share)	150.05	114.71	102.90
Awards vested, Weighted average grant-dated fair value (in usd per share)	110.66	96.83	86.37
Awards forfeited, Weighted average grant-dated fair value (in usd per share)	0.00	0.00	0.00
Nonvested, Weighted average grant-dated fair value, ending balance (in usd per share)	$ 131.09	$ 107.95	$ 97.61
Restricted Stock
Number of shares:
Nonvested, beginning balance (in shares)	427,715	505,926	481,777
Awards granted (in shares)	128,538	193,730	209,912
Awards vested (in shares)	(203,090)	(271,941)	(185,763)
Awards forfeited (in shares)	0	0	0
Nonvested, Ending balance (in shares)	353,163	427,715	505,926
Weighted average grant-dated fair value:
Nonvested, Weighted average grant-dated fair value, beginning balance (in usd per share)	$ 103.61	$ 95.09	$ 87.36
Awards granted, Weighted average grant-dated fair value (in usd per share)	148.79	112.59	102.22
Awards vested, Weighted average grant-dated fair value (in usd per share)	101.08	94.15	83.10
Awards forfeited, Weighted average grant-dated fair value (in usd per share)	0.00	0.00	0.00
Nonvested, Weighted average grant-dated fair value, ending balance (in usd per share)	$ 121.51	$ 103.61	$ 95.09