Stock-Based Incentive Plans (Details) (USD $)	3 Months Ended		1 Months Ended	3 Months Ended		3 Months Ended		1 Months Ended
	Mar. 31, 2012 Y plan	Mar. 31, 2011	Jan. 31, 2012 Restricted Stock Units	Mar. 31, 2012 Restricted Stock Units	Jan. 30, 2012 Restricted Stock Units	Mar. 31, 2012 1994 Plan Granted on 3 Feb 2011 Y	Mar. 31, 2012 1995 Plan Granted on 15 Feb 2011 Y	Jan. 31, 2012 Independent directors Restricted Stock Units
Stock-Based Incentive Plans
Number of stock-based incentive plans	1
Number of stock option plans superseded	2
Black-Scholes option pricing model assumptions for options granted
Restricted stock units awarded (in shares)			361,061	361,000				8,550
Risk Free Interest Rate (as a percent)						2.62%	2.92%
Dividend Yield (as a percent)						1.75%	1.76%
Expected Life (in years)						6.2	6.6
Volatility (as a percent)						39.00%	38.00%
Exercise price for options granted, low end of range (in dollars per share)						$ 29.66
Exercise price for options granted, high end of range (in dollars per share)						$ 32.63
Exercise Price (in dollars per share)							$ 29.58
Weighted Average Fair Value (in dollars per share)						$ 10.33	$ 10.49
Restricted stock unit activity
Awarded (in shares)			361,061	361,000				8,550
Vested (in shares)				(93,000)
Forfeited (in shares)				(1,000)
Outstanding at the end of the period				267,000
Outstanding and expected to vest at the end of the period (in shares)				259,000
Non-Qualified Stock Options activity
Outstanding at the beginning of the period (in shares)	2,134,000
Granted (in shares)						1,362,000	30,000
Exercised (in shares)	(74,000)
Forfeited (in shares)	(17,000)
Outstanding at the end of the period (in shares)	2,043,000
Outstanding and expected to vest at the end of the period (in shares)	2,000,000
Exercisable at the end of the period (in shares)	963,000
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 31.15				$ 33.23
Granted (in dollars per share)				$ 33.23
Vested (in dollars per share)				$ 33.23
Exercised (in dollars per share)	$ 23.68
Forfeited (in dollars per share)	$ 34.86			$ 33.23
Outstanding at the end of the period (in dollars per share)	$ 31.39			$ 33.23	$ 33.23
Outstanding and expected to vest at end of the period (in dollars per share)	$ 31.44			$ 33.23
Exercisable at end of the period (in dollars per share)	$ 33.82
Weighted-Average Remaining Contractual Life
Outstanding at the end of the period (in years)	4.6
Outstanding and expected to vest at end of the period (in years)	4.5
Exercisable at end of the period (in years)	3.2
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	$ 5,105,000			$ 8,612,000
Outstanding and expected to vest at end of the period (in dollars)	$ 4,976,000			$ 8,356,000
Exercisable at end of the period (in dollars)	1,835,000
Closing price of share (in dollars per share)	$ 32.25			$ 32.25
Total intrinsic value of RSUs vested (in dollars)	$ 700,000	$ 40,000		$ 3,100,000
Number of Shares, Unvested Options
Unvested at the beginning of the period (in shares)	1,242,000
Granted (in shares)						1,362,000	30,000
Vested (in shares)	(159,000)
Forfeiture (in shares)	(3,000)
Unvested at the end of the period (in shares)	1,080,000
Weighted-Average Grant-Date Fair Value, Unvested Options
Unvested at the beginning of the period (in dollars per share)	$ 10.11
Vested (in dollars per share)	$ 9.82
Forfeiture (in dollars per share)	$ 10.33
Unvested at the end of the period (in dollars per share)	$ 10.15
Unrecognized compensation cost and vesting period
Unrecognized compensation costs related to unvested share-based compensation arrangements (in dollars)	$ 14,400,000
Weighted-average period for recognition of unrecognized stock-based compensation expense (in years)	2.8
Period over which award restrictions lapse with one quarter on award date and one quarter on each anniversary date			3 years