Share-Based Compensation Plans Share-Based Compensation Plans, Restricted Stock Activity (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	May 29, 2013	Mar. 21, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 6,200,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	4,900,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized				155,000	92,000
Allocated Share-based Compensation Expense	21,482,000	13,993,000	9,730,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Trading Days	20 days
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	14,900,000
Omnibus Stock Incentive Plans, 2007 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 5,300,000	$ 6,400,000	$ 4,200,000
Churchill 2004 and 2007 Plan [Member] | Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Shares outstanding, beginning of period	379,000	419,000	334,000
Shares, granted	611,000	182,000	156,000
Shares, vested	(316,000)	(221,000)	(70,000)
Shares cancelled/forfeited	(1,000)	(1,000)	(1,000)
Shares outstanding, end of period	673,000	379,000	419,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Shares outstanding, weighted average grant date fair value, beginning of period	$ 42.97	$ 40.01	$ 38.96
Shares, weighted average grant date fair value, granted	$ 60.21	$ 51.99	$ 42.95
Shares, weighted average grant date fair value, vested	$ 53.90	$ 44.77	$ 42.21
Shares, weighted average grant date fair value, cancelled/forfeited	$ 38.75	$ 39.12	$ 35.81
Shares outstanding, weighted average grant date fair value, end of period	$ 53.64	$ 42.97	$ 40.01
Performance-Based Awards [Member] | Churchill 2004 and 2007 Plan [Member] | Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Shares outstanding, beginning of period	60,000	112,000	112,000
Shares, granted	324,000	0	0
Shares, vested	(60,000)	(52,000)	0
Shares cancelled/forfeited	0	0	0
Shares outstanding, end of period	324,000	60,000	112,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Shares outstanding, weighted average grant date fair value, beginning of period	$ 45.90	$ 43.76	$ 43.40
Shares, weighted average grant date fair value, granted	$ 53.71	$ 0.00	$ 0.00
Shares, weighted average grant date fair value, vested	$ 45.90	$ 41.31	$ 0.00
Shares, weighted average grant date fair value, cancelled/forfeited	$ 0.00	$ 0.00	$ 0.00
Shares outstanding, weighted average grant date fair value, end of period	$ 53.71	$ 45.90	$ 43.76
Service Period Awards [Member] | Churchill 2004 and 2007 Plan [Member] | Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Shares outstanding, beginning of period	319,000	307,000	222,000
Shares, granted	287,000	182,000	156,000
Shares, vested	(256,000)	(169,000)	(70,000)
Shares cancelled/forfeited	(1,000)	(1,000)	(1,000)
Shares outstanding, end of period	349,000	319,000	307,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Shares outstanding, weighted average grant date fair value, beginning of period	$ 42.42	$ 38.63	$ 36.72
Shares, weighted average grant date fair value, granted	$ 67.55	$ 51.99	$ 42.95
Shares, weighted average grant date fair value, vested	$ 59.54	$ 45.85	$ 42.41
Shares, weighted average grant date fair value, cancelled/forfeited	$ 38.75	$ 39.12	$ 35.81
Shares outstanding, weighted average grant date fair value, end of period	$ 53.58	$ 42.42	$ 38.63