Stock-Based Compensation Plans - Activity for Awards Made Outside of Share-Based Compensation Plans (Details) - ELTI Plan, the 2013 New Company LTIP, the 2007 Incentive Plan and awards made outside of stock-based compensation plans - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares/Units
Shares outstanding, beginning of period (in shares)	596	440	590
Shares, granted (in shares)	188	449	238
Shares, performance adjustment (in shares)	87	70	45
Shares, vested (in shares)	(287)	(346)	(430)
Shares cancelled/forfeited (in shares)	(5)	(17)	(3)
Shares outstanding, end of period (in shares)	579	596	440
Weighted Average Grant Date Fair Value
Shares outstanding, weighted average grant date fair value, beginning of period (in dollars per share)	$ 68.66	$ 47.23	$ 37.23
Shares, weighted average grant date fair value, granted (in dollars per share)	93.96	75.39	53.25
Shares, weighted average grant date fair value, adjustments (in dollars per share)	55.75	47.01	51.00
Shares, weighted average grant date fair value, vested (in dollars per share)	61.57	46.60	39.98
Shares, weighted average grant date fair value, cancelled/forfeited (in dollars per share)	77.59	54.49	41.92
Shares outstanding, weighted average grant date fair value, end of period (in dollars per share)	$ 78.45	$ 68.66	$ 47.23
Market Condition & Performance-Based Awards
Number of Shares/Units
Shares outstanding, beginning of period (in shares)	321	124	110
Shares, granted (in shares)	58	256	65
Shares, performance adjustment (in shares)	87	70	45
Shares, vested (in shares)	(152)	(129)	(96)
Shares cancelled/forfeited (in shares)	0	0	0
Shares outstanding, end of period (in shares)	314	321	124
Weighted Average Grant Date Fair Value
Shares outstanding, weighted average grant date fair value, beginning of period (in dollars per share)	$ 65.77	$ 51.59	$ 48.86
Shares, weighted average grant date fair value, granted (in dollars per share)	92.90	68.32	55.75
Shares, weighted average grant date fair value, adjustments (in dollars per share)	55.75	47.01	51.00
Shares, weighted average grant date fair value, vested (in dollars per share)	55.75	47.01	51.00
Shares, weighted average grant date fair value, cancelled/forfeited (in dollars per share)	0	0	0
Shares outstanding, weighted average grant date fair value, end of period (in dollars per share)	$ 72.84	$ 65.77	$ 51.59
Service Period Awards
Number of Shares/Units
Shares outstanding, beginning of period (in shares)	275	316	480
Shares, granted (in shares)	130	193	173
Shares, performance adjustment (in shares)	0	0	0
Shares, vested (in shares)	(135)	(217)	(334)
Shares cancelled/forfeited (in shares)	(5)	(17)	(3)
Shares outstanding, end of period (in shares)	265	275	316
Weighted Average Grant Date Fair Value
Shares outstanding, weighted average grant date fair value, beginning of period (in dollars per share)	$ 72.03	$ 45.51	$ 36.90
Shares, weighted average grant date fair value, granted (in dollars per share)	94.42	84.78	52.31
Shares, weighted average grant date fair value, adjustments (in dollars per share)	0	0	0
Shares, weighted average grant date fair value, vested (in dollars per share)	68.15	46.35	36.79
Shares, weighted average grant date fair value, cancelled/forfeited (in dollars per share)	77.59	54.49	41.92
Shares outstanding, weighted average grant date fair value, end of period (in dollars per share)	$ 85.07	$ 72.03	$ 45.51