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, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares/Units
Shares outstanding, beginning of period (in shares)	579	596	440
Shares, granted (in shares)	131	188	449
Shares, performance adjustment (in shares)	41	87	70
Shares, vested (in shares)	(211)	(287)	(346)
Shares cancelled/forfeited (in shares)	(3)	(5)	(17)
Shares outstanding, end of period (in shares)	537	579	596
Weighted Average Grant Date Fair Value
Shares outstanding, weighted average grant date fair value, beginning of period (in dollars per share)	$ 78.45	$ 68.66	$ 47.23
Shares, weighted average grant date fair value, granted (in dollars per share)	159.3	93.96	75.39
Shares, weighted average grant date fair value, adjustments (in dollars per share)	90.73	55.75	47.01
Shares, weighted average grant date fair value, vested (in dollars per share)	90.32	61.57	46.60
Shares, weighted average grant date fair value, cancelled/forfeited (in dollars per share)	121.39	77.59	54.49
Shares outstanding, weighted average grant date fair value, end of period (in dollars per share)	$ 94.14	$ 78.45	$ 68.66
PSUs
Number of Shares/Units
Shares outstanding, beginning of period (in shares)	314	321	124
Shares, granted (in shares)	37	58	256
Shares, performance adjustment (in shares)	41	87	70
Shares, vested (in shares)	(90)	(152)	(129)
Shares cancelled/forfeited (in shares)	0	0	0
Shares outstanding, end of period (in shares)	302	314	321
Weighted Average Grant Date Fair Value
Shares outstanding, weighted average grant date fair value, beginning of period (in dollars per share)	$ 72.84	$ 65.77	$ 51.59
Shares, weighted average grant date fair value, granted (in dollars per share)	182.45	92.90	68.32
Shares, weighted average grant date fair value, adjustments (in dollars per share)	90.73	55.75	47.01
Shares, weighted average grant date fair value, vested (in dollars per share)	90.73	55.75	47.01
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)	$ 83.40	$ 72.84	$ 65.77
RSAs and RSUs
Number of Shares/Units
Shares outstanding, beginning of period (in shares)	265	275	316
Shares, granted (in shares)	94	130	193
Shares, performance adjustment (in shares)	0	0	0
Shares, vested (in shares)	(121)	(135)	(217)
Shares cancelled/forfeited (in shares)	(3)	(5)	(17)
Shares outstanding, end of period (in shares)	235	265	275
Weighted Average Grant Date Fair Value
Shares outstanding, weighted average grant date fair value, beginning of period (in dollars per share)	$ 85.07	$ 72.03	$ 45.51
Shares, weighted average grant date fair value, granted (in dollars per share)	150.12	94.42	84.78
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)	90.01	68.15	46.35
Shares, weighted average grant date fair value, cancelled/forfeited (in dollars per share)	121.39	77.59	54.49
Shares outstanding, weighted average grant date fair value, end of period (in dollars per share)	$ 107.90	$ 85.07	$ 72.03