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, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares/Units
Shares outstanding, beginning of period (in shares)	440	590	855
Shares, granted (in shares)	449	238	247
Shares, adjustments (in shares)	70	45
Shares, vested (in shares)	(346)	(430)	(501)
Shares cancelled/forfeited (in shares)	(17)	(3)	(11)
Shares outstanding, end of period (in shares)	596	440	590
Weighted Average Grant Date Fair Value
Shares outstanding, weighted average grant date fair value, beginning of period (in dollars per share)	$ 47.23	$ 37.23	$ 27.90
Shares, weighted average grant date fair value, granted (in dollars per share)	75.39	53.25	45.24
Shares, weighted average grant date fair value, adjustments (in dollars per share)	47.01	51.00
Shares, weighted average grant date fair value, vested (in dollars per share)	46.60	39.98	22.54
Shares, weighted average grant date fair value, cancelled/forfeited (in dollars per share)	54.49	41.92	29.64
Shares outstanding, weighted average grant date fair value, end of period (in dollars per share)	$ 68.66	$ 47.23	$ 37.23
Market Condition & Performance-Based Awards
Number of Shares/Units
Shares outstanding, beginning of period (in shares)	124	110	51
Shares, granted (in shares)	256	65	59
Shares, adjustments (in shares)	70	45
Shares, vested (in shares)	(129)	(96)	0
Shares cancelled/forfeited (in shares)	0	0	0
Shares outstanding, end of period (in shares)	321	124	110
Weighted Average Grant Date Fair Value
Shares outstanding, weighted average grant date fair value, beginning of period (in dollars per share)	$ 51.59	$ 48.86	$ 51.00
Shares, weighted average grant date fair value, granted (in dollars per share)	68.32	55.75	47.01
Shares, weighted average grant date fair value, adjustments (in dollars per share)	47.01	51.00
Shares, weighted average grant date fair value, vested (in dollars per share)	47.01	51.00	0.00
Shares, weighted average grant date fair value, cancelled/forfeited (in dollars per share)	0.00	0.00	0.00
Shares outstanding, weighted average grant date fair value, end of period (in dollars per share)	$ 65.77	$ 51.59	$ 48.86
Service Period Awards
Number of Shares/Units
Shares outstanding, beginning of period (in shares)	316	480	804
Shares, granted (in shares)	193	173	188
Shares, adjustments (in shares)	0	0
Shares, vested (in shares)	(217)	(334)	(501)
Shares cancelled/forfeited (in shares)	(17)	(3)	(11)
Shares outstanding, end of period (in shares)	275	316	480
Weighted Average Grant Date Fair Value
Shares outstanding, weighted average grant date fair value, beginning of period (in dollars per share)	$ 45.51	$ 36.90	$ 23.99
Shares, weighted average grant date fair value, granted (in dollars per share)	84.78	52.31	44.68
Shares, weighted average grant date fair value, adjustments (in dollars per share)	0.00	0.00
Shares, weighted average grant date fair value, vested (in dollars per share)	46.35	36.79	22.54
Shares, weighted average grant date fair value, cancelled/forfeited (in dollars per share)	54.49	41.92	29.64
Shares outstanding, weighted average grant date fair value, end of period (in dollars per share)	$ 72.03	$ 45.51	$ 36.90