Stockholders' Equity, Restricted Stock Unit Activity (Details) - Restricted Stock Units [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Number of Shares [Abstract]
Non-vested at beginning of period (in shares)	751
Granted (in shares)	346
Vested (in shares)	(270)
Cancelled/forfeited (in shares)	(49)
Non-vested at end of period (in shares)	778	751
Weighted Average Grant Date Fair Value per Share [Abstract]
Non-vested at beginning of period (in dollars per share)	$ 47.47
Granted (in dollars per share)	41.79	$ 65.69	$ 44.94
Vested (in dollars per share)	39.22
Cancelled/forfeited (in dollars per share)	49.38
Non-vested at end of period (in dollars per share)	$ 47.68	$ 47.47
Unrecognized Compensation Expense [Abstract]
Unrecognized compensation cost related to non-vested RSUs	$ 13.3
Weighted average period for recognition	1 year 2 months 12 days