Stock-Based Compensation (RSU Activity) (Details)	1 Months Ended		12 Months Ended
	Apr. 30, 2016 USD ($) $ / shares shares	Mar. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) installment $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares
RSUs
Additional Disclosure
Number of equal annual installments | installment			3
Fair value (in dollars) | $			$ 8,600,000	$ 9,400,000	$ 9,100,000
Number of Shares
Balance at the beginning of the period (in shares) | shares			682,000
Granted (in shares) | shares			605,000
Vested (in shares) | shares			(319,000)
Cancelled (in shares) | shares			(97,000)
Balance at the end of the period (in shares) | shares			871,000	682,000
Weighted-Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share) | $ / shares			$ 30.18
Granted (in dollars per share) | $ / shares			27.50	$ 30.65	$ 29.05
Vested (in dollars per share) | $ / shares			30.27
Cancelled (in dollars per share) | $ / shares			29.02
Balance at the end of the period (in dollars per share) | $ / shares			$ 28.42	$ 30.18
RSUs | Performance-Based Vesting
Additional Disclosure
Fair value (in dollars) | $			$ 163,000	$ 211,000
Grant-date fair value (in dollars) | $	$ 329,000	$ 368,000
Number of Shares
Balance at the beginning of the period (in shares) | shares			6,000
Granted (in shares) | shares	11,720	13,533	12,000
Vested (in shares) | shares			(6,000)		0
Cancelled (in shares) | shares			(12,000)
Balance at the end of the period (in shares) | shares				6,000
Weighted-Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share) | $ / shares			$ 27.21
Granted (in dollars per share) | $ / shares	$ 28.09	$ 27.21	28.09	$ 31.12	$ 27.21
Vested (in dollars per share) | $ / shares			27.21
Cancelled (in dollars per share) | $ / shares			$ 28.09
Balance at the end of the period (in dollars per share) | $ / shares				$ 27.21
Restricted Stock | Outside directors
Additional Disclosure
Fair value (in dollars) | $			$ 200,000	$ 200,000	$ 230,000
Number of Shares
Granted (in shares) | shares			6,970	7,365	8,209
Weighted-Average Grant Date Fair Value
Granted (in dollars per share) | $ / shares			$ 28.65	$ 27.10	$ 29.97